I've got a 1985 GMC Brigadier, Cat 3208, 67,xxx miles. I bought it with an oil leak at the rear of the engine. Also the oil pressure seemed high...70-80psi with the leak. Long story short(well not really keep reading)...I discovered that the bolts behind the flywheel had backed out. Didn't find any thread locker evidence on those bolts. So I dropped the 5 speed, pulled the flywheel and pulled the pan. I did a bit a research and read a few places that the oil pressure relief valve was connected to the oil pump. I spent the $150 from Cat and replaced the relief valve (plunger, spring and cylinder they go in). I hand screwed in the cylinder until it was snug...then torqued to 30ft lbs. Put the rest back together (with thread locker)...new clutch, seals and all. Unfortunately I still am seeing high oil pressure....80-90, 95? My guage only goes to 80....so I'm guessing on the needle. I pulled the guage out....set the air compressor at 40psi...blew into the fitting with blow gun... 40psi on the guage, tried 60, 80....read out was right on. So the guage is good... I noticed that the hose connecting to the guage....goes to a "T" on the engine block. The other leg of the T goes to the bottom side of the air compressor. I read that oil from the engine is used to lube the compressor pump. So I wondered if perhaps some how the compressor was jacked up and pushing air back into the engine? So while it was idling...I cracked open the line at the back of the pump. Figured if I get air...bad....oil..then good working as it should. I got oil...so I don't think that's it. I also read in the manual that "normal" oil pressure range was 45-85psi. ? The only thing the book says regarding high oil pressure is that the relief value isn't working... So perhaps I tightened the valve too tight? It's hard for me to believe.....especially since the engine produces a good amount of vibration. Afterall those rear bolts backed out.....so I would think that valve would need to be snug prior to torque? Anyone out there that has experience with this? Ideas on anything else that could be causing my issue? Any help is appreciated!
If the gauge is good and the relief valve is good the only thing that will increase pressure is a restriction in the oil galleries somewhere like a big glob of RTV. The restriction would have to be after the oil pressure pick up point. This is assuming the engine was right to start with.
The specs are very broad for oil pressure, the spec for a 3208 is 35-90psi using 10w30.
the original high pressure is at start up 700-800rpm, 60-70 degress (F) outside. 15w-40 I warmed the engine up to 170 degress(F)...and the oil pressure was 72psi @ 500rpm 79psi @ 750 rpm 85psi @2000 rpm heck maybe this is ok?...probably worried for nothing. it's just odd to see the oil guage go past it's upper limit... thanks for the comments!
That isn't something I'd worry about.
MY 3208 runs 85 or more. LB
We have four different 3208's. Everyone runs between between 50 and 90 psi. As far as I'm concerned they're the best engine ever made.
Haven't run into a problem with too much oil pressure yet, its always been too little.
I don't hate them but that's the only time I've ever seen that comment made about them.