Pontiac Repair: Engine Clatter, oil pressure gauge, timing chain cover

Question
Thanks for your prompt response.

I haven't noticed the oil pressure.  It's my daughter's car and I don't drive it often.  I don't think it has an oil pressure gauge.  I'm pretty sure the warning light isn't coming on, though.  I think she would have noticed and mentioned it.

If we did nothing, just let the problem continue, what could happen?  The clatter sounds bad but is any real damage being done to the engine?

If we decide to have the oil pump repaired, is it an major, expensive job?

Thanks.
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Followup To
Question -
1997 Pontiac Grand Am
2.4 four cylinder
Approx. 91,000 miles

We have a good deal of what sounds like valve clatter.  It's quite noticeable at idle but seems to diminish as engine speed increases.

It started after a repair to the serpentine belt.  As I recall, the mechanic replaced the belt tensioner, too.  We told him about the clatter and he said it was related to the age of the oil pump.  He said, the oil pump isn't delivering sufficient pressure at low speed to serve the new tensioner and that creates the clatter.  He said he could replace the oil pump.

Does this theory of the problem sound reasonable?

Answer -
Hi, it could be the pump. the oil pump screen could be clogging up. How is the oil pressure is real low?

Answer
Hi, jack this can damage the engine. Make sure it is the pump, befor you spin the money on it. Now why i say this, it could be the timeing chain and guides that is causing the noise. Now you going to say how am i going to check this. It might sound funny but here i go. Take a piece of hose put one end to your ear and the other end over the valve cover. you can hear the valve chatter. Do the same at the timing chain cover. This is to make suer befor you put 200.oo or more in it. And still have the same problem.