Two problems with a 1992 Grand AM SE

[kathodos]

I purchased this car used in July 2005. It had about 116,784 miles when I purchased it and it has roughly 118,000 as of 9/15/05. I recently had the vehicle serviced at a local Midas. One of the many issues I had when I brought it in for service was that the "low coolant" light was on even though it had plenty of coolant and that the check gauges light came on every now and then. When I picked the vehicle up from Midas, the coolant and gauge warning lights were off. However, as I was driving it home, the "check oil" and "check gauges" lights came on. When the car was in for service, I had the technician perform an oil & filter change, so I know for a fact that there isn't something wrong with the oil. I believe that the problem may exist within the vehicle's computer, hence the "check gauges" light turning on. However, I also noticed that the oil pressure gauge behaves erraticly. Sometimes it functions properly, other times it hardly moves, even when I have the engine up to about 3k RPMs.

I related this problem to a co-worker who's husband is a mechanic, and they both believe that I might have a problem with the oil pump. I believe it's a problem with the vehicle's computer since the "check gauges" light turns on and off. If there was a problem with the oil pump, wouldn't the service technician noticed when the oil change was performed?

What is your opinion: oil pump, computer, or both?

My other problem is in regards to when the vehicle is first started. I put the key in the ignition, turn it and the car starts fine. However, about a few seconds after the vehicle is running, I hear what I can only describe as a "grinding" noise coming from under the hood. I noticed that when I start the car and have the interior lights or any of the other electronics on, the lights and display on my stereo appear to dim. It's very brief and you wouldn't notice it unless you really watched for it, but since this is an older car, and my primary mode of transportation, I am concerned that there is yet another problem brewing. I have a basic understanding of automobiles, so one day I popped the hood and had a friend start the car for me. The sound appears to come from the serpentine belt area, perhaps a problem with a gear or pulley.

Does anyone know what could be causing this "grinding" noise?

EDIT: This vehicle has the 2.3L Quad engine with an automatic transmission, if that helps.

[skibum1111]

Your oil problem has nothing to do with the computer. The check gauges light is coming on because its detecting low oil pressure, which means several things could be wrong: Bad oil pressure switch, cost about $20 and fairly easy to change. Excessive gunk built up in the motor, a shot of seafoam should cure that just follow the directions. Bad oil pump which means the oil pan has to come off, the pump on your car is driven directly off the crankshaft and is a messy but not too dificult job to do.

As for the grinding noise, its hard to diagnose that without hearing it, but I would suggest the timing chain guides and tensioner are worn, most manufactures recommend changing them around 100k miles, depending on the quality of maintenance that has been done and what kind of oil you use. I have used synthetic oil in my 95 gt quad 4 and when we changed the head and headgasket the timing chain guides showed little wear. I have also seen chain guides with conventional oil that have shown some extreme wear, but the oil hadn't been changed on that car very often. Hope this helps you out, any other questions let us know here, someone will have an answer for you.

[kathodos]

but I would suggest the timing chain guides and tensioner are worn, most manufactures recommend changing them around 100k miles

How much would something this usually run? Also, what kind of risk would driving without getting this serviced pose? I use the car primarily for work, which is a 16 mile round-trip, 6 days a week.

[MacCardwell]

I also believe the "dancing" oil pressure is probably the sending unit.
The grinding noise may be brushes or armature noise from the alternator on cold startup, since the electrical items weaken.

[skibum1111]

Worst case, and keep in mind this is the worst possible scenario, the oil pump could fail (if thats the problem) resulting in a lack of lubrication and destroying the engine bearings. Timing chain (again, if thats the problem) could possibly break, resulting in bent valves (quad motors are an interference fit meaning that the pistons will hit the valves, bending them and possibly putting a hole in a piston) and a large bill for tearing the motor apart and fixing it. If its the belt tensioner, the belt could come off, resulting in no charging of the battery and no ac as the water pump is run off the timing chain and the power steering is run off the intake cam. If the grinding noise is the alternator, the alternator could fail, resulting in the battery not being charged.

I would start with changing the oil pressure switch, that was a problem I have run into in the past.

[kathodos]

I used both of your posts to compile a "to do" list for the tech at Midas. Please let me know if this is adequate:

- "Check gauges" & "Check oil" lights on
Oil pressure gauge "dances"
Inspect oil pump.
Inspect oil pressure switch.


- Brief "Grinding" noise on start-up
Inspect timing chain.
Inspect belt tensioner.
Inspect alternator.
Inspect timing chain guides and tensioner.

I will pick up some of that seafoam product tomorrow. I was also checking out another product called "Mystery Oil." Anyone ever heard of it? Would it be appropriate for use on my vehicle based on the problems I've been experiencing?

[MacCardwell]

I think your tech will be able to check your true oil pressure and sending unit. The timing components won't be readily accessible without removing cover(s) and gaskets. However, if the grinding noise is easily reproduced, he may be able to locate the noise source with a mechanic's stethoscope and probe. (Commonly used in shops).
Good luck

btw - I personally wouldn't spend my money on that "mystery oil". I see it at all parts places.

[Frazhe]

I agree with MacCardwell don't waste your money on the mystery oil. I too have used the seafoam product and it works great. Also with a high milege car a synthetic or synthetic blend would be a wise investment. When I change my oil I substitute a quart with the lucas oil stabilizer just for safe measure, an dit seems to smooth the idle up a little too.

Hope this helps even if just a little-Zack