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dumbfarmboy
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That's why I'm a dumbfarmboy.
YM336D Wet Stacking?
- Thread starter dumbfarmboy
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rScotty
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- Apr 21, 2001
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- 8,277
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- Rural mountains - Colorado
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- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 8,277
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
We had a YM336D. Best tractor I ever owned...bar none. Remarkably powerful and handy. Might be the best 30 to 40 hp tractor period with the powershift, PS, fancy loader, draft, and optional creeper gearing. If I could buy a new one today I would just to have it.
But it sounds to me like your measurements are being done correctly . If not, run them again. The numbers you are getting are simply too low to provide good combusion of the diesel fuel so you are getting incomplete combustion blown out the exhaust. Maybe sitting caused the rings to be stuck and that is the cause, but also likely is a leaking head gasket or leaky valves. Again, your measured compression method sounds good, but the compression is showing something wrong - something that would lead to exactly the wet stacking you are seeing. Your compression test should be reading in the 400 to 600 psi range depending on the cranking RPM. Most starters will crank somewhere from from 100 to 300 RPM.
Yes, 21:1 is correct, and yes, the JD 1050 with its turbo did run a little lower C.R. .... more in the range of 20:1. That is not enough to make a difference. Your bafflement at the disparity between calculated compression ratio and what you should be measuring is because compression ratio is more than just the ratio of the swept volume. Swept volume is about half of it. The other half of the pressure you will measure comes from the expansion heating of the air that is being compressed. That expansion of heated air due to compression heating at cranking RPM is where your error is.
BTW, just to be a technical geek, when you are calculating the part of compression that is due to the change in swept volume there is also a volume of the combustion chamber volume that is not swept and doesn't change. BUT THAT DOESN'T MEAN IT CAN BE IGNORED IN THE COMPRESSION CALCULATION. You can prove this to yourself if you calculate your swept volume compression ratio and while adding a compression chamber volume to both sides of the ratio. The combustion area didn't change, but the compression ratio will. Nifty... hot rodder stuff.....
Getting a number for that static part of the volume up there in the head where the explosion takes place isn't easy. On diesels like the YM336 with it's indirect injection type of head geometry it is even more of a problem....being really a ***** to measure. The good news is it doesn't matter for what you are doing. If you really want to measure the combustion chamber volume, hot rodders measure using fluid when the head is off and inverted.
Just for completeness, you probably should check the thermostart mechanism on the intake manifold like "nyone" says. There were two forms of thermostart depending on whether the fuel bowl is fed by pressure from the injectors (and then to the tank) or whether the fuel bowl is just filled by the operator once every few years manually. Both have a snap open top. Whichever it is, either dry it out and/or bypass it to make sure it isn't the culprit.
Oh, here's a sheet that Yanmar put out for all their engines back when those tractors were being sold in the US. It's good info.
rScotty
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dumbfarmboy
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Thanks for all the great suggestions and info. I hope to get back on this in a day or two. Early on I did see some pressure seeping between the block and head in the form of fine bubbles. I retorqued the head and it seemed to subside. Also after running a tiller for several hrs the next time I started it wouldn't turn over. Turned out the back cylinder had coolant in it which I discovered by pulling the injectors. I probably should order top end gaskets in prep for pulling the head. I'll look at the thermostart to check for leakage. I have the manual so I'm sure testing procedure is in it. I'm guessing if it's leaking it could cause carbon fowling and reduce compression. Since rebuilding it this tractor has always fired right up and still does. Hopefully I can report something back in a few weeks. Again thanks for helping.
alexpops
Platinum Member
If you have coolant in the cylinder, it's the head gasket or a crack. White smoke is water, the oily exhaust could be from that cylinder running too cool to burn your diesel due to coolant contamination. Any oil in the coolant? Coolant in oil?
Is the back cylinder (the one you hydro-locked) the same one showing low exhaust temps? I'd pull the head, check for signs of head gasket failure & figure out why. Do you need to machine the head? Deck? Or was it simply insufficient torque on the head bolts/studs when you reassembled? New head gasket, new bolts/studs, proper torque specs, change oil & filter & coolant flush, then see if it's fixed. & hope that you caught before bearings were destroyed by coolant in the crankcase.
Why did you need to rebuild in the first place?
Is the back cylinder (the one you hydro-locked) the same one showing low exhaust temps? I'd pull the head, check for signs of head gasket failure & figure out why. Do you need to machine the head? Deck? Or was it simply insufficient torque on the head bolts/studs when you reassembled? New head gasket, new bolts/studs, proper torque specs, change oil & filter & coolant flush, then see if it's fixed. & hope that you caught before bearings were destroyed by coolant in the crankcase.
Why did you need to rebuild in the first place?
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dumbfarmboy
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The reason for the rebuild was the previous owner left it sitting with an open stack for several years. I traded for it and had to do a full rebuild of the engine. Including sleeves/pistons and having the head tested and surfaced. Then I split the case an did the whole transaxle. Anyone with more than half a brain would have sold it for scrap. I guess I like a challenge or am a glutton for punishment. Regardless the coolant in cylinder 1 has never happened again. I serviced the hydraulics last night and tested the thermostart this morning. Hooked up the disc and broke some ground running it a full throttle as previously suggested. Now when I throttle up I get black smoke, no more blue or white which can be caused by low compression as well as coolant. After close examination I did see some tiny bubbles between block and head so I'll be pulling the head at some point to address the low compression issue, just not this winter. I'm suspecting that I haven't ran it hard enough lately as mostly I've been moving round bales.
Funny thing about this is the compression test was well under 426 and it starts right up and always has. I checked the thermostart for leaking today and it passed. I also ran it hard pulling a disc at full throttle for several hrs. I'm getting black smoke now when I throttle up with just a little blue. Not slobbering like it was either. I will check compression again when I have time and probably give a good workout prior. I'm wondering it the HF compression gauge is faulty. I also should verify my DIY adapter isn't leaking. I didn't hear any air escaping but may not have been paying close attention.
rScotty
Super Member
- Joined
- Apr 21, 2001
- Messages
- 8,277
- Location
- Rural mountains - Colorado
- Tractor
- Kubota M59, JD530, JD310SG. Restoring Yanmar YM165D
Weil, I'm glad it cranks up and is running better. Those 3 cylinder Yanmars were extremely smooth and quiet running engine. I've heard the stories about running engines hard to make them run better, but no experience doing that.
The white smoke might have been unburned diesel fuel. When diesel is vaporized but not ignited it can come out of the exhaust as puff of white smoke. You'll see that as a regular puff of white when one cylinder is not firing & others are. Often an injector.
I don't know what to say about the compression test, but you might want to to get numbers that make sense before pulling the head. Most old time automotive machine shops will have a Steward Warner hand held-tach you can use to get cranking speed.
Apparently you don't have a problem pulling the injectors. Any chance they need attention?
rScotty
The white smoke might have been unburned diesel fuel. When diesel is vaporized but not ignited it can come out of the exhaust as puff of white smoke. You'll see that as a regular puff of white when one cylinder is not firing & others are. Often an injector.
I don't know what to say about the compression test, but you might want to to get numbers that make sense before pulling the head. Most old time automotive machine shops will have a Steward Warner hand held-tach you can use to get cranking speed.
Apparently you don't have a problem pulling the injectors. Any chance they need attention?
rScotty
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dumbfarmboy
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When I rebuilt the engine, I disassembled the injectors and installed new nozzles. Took them to a local tractor shop for a pop test. I know some trash might have been present in the lines, pump, etc but tried to make sure everything was clean when it went together. I found that a 3/4" merchant coupling has a 1.25" dia and used one to make adapter for the compression gauge. Next time I check it I'll use either soapy water or talcum powder to make sure it's sealing.
I'm interested to know what you find out, dumbfarmboy. Not to insult your intelligence, but when you rebuilt it did you hone the cylinders and then go through the break-in procedure? Without that, rings won't seat well, cylinders can glaze, and then comes low compression... Part of break-in is to run it hard, so that's a good thing to do even after the fact.