NOISEY 98 olds LS - OIL pressure?

Good afternoon,
This last weekend I bought a 1998 Oldsmobile LS with the 3.8. The car was actually owned by a 72 year old reverend and had some recent work. The tires are new and brakes recent. I paid $750 for the car knowing that it had a noisy lifter. The car drove for about two hours to get it back home and everything ran great. Perfect Car.

The problem is that the noise is starting to sound like a bearing thud but when you rev the RPMS up you can hear what sounds like rod noise as well but the bearing goes away. The oil in the car looks thin like 5W.

I took the car to a mechanic that I know and after looking it over he called me back and suggested that the oil pump was worn or that I should change the oil. He also noticed that the upper plenum (intake?) was brand new. He said that perhaps there was a problem with it recently and coolant contaminated the oil.

Tonight I plan to do an oil change with a mix of 10W40 and 20W50. I think that if the noise goes away I will look into doing the pump.

-Does anyone have any ideas? I dont want to do the pump if the main crank bearings or rods have a problem. The pump and front cover look like a pain.

-Shouldn't my Oil light be on? If pressure is low enough to cause any engine noise I would hope that the dash would light up.

I would first check to see if the lamp lights when the key is first turned on,then do what the machanic suggested.good luck with the car and many happy troublefree miles.

Tonight I changed the oil with 20W50 and removed the belt off of the crank and there was no change in the noise. If anything the engine was quieter and you could focus on the noise better. It does sound like it is coming from low, center of engine and goes from a Mid thud to light and very fast increasing with engine RPM acordingly. I am inclined to believe it is the pump or something driven direct off the cam.

Can an oil pump sound like this?

Never heard any oil pump make a noise as you describe. I would get a mechanical gage on the oil press. sender port and see what the op actually is before doing anything else, as your mech says coolant may have damaged the bearings.

Good morning,
I found someone on craigs list selling a 3.8 engine out of a 1999 Pontiac Bonneville located the next town over. He wants $300 for it and it has 75,000. I think I may consider buying the engine and doing a swap.

It worries me that with 140,000 miles the current engine may not hold up even if it is just an oil pump. The cost of replacing the pump and front seals if fairly high anyway.

For $300 I think its worth considering, any thoughts?

I would not suspect just a pump failure, never saw this on a newer 3800, remember the other engine is subject to the same intake/coolant problem yours had.

$300 is fairly low,I would want to hear that engine running before buying it.

Rather than an engine swap, it may be reasonable just to drop the pan on the existing engine and remove some bearing caps and take a look first. If the con rod bearings look bad, you may get away with just replacing them and polishing the crank journals with fine emery cloth. This is easier than swapping an entire engine.

Thank you. I am going to run seafoam in the intake and in the oil just in case it could be carbon or bad passages. I still dont have an engine light alerting low oil pressure. I have coils and wires sitting around that are brand new, I may try these just in case ( cant hurt ). I have to pull the plugs and see what they lookl like.

After the seafoam I will have to change the oil again so it will be a good time to drop the pan and look. I am thinking that it could be a rod because the 20W50 didnt seem to do anything to affect the noise.

Worst case scenario I get no where with it and have to go with the engine swap.

*note* The car was owned by a 72 year old preacher and I dont think it ever saw 3000 RPMs. That is why I am hoping it is a severe carbon problem.

Does anyone know the steps for replacing the rod bearings? I cant seem to find any online.

Check autozone.com, repair guides, this is usually not a job for a 1st timer, measurements should be taken of the crank journals, step one. On top of you still do not know what is wrong!

I went straight through the car Saturday night.
-Seafoam oil, gas, intake -Via brake booster
-Fuel injector cleaner
-Oil flush, with Gunk high mileage flush and 1/2 can of seafoam prior (wanted to make sure oil galleys were clear.
-Oil change, changed out. Oil looked awfull but thats the flush. Original oil looked pretty good. Used 10W30.
-Plugs (had original Itaniums) originals looks great but had very small tips. Looked like it was time.
-Plug wires, wires on the car were carquest and took forever to get off, the metal contacts each needed to be removed from the plugs with pliers.
-Coil packs, original packs were badly arcing

Result = Car runs great but still makes noise.

I agree that I need to diagnose the car better before jumping to any conclusions. I may just have a stuck lifter or something simpler. I just want to be prepared. I watched a lot of YouTube videos with cars that have rod bearing problems and the sound of the engine is similar.

I read that if I drop the pan I can feel the rods for play. This may be a cheap way to see if something is wrong with the rods.

Can anyone confirm this and to how much play would be reasonable?

I am going to try to get the car looked at tonight.

I just dont want to drive it too much in case of further damage and I haven't registered it yet. It runs perfect other than the noise.

I wanted to take a second to thank everyone for your input. I have always had great luck with this site.