Yanmar 3TNV82 Troubles

[66babyblue]

I recently acquired a Tak TB 125 mini ex with a Yanmar engine. This unit has some real problems. I could use some help where to start diagnosing the problem. The engine starts and runs fine at idle, at about half throttle it starts to puke out and actually drops in RPM. I have put in fresh fuel, cleaned out the water separator (full of sediment), replaced the fuel filter, changed oil and filter (oil was overfull). Additionally, the coolant looked contaminated with exhaust (blackish film in the reservoir) and there is bubbling in the reservoir as if there is exhaust pressure in the coolant system. So now I'm think bad head gasket or worse. Where should I start? Leak down test? This is my first diesel engine so no experience with them but i'd like to learn. I am mechanically inclined and if I could find a good manual should be able to do some troubleshooting and medium duty repairs Any help would be appreciated. Thanks

 

[johndeere7530]

Do a sniffer test on it. Not sure what u call it over there its basically a fluid that changes color if exhaust gas is present.
If it does then ur gasket is bad.

 

[66babyblue]

Do a sniffer test on it. Not sure what u call it over there its basically a fluid that changes color if exhaust gas is present.
If it does then ur gasket is bad.

Yes, I'll try and do that soon and give update. i'm almost positive it's exhaust. I don't know where else all that air could be coming from. Plus the temp fluctuates widely while running at low rpm. Thanks

 

[caterpillar13]

you have a head gasket leaking,i have a cat d5h that was doing same thing and there was a crack in the gasket.. and watch the oil level you may a seal leaking in the injector pump letting diesel in the crank case. if you use this machine for serious work you may look into up grade to a better one, if its a toy and you have time putter around with it(just my 2 cents)

 

[lantraxco]

The other thing you need to do is pull all the banjo bolts in the fuel system one at a time, blow them out, blow the line from the tank out with the fuel cap off. Inspect each banjo bolt looking in the hollow center for a very small strainer screen, if it has one it's usually in the first fitting from the tank to the lift pump, but not always. If it has a diaphragm type lift pump check that out as well, and the fitting where the return line attaches to the injection pump area. If it has a piston type transfer pump, clean the check valves and check the piston seals, you may be overfull on engine oil because it's leaking fuel into the sump.

 

[66babyblue]

you have a head gasket leaking,i have a cat d5h that was doing same thing and there was a crack in the gasket.. and watch the oil level you may a seal leaking in the injector pump letting diesel in the crank case. if you use this machine for serious work you may look into up grade to a better one, if its a toy and you have time putter around with it(just my 2 cents)

Thanks for the reply, I'm thinking you may be right about the head gasket. I'm not sure yet about diesel in the crankcase since it was overfull when i got the machine. I'm wondering if some bozo put an additive in the oil without draining some. Not sure but I'll be watching it. Is more of a toy than for making a living but I would like to get it operating decent.

 

[66babyblue]

Update on block test. I did the test and it came back negative BUT the directions say it is not for use on diesel engines. So not sure if that was helpful or not. I still have a steady stream of bubbles in the reservoir that start after about a minute of running. Could this just be a bad rad cap? Does anyone know if they make a block tester for diesel engines? I'm not sure if I should pursue this further or just pull the head.
I also noticed two other troubling things: When i pull the dipstick at idle it spurts a fair bit of oil (oil at top line on dipstick). Also i see a small pool of diesel next to the injector on cylinder one and it seems as though there is a little bit of compression leakage around the injector itself. Not sure if the fuel is coming from inside the cylinder or leaking externally.
I intend on following Lantraxco's advice and cleaning/blowing out the fuel lines. I'm also going to replace the feed pump to see if that helps before touching the injection pump. I'm thinking I have a fuel problem and a head gasket or other problem. Trying to sort through it without spending too much in case this engine is junk. Any further thoughts/suggestions would be greatly appreciated.

 

[rorybagleys]

Sounds like a blown head gasket or a cracked head.