Just wondering if anyone has seen this before. Under normal driving conditions The oil pressure is fine. When I brake really hard the gauge dives to zero and the check gauges light comes on. Once I am off of the brakes it shoots right back up to about 30. It runs between half and a quarter all the time. I am running mobil 1 10-30 and the oil level is fine. I was thinking maybe the sending unit is going bad but why would it be only when I break hard. This just started happening since I put cross drilled slotted rotors and good pads on. Thanks in advance

Adam

 

Probably a pick-up problem... I'd stop driving your car ASAP until you get that fixed.

 

Or it could mean the oil pickup tube has fallen off the oil pump, and its running dry under hard braking.

Put a mechanical gauge on it to check the oil pressure vs. the factory gauge. There's an extra pressure port in the block right above the oil filter (94 and newer only... the 93's use that for the stock oil pressure sensor).

 

It's the oil pickup tube for sure - very common problem. Get it fixed ASAP.

Greg

 

Thanks for the quick responses guys, one more quick question. What would a shop charge me to fix it??

 

I paid $800, but I had my oil pump replaced instead of repaired. My car had 104K on the original pump, so I thought it was cheap insurance. Get ready, it's not cheap.

You can do it yourself if you want though. You'll need to lift the engine (or drop the K-member with the engine supported) to remove the oil pan.

Greg

 

ok just got off of the phone with a shop that only builds f-body's and vets. He said there is pretty much no way the pickup is bad or fell off. He said that either the gauge or the sending unit is on the fritz, and if the pickup had fallen off I would A-hear it and B-there would be very little pressure across the board, unless I put 8-9 quarts in the pan. Any thoughts??

 

That shop guy sounds like he knows what he is talking about. I too thought it would be bad sensor, its wierd that it is doing it only while braking. In any case you certainly should avoid driving the car.

- Z28WannaB

 

Knock on your oil pan and see if you hear anything maybe.

I think "Spinner" had the same problem as you, and ended having to rebuild his bottom end because of this. Spun a few mains... and you don't spin bearings when your gauge is on a "fritz"

 

the oil pump pickup is pressed in, it can be loose and move up and down without falling off. he is right, if it was all the way off you would have no oil all the time. shop should charge about 500$ for a new pump installed and pinned or welded pickup.

 

What he said. That guy at the shop is a fuxing moron, and has no clue what he's talking about.

Drain your oil, and shine a flashlight up into your oil pan drain hole. $5 says your pickup tube will be laying there in plain sight. Get it fixed, or lose a motor. Been there, done that, your choice. And dave, your completely wrong. With the car stopped, or driving, the oil pump itself will be submersed in oil, and you WILL get oil pressure. It's not until you brake that the oil moves to the front of the pan, and you starve the oil pump. (which is why you lose pressure on hard braking). THIS is the purpose of the pickup, to constantly be able to draw oil, and hold a small amount in reserve for such a situation as hard braking. If there's anything else, I'd be HAPPY to send the pics of my *destroyed* bearings and crank to prove my point .

I caught the problem, got it fixed, and the bearings spun the next day. No oil = not good

 

Um I've built a motor or two spinner, and I had my pickup come LOOSE, not off, and move up about an inch, then once or twice when i floored the brakes i lost oil pressure. hence the reason I pinned my pickup tube and installed a solenoid operated oil pressure accumulator. Now I have oil pressure before startup and in case of G-forces (brakeing, cornering, accelerating,) I have pressureized oil that will step in and seemlessly cover for several seconds...

 

I'm going to be fixing the same problem on Monday. I'll pull the pan and let you guys know if the pick up fell off or just shifted. I can't wait to get this fixed because like a moron i've been driving the car for about a month with this but i have been going easy on the braking without loosing pressure. Once in a while i'll hit it harder and i'll drop the pressure. Plus i'm running with 6 1/2 quarts of oil.

 

What part of that contradicts ANYTHING i said. All I said was if the pickup is out, the motor will still get pressure at idle and on the gas. If it's partially out, IE: an inch like you said, sure that could happen. Either way, it's an issue with the pickup that needs to be fixed because the motor is starving under braking.

 

heh, I was running on 10, Note that there was 2 in the accumulator and 1 the external cooler and 1 in the lines.... stock pan....