Excessive blow by?

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9 LIVES

Demolition Expert
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Oct 29, 2006
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What would cause excessive blowby? VP 24V truck...?

Compression check was flawless

It was pushing oil out the blowby hose & just the other day it blew out the side cover gasket on the driver side of the block.

Almost as if compression is getting into the crankcase & pushing the oil out....but if it was a broken ring wouldn't it have showed a bad cylinder while compression testing?
 
can you hear anything different while the engine is idling? ive noticed that almost everytime there is a broke ring you can hear it while idling. Its not a loud noise at all and you have to listen very carefully to hear it.
 
Turbo seals can cause massive blowby when they let intake or exhaust pressure into the crankcase through the oil return line. Or something like that.
 
Dont go by what a compression test shows do a leak down to pin point any leaks or problems. You could prob. buy a kit, but I made one from an old injector and it works great. Remove the pintle, cut off the tip of the nozzle, weld a air hose fitting on the top and weld up the fuel rt hole. A leak down is so much more accurate and even faster to do....Ryan
 
If you get a big vacuum leak, the vacuum pump will pump air into the crank case.
 
I know the turbo seal has been leaking a bit of oil for the last couple of sled pulls.
 
Begle1 said:
Turbo seals can cause massive blowby when they let intake or exhaust pressure into the crankcase through the oil return line. Or something like that.
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^^^ that would be my guess too. we run into that every now and then at work.

the ones we have found, compressed air (boost) is leaking past the compressor seal, into the base through the oil drain line.
 
Check for a vacuum leak, does your ac/heat only blow out of the defrost? or does your cruise or 4wd not work, if any of the above are answered yes then you have a leak and its what could be causing your problem along with the other suggestions mentioned above, I just fixed a 99 last week that had the same issue.
Follow the main vacuum pump line from the pump up to the junction on the drivers side firewall area, you will see a few vacuum fittings, check for leaks, the hose from the factory will rot and even though it looks solid will still leak, also check the line going above/behind the turbo, it is known to get brittle and crack in that area, also check where it goes into the firewall, good luck.
 
blkram said:
Check for a vacuum leak, does your ac/heat only blow out of the defrost? or does your cruise or 4wd not work, if any of the above are answered yes then you have a leak and its what could be causing your problem along with the other suggestions mentioned above, I just fixed a 99 last week that had the same issue.
Follow the main vacuum pump line from the pump up to the junction on the drivers side firewall area, you will see a few vacuum fittings, check for leaks, the hose from the factory will rot and even though it looks solid will still leak, also check the line going above/behind the turbo, it is known to get brittle and crack in that area, also check where it goes into the firewall, good luck.
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im thinking this is what my problem is.. the "t" on the drivers side is messed up a little.. how can you fix this? do you have to buy a whole new setup? sorry to hijack, but this thread caught my attention after mine started spitting oil out also..
 
weazel said:
im thinking this is what my problem is.. the "t" on the drivers side is messed up a little.. how can you fix this? do you have to buy a whole new setup? sorry to hijack, but this thread caught my attention after mine started spitting oil out also..
Click to expand...

I just replaced all the hose pieces, also replaced the end at the vacuum pump, if the T is cracked you should be able to fab something up from either your local hardware store or some of the guys parting trucks out, also check the 4wd actuator on the passenger side front axle, the hose can come off at that location also.:Cheer:
 
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