How to tell if an engine has execess blow-by?

[Bullet]

I have 94 dodge Dakada with a V6 engine that has about 165,000 miles. Last year I changed the valve seals. The truck uses almost no oil, but it does have some blow-by. I don't know how much blow-by is to much. Its only a back up vehicle now. I lent it to my brother who put 9000 miles in 5 months with no oil change, with no oil added, and down about 1/4 of a quart. Oil was $1.00 a quart Trop Artic 10w30 semi senthetic from dollar tree.

Will an oil analysis tell anything (like fuel in oil)?

 

[Kestas]

I believe a quick test is to remove the oil filler cap and see how much air is puffing out during brief revving.

 

[bdcardinal]

oil analysis can tell you, you can also do a leakdown test.

 

[Clyde65]

Do a compression test. The cylinder with the lowest reading; pull the spark plug and squirt some motor oil on top of the piston. Do a recheck. If the reading improves, that means the rings are worn on that piston.

 

[mechtech]

There is an actual leak down test.
Pressurized air at a constant is compared to the pressure in the cyl., when testing.
But lets assume there is blowby. Are you going to fix it, or live with it?

 

[Quest]

compression + leakdown test shall tell you your ring-t0-cylinder wall conditions thus translated to blowby conditions.

 

[alreadygone]

First thing on a high mileage Dodge would be to replace air canister/inlet on valve cover. They plug up with "goop" and cause pressure buildup inside engine.

Having a brain ****,, can't remember correct name at present!
Bob

 

[Gary Allan]

Here's the definition of excessive blow by. If your PCV system can't handle the flow ..and the blow by is being forced out of the intake vent and fouling your throttle body from the upstream intake (where the vent is affixed) ...then that is excess blowby. That is, if the blowby managment system can handle it ..and you have no undue consumption ...it's not excessive.

 

[Leo]

I would have thought that an engine with excessive blowby etc would consume quite a bit more oil than just 1/4 quart in 9,000 mi?

 

[Quest]

Leo-

Nope. Excessive blowby and oil consumption are 2 separate things that have no direct correlations whatsoever.

Note: you can have an engine that starting to consume a lot of motor oil (burned inside combustion chamber) and yet the blowby is acceptable.

This is mainly due to (a)stuck oil control rings or (b)worn valve guides. Esp. (2) where there is absolutely 0 correlations with blowby.

You can also have a tired, worn engine with worn out of taper cylinder wall that causes unacceptable blowby but yet it does not consume oil.

(last one would be a bad/stuck PCV valve which as nothing to do with either blowby nor mechanical issues)