OT...diesel diagnostics

lastcowboy32

Well-known Member
I know there may be other places for this, but I'm familiar with the group here. This group also gets more traffic than the "Lesser known Classics"

Our tractor, other than the 2N, is a little three cylinder diesel. (Jinma 284 with Yangdong Y385 engine).

(Ironically, I set it aside to minimize damaging it, and I was "rescued" by a Ford 640 that I work on for a friend, he let me borrow it, since I do his mech work for him...so...old Fords to the rescue.)

It's been running for about two months now. A couple of weeks ago, it came to a head. I could barely get one lap around the field with the mower or baler without antifreeze boiling out of the radiator. I could hear a compression leak near the head gasket, so I took the head off. I sent the head to the engine shop for vacuum testing of the valves and flattening (they shaved just the tiniest amount off of it). I also found one of the copper seals on an injector was cracked. With that seal replaced, a new injector, the shaved head and a new gasket, also a brand new thermostat, new coolant hoses, drain/flush/refill of coolant, it ran well again....but still too hot..and it's starting to sound like crap again.

So here is a list of what symptoms are and aren't showing:

Symptoms that are showing:
-Quickly overheating. Less than five minutes under load.
-Smoking (it stopped for a while after head fix, but it's back...somewhat white)
-Knocking during revving, which also stopped after head fix and came back . (sounds a lot like a low octane knock in an old gas car)
-Oil pressure starts good and then drops quickly as it heats. (but it's done this for about two years now)
-A lot of "cake" in the coolant system. I replaced all three coolant lines. (upper, lower and pump bypass). The thermostat and water pump housings are aluminum...connected to an iron block...and all of the hoses are "cakey" at the end that connects to these aluminum housings)
-Looking into the top of the radiator, the engine heating process goes like this: coolant is stagnant, coolant is flowing, coolant then starts to froth and bubble violently.
-It DOES use coolant, but it's hard to tell if it's going into the engine somewhere or only losing it when it boils over.



Symptoms that ARE NOT showing:
-No leaks around water pump.
-No squealing or looseness of water pump bearing.
-No coolant in oil.
-Not using or leaking oil. I haven't needed to add any since my last oil change a few months ago.
-No squealing of engine bearings.
-Both upper and lower radiator hoses get hot (if one was still cold...I would suspect thermostat...even though it's new...or water pump)
-I DO see movement of coolant in the radiator after the engine gets warm. So I believe the thermostat is opening and the pump is pumping.


Any tips where I should look next from the gurus?

I'm thinking a compression test? I have the old injector that I replaced. I think that I could rig that up with an adapter to my compression tester.

What about these diagnostic fluids that you add to the radiator and then check for color change to see if compression is getting into the cooling system?

Fuel issue? Perhaps too much water in a sediment bowl or filter somewhere?

Coolant system blockage?...although I did just have the head off and had it all cleaned out at the shop...
 
"It's been running for about two months now"

Should say:

"It's been running HOT for about two months now."
 
white smoke and loss of coolant at least to me means a cracked head or bad gasket, coolant in the combustion chamber would also create a slight knock.
 
Ask on Tractor Talk.
Bigger board, more diesels, more experts.
You might also try tractorbynet - Google it.
Big site, lots of experts and they probably
have a Jinma specific forum.
 

Good point. I never thought about the head itself being cracked. The engine shop probably didn't specifically look for that.

I wonder if the flattening could have smeared over the crack, so that it ran a little better for a while and then it came back once the engine got up to temperature.

Very good point...and something that I wasn't thinking about.
 

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