Burning wood - not sustainable?

Question from a sustainability student:

In the last few years I've seen demands that using wood as a power/heat source (by burning it) should not be declared sustainable.

I understand that burning wood releases particulates. I also understand that sometimes we burn woods from forest that are not reafforested which is obviously unsustainable.

However, if we filter the particulates while burning wood and we reafforest the forests that the wood comes from, isn't burning wood sustainable? What am I overlooking?

Mick's answer: 

We burn wood for 80 of our heat (in total energy terms), about half or less our heating costs. We harvest about half of it from our own woodlots at a rate of about two cords a year. The remaining trees in our woodlots are growing, and some are growing faster as a result of "tree release", getting more sunlight. Our trees are sequestering far more carbon than the small amount we take each year. We have seven acres and take up to two cords. Using typical averages (of cords produced per acre and weight per cord) for New England hardwood forests, that means we are sequestering 8 to 10 tons/tonnes a year (very roughly), some of which forgives the logging needed for our other two cords which we buy and some proportion of the fossil fuel needed for our stove and vehicles. The trees we take are all ash, which is threatened by the invasive emerald ash borer and will very likely die anyway. The larger mass particulate pollution from wood burning, which contains far less aerosolized component than the equivalent from gas, oil or coal, typically falls out of the atmosphere after only a few miles at the most. It is a form of pollution that is predominant (and harmful) in cities, not in low density rural areas like ours, where they are only 21 people per square mile, and so what particulate there is, is diluted. The biggest sustainability problem with wood burning is when large scale power plants add wood biomass to the fossil fuels used in turbines. So, for instance, woody biomass in the southern US is clear cut from plantations and even natural forests, then shipped to Britain where is is burned in old coal fired plants like Drax in Yorkshire. This industrial use of wood is far less sustainable because a) natural forests store carbon in the soils and much of this is lost when clearcut, b) the fossil fuel used in transportation and processing, and c) the much larger density of particulate produced on-site. It is only cost effective because of "perverse" economic incentives set up by EU carbon regulation.

https://newenglandforestry.org/wp-content/uploads/2019/10/NNE-carbonstorage-100119.pdf

https://www.bbc.com/news/science-environment-63089348

BTW, what I like about this question is that it neatly illustrates the wide variety of disciplines needed to solve sustainability problems. 

Alternatives to oil heat?

Maine homeowner: We live in Wiscasset well off the main road, and have always had an oil furnace to heat our 2600 square foot home. Lately, the cost to fill the tank has rapidly risen past $1000.

Our house is quite old, but we have replaced the windows, roof and added insulation in the last few years to try and reel in energy costs. Unfortunately, though this has helped a little, it hasn’t had nearly the impact we had hoped.

My wife and I are far from wealthy and the rising oil cost has become a huge concern. It’s hitting the point now where we seriously have to look into alternative heating methods if we don’t want to leave the house after retirement.

I’ve done plenty of homework on the subject of energy-efficient heating and mostly see solar and heat pump as our options. Does anyone have experience converting from oil to either of these options in a similarly-sized home?

Intelligent Tinkering: Our old farmhouse isn't that large, about 2000 feet with a recent extension, but it has distant wings, so doesn't heat easily.

When we got it, it wasn't insulated. The previous occupants used 700 gallons oil and ten cords of wood a year. We didn't exactly convert the place from oil. The oil furnace is still there. What we did was make incremental improvements. First we put in a wood stove and used that instead of the oil hot air furnace for about 80% of the heat. Then in stages we air sealed and insulated: new windows and doors, R40 cellulose blown in the attic, four inches cellulose blown into the stud bays, and two inches R10 foam board over the entire outside. Spray foam on the upper four feet of the cellar walls and joist bays. Smarter thermostats for the furnace and baseboards. Every year for five or six years we did something to improve on air sealing and insulation. We did it all ourselves.

Then we built an extension that had R10 foam board and six inches cellulose in the walls and R40 in the attic. We added a heat pump in the kitchen where we can feed both wings, although not well enough to get to the far corners where we have electric heaters to top up. We added solar, 2.7kW/hour of sunshine, which cancels out some of the extra power needed for the heat pump and baseboards. Right now we use 3-4 cords firewood, less than 50 gallons oil, and our power bills go from $40 in summer to $100 in late fall and spring to $300 in January and February. Quite a bit of that is tank heaters and heat lamps for livestock and block heaters for a tractor, though. We measured their consumption with a meter and it is high, as much as $80/month. If we didn't want to keep stock then we'd have only $120 to $180 more electrical consumption/month in winter. Our power bills would top out just over $200/month. I estimate our total actual heating costs at about $1200/year. Right now we are replacing the furnace with an identical newer used model. We don't use it much -- we've gone only from from 1/3 to 1/4 of a tank so far this year. But when it's really cold we do use it to keep the house warm when we're not here. It sits in the cellar so it keeps the pipes from freezing. The old one is getting rusty because the 120-year old cellar is damp and floods occasionally. And the insurance company wants us to have one, even if we barely use it.

(Full disclosure: I was an energy academic before retirement. Now I'm just a grumpy handyman.)

Wire in the brain

VW bus owner: Back at it again with the 72 bus. The old hazard switch was melted. Replaced the hazard switch with new one.  All 4 lights flash. Headlights turn on,  but won't switch from low to high,  but I can hear the relay clicking when I use the switch on the column. Turn signals won't light up with the column switch, both in the dash indicators and outside at the bulb. But they light up with the hazard switch... I'm sure this isn't uncommon,  but can't seem to figure it out. Any help is appreciated!!! Thanks all!

Intelligent Tinkering: The advice for all troublesome VW electrical problems should be pretty much the same: When all else fails (or before, if your time is valuable to you), get a 12V test lamp and a good quality multimeter or Volt-Ohm-meter (VOM) and a couple long pieces of wire with alligator clips, and use a process of elimination. Always test the test lamp or VOM before you start and keep the device's battery fresh. If I can't figure out why a light won't come on, I start with the light, probing for power and ground, sistering to run tests, and so on, and work my way back to the fuses. If you have a couple 15 foot bits of wire with alligator clips on both ends, you can sister right back to the battery terminals to test lamps and horns and wotnot. The pointy end of a 12V test lamp is designed to be pushed through insulation to test for power or ground. Find a good known ground for the other end, or, if you're testing for a good ground, find a good known hot. Use the longer pieces if your test lamb wires son't reach. When you get done just roll each wire in your fingertips and the hole you made will close. The continuity setting on the VOM is your best friend for testing switches and relays. Isolate the switch or relay and actuate it, then test for continuity. You can connect the low amp side of a relay to a hot and a ground with the wires and alligator clips to actuate it, and test the high amp side for continuity with the VOM.

Series Landy 4WD lore

Landy owner: Hey guys. On my series 3 Is my universal joint on the prop shaft meant to be spinning in 2 wheel drive? it’s making a clunking noise when it engages and starts spinning. 

Should it only spin in 4 wheel drive ?

Intelligent Tinkering: You must mean the forward drive shaft, right? Because of course the rear one spins in 2WD. Push down the yellow knob with the red lever already in the forward position and you go from 2hi to 4hi. Pull the red lever back and you have 4lo. Assuming your wheel hubs are locked. Your transfer case is supposed to disengage the front shaft when the red lever is pushed first back all the way then forward (from 4Lo to 2Hi). The yellow knob should pop back up. But if the transfer case hangs up or the yellow knob and red lever are not worked, or working, properly, you might still be in 4hi or lo. Make sure the yellow knob pops back up more or less smoothly when you work the knob and lever in the right order. It's possible to get the knob bound up by incorrect assembly of the floor plates and guide, so if it sticks disassemble the RH floor and tunnel and try again. You can also lose transfer case oil and get it bound up that way. The transfer case has a separate oil filler plug from the gearbox. It's on the case to the left of the emergency brake drum. You may want to take this out, stick your pinky in, and see if there is anything in there. This is easy to do with the floor out. Finally, if your wheels are locked the shaft will spin all the time too. If all of this checks out and is not the cause, it may be time for a transmission/transfer case refresh or rebuild. I always get new floor plate fasteners as needed when I have the plates out for any reason. It's better than having to cut heads off bolts. I'm not a keen originalist so I just use hardware store galvanized stuff, because my Landy has to work for a living.

Grumpy bus owner needs to do tests again

VW bus owner: 1974 bus with fresh 2.0.  Started fine, heading to fill with gas and it sputters a bit and dies. When I turn the key at ignition, slow crank “wah, wah, wah.” and nothing.

Headlight go off when I turn the key.  Battery checks out good.

New ground straps.

New positive lead battery to starter.  Starter spins on bench. Will not turn over engine.

Engine not locked up. Getting 12v at starter from ignition switch.

Thoughts?

Intelligent Tinkering: 12V is low for a cold day. You need 12.5V for a fully charged battery. Some of these engines also settle into a place where they are harder to start after they have been started once on a cold day, stall out and need to be restarted. Mine is like this if I try to move off before it's warmed up. It was actually a lot worse until I switched from a single progressive to twin carbs. It seems to get a little hydraulic locking on the second start. Charge the battery up good and try again, or clip a 200 amp shop starter/charger on it and amp it up good. It might start.

VW bus owner: tried that. Same

Intelligent Tinkering: OK. Did you just charge the battery or did you also try the 200 amp? Or try a known good battery borrowed from some other vehicle or a jump start from another vehicle? Because a battery can be charged, read 12.5 V, spin a starter on the bench, and still not turn an engine. One or more compromised 2V cells would do it. Battery cell chemistry means it's possible for a cell to short out (apparently) overnight if precipitation between the cathode and anode occurs and finally connects or if that cell boils dry. And it never hurts to repeat a test, just to make sure you are not fooling yourself. It's far more likely to be the battery than anything else. But assuming that you have done a good test: use a process of elimination: If the battery is for sure good, and charged, and you can prove this to yourself positively, I'd start by taking all the battery and starter connections apart and cleaning them with sandpaper and a wire brush, then putting them back together. If that doesn't help, suspect the solenoid. The solenoid connector is the LH 13 mm nut when looking at the starter (in place) from the front. Test by shorting between the solenoid and the starter hot (positive) with a screwdriver you don't care about much. Sparks will fly and parts and the nut and tool will weld themselves together momentarily, but if the solenoid is the (only) problem, the motor will turn. If the key is on it may even start. Make sure the vehicle is chocked and in neutral before you do this, unless on a lift with all four wheels in the air, then just in neutral. If it turns over better, you will need to change the starter. You can buy just a solenoid, or at least this used to be the case, but the coils in the solenoid will most likely be just as old as the ones in the starter motor proper, so the motor is going to go soon anyway. If shorting the solenoid makes no difference, call it good for now, and test the battery to starter cable. Jump the battery positive to the solenoid and starter at the same time with a single jumper cable. It's easy enough to touch it to both nuts at the same time. If it turns better, refresh the starter hot cable, which comes directly from the battery to the RH 13 mm nut. The internal copper strands of any wire can deteriorate over time. It's about four or five feet long and you can use a good quality generic one from the parts store. If jumping makes no difference, or switching out the cable doesn't help, suspect similar deterioration in the starter coils. Either bite the bullet and buy a new one right away or find a known good one from a temporary loaner and try that. If you do the tests well and repeat them, you will be able to identify which of the three possible components it is: battery, cable, or starter/solenoid assembly. It could be two or even three, so it doesn't hurt (that much) to switch them all out. To be honest, unless I was feeling particularly Zen and had lots of time and coffee and it was nice and warm out under my lift, I would just go from switching out the battery to switching out the starter and cables at once, two steps. If I needed to conserve money I'd borrow and sub parts first before buying them. The battery is particularly easy to sub, with the 200 amp, or with a known good loaner. My time doing time-consuming tests that can be shortcut by parts-switching or subbing is worth something, and on an old bus nearly every part that hasn't been could use to be switched. There are guys that go on about the better quality of OEM German parts versus aftermarket new, and there is some truth to this, but you can take it too far and my bus works for a living.

Water pump versus head gasket failure

Camry owner: Can someone confirm my suspicion of this being a 5SFE water pump failure?

Coolant was low earlier today so I filled to the top.

Later this evening in a drive thru, a bunch of white smoke comes out of the passenger side front of the hood.

Shut it off and wait a while. I add coolant to the top after 25 minutes and start it up. Temp reads 2/3, hot air in the interior blows cold, and I start driving home 10 minutes away. Even though I added coolant to the top, and I’m driving on the highway in cold winter storm weather, the temp creeps up to the red again so I pull over and wait another 15 minutes for it to cool down. I eventually make it home after 2 cooling rest stops.

The coolant is slightly below the minimum level when I get back. 

Could this be anything other than the water pump? Gotta fix this ASAP.

Intelligent Tinkering: Might have a cylinder head leak: coolant into one or more cylinders. Not hard to test for: Sniff the exhaust for a whiff of coolant. Pull the plugs. Look for one or more cleaner than all the others. If it whiffs and if you have a clean plug, borrow or buy a radiator pressure gauge kit and put it on the radiator cap. Radiator pressure too high and pulsing with engine running is head gasket leak.

Kubota winter transmission problems

Kubota B8200 owner: Why does it take 20 minutes of running time before my 3 point lift will work on my B8200? I’ve replaced the fluid and cleaned the screen. It just won’t work until it hits temperature and it’s jerky at best then. The longer it runs the better it gets. And help is appreciated as I’m frustrated at this point.

Intelligent Tinkering: Here in Maine with a B6000 4WD, I chain the tiller, which lives on the 3pt, up for the winter. It makes a good counterweight for a loader filled with snow, so I don't use the 3pt. But the loader, which has a belt-driven pump and regular hydraulic fluid, takes fifteen-twenty minutes to warm up when it's cold. The warmer it is, the less time it takes. But it then runs fast and smooth. But do you keep it out of the rain the rest of the year? And is your state humid? The transmissions on these things can too easily get water in them from condensation from atmospheric humidity and leakage through the gearshift bellows, so check the oil for "milkshake" emulsion. Even if there isn't any milkshake, there can still be separated water in the bottom, so pull the plugs too and drain out the first pint or so. (If it's clear you can put it back in.) Go steady with this. If the water freezes in the reduction gear, you can break a half shaft. (I know from experience.) It takes a long time for engine heat to thaw the trans, and in even moderately cold weather it can't. The aluminum cases on the transmissions on these things won't accept a magnetic block heater, but if I put a farm heat lamp under the rear end I can speed things up.

Gas station sticker shock

Titan owner: 2006 Nissan Titan 4x4 200,000km (120,000miles) fuel milage

Hey all, I'm averaging 350km a tank (aprox: 217miles), which is just over 7mpg in the city.

How can I improve this? Is theres a tune-up program I can flash the ecu with?

Intelligent Tinkering: I don't know if this is what you're doing, and apologies if not, but it's often a math error to drive an unloaded big truck for every little errand because you think you can't afford a second, more efficient vehicle. "Buy a Prius" is perhaps intended as funny or even a snarky jab, but the basic reasoning is (paradoxically) correct. Try a "round numbers" thought experiment: If you're doing 10K miles a year at 10mpg, you're spending, say, between $3 and 4K on fuel, depending on market price and different state taxes. If you could instead get 30mpg for half that 10K miles, that would be between $1340 and $1500 less per year to pay for something cheaper. In Maine a running "econobox" with some dings but also some miles left on it might run $5K, so if it ran for three years more it would (roughly) pay for itself and any subsequent years would be gravy. This assumes you're an old fart like me with no tickets or claims and your insurance is dirt cheap, that you can identify a good econobox in the marketplace and avoid a lemon, and you can fix the thing yourself. The repair costs on the Titan for that extra 5k miles are likely to be double that of the econobox in any case, so even if you can't fix it it's still a savings. I put less than 3k miles a year on the Titan, mostly for hauling and plowing snow. My 97 Camry does around 5K. The Camry, which cost $3,500 in 2011 with only 44,000 miles, finished paying for itself about ten years ago, doesn't owe me a penny, and by my lights still has a 100,000 or more left to go. Because it's easy to maintain shifting wear to the Camry gives me extra time to take better care of the Titan. Because this is Maine, when you need it, you need it. Having it cost less helps a good deal. My particular masculine ego doesn't need a big truck to go to the hardware store. It does need one to plow the snow from my driveway so my wife can get to work and my kid get to school (and the frigging mail lady can deliver all the wicked high bills I have to pay).

Troubleshoot vehicle lights -- general instructions

These instructions work for all rear lamps: brake, reverse, tail, and flasher, and can be adapted to front and other lamps. Basically, you need a multimeter or volt-ohm-meter (VOM) and it has to have settings for direct current 0-20V and for electrical continuity. (A multimeter would also have amps, generally up to 10A, which can be useful but not for this task.) The voltage setting tells you the volts in a circuit. The continuity setting tells you power is getting through a wire or connector or switch. It's helpful if the continuity setting beeps. Usually these meters take 9V batteries and you need to know how to test the meter and probes to make sure they are working. The probes need to located in the correct socket for each test. All this is usually in the meter's instructions. You also need a high quality 12V test lamp, which is usually a device shaped like a screwdriver with a sharp probe end and a wire with an alligator clip on the end. You test these by putting the probe on one side of the vehicle's batteries and the alligator clip on the other. Two long bits of heavy wire with alligator clips on each end are also helpful. Ten gauge multicore wire is best, but long jumper cables can be used too. If only one rear light is bad, start by removing the rear lamp housing and check the bulb. If both are bad, check the fuse before you do anything else. If it's fried, replace it and hope for the best, but keep checking the lights periodically for a few days because you don't know why the fuse fried. If there is only one bad light on one side, start with the the bulb(s). If they are incandescent, check the filament to make sure it's there. Compare with the other side. If they are LED look for discoloration. Then test the bulbs using the long wires to jump to the battery. Make sure they work. If they don't, replace them and you may be done. If they do, turn on the switch or apply the brakes or put the car in reverse with the ignition on but engine off, whichever applies. Check for 12V at the empty lamp unit bulb holder with the switch on, using the test lamp with the alligator clip attached to a known good ground, which could simply be your long piece of wire routed back to the battery negative. It doesn't matter for now if you don't know which bulb connector is the hot and which one the ground. Just test each one in turn. If the test lamp lights, remember which connector it was, put the bulb back in, and find a way to jump the other connector back to ground. If it lights, repair the lamp housing ground. If the test lamp doesn't light at any of the bulb holder connectors, start using the sharp probe on the end to work back through the wiring methodically to find the missing 12V. This probe is designed to push through the insulation on wires to test for power. It can also probe connectors. At this point the wiring diagram starts to become useful. Somewhere back in the harness you will find 12V and then you can repair the wires back to the bulb holder by "sistering" or replacing wires or replacing connectors. I try to use the same color and gauge of wire and rating of connector, but it's ok to go up a size if you have to. Never go down. I keep a collection of good new and used wire and connectors. I also have a heat gun and a selection of heat shrink connectors and heat shrink sheath to repair harnesses well so they can keep working in wet and salty conditions. If you are really unlucky it will be the switch in the cab (or the brake pedal or transmission reverse switch). These can be bought new or sourced at a salvage yard or online salvage operations. You can get usually get an entire fuse/relay box from a salvage operation with the fuses and relays still there for fifty or so bucks, a good investment for owners of older vehicles. In general, you just need a logical mind and some gumption and you can trace just about any electrical fault. It's certainly not the hardest job you can do on a vehicle, and you stay cleaner than you do with other kinds of wrenching.

Kubota dynamo not very dynamic

Kubota owner: Knowledge/Help requested!!: I have a B6200 i bought in the fall at an auction. After i bought it i talked to the actual owner and if i recall correctly he told me the alternator was going bad and discharging the battery.... I used it all fall to chop up leaves, and plowed snow twice this winter. The last time i was plowing there was a light rain. The charging icon has always been lit since i bought... well while plowing snow in the rain/mix weather, this light went out finished plowing and parked it. Went down today to start the tractor and glow plug light did now show it was on, no lights worked. Pulled the battery and put on charger which said the battery was 90% charged. If the alternator is in deed bad, will the tractor always continue to start and lights work as long as the battery has a charge? Thank you in advanced.

Intelligent Tinkering: My glow plug light is a poor indicator of battery condition. It seems to glow sometimes when the tractor won't start and not glow when it will. It seems dependent on weather more than state-of-charge. There may not be anything wrong here, with either battery or dynamo. The weak dynamos in these things only produce enough amps to replace the battery energy used from a start, especially a hard start, in about ten-fifteen minutes at 2000 rpm. If you need evidence, get a half-way decent clamp meter and measure the amps on the battery positive at different rpms in neutral right after a start. Or measure the voltage, focussing on volts and fractions of volts before a short run and after. If it's cold and you only use the tractor for a few minutes or let it idle a lot you'll run the battery down. It might be best to get a ten-dollar trickle charger. That's what I use in winter. Having said that, it never hurts to keep your battery terminals clean.

Titan hub bearing diagnosis

Titan owner: Just to make sure before I start buying things, could [bad] wheel hubs cause an axle to not spin freely.

Intelligent Tinkering: Assuming you are talking about front hubs on a 4WD, no. The hub bearing might though. These bearings are hard to test by feel because you can't spin them without also spinning both CV axles and the diff. There's no free running hub. The diff turns all the time when the wheels turn even in 2WD. With both wheels off the ground and the car in 2WD, you can spin one wheel forward and the other will go backward and you can try to get a feel of the bearing, but it's not as easy to decide if its bad as it would be with a 2WD, rear wheel drive vehicle. You will likely have to take it apart anyway to replace whatever is making it spin poorly, so just do so. You can do this by just removing the bearing assembly as in the YouTube vid below or by taking the whole steering yoke off. I would do the latter because it gives you access to other components that need to be inspected and likely replaced, such as the CV, balls joints, tie rods, etc. It will take about two-three hours the first time you strip it down but you can do it in 45 minutes with practice. You'll want a good pneumatic impact with lots of rated torque (or you'll need to be the proverbial 500 lb gorilla). Take the yoke assembly off (by removing the ABS hex bolt and sensor, the big axle/CV nut, caliper, disc, strut top and bottom, sway link top, tie rod end, lower pinch bolt and upper ball joint, and then put the whole thing in a vise and stick your fingers inside the bearing and see what it feels like. Then take the CV joint off and manipulate that too to see if it is causing your rough spinning. The CV joints are not expensive. The bearing assemblies are more expensive but can usually be replaced by cracking them with a hammer so you don't (usually) need a press. Pay close attention to the torque loadings on reassembly, especially the caliper bolts, which need something like 140 lbs feet. A little locktitie on these doesn't hurt. https://www.youtube.com/watch?v=ChhUMwy5JD0

Blue smoker

Titan owner: Question for all and I hope somebody could help me out with this. 

I have a 2007 Nissan titan I’m the original owner I currently have 185,000 miles on it.  I had the 2 catalyst converters gutted out a few years ago because they were clogged from which I was told was because of the fact that the engine blows a lot of blue smoke out the tailpipe. 

Obviously getting an inspection to pass on this vehicle in my State is almost impossible yet I was able to do it 2 years ago. I was given an estimate to replace the front 2 Catalyst converters which are part of the exhaust manifolds at a price of almost $4000 dollars. My issue here is the engine smokes a lot every time I turn the ignition on and then it disappears while I’m driving. Since I am now past due on my inspection I can no longer reregister my truck in my state unless it passes inspection. I would hate to invest all that money into the exhaust manifolds/Catalyst converters only to have them clog up again. 

I was told by another mechanic that it is very common for my year titan to do that and I can simply correct that issue by merely replacing the valve cover gaskets. I was told that oil is seeping through the center of the gaskets and down into the spark plugs . I also have to change out my coil packs which on the average is one per year. The only noticeable thing is that some of the spark plugs are drenched with oil when I remove them. Does this make any sense to anyone that may or may have experienced the same situation that I’m experiencing ? If so what if anything did you do to correct this problem. Thanks. 

Intelligent Tinkering: Either your mechanic is muddled more than any professional should be or you muddled what he said. Rocker cover gasket leaks cause smoke and smell from the engine bay and below. Leaky piston rings and/or valve guides causes blue smoke at the tailpipe. You seem to have both going on, but the tailpipe is the real problem. If it occurs at start up and not later, suspect valve guides. If it's rings you'd know because high oil consumption. (White smoke at the tailpipe is running rich.) What is the oil consumption? And the oil pressure (which tells you how good your main bearings are)? That and some idea of the condition of the transmission and body will tell you if it's worth fixing the cats, with or without rebuilding the engine. By far the easiest thing to do would be to put in a known good engine, either a reconditioned under warranty or a take-off from a recycler that has low miles. That way you can do the cats and headers too and you'll get good rocker gaskets and coils with the new engine. But only if the rest of the truck is worth the trouble. One way to think about it is that a decent older second hand truck is worth at least $10, 15, 20K depending on the condition. You can get there by buying a truck, or by spending money on this one. If it adds up to less, either way, you're ahead.

VW heat exchangers

Bus owner: How can I check my heat exchangers to see if they're still good or should be replaced? I have the engine out for the winter waiting on a transmission rebuild. Trying to determine if I should replace the exhaust system, and if so, do the heat exchangers as well, leave them as is, or use JTubes. Bus is '74 with single progressive webber. Based on rust, the exhaust looks original  origional.

Intelligent Tinkering: A visual examination. Look for loose connectors, gaps, rusty tin, flap valves not working, seized cables. Take the concertina tubes off and check for air with the engine running. Look for evidence of oil leaks from the rocker covers. If you change the heat exchangers, you will need to fix the leaks too or your expensive new heat exchangers will get fouled up toot sweet. Check all the other pipes too, all the way to the front. A mouse nest anywhere in the line can easily stop the whole shebang up. If you don't change them you should also fix any leaks while the motor is out. It's not hard to switch out the valve cover gaskets. Depending on the mileage since the last one, I'd be at least thinking hard about taking the opportunity to do a top end rebuild. And don't get your hopes up about heat, especially if you live in a cold state. These things were never that effective even when the bus was new. I gave up, disconnected mine and got a diesel cab heater that cost less than one replacement heat exchanger.