Why is gunk / sludge built up in my intake tube? Volvo 1990 740 GL

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03-01-2015, 10:01 PM

rspi

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Why is gunk / sludge built up in my intake tube? Volvo 1990 740 GL

I decided to tune up my 745 and part of that service (to me) is to clean out the intake system, throttle body. When I pulled the intake tube, it had a lot of oil/gunk in it. Does anyone know why?

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03-01-2015, 10:29 PM

Blue91SL

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Holy **** dude.
That's pretty bad. Looks like blowby going through the intake. Too much oil/too high pressure maybe?

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03-03-2015, 03:10 PM

lev

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That's oil, not sludge. Normal to have some, may be a little too much in your case. Make sure the PCV (flame trap, separator, nipples, hoses, etc.) are unobstructed. Have you taken compression readings?

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03-03-2015, 10:44 PM

rspi

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No I have not done a compression test. I just fired this car up after sitting for YEARS. There was a lot more than that. I did replace the flame trap and will check it again in a week or so.

Last edited by rspi; 03-05-2015 at 11:11 AM. Reason: correction

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03-04-2015, 08:19 AM

Hylton

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Funny enough, this is very normal in today's GM engines and many simply buy a catch can to keep the oil out of the intake.

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03-04-2015, 03:36 PM

pierce

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said bypass/blowby catch can won't fly in California as they inspect the PVC as part of the biannual smog check.

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03-05-2015, 11:12 AM

rspi

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Mine passed here, 2 years. I also think the exhaust manifold to pipe is loose. Makes that noise.

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03-12-2015, 09:10 PM

91-740Turbo

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Not sure if I remember correctly, did the 745 have a turbo on it? If there is a turbo, it could be leaking oil into the intercooler and then going to the intake.
If no turbo, then check the PCV system.

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03-13-2015, 12:40 AM

pierce

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phew, both the intake and outgo side of the intercooler are on top. I would think the thing would need to be mostly full of oil before it would be sucked into the throttle.

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