I drove my car today for about 3 hrs. and visited a friend. I was there about 2 hrs. and when I started my car it made a horrible tapping sound. It stopped after a few minutes but does it everytime I shut the car off and is louder and longer the longer I let the car sit. I also noticed the oil pressure dropped around 8-10psi idling and driving. The oil level is ok and the oil life indicator is on 18%. It's a '98 and I have only had it about 2 months. I haven't had to change the oil yet. Could a lifter or oil pump have went bad all of a sudden? The car runs smooth, no skipping or anything. Thanks.

 

Whatever has happened you should not drive the car anymore and take it in right away for repairs. It has starved itself of oil for whatever reason, Possibly spinning a crankshaft bearing. This could be one of the reasons why the pressure has dropped so much all at once. Is the car under warranty? Let us know what happens ok?

vetterdstr :cheers:

 

This is serious, I am sorry to say (especially since your car is no longer under warranty). Do not drive the car any more, but the noise means that damage has already been done. Your oil pump pressure relief valve has stuck in the open position, and you cannot build good oil pressure. The rod and main bearings that are the furthest downstream from the pump will suffer first. The bearings will overheat and disintigrate. One of the forum members with this problem found pieces of bearing materal in the oil pan. It is reported that this pressure relief failure is caused by inproper factory assembly using too much locktite (or some other similar sealer) in the area of the pressure relief valve. Good luck, but this engine is in for a major rebuild........Also, (for those of us who may have this problem in the future), tell us honestly, did you get a "low oil pressure", readout prior to hearing noise?


[Modified by Supercharged, 8:47 PM 12/24/2001]

 

did you get the "low oil pressure" warning on the DIC when you started the engine?

Here is what you should do:
1. continue to get opinons on your situation, mine is based on my situation, which involved a sticking Oil Pressure Relief Valve (with loctite). I finally needed an engine rebuild with new bearings, bolts, oil pump, lifters, pistons/rings, etc.

2. remove oil pump and inspect for stuck OPRV
3. remove and inspect lifters. Roller lifters are durable and may be O.K.
4. inspect oil for burnt, coked oil. you may be able to do this via testing. Dealer pulled the pan(s) and found coked oil on mine. They had to pull of the front sub-assembly to get to the pans though.
5. If you find burnt oil, a main bearing is most likely fried.
6. At this point the motor is disassembled and you are rebuilding the engine, might as well do the heads, cam, and headers.

To reference your situation to mine I'll recap what happened to my engine.

March 2001 cold engihe starts with "low oil pressure" warning about 1 out of 20 starts. I take it to the dealer but they are "unable to replicate problem"

July 2001 frequency of the zero oil pressure at cold start up is 19 out of 20 times and finally I hear lifter noise. Noise goes away after a minute and I drive it about 10 miles and get lifter noise when I start the car warm. Noise goes away, I drive home, call dealer the next day and have the car towed to the dealer. They want to replace the engine but GM tells them to replace the lifters and give me the car back.

August 2001 still getting the oil pressure warning on cold start up and often when warm. I can't get the dealer to look at the issue because the mechanics are on strike.

September 2001 while driving the oil pressure drops, DIC is in panic mode and issues multiple warnings. engine has oil pressure but extremely low like 9 lbs. Another flatbed tow to dealer. Dealer removes oil pans and finds coked oil and has no explanation. They also find the coked oil has clogged the oil pick up tube. They clean the pans, replace the tube and give me the car back.

BTW: from what I had read here, on the forum, I told the dealer that the oil pump was bad and it had a sticking OPRV back in July.

When I picked the car up I ask why they didn't replace the oil pump, they said it's not in the oil pan and requires more work to get to.

When I got home I found the car 2 qts low on oil and I called the Service Manager and ask why they haven't tried to fix the problem and why they won't look at the oil pump. He tells me he will call the GM rep and get back to me.

4 days later I'm in the SM's office with the GM rep. After an hour of me explaining things to them I tell them BTW since the lifters were replaced we (the service writer and I) have been tracking the oil consumption and it's used 2 qts in 2k miles. When the GM rep hears this he starts talking about piston slap and then I talk about piston rings and then the GM guy wants to bore the engine and hand fit pistons. He says while they are disassembling the engine they will check everything else (I had ask for a new engine) and make it right. I told them that was a good starting point and that when the took it apart they would find the OPRV stuck open.

When they took it a part they did find the OPRV stuck open, had red loctite on it, the #8 main was bad (furthest from pump). They also found the pistons to be under tollerance clearance by twice the tollerance. piston to cylinder wall tollerance is .002, mine was .004.

I'm not sure why they wanted to bore the engine and hand fit pistons before they took the engine apart, but I think GM was looking for fixes for the oil consumption issue because some of the ring replacements have not stopped the oil use and have resulted in some GM buy backs.

Not a good Christmas present, but you may not have done serious damage yet, and if so you have the chance the end up with a rebuilt 500 hp engine.




[Modified by Gary2KC5, 11:34 AM 12/25/2001]

 

I have noticed loud tapping at times also when I start my '01 on a cold morning. It comes from the right front of the engine, though I do not have any low oil pressure problems. It is about 43-44 when I start at idle. One time the car even had a diesal engine sound until it warmed up. After reading this post, it worried me and I just went and tried my car again. Hasn't been a problem lately. Could I just have had something clogging the oil flow that has now been cleared? Sounds like I need to get it into a dealer to get checked out.

Appreciate any thoughts.

 

Mine did the same thing!!!Sort of ,but I wasn't driving it when it happened.Got all my parts fixed under warranty,but I'm going to up-grade the oil pump to ARE high volume unit!!!!Hope you didn't do anymore damage to the rest of the motor!!!