98 Grand Am 2.4L DOHC - Oil Pressure Problem

Hi all.. I have a stumper for you all. Hope you can help as at this point I could have put a used engine into this car for less.. LOL.

Anyhow.. Here is the story.

We bought this wonderful 5-speed standard 2.4l car a few months back. It RUNS wonderful and looks great. Never seen a newer looking used car.

Thing is I noticed that the engine seemed a bit noisy.

  1. Our favorite Mechanic said he was sure it was the Timing Chain so we gave it to him to pull apart and fix. He determined that it was NOT the timing chain creating the noise.

  1. Okay.. It was time for me to do some reading so I spent days reading about other peoples 'noisy' engines and because this is an overhead cam engine and it appeared all the noise was up in that area (to me) I once again pulled apart the timing (myself this time) and continued on to pull the cams so I could inspect them. Sure enough there was some minor scoring so I changed them and put it all back together again.

Guess what.. still noisy.

Well.. whats next. I wondered what the oil pressure was like. Seemed hard for me to believe it could be bad as the light wasn't on and it ran VERY well.. but to be sure I pulled off the pressure sender and installed a mechanical tester to test it.. LOW PRESSURE. Almost none to be more exact.

  1. Back to the mechanics.. this time to have the oil pressure double checked (just in case my guage was bad) and if so to replace the oil pump. Well, the oil pump was replace and the opinion of this mechanic (and a couple of others) was that the main bearings were fine and not the cause of the low oil pressure.

What is left? Why would the mechanics agree that it appears the lower end is getting pressure and the upper end isn't? Where could it be losing the pressure? It leaks NO oil.. The whole system is VERY clean so a blockage seems very unlikely (have already tried flushing it).

Any suggestions? The last mechanic had one, but I would rather hear from the experts on here before I tell you what it was..

Thank you in advance for ANY and ALL suggestions and comments.

Reply to
amcswebs
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It was common for this engine to develop problems with the oil drain back valve that is located in the engine block. The small ball that is in the valve would often beat out the seat until it was enlarged enough for the ball to get stuck in the seat. At this point, you have full oil pressure to the bottom of the engine, but no oil pressure to the cylinder head and camshafts. When you take an oil pressure reading in the head (which is where the sending unit is located), you will see no pressure, but if you tested the pressure at the oil filter (which can be done with the proper adapter) you will see full pressure. You will need to pull the head and extract the drainback valve in order to confirm this, but I suspect this is what you will find. Install a new one, and you should be good to go.

Of course, the valve is cheap, but getting at it is expensive.

Ian

Reply to
shiden_kai

I assume the oil pressure is no more than 5 psi. Check the pressure relief valve.

Reply to
=?x-user-defined?Q?=AB?= Paul

Cam shaft was scored? Likely chewed the bearing surfaces out of the head. No cam bearing inserts, right?? Had a Peugot 204 go that way as well as a MitsuShiti 2.6. No way to make it build oil pressure without replacing the cyl head. On the MitsuShiti that was combined with a total engine rebuild (more like replacement) after it spun a main bearing. I managed to salvage and re-use a FEW parts of the original engine in the replacement block.

Reply to
nospam.clare.nce

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