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Good morning guys... I've got a 2001 LeSabre with an L36. I've done every type of search possible looking to a solution for this horrible squeal. I've replaced the pcv assembly with a Dorman #47033 (pic attached), removed and cleaned the throttle body, sea foamed the UIM through the fuel pressure regulator, and the squeal is still present once the car warms up. I remove the oil cap and the noise goes away. The car has 138k on the clock and runs like a top otherwise. While searching this particular topic I've seen that there are plenty of people with this problem that have replaced and done everything I have yet the problem remains.

http://www.dormanproducts.com/p-11529-4 ... origin=YMM

TIA for any recommendations you guys might have

Check to make sure you have both O-rings installed. There's a black o-ring that goes on the PCV valve itself, and the orange o-ring mates to the housing that the MAP sensor attaches to. I can almost guarantee the o-rings will be your problem.

Jfridge92 wrote:Check to make sure you have both O-rings installed. There's a black o-ring that goes on the PCV valve itself, and the orange o-ring mates to the housing that the MAP sensor attaches to. I can almost guarantee the o-rings will be your problem.

When I originally inspected the pcv area both o rings were present and in good form. Just in case, I installed two new o rings that came with the kit. New o rings, pcv valve, spring, and top that the map sensor clips into.

If the O-rings are installed correctly, the only other option would be a vacuum leak at the UIM gasket there, or it's also possible that the end seals on the LIM didn't set in properly and are sucking in air on that side. Those are really the only spots I've experienced that will cause the "shrieking" around the PVC side. When you pull the oil cap off while it's running, does it kill the engine/have a really strong resistance when trying to pull off the cap?

Jfridge92 wrote:If the O-rings are installed correctly, the only other option would be a vacuum leak at the UIM gasket there, or it's also possible that the end seals on the LIM didn't set in properly and are sucking in air on that side. Those are really the only spots I've experienced that will cause the "shrieking" around the PVC side. When you pull the oil cap off while it's running, does it kill the engine/have a really strong resistance when trying to pull off the cap?

I sprayed brake cleaner around the entire UIM including the pcv housing and throttle body while the car was idling and there was absolutely no fluctuation in idle speed or hesitation of any sort. So there are no leaks present based on this test. The squealing isn't coming from the pcv area, it's coming from the rear of the motor where it mates to the transmission. Based on my research, this is one of the most common areas the motor pulls air from. The crank shaft seal. When I remove the oil filler cap, the noise stops and the car idles smoothly. It doesn't die or hesitate. ...and yes, there is a substantial amount of resistance when removing the oil filler cap.

Gotcha, I was assuming since you said you had a leak in the PVC area that's where the leak was. If you're getting a good amount of resistance to pull the oil cap off while it's running, you've definitely got a sizeable vacuum leak somewhere that's allowing the crankcase to create vacuum. I can't say I've had problems with the crank seal, so someone else will have to chime in about that, but a leak that big should be detected by some carb cleaner.

Jfridge92 wrote:Gotcha, I was assuming since you said you had a leak in the PVC area that's where the leak was. If you're getting a good amount of resistance to pull the oil cap off while it's running, you've definitely got a sizeable vacuum leak somewhere that's allowing the crankcase to create vacuum. I can't say I've had problems with the crank seal, so someone else will have to chime in about that, but a leak that big should be detected by some carb cleaner.

Thanks for your input