Engine/Transmission (1994 - 1998) How much water vapor is OK from Crankcase Vent?

[LFalconer]

All, My 97 12v with 152K is releasing more white vapor than I can recall from the past. Oil level is fine, had Head Gasket replace at 146K due to head warp and blown HG [assume overboost and EGT played a part]. Since then have not exceeded 1300 F egt momentarily, 1200 for longer term. Max boost is 35PSI.



How much white smoke / vapor is OK? We get some drips from this tube , not all oil.



Thanks!



Luke

 

[Vaughn MacKenzie]

Luke it would only be oil vapor, no water vapor unless you do have a HG problem. Other causes of increased blowby vapor are problems with the vacuum pump or a leak in the vacuum system, and a turbo with deteriorating bearing seal can cause it too. How is your oil consumption . . . if it's low I wouldn't be too concerned about it.



Sounds like you run your EGTs up a bit, sustaining 1200 for more than a couple minutes can be risky. . . virtually no margin of safety. A short 1300F blast is fine (unless you were already cruising at 1200 for awhile). 1100 - 1150 is the highest I ever run mine.



Vaughn

 

[Signal73]

Since it is cool out now, if you do alot of short trips you may get a little condensation forming in the draft tube causing some milkyness to seep out.



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[LFalconer]

Darn, HG seems to be blown again

Gents, Thanks for the heads up. Looking at the cc tube - it was more white vapor than a little.



Investigation revealed the same issue as when HG went before - Antifreeze level going down, oil in Antifreeze. We had the HG replaced 6k miles ago.



Running boost about 35PSI max, although most of the time my son [aged 18] drives this truck, with the fuel turned up I suppose the stock HG just can't take the abuse. I had the head checked and machined for flatness, used a oversize HG . 010 to ensure no valve piston contact after machining.



What should be max boost with stock HG? Although when we do the HG again, we will stud and fire ring... . It'll be awhile though as in the last 3 months we have put a NV4500 and new brakes on this truck... . THe HG replacement was in May... . Can u say Money Pit?



Thanks, Luke:{

 

[Vaughn MacKenzie]

Hope it's not being driven much with coolant getting in the oil. . . it'll destroy bearings real fast (speaking from experience).



It's a bummer when you have to do a HG job twice in a short amount of time. Just one question to ask, is the engine allowed to warm up good before pushing it. . . boosting a cold engine is a good way to pop one fast.



As far as HG thickness goes you can have the head machined at least 2-3 times before valve clearance is a concern with a stock-thickness HG. But if you're running up to 35psi boost often might as well use the . 010" over.



Vaughn

 

[LFalconer]

Good Point..

Vaughn, Thanks for the reply. I can imagine how you know about the bearings... Painful I'm sure. .



The truck is parked until we put another HG on. The head was machined last time at 146K.



Any recommendations on aftermarket HG - but not studding / firering treatment? I know other folks running up to 40 PSI on non studded trucks.



Thanks, Luke