YACT: Causes and solutions to blow by

[iamwiz82]

So my Jeep has some blow by. Its not bad, but there is alittle bit of oil resting on the air filter every few thousand miles. I have been told it could be because of a bad PCV or excess sludge built up on the valve covers, along with bad rings. Are there any other causes?

As for solutions, other than replacing the PCV or cleaning the valve covers, are there any other solutions?

 

[toph99]

depending on where your breather is located, a dirty breather filter can also be the cause. Are you burning oil?

 

[Sluggo]

At least replace the PCV valve, it only costs a couple of bucks and if you have some miles on the truck it sure isnt going to hurt anything.

You can also try some of that motor flush stuff next time you change the oil, might help get rid of some "stuff" thats built up.

 

[Brutuskend]

Take the PVC valve out and shake it.

If it rattles it's good.

If it's good, take a piece of paper and place it over the oil filler hole, if it get blown off your rings are probably going.

 

[iamwiz82]

yes, that is due to my intake plenum gasket. I'm alittle leary to fix it since its a PITA.

The breather uses the air filter.

 

[iamwiz82]

Originally posted by: Brutuskend
Take the PVC valve out and shake it.

If it rattles it's good.

If it's good, take a piece of paper and place it over the oil filler hole, if it get blown off your rings are probably going.

rings are good. The only consumption is the intake plenum

 

[iamwiz82]

up

 

rings are good. The only consumption is the intake plenum

Blow-by is combustion gasses escaping past the rings, these gasses enter the crankcase and are drawn into the intake through the PCV valve, a certain amount of blow-by is absolutely normal.
If you are really concerned about the amount of blow-by, have a leak-down check run on all the cylinders, anything more than 8% is a cause for concern.
Ideally you want 2%, most engines run in the 5% range, the more blow-by that is present, the lower the fuel mileage, oil mileage and engine life, also the oil run hotter and cylinder wear is accelerated because of oil wash off.

 

[iamwiz82]

Originally posted by: Roger

rings are good. The only consumption is the intake plenum

Blow-by is combustion gasses escaping past the rings, these gasses enter the crankcase and are drawn into the intake through the PCV valve, a certain amount of blow-by is absolutely normal.
If you are really concerned about the amount of blow-by, have a leak-down check run on all the cylinders, anything more than 8% is a cause for concern.
Ideally you want 2%, most engines run in the 5% range, the more blow-by that is present, the lower the fuel mileage, oil mileage and engine life, also the oil run hotter and cylinder wear is accelerated because of oil wash off.

i'm getting fairly good compression though, for a 5.2 that has 115k miles on it. My issue is that the oil/gunk is being blown out through the air cleaner tube, rather than sucked back into the intake manifold.

 

i'm getting fairly good compression though, for a 5.2 that has 115k miles on it.

A compression check will not show blow-by unless it is in large amounts, the only true way to check blow-by is the cylinder leakdown method, an air hose with a pressure gage is screwed into the spark plug hole, the cylinder is brought to bottom dead center on the power stroke, air is admitted to 150 P.S.I. and then shut off, the gage will indicate leakdown after a period os 10 seconds.

 

[Quixfire]

Originally posted by: Roger

i'm getting fairly good compression though, for a 5.2 that has 115k miles on it.

A compression check will not show blow-by unless it is in large amounts, the only true way to check blow-by is the cylinder leakdown method, an air hose with a pressure gage is screwed into the spark plug hole, the cylinder is brought to bottom dead center on the power stroke, air is admitted to 150 P.S.I. and then shut off, the gage will indicate leakdown after a period os 10 seconds.

Roger's right on this one. But think about your system, PCV valve, by engine vacuum, pulls the crankcase gases from your engine, if the pressure from worn rings exceeds the volume the pcv valve can remove then it will find another way via your breather or even your gaskets. The only other possibility would be if the pcv valve opening is blocked by engine sludge or other debris it would quit operating normally.

 

[iwearnosox]

Originally posted by: toph99
depending on where your breather is located, a dirty breather filter can also be the cause.

Aren't most breather's dirty?

 

[iamwiz82]

ok, i'll do a leakdown test. I found some plans for a homemade one I'll hook up my compressor to it and we'll see what happens. I would assume if there is a leak then I would hear it, right? Like if i listened to the TB i would hear air escaping if it was the intake valve, or exhaust valves would resonate through the exhaust, etc, Right?

 

[Quixfire]

Ahh, yep and if it's the rings your hear air from the oil fill cap or such. But if your compression is good, 115 psi, you most likely doesn't have a valve problem. Don't forget to make sure the valves are closed before testing the cylinder.

BTW, where did you find the plans for a homemade tool?

 

[Lola]

Originally posted by: iamwiz82
ok, i'll do a leakdown test. I found some plans for a homemade one I'll hook up my compressor to it and we'll see what happens. I would assume if there is a leak then I would hear it, right? Like if i listened to the TB i would hear air escaping if it was the intake valve, or exhaust valves would resonate through the exhaust, etc, Right?

OH god!!! i can just hear the b!tching now!

 

[iamwiz82]

Originally posted by: Quixfire
Ahh, yep and if it's the rings your hear air from the oil fill cap or such. But if your compression is good, 115 psi, you most likely doesn't have a valve problem. Don't forget to make sure the valves are closed before testing the cylinder.

BTW, where did you find the plans for a homemade tool?

Right here. I have most of the fittings and such already from another project

 

[Eli]

Originally posted by: Quixfire
Ahh, yep and if it's the rings your hear air from the oil fill cap or such. But if your compression is good, 115 psi, you most likely doesn't have a valve problem. Don't forget to make sure the valves are closed before testing the cylinder.

BTW, where did you find the plans for a homemade tool?

Can't really throw numbers around like that. 115PSI might be good for one engine, and not so good for another.

 

[Quixfire]

Originally posted by: Eli

Originally posted by: Quixfire
Ahh, yep and if it's the rings your hear air from the oil fill cap or such. But if your compression is good, 115 psi, you most likely doesn't have a valve problem. Don't forget to make sure the valves are closed before testing the cylinder.

BTW, where did you find the plans for a homemade tool?

Can't really throw numbers around like that. 115PSI might be good for one engine, and not so good for another.

My mistake, I though he mentioned the "115psi" in an earlier comment, he actually mentioned his mileage, 115K.

I'm sorry...