C12 Black & White Smoke

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 Ask Dave / Posted 8 months ago / 136 views

Question:

1999 Cat C12: On rare occasions, usually upon hard acceleration the engine will blow heavy black smoke and will have minimal power. Usually a minute or less later after I release the accelerator the coach will puff white/grey smoke then accelerate fine and will be back to normal. Sometimes, this will not happen for another 5000 plus miles. Today the heavy black smoke and limited power lasted a while then all of a sudden it was better. I am not positive, but I believe when this was happening the boost gauge showed 0. I looked for any air leaks and did not see any. Any thoughts or suggestions?

Dave’s Answer:

What this sounds like is a leaking or blown rubber coupling hose going from turbo charger to the inlet of the Charged Air Cooler (CAC) and/or exit from Charged Air Cooler to intake on engine. You can locate this problem because air will blowing out of rubber coupling hose or from a loose clamp. This occurs only around 1400 rpm and above.

A second possible reason for your problem could be within the Charged Air Cooler (crack where it is fastened to bracket) or a stress crack along the side of the housing on the CAC itself.

The intermittency may be due to the stress crack opening and closing due to twisting of the bracket and road conditions.  There are several possible other areas but with the black smoke along with later gray/white smoke the above would be the most probable areas to look. If you attend a rally when I’m there, we can run the CAT ET and get a better idea of the possible cause.

Dave

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