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Blow By

1K views 9 replies 3 participants last post by  flyboy86q 
#1 ·
So I'm looking to buy a 97 12 valve and have a question about blow by everyone I've talked to said blow by is normal for 12 valve but how much is normal? The truck has 187k miles at idle it does blow white smoke from the blow by tube oil dip stick and exhaust when you take off the oil filler cap and place it on it to do a blow by test it doesn't really bounce up and down like I've seen them do with bad blow by but it does put out an amount of smoke from the filler hole. Sound like bad blow by or a normal amount?
 
#2 ·
If it doesn't blow the cap off, you're good to go.
 
#5 ·
Yes. Out of the oil fill it's normal to have a little "puff" while it's running. Like common said, if the cap stays put, it doesn't have too much blow by. The stuff coming out of breather is normal also. It has to do with how the rings/cylinders are machined on these engines. Smoke from exhaust is low combustion/cylinder temps. Dipstick tube is same as breather and filler because they're getting their puff from the same place
 
#7 ·
If it's extreme white smoke it could be slipped timing, bad injector, coolant burning....

How bad is it?
 
#10 ·
My 90 would give a little white smoke at idle even on a summer day if the engine was cold, it had 275k ish on the factory injectors, but never missed a lick. The "service life" of an injector in these older trucks is said to be about 200k (not that they don't go further).
 
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