turbo boost

I farm 1200 acres with my son and this fall we purchased at a dealer auction a 1971 Cat 824B wheel dozer to use on our farms. Cat runs real good with no load but if you put the coal to it under load she bellows black smoke. It has a Cat D343 six cyl engine turboed and after/cooled. we took out the air filters but that didnt help much. My question can a turbo get slugish and loose its boost? It burns no oil, doesnt smoke iteling but doesnt seem to have the snap that big engine should have thanks 4 any help

You need to check the boost before and after the intercooler. It is probably leaking off some of the boost. I once had a semi that did that. Ran ok. but had no power. Ran like a new truck after I put in a new intercooler.

Yes, turbo could be the trouble. Diesels with turbochargers have higher full load fuel settings than naturally aspirated engines because the turbo boost will burn the extra fuel. If it fails, exhaust smoke under load will increase along with exhaust and water temperatures. See if there's a boost port plug/tap on the intake manifold and put a 30-40 PSI gauge in to test it under load. Turbo could have failed bearings, or impeller damage on either side.

Hello bigdieselman,

One possible cause is an air leak from the turbo outlet, to the intake manifold. Inspect the piping real close. Start at the clamps, they may look tight.


You may get lucky and find a stripped clamp. Also check the piping for chafing. You can also plug one end, and put a few pounds of air pressure on the other end of the piping.

Turboes do not fail by reducing air flow, that is what K am saying. I am also guessing that you have a leak from the turbo outlet to the intake manifold. If it was a overfuel problem, it would smoke most of the RPM range, not at full load/RPM only,

GUIDO.

You would be surprised of how much power/boost you loose with a small leak, or a turbo where the impellor clearance is loose. You could have a worn turbo that won't leak oil.

It could be as simple as coke on a turbo bearing from shutting down with a full load. It shouldn't be too hard to pull the pipe off the turbo inlet and see that it spins freely.

Yes they can loose boost from just use. I have a truck that after a million miles the turbo would just not spool up only get about 20 PSI on the pressure gage. I found a couple of bad hoses. I changed them pressure checked the Air to air. No leak off there, still no more than about 20. Changed turbo and all was fine then. Never leaked oil or anything.
Talked to MI Turbo about it, they told me I was one of 3 they had talked to that got a million miles on a turbo in a cat engine in a truck. When I took it in they said yup fins were worn and shot. Bearing was still good.
As for the leaks causing boost problems. Read about how much a charge air cooler can leak and still be good. It amazed me they could leak that much. Mine held 30 PSI for 10 -15 minutes. Then dumped the pressure since it was good.
SO I would guess your turbo is on the downward spiral. Most important thing for turbo longevity is cooling them down before shut down. Give them 5-15 minutes depending on how hard they were working just before you want to shut down. And keeping them from getting high temperatures during use. Yes you can do that. Like pulling mountains with trucks just back off after it gets to a certain point. I used 1000 degrees as my limit. yup it will go to 1200 or more also will burn the rust off the manifold too. looks like a new casting when that is done.

You checked the air filters and I gather they were OK. What about the muffler? Either one can be a source of restriction. If they"re OK, I"d expect a worn or dirty compressor. They loose flow capacity under these conditions. In the "old Days" aircraft turbojets and early turbofans used ground walnut shells blown into a running engine to clean up the compressors. Now a days, they use a water wash technique.

How about a waste gate? Is that functioning properly?

dozer is too old for a waste gate, has no muffler, staight pipe. I will has to pull turbo off and check rotation. Thanks for all the feed back

I would guess that there is nothing wrong with your turbo, someone has turned the pump up to watch the smoke blow! Some of the old Cats only required a spring to be stretched to over fuel them.