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Cleaning the crankcase?

This is a discussion on Cleaning the crankcase? within the GM Trucks forums, part of the Vehicle Specific category; I don't usually post here. I'm usually talking with the 4th gen F-body crowd. About a year ago, I picked ...

  1. #1
    Drivin It Like I Stole It JWSmythe's Avatar
    Join Date
    Dec 2005
    Tampa, FL

    '00 TransAm WS/6

    Cleaning the crankcase?

    I don't usually post here. I'm usually talking with the 4th gen F-body crowd.

    About a year ago, I picked up a '99 Tahoe (350 Vortec motor) for real cheap. I was told the engine and transmission were rebuilt about 50k miles ago. Ya, I took that information just like "it was driven by a grandmother on Sundays to get to church".

    It suffered from an intake manifold leak. At least I think that's what it was. It was kind enough to dump an awful lot of water into the crank case. About 4 gallons, it appears. That's been dumped, bottled, and replaced with clean oil. I wasn't daring enough to even start it without fixing the actual problem.

    So in taking it apart, I started getting more and more annoyed by the design. I got to the lower intake manifold and said "ok, it's not going back together like this." I went ahead and ordered an air gap manifold, 750 cfm Edelbrock carb, and pressure regulator, and HEI distributor.

    Now the problem. Don't worry, it's an easy one. I just wanted to lead in with something more interesting than starting here.

    I got the lower intake manifold off. The oil galley had a nice thick layer of sludge on it. It was about 1" thick, and I scraped it out with my fingers (wearing gloves, of course). I have to assume there's a similar situation in the oil pan. The heads were pretty clean.

    I'm not going to pull the motor to clean it out. If I did, I'd rebuild the whole thing, and I'm just not inclined to do that right now. We're coming up on hurricane season, so I'd like it to be available to escape flood waters, rather than saying "yup, I could have gotten out, if the motor wasn't in pieces in the garage".

    Does anyone have recommendations on cleaning the sludge out? I'm not partial to the diesel or kerosene method. I've read good stuff about using seafoam, but I've also heard people say that putting magnets on their fuel line doubled their fuel efficiency.

    Should I just scrape out what I can, run a light weight oil in it, and change it frequently for the first few hundred miles?


  2. #2
    Super Moderator
    pajeff02's Avatar
    Join Date
    Feb 2009
    Mansfield, PA

    Black & Blue
    '02 WS.6 / '07 Suburban

    Maybe run one or two shorter oil change intervals with something like Penzoil Platinum and a quality filter. Seafoam is essentially a solvent and I don't really recommend going that route. If you want to run a cleaning agent through the oil, check on Auto RX -- it's not advertising hype and actually does work. You can also run one (1) ounce of TC-W3 rated 2 stroke oil per every 5 gallons of gasoline to help clean out the combustion chambers and fuel system. This also works and is not b.s.

  3. #3
    Moderator Firebirdjones's Avatar
    Join Date
    May 2006
    I'm going through this right now. I have an original low mile SCJ mustang that has been sitting for 25 years. Just got it running yesterday.

    Had stuck intake valves from bad gas (gummed up the valve stems) and bent some pushrods.

    After I worked the valves free by hand with PB blaster I also pulled the oil pan to check things, no sludge and looked good. I changed the oil with a quart of Marvel Mystery oil mixed in. This stuff has been around since the 30's that I know of, and has always been the "go to" cleaning agent for sludged up motors. Looks like transmission fluid to me, which will do the same thing.

    I also put a small amount in the gas tank mixed with gas, and after it started, I slowly introduced it through the top of the carburator for about 15 minutes to make sure it got to all the intake valves.
    I'll leave it in the crank case for about 2-300 miles of driving and change the oil again. For oil I'm currently using diesel oil for it's high detergent content (cleaning) and also for it's higher ZDDP content (flat tappet camshaft),,,plus it's cheap to buy for those quick flush type oil change intervals.

    It's worked great for me in the past, and it seems to have saved this engine from being torn down for a rebuild. It purrs like a kitten now.

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