Sudden Excessive Blow By

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hrtull
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Sudden Excessive Blow By

Postby hrtull » Sun Nov 22, 2020 10:06 pm

Very Excessive Crankcase Blow by.

YM 186 D with Yanmar 3T72HA engine. Purchased this tractor about 2 years ago and refurbished it. I posted the rebuild on this site under Tractor Projects( YM 186 Build). Tach time indicated about 800 hrs. I have used it about 30 hours with no issues. Starts well in cold weather ( never used starting fluid), leaks no oil, runs fine and plenty of power until a few days ago. Temperature was about 40 degrees in Ohio. Usual start up is switch to glow for a few seconds, decompress and free spin for a few seconds and then engage compression and start up never an issue.
This time however it was very hard to start and needed extra battery boost to do so. After starting I let it warm up for about 20 minutes,engine seemed to tun fine but then I noticed crankcase vent hose blowing excessively and starting to drip oil from it. I then took off oil filler cap while engine running and air was gushing out heavily. It had enough pressure to lift the fill cap off after unscrewing.
I then started researching everything regarding excessive blow by. Stuck rings, broken rings, worn rings ,damaged pistons, blown head gasket , cracked head and just about everything else. I realized engine would need inspected. I removed head and all seemed to be in order. Head gasket good (anti freeze clear and no oil). Valves and all valve components appear good. The one thing that really got my attention was when I hand turned the crank to look at piston action the center cylinder sleeve came up with the piston upstroke. I could easily push it back down. After watching many videos of people struggling to remove sleeves this seems not right. I stopped at this point and will remove pistons tomorrow. Before stopping for the evening I added about an inch of rubbing alcohol in each cylinder and it appears to be holding. My question, could this loose sleeve /bad sleeve O ring be causing blow by and such a high crankcase pressure. Also the piston tops looked good as well as interior sleeve walls. The cross hatching appears to be even wear. Any help or advise greatly appreciated, Thanks HRTULL

winston
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Re: Sudden Excessive Blow By

Postby winston » Mon Nov 23, 2020 6:11 am

Wow, hard to understand just what has happened. No doubt your crankcase blow by tells us a lot of compression going into the crankcase. Reading your post about the loose liner would tend to indicate that is the cause. However, I am trying to understand how the liner could move with the head setting on it, but then, maybe it didn't move. Your liners do not have o-ring seals. I believe you have what is called dry liners. https://www.hoyetractor.com/PROD/DS-72.htm

Bottom line thought from me is the problem is involving the loose liner.

Back again with a couple of pages from the 169 service manual, basically same engine as your 186.
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hrtull
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Re: Sudden Excessive Blow By

Postby hrtull » Mon Nov 23, 2020 9:46 am

Winston, Thanks for the liner information. It does state that the liners are set by hand and removing requires no special tools. So I guess it could be normal. I am puzzled how much blow by could exist even if loose. Like you said the head holds it in and all of that looked good. I thought upon removing the head that I was going to see a very obvious problem. I thought after adding alcohol that one of the cylinders would quickly drain down and didn't but I am probably under estimating how that can change with a hot engine and high compression. I am going to drop pan and remove pistons today hoping to find the obvious problem. I will post my results. Thanks again, Harmon T

hrtull
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Re: Sudden Excessive Blow By

Postby hrtull » Mon Nov 23, 2020 3:18 pm

Found the problem. Broken piston flange on front cylinder (A). Going to replace piston and add new rings to the other 2 good pistons. Lap the valves, new head gasket with all other require gaskets and reassemble. A minimum repair but everything else in good shape and before this broken piston it was running perfect with no oil consumption. Thanks, Harmon T
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winston
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Re: Sudden Excessive Blow By

Postby winston » Mon Nov 23, 2020 4:27 pm

Sounds like your on top of it. Let us know when she is running fine again.

hrtull
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Re: Sudden Excessive Blow By

Postby hrtull » Sun Dec 06, 2020 9:20 am

I got this engine reassembled. Installed the new piston and added new rings to all 3 pistons. Lapped the valves and reassembled . Cleaning the old head gasket was probably the longest one thing, lots of razor blades and WD40. I gapped the valves, purged the fuel system and it started right up. Do I need to do any special break in. Thanks and have a great day, HRTULL

winston
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Re: Sudden Excessive Blow By

Postby winston » Sun Dec 06, 2020 1:27 pm

Only an opinion on my part. I would use as normal.

hrtull
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Re: Sudden Excessive Blow By

Postby hrtull » Sun Dec 06, 2020 8:27 pm

Winston, thanks for all your info and help., HRTULL

hrtull
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Re: Sudden Excessive Blow By

Postby hrtull » Fri Feb 12, 2021 7:39 pm

Well Im back to a blow by problem again. After what I thought was a successful repair the problem is back. I used the tractor for about an hour after repair and all appeared well back in December. I started tractor yesterday morning in 20 degree weather. It started as expected for cold weather but nothing abnormal. It did what I expected, rattle and knock a little , blow some smoke and then smooth out and run well. Pushed snow for about an hour and parked it. This morning I again started it in 20 degree weather. This time when it started it seemed like it started on 2 cylinders and after 15 to 20 seconds later the third cylinder kicked in with lots of black smoke and a louder than normal diesel knock. I let it warm up for 15 minutes . The knock silenced a little but still louder than normal. At full RPM it would go away completely and re appear at low RPM. I pushed snow for about 30 minutes and noticed oil drops in the snow. Crankcase vent tube started blowing oil again. I suspect it is the front cylinder ( nearest the radiator) creating the problem. I parked it and shut it down.It acts just like the broken piston I replaced. I am confident I made the prior repair correctly and per specs. I will disassemble again. I am guessing at the cause. Was the new piston bad, did a ring break, head gasket etc. Can a bad injector destroy a piston. Why does knock go away at high RPM and knocks at low RPM. Can a bad rod bearing cause it. If anyone has any ideas or suggestions I would really appreciate your input. Thanks, HT

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Re: Sudden Excessive Blow By

Postby Aaron » Fri Feb 12, 2021 9:36 pm

Did you use starting fluid? Sounds like probably no but just want to be sure.

Do you have any bubbles in the radiator?
https://www.hoyetractor.com/BlownHeadGasket.htm

Did you retorque your head after a warm/cold cycle
https://www.hoyetractor.com/head-gasket.htm

hrtull
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Re: Sudden Excessive Blow By

Postby hrtull » Sat Feb 13, 2021 9:24 am

Aaron, Thanks for the reply. No starting fluid used just glow plug and good battery. I have not checked for bubbles in radiator yet, got a little frustrated with it so parked it and walked away and started researching the problem. Will check for cross contamination in coolant/oil . No I did not re torque the heads. Was thinking I needed to get a few more hours on it before doing so, wrong thinking. . I am hoping it is the head gasket, it would explain the problem. I appreciate the reply and I may try and contact you when I disassemble, Thanks again and have a great day, HR Tull

hrtull
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Re: Sudden Excessive Blow By

Postby hrtull » Tue Feb 16, 2021 9:27 pm

I did another cold start in about 20 degree temperature. It started in the usual cold diesel start way. It repeated the previous cold start. It seems as tho it fires up and runs for a bit on 2 cylinders and then the 3 cylinder kicks in with lots of smoke and what seems to me, too loud of that diesel knock. Did this to get into shop. Thought the best approach was doing a compression test and borrowed one from a friend. Here are the results . I am labeling the cylinders 1,2 and 3 from front of tractor back and block temperature was 45 degree. So number 1 (nearest radiator) was 300psi, number 2 (middle) was 300psi and the back ( at firewall) was 160psi. I took pictures of the injectors as they came out. This is my first go at dealing with injectors. They have a lot of carbon at tip but cleaned up nicely with the tooth pick approach. The needle was freely moving inside. I have only cleaned one so far. I guess an injector could cause rough starting but to my knowledge does little to explain the 160 psi reading and blow by. In review or chain of events. I started this thread a few months ago late November, discovered the number 1 front piston was broken causing some major blow by . So I replaced piston and added new rings to all three pistons. Head was flat, lapped valve and alcohol flood test valves. The cylinder sleeves were in good condition with most of the cross hatching visible. Re assembled with all new gasket set. Torqued per specs in proper sequence ,all pistons, rod and sleeves in correct orientation. Re set valve lash 2 times. I started it with little issue and all seemed well. Now mid February and a similar problem. My question are A) What is best guess on the 160psi cylinder. Radiator fluid does not bubble and there appears to be no cross contamination of oil and coolant, thinking its not head gasket maybe. B) Engine only has a few hours of light usage since full ring replacement, are the two producing 300psi with very cold block capable of improving with more usage. What should the reading be for an assumed 820 hour engine. C) Do the pics of injectors give any clues,can a bad injector destroy a piston Any suggestions or advice will be appreciated. Thanks, HT
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Heidegeist2000
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Re: Sudden Excessive Blow By

Postby Heidegeist2000 » Wed Feb 17, 2021 3:10 am

Good Morning. I followed your thread for a while and it seams you are quite more an expert than I am. But sometimes it's good to get a second opinion.

From my point of view, it looks like an other failure at the 3rd cylinder. May be something went wrong during reassemle or there was something wrong with the spares. As far as I understood, you cleaned the cylinder gasket and did not replace it.That might be also a reason. I don't have any specific data for Yanmar engine, but I also have a 'Porsche Diesel' tractor built in the 1950th. The manual says compression from 400-350psi is excellent, 350-320psi is good, 320-260psi is still ok, and everything below 260psi has to be replaced / overhauled (all pressures at warm engine). I think that might fit to many older diesel engines. The measured 160psi are to low for a proper running and match more with a gasoline engine. Regarding your questions, yes a faulty injektor can destroy a piston. If the gasoil doesn't vaporize propper, there might be always a little bit liquid fuel on the piston bottom. That burns in contact with the alloy and at that hotspot it burns through the material. I don't expect that after such a few running hours. I think the injector looks how it looks, because there is not enough compression on the cylinder and the fuel doesn't burn sufficent. I guess the carbon is more a result than a cause.

I would open the cylinder again or if you have the chance, put in a boroscope and take a look.

Again, I'm not an expert on those engines and may be I'm totally wrong. Hope you get this thing running again and please keep posting. It's very interesting.

Greetings from Germany
Roman

winston
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Re: Sudden Excessive Blow By

Postby winston » Wed Feb 17, 2021 8:04 am

No idea why it happened but have to believe busted piston lands or rings on the low cylinder. Instant change to blowby and low compression just doesn't point to anything else.

hrtull
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Re: Sudden Excessive Blow By

Postby hrtull » Wed Feb 17, 2021 9:25 am

Waiting for shop to heat up a little. Going to take head off and go from there. I do agree that its an issue with piston. I will post findings . Thanks, HT


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