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Pressurized engine - Scoot5869 - 02-05-2026
Recently I have had truck in shop fixing multiple items while I have down time.
2010 cm871 550 hp tuned by Rawze.
One of the items I replaced was the turbo again I would not recommend Hd turbo. Anyway
It was letting a significant amount of oil into the intake so I replaced it with a factory reman like I should have the last time.
Before i replaced it I could not get the truck to boost past 30 on hard pulls or hills anything pulling 80k. After the replacement i still seam to have to same issue. Actuator passed calibration cac had no leaks. I plugged off exhaust side of turbo an put pressure to the intake side. As I understand it doing that I should not have any leaks correct?
So when i put pressure to it 20psi I had air coming out of the hole I drilled in the crankcase filter and if I opened the oil cap from there as well. Those were the only places I had air coming from.
So I’m not sure what my problem is and if this is why I can’t get the boost any higher on hard pulls
I just replaced all the valve guide seals as well and everything looked fine there.
Any guidance would be appreciated
RE: Pressurized engine - marek4792 - 02-05-2026
A wore out or reman air compressor will push air into the crankcase if the intake is pressurized. Try converting it to a naturally aspirated intake using a 1 1/4 inch crankcase breather filter and repeat.
RE: Pressurized engine - Scoot5869 - 02-05-2026
Ok the compressor was put on in 2019. Honestly don’t know what to do for the second part.
RE: Pressurized engine - marek4792 - 02-05-2026
This is how I done it on my x15, but the yours you just keep the straight silicone hose and install the filter to it and change it yearly. Then just get a plug for the intake manifold. It's what I've done while I was at Rawze's years ago with my 870 truck.
See the 3rd pic on my post..
https://rawze.com/forums/showthread.php?tid=6851
RE: Pressurized engine - tree98 - 02-05-2026
Sounds like a lot of blowby or bad valve seals. 20 psi shouldn't be leaking out like you described. Your losing boost out of those leaks!! That could explain your power loss.
Also check compressor like mentioned above.
RE: Pressurized engine - Scoot5869 - 02-05-2026
(02-05-2026 )marek4792 Wrote: This is how I done it on my x15, but the yours you just keep the straight silicone hose and install the filter to it and change it yearly. Then just get a plug for the intake manifold. It's what I've done while I was at Rawze's years ago with my 870 truck.
See the 3rd pic on my post..
https://rawze.com/forums/showthread.php?tid=6851
Ok this makes more sense to me picture works wonders as well!!
RE: Pressurized engine - Scoot5869 - 02-05-2026
(02-05-2026 )tree98 Wrote: Sounds like a lot of blowby or bad valve seals. 20 psi shouldn't be leaking out like you described. Your losing boost out of those leaks!! That could explain your power loss.
Also check compressor like mentioned above.
I just changed the valve guide seals. truck really doesn’t use any oil except for the front structure but I just fixed that.
What other way can I check compressor to see if it’s bad?
I can fix things if I know how and this forum is a god send and quick serve!
I just don’t know how to diagnose things without researching
Thanks
RE: Pressurized engine - tree98 - 02-06-2026
Block off the compressor air INTAKE and pressurize it again.
RE: Pressurized engine - Scoot5869 - 02-06-2026
Any idea what I need do a plug size wise? Save from me stopping at 20 places lol