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What Creats Blow By & How can you Reduce it ???

71402 Views 3 Replies 4 Participants Last post by  ITowBoats
Hello everybody,

I have a friend who just bought a truck that has heavy blow by in it. He got it from the most famous auction site. When we remove the oil cap there is white smoke puffing out like a choo choo train... and when you remove the oil dipstick you can see white smoke coming out of that too..... the exhaust has some smoke when the truck is cold but that kind of goes away as it warms up. The truck does run excellent but the blow by is there.... What really causes blow by??? and is there any way to stop the blow by in this truck or reduce it???

The truck is:

1999 Ford F250 XL with 126K miles on it PowerStroke Automatic.

Thanks !
1 - 1 of 4 Posts
All diesels have blow by at idle. Usually more than people are used to seeing from a gas engine. The rings are designed to cope with very high cylinder pressures and for maximum durability. A softer ring (like is used in a gas engine) would seal better at low CP's and reduce blow by but would not last 300,000mi which is what is expected from a diesel. If it smokes when cold, I'd look at the glow plug system first. If even one GP is not fuctioning, that cylinder will smoke until warmed up. After that, I'd get some oil samples tested for excessive soot and carbon (from unburned fuel bypassing the rings under power) before a tear down. Watch the oil consumption, if it is more than 4qts per 5000mi you might consider a rebuild.
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