I have an 89' Iroc TPI 350. It has 70k on it but the motor has about 8k on it. It has kept awesome oil pressure until recently. When coming to a stop the pressure drops to 0 but the really strange part is that it jumps right back up to 30+psi after a few seconds while I'm idleing not hitting the throttle. This only happens after the car has been warmed up to normal operating temperature. It typically runs at 55psi@2000rpm like the manual says it should. After the pressure drops to 0 it will run at 45psi@2000rpm. The only thing I can think of is that the pick up for the oil pump is too close to the bottom of the pan and the force of stoping causes it to fall. Any ideas???

Thanks

 

thats odd.... does the engine stumble or anything..

and feel lucky. with full oil my pressure is never higher than teh first mark above redline

 

Could just be a faulty sending unit if you are luckier than me. I would swap in a mechanical guage and tape it to the windshield. This will tell you if it a real problem or just the sender.

 

I'm with Floor Guy. The oil sending units on these cars are notorious for going bad. Check (with a mechanical gauge) and replace as needed. After that, if it still reads low, then start to be concerned.

 

I would agree with the sender assessment, except mine has acted in exactly the same manner for the last 3+ years. Since I only use synthetic oil, and the symptoms only occur in a no-load situation, I haven't worried about it.

I'll be pulling the engine soon, if I find anything wierd I'll let you know.

 

Check the sending unit, by simply replacing it. Instinct tells me it won't help; but you've gotta at least try it, being the cheapest and easiest thing.

If it still does it, then the pickup has probably fallen off of your oil pump. If you can put an extra quart of oil in it and make stop doing it, or at least make a substantial improvement, then that's it, for sure.

 

I've read on other posts about the quality of the sending units as well so I will defintely give that a try. When I put the engine together I should have replaced the pump but I was being cheap which never pays off. I could move the pickup part of the pump independent of the body fairly easily. Is that normal????

 

If it isn't the sending unit or pick up the relief valve in the pump could be acting up. Regardless, the pump and pick up are only $30 or less for both. More labor than parts.

 

The pickup just sort of presses into the pump. If it was easy to move with the engine apart, then it probably did fall out. There's alot of vibration on the rear main cap.

Sounds like you'll probably be pulling the motor out.

It should be installed so that it's about 3/8" above the bottom of the pan, with the pan fully installed with gaskets and all.