98 2.4L DOHC Low Oil Pressure STILL

[amcswebs]

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.

2. 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.

3. 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.

[GTP Dad]

Usually on most cars the oil pressure is determined by cam bearing clearance. If the cam bearings are worn then the pressure will be too low. I would pull the cams back out and replace the bearings. Also, make absolutely sure that the oil pickup in the pan is not too close to the pan itself. This can cause low or no pressure. A bent pan or a damaged pick-up can cause this.

[amcswebs]

Originally Posted by GTP Dad

Usually on most cars the oil pressure is determined by cam bearing clearance. If the cam bearings are worn then the pressure will be too low. I would pull the cams back out and replace the bearings. Also, make absolutely sure that the oil pickup in the pan is not too close to the pan itself. This can cause low or no pressure. A bent pan or a damaged pick-up can cause this.

Ah... it would be something to look at, but in this case, the cam bearings are built into the housing and solid on the Camshaft itself... The problem remains the same with both the OLD and the NEW camshaft/housing/lifters and are NOT replaceable or changeable... Is it possible that it is the problem? YES, but it is unlikely that both are bad in the same way.

Any other suggestions?

Remember.. Oil appears to be delivered to the bottom end just fine.. but does NOT make it to the Top end...

Glen.

[GTP Dad]

The only other possibility is that the pressure relief valve in the oiling system is stuck open. This would account for the low oil pressure even though you have a new pump.

[amcswebs]

Originally Posted by GTP Dad

The only other possibility is that the pressure relief valve in the oiling system is stuck open. This would account for the low oil pressure even though you have a new pump.

Yup.. all the troubleshooting steps say that is all that is left as well.. but guess what.. the old one was good.. the new one in the new pump.. also good.

Here is a new question then... On the Quad 4 you would remove the timing chain cover (well a mess of stuff first) to get to the timing chain.. BEHIND the timing chain there are a number of gaskets.. There are a couple behind the plate that holds one end of each cam shaft.. Another down by the water pump (probably).. There is even an oil seal in there around the crankshaft if I am not mistaken..(with a cover holding it in place)..

IS it possible that if this oil seal (or one of the other internal gaskets) were blown out that the oil would circulate to the lower end, but then lose pressure inside the timing assembly (thus robbing the top end of pressure)?

Glen.

[gmack221]

I had a 95 quad 4 (2.3L) DOHC (alot like the 2.4L) thought I had lifter noise, went thru the top end, nothing changed, got a cheap oil pressure gauge from autozone hooked it up, showed low oil pressure, replaced the oil pump, no change, got my buddy thats a GM mechanic to check the oil pressure, it was bouncing all over the place on his gauge, he told me I had a bad rod bearing, so I tore it down, sure enough #rod bearing was gone, crank was shot, #3 was going. Rebuilt it myself, had the machine work done, put about $800 into rebuilding it, once I got the cams timed right it runs perfect. Were there any metal shavings in the oil or in the pan when you changed the oil pump? That was my first sign of trouble. Hope its not so for you, but the song has a familiar tune.

[gmack221]

oops, rod #2 was bad