BRAKE BOOST BLOWBY TEST

[Txcummins2013]

Hey guys, I had a rebuild done on basically EVERYTHING this time last year...build has about 40k on it...i have noticed for about a month that my truck leaves a few oil spots of oil on the floor every morning. I am fairly modded and run between 40-50lbs of boost and am trying to determine if its just a typical 5.9 leak or if I have a problem.
I do not have oil in my coolant and no fuel in my oil. I hve tested blowby throughout the rpm range and hot or cold get nothing but a slowly rotating oil cap. No pressure or smoke. The truck runs Rotella T6 full syn and JUST did a oil change this week.
Now i tried a different kind of blowby test where i brake boosted to 10psi and check for motion and the cap raises up but did not fall out when I got above 7psi....should I expect this to be normal as the valvtrain needs pressure to move oil around?
I have recently cleaned the ccv and breather tibe but not the drainback tube yet...so i might do that still. Truck runs great great mileage and is not burning oil or leaking enough to put drops on my tailgate.

 

[Txcummins2013]

Hey guys, I had a rebuild done on basically EVERYTHING this time last year...build has about 40k on it...i have noticed for about a month that my truck leaves a few oil spots of oil on the floor every morning. I am fairly modded and run between 40-50lbs of boost and am trying to determine if its just a typical 5.9 leak or if I have a problem.
I do not have oil in my coolant and no fuel in my oil. I hve tested blowby throughout the rpm range and hot or cold get nothing but a slowly rotating oil cap. No pressure or smoke. The truck runs Rotella T6 full syn and JUST did a oil change this week.
Now i tried a different kind of blowby test where i brake boosted to 10psi and check for motion and the cap raises up but did not fall out when I got above 7psi....should I expect this to be normal as the valvtrain needs pressure to move oil around?
I have recently cleaned the ccv and breather tibe but not the drainback tube yet...so i might do that still. Truck runs great great mileage and is not burning oil or leaking enough to put drops on my tailgate.

Bump

 

[Txcummins2013]

Bump

 

[Txcummins2013]

Anybody else?

 

[cerberusiam]

Nothing you have posted indicates a problem. Mine has always dripped just a little even when new. Look at this way; it isn't leaking oil it is sweating HP.

 

[Txcummins2013]

Nothing you have posted indicates a problem. Mine has always dripped just a little even when new. Look at this way; it isn't leaking oil it is sweating HP.

Oh man the dieselfather Cerb himself!! The forum go to man!!

I was told that brake boosting like that was an unreliable boowby test in relation to the cap moving under boosted load since the motor uses pressure to move oil up into the valvetrain crank case is that correct? So in reality unloaded unboosted blowby is the only variant of the oil cap that applies?

 

[cerberusiam]

I think somebody is out in the weeds with that idea. Oil is supplied the the rockers thru oiling galleries pressurized by the oil pump, nothing to do with crank case pressure. Oil has to drain back to the sump thru the galleries that would be subject to crank case pressure, would not be a good thing.

If the cap stays on at 10 psi of boost your build is solid, there isn't enough blow by to even worry about.