4.3 High oil pressure - top end rattling

[glenmoore670]

It seems my rattling Vortec is back to it's old tricks. A couple of weeks ago, my 96' Blazer 4.3L 4x4 started rattling when started cold. The oil pressure was showing 60 psi -- about 20psi over what it normally is. After letting the motor warm up, it would stop rattling and the oil pressure would drop back down to the normal 40psi at idle. After a post here and several good tips, I changed the oil and filter and magically it stopped rattling and the oil pressure was normal again. I assumed the problem was a bad valve in the oil filter, and figured the problems were over.

Wrong again. I've put about 1800 miles on the new oil, and it's doing the same thing. However, an oil and filter change didn't stop it this time, and it's much louder. I still think it's lifters rattling, but I haven't let it warm up this time to see if it stops.

When I changed the filter this time, I noticed that there was oil all over the remote filter adapter and hoses. It could have been there before, but I didn't notice it, and it looks pretty fresh. I'm wondering if that remote filter adapter can fail resulting in no upper engine oil? I don't think so, but I wanted a second opinion.

For what it's worth, I noticed that the radiator is a little low -- about 1/2 gallon. The last time I checked it the engine was warm, but it was full. That's been about 3 months ago. The oil does not show signs of water at all. It's clean and clear with no frothy white stuff under the cap, or anywhere else that I can see. Another thing I've noticed in the last few months is the PCV rattling at idle. A replacement didn't fix it and I never went any further on determining what was causing it.

I know the list of possibilities is a mile long in this case, but I thought there may be someone out there that's had a similar problem.

Any thoughts?

Thanks!

[muddog321]

PVC is usually the throttle cable plastic holddown to the intake is broken so against the PCV - secure the cable and check the L hose to the intake too. The canister can rotate too on the intake so looka t that too.
Sorry to tell you but the leaking intake usually never shows any water in the oil - it sprays into the valley, hits the lifters/cam/balace shaft and evaporates. The 3 intake jobs I did never showed any water but the valley areas were all orange from the spray - if the reservior is dropping its the intake, head gasket, water pump, or hoses - it is not simply vanishing. As for the filter adaptor, yes they leak and have a $5 kit to fix but usually the oil cooler line pressure fittings are the cause. Sometimes on 4wd its the front diff pinion seal - check by smell - oil or gear oil smell totally diff.

[534BC]

It could be a restriction in the oil system after the pump discharge, also can be the pressure control valve in the pump. If it is a restriction then it must be after the sending unit (downstream). The noise it what I worry about,,,

[AJT1961]

Sounds to me like a bad lower intake manifold gasket. I didn't see any evidence of coolant fouling my oil either, but it did, leaving an almost undetectable gunk which fouled my lifters. Drain your oil into a white plastic pan and you can see it on the bottom. I replaced the intake gasket and the lifters and the problem was solved. Luckily it didn't destroy my rod and main bearings, but in time it would have. You probably also need new oil hoses, but I doubt that has anything to do with your engine noise. I'd start by pressure testing the cooling system.