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Blow By

The CDR is normally open to the turbo and the turbo sucks the blowby gasses out and pushes it to the intake.
When the turbo spools up and reaches a "certain" vac level in the crankcase the CDR valve closes and blowby stays in the crankcase til pressure buildup in the crankcase overcomes the CDR valve and it opens again to let blowby pass to the turbo.As long as boost is maintained the valve will open and close as requared based on vac on the turbo side and pressure in the crankcase.
The turbo can handle only a certain amount of blowby and when there is much more as you find in a worn engine you'll get positive crankcase pressure at all times resulting in steaming from dipstick and or leaking oilseals and gaskets. A stuck closed CDR will cause the latter as well.

Anyway that is my understanding of the matter
 
Maybe the CDR never closes,..how do you tell?

Wife's 95 has a road tube,i might put a vac gauge in the old turbo hookup and see how much vac the turbo actually pulls there.
 
I kinda forgot about that tread but AK tested for vac at the dipstick with engine running.
I plan on measuring the vac at the CDR inlet at the turbo.... taking the engine blowby out of the equasion.
 
So yall have a turbo, I dont. I have some blowby from the fill cap if I take it off and from the dipstick. Can I vent the CDR to the world or eliminate it and improve my blowby, oil consumption? I use a quart from 500-700 miles depending on if I am towing. Got 320000 on it if its the original engine.
 
You can't eliminate blowby by venting to the road but maybe you can curtail the oil consumption so it is worth trying,altough i think it won't make any diff on a NA engine as here is no boost to keep the oil from coming up past the piston rings and down the valve stems
 
I ran an OLD Cat engine in a front end loader with a LOT of blowby. in cold mornings the oil vapors would condense in the draft tube and drip. I stuck an empty coke can on the end to catch the drips and avoid EPA construction site fines. I don't remember changing the can, but I must have sometime. It had the added advantage of not having a steam/smoke/vapor trail shooting out the bottom; it sort of dispersed it upwards.
 
Yes its connected and it dont come off easy, the hose is hard, I tried last summer to get it off to clean it and gave up for fear of breaking the hose. I follow the theory, remember I am a cowboy n not a mechanic, anyway my theory on this old piece og GM iron is she is mostly better off if I dont mess with her. However ever since I heated her up with the bad fan clutch crossing Fancy Gap last year on My Trip she uses oil, used to be a quart every 1500 -2000 miles but on The Trip and afterward its twice as much plus before almost no blowby n now there is definite blowby. It has a lot of vaccum it sucks big time if you loosen the CDR, I didna get it off but it was loose enough that I had to wiggle it n grease it around the edge to get it to quit suckin air. Is it gonna hurt if it uses oil or should I get some that RX stuff?
 
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