CAT D9N Low Power Issues

Later model Cat D9N with very low power issues. Serial 1JD00972. Black exhaust fumes when engine is under load. Tracks will not spin now when machine is under heavy load- ie when pushing a tree or digging deep (would normally expect tracks to start slipping). The strange thing- turbo is always very cool. Can pretty much put your hand on the intake side of the turbo after 30 mins work. Have recently replaced the turbo after being advised that this could be the issue. At the time I thought about cleaning the aftercooler, however I blew on the aftercooler fins with my mouth and thought the air flow seemed adequate. Immediately after the turbo fix the machine seemed to once again have good power, although there did not seem any issue with the previous turbo- no broken shaft etc. The exhaust system has had a fair few leaks of late. I wouldnt say enough to lower boost, just enough to be very dirty around the engine. A bloke recently told me he had a similar problem with a diesel engine on a bus, where he had exhaust leaks everywhere. He replaced the turbo and fixed the leaks with no improvement. He then cleaned a filthy aftercooler and away he went. I have now fixed the majority of the exhaust leaks on my machine. I pulled a plug out of the pipe that connects the turbo to the aftercooler and found a thick black sludge type material on the plug. There did seem to be a suction in that pipe too which I thought would mean a reletively clean aftercooler. Anyway, I am going to be cleaning the aftercooler in the next coming days. Wondering if anyone has any other tips? Cheers everyone. Hope that all makes sense.

How many hours on the engine? I wouldn’t rule out injectors causing low power, need to do a 3rd gear full rpm torque converter stall to get a baseline on engine RPM and boost pressure. Speaking of engine RPM, is the high idle no load rpm correct? A dirty aftercooler can definitely cause issues but unless the turbo seal has blown oil into it or it’s sucked a tremendous amount of dirt, I wouldn’t think it would be damaged as it is not exposed to any elements.

If this is a 3408 with the exhaust manifolds covered by shields it will be hard to see exhaust manifold leaks. If you have any black smoke coming from the manifold area you will be loosing exhaust pressure before it gets to the turbo. Make sure you check this.

988Driver said: Wondering if anyone has any other tips? Click to expand... What ahart said. High Idle No Load RPM, TC stall RPM, and turbo boost pressure @ TC stall ought to be measured before you go opening anything up IMHO. Post a Serial Number if you want any information regarding what the specs are.

Ok. Thanks fellas. Serial: 48W24734 In regard to testing, do I just drop the blade and put it in 3rd gear full rpm and get a check on boost pressure? Thank you.

Approx 9000 hours engine.

988Driver said: In regard to testing, do I just drop the blade and put it in 3rd gear full rpm and get a check on boost pressure? Click to expand... Put the blade up against something hard & unyielding if it's available. Otherwise stand on the brakes hard. Are you sure about that Serial Number.? 48W24374 is a 3408 engine but it was originally installed in a 988B Wheel Loader in 1987. Ideally need the tractor S/N to look up the specs. It should be 6XJ or 1JD followed by 5 digits.

1JD00972 nige. 3rd gear with brake depressed, shouldn’t move as long as your brakes work. It will pull through them in 1st gear with a proper running engine.

As shipped above. 35 years later, could be anything.

Dyslexia strikes again........ I read 24374 for 24734. 1JD00972 it is then.

Did you figure anything out on this one, I am having the same issue. I haven't changed the turbo yet though.

Race5118 said: I haven't changed the turbo yet though. Click to expand... Why fire the Parts Cannon before doing some proper diagnostics.? Start with a Serial Number, symptoms, and what have you tried/tested so far.? How does it behave when you stall it in 3rd speed against the brakes.?

1JD01775 This machine is new to me. I haven't started checking anything yet, just trying to get some ideas of what i should be looking for. 3rd gear stall seems to get to about 3/4 of full rpm pouring black smoke and torque converter temp shoots up quickly. It does seems to get stronger once it warms up but still pretty doggy. Air filter is new I haven't checked fuel but it seems more like an air issue.

Does the machine have a tachometer.? If not then you’ll need a photo-tachometer to measure the engine RPM at stall. At the same time the boost pressure at stall could be measured. How many hours on the machine/engine and do you have any previous history on it.?

sounds like a blown diaphragm in air fuel ratio valve

pittsburgh cat man said: sounds like a blown diaphragm in air fuel ratio valve Click to expand... Certainly worth taking a look, it's simple enough to get at. #16 in the illustration below.

Nige said: Does the machine have a tachometer.? If not then you’ll need a photo-tachometer to measure the engine RPM at stall. At the same time the boost pressure at stall could be measured. How many hours on the machine/engine and do you have any previous history on it.? Click to expand... The Machine has 24000hrs with around 8000 on the engine. I do not have a tachometer on the machine. I will test it all out.

I had some time to take this apart today. I'm guessing this isn't suppose to be like this.

Race5118 said: I had some time to take this apart today. I'm guessing this isn't suppose to be like this. Click to expand... You would be correct in that assumption.