Oil & Fuel Jinma 254 Blowby Compression Testing

[Willl]

and some dings on top of the pistons in all cylinders

Just a bit

Deep gouge in #3 or just a dark spot ?

 

[sd455dan]

Looks like a few pieces of (something) got past the air cleaner- and the mention of blow by, and the rotted head gasket..

Well other than the head work and new gaskets , my main worry would be ring damage, or the ring lands in the piston... from whatever was bouncing around in those cylinders- and your mention of a fair amount of blow by , screams ring seal or ring damage to me...Yet the overall compression #s are not that low...
if it were me I would pull the pistons and replace the rings and hone the cylinders as a minimum...I would also check the blocks surface straightness, under aprox. .002 " hopefully ,
Little bit confused, lots of blowby, 25% leakage ,but no change with the addition of oil?

Normally introducing oil when there is ring leakage will bump up the #s- that didn't happen.. which tends to point to valve /seat seal.. but valves do not cause blow by...

But whatever was rattling around had to get out somehow, past the exhaust valves and seats usually.. now that would increase leak down.
The blow by still bothers me I would dig a little deeper... :2cents: also looks like you are well on the way to getting the Jinma fixed :thumbsup:

 

[quicksandfarmer]

My armchair mechanic opinion: It looks to me like the pitting was caused by coolant entering the cylinder and boiling, which would be expected when the head gasket fails. I think all of your problems were caused by a head gasket failure, very common with this engine.

 

[Bob Rooks]

IMHO,
The liners look glazed. This can be from high engine hours or running with a dirty air cleaner that has channeled, and/or dirty (heavily sooted) engine oil. The liner on the right appears to have vertical marks (scoring?) which would indicate broken piston rings. How much of a ridge is there on the liners?
Yes, you can still have decent compression with broken rings, and conversely you can have a lot of blow-by with good rings if your valve guides are badly worn.
When you did the leak-down test, did you put your ear to the intake manifold, the exhaust, and the crankcase breather for each cylinder to get an idea of how much air was escaping from each area?
And I can definitely tell from the red/orange coolant passages that this engine has been subject to very poor maintenance practices.

 

[sd455dan]

My armchair mechanic opinion: It looks to me like the pitting was caused by coolant entering the cylinder and boiling, which would be expected when the head gasket fails. I think all of your problems were caused by a head gasket failure, very common with this engine.

I disagree about all the damage being caused by the head gasket failing. ( not saying some of the damage wasn't done by boiling coolant) -but zoom in on piston # 2- that appears to be mechanical caused damage... I would pull those pistons - it's not that much more work...just to be sure the rings or ring lands aren't damaged... Maybe it is harder than I thought / does the Jinma have a crankcase inspection window so that the rod caps can be pulled???

 

[quicksandfarmer]

I disagree about all the damage being caused by the head gasket failing. ( not saying some of the damage wasn't done by boiling coolant) -but zoom in on piston # 2- that appears to be mechanical caused damage... I would pull those pistons - it's not that much more work...just to be sure the rings or ring lands aren't damaged... Maybe it is harder than I thought / does the Jinma have a crankcase inspection window so that the rod caps can be pulled???

To remove the oil pan you have to split the tractor and pretty much take the engine out, the front wheel assembly bolts to the pan. Some Jinma's have a hatch in the bottom of the oil pan that allows limited access to the bottom of the engine so you can replace the oil pump without splitting the tractor. Mine doesn't have the hatch, so I don't know if you can detach the pistons (and more important, re-attach them) that way.

Instructions for splitting the tractor are in this thread:
http://www.tractorbynet.com/forums/...35-jinma-304-tractor-running-low-2-print.html

 

[quicksandfarmer]

Here's a picture of what the oil pan with the hatch looks like:
Engine sump pan

Looking at that, I think you could possibly remove the pistons with the oil pan on (and the engine still attached to the tractor).

 

[sd455dan]

Here's a picture of what the oil pan with the hatch looks like:
Engine sump pan

Looking at that, I think you could possibly remove the pistons with the oil pan on (and the engine still attached to the tractor).

I see what you mean. If the OPs style does not have a removable bottom inspection cover, it means pulling the whole front half of the tractor apart...

 

[gromitbeast]

Hey Guys,

Thanks for all the great feedback. Valves, etc came in this week and I dropped them off to be installed on the head once it's re-faced. As you guys all mention rings are a high concern for me. I got optimistic at the mention of the inspection port by quicksandfarmer. I was expecting if the rings are shot than I'll need to split the tractor. I went out and looked but no luck on the inspection hatch on my model.

I need to send some updated pictures with head surface and block surface scraped off...it doesn't look as bad after all that old rotted gasket material is removed.

Bob, I'm in full agreement on the poor maintenance practices. I just recently picked this tractor up at what I thought was a steal (may still be if I can get her running right). We shall see though. I did use a stethoscope to try and pinpoint noise during the leakdown but could only really hear anything @ the intakes.

I have a week long out of town trip coming up this week which is OK because I'm still waiting on some more pieces to come in to check injector pop off and for the head to get finished. I plan to put it all back together next week and see how it run with new gasket, valves, etc. If I'm still getting poor performance and blowby I fear splitting and rings/sleeve are my next move (fingers crossed that I won't have to do that!)

Thanks everyone for the great discussion and valuable input. I'll update again in a week or so.

-Nick

 

[gromitbeast]

Hey All,

I'm back. Sorry for the long lapse, life took over for a while and the tractor had to be put on standby. After a lot of cleaning/replacing of parts, sanding of surfaces, etc. I got it all back together today after doing the following:
- New Head Gasket
- Near intake and exhaust gaskets
- New glow plugs
- New #1 injector (took it apart like a dope and cheaper to buy a new one than to re-calibrate)
- New Temp Plug Housing (over-tightened the temp sensor and cracked it...geez)
- Thoroughly cleaned head, machined flat and tested with new valves, collets, guides
- New valve cover gasket
- Fresh valve lash adjust, head re-torque
- Cleaned radiator and fuel tank, new fuel filters (in tank and in bowl). Lots of crud in fuel tank with in tank filter completely destroyed

The result...NO Improvement. Still hard starting, crazy loud knocking, lots of blowby (indicated by smoke coming out crankcase breather) and a lack of power. A few other notes:
- After a lot of cleaning I noticed what appears to be a very small crack in the block between cylinders 2 and 3.
- Running temp on cylinder 1 appears to be ~100 F lower than #2 and #3 (running at ~200 F on #1 vs. ~300 F on #2 and #3) Checked with Infrared Thermo on exhaust manifold

So I'm stuck thinking I need to do the following:
- Split the tractor (appears to be on the order of several days worth of work for a shade tree mechanic like me based on what I'm reading at: Benye Tractor with Yangdong Diesel Engine | CHINESE TRACTOR OWNERS CLUB FORUM)
- Replace cylinders, sleeves, rings and probably the block (note crack above) (~$1,700 in parts) or the entire engine (~$3,000)
- Pray i can re-assemble and pray again that it runs

Or...give up, cut my losses and see if somebody wants to buy as is...I'm seriously considering this option.

Advice and ideas are welcome!

Thanks,

Nick