Thread: Leaking oil - is it the pan or seal?

• 1998 GTP
• 128k miles
• runs like a swiss watch otherwise - small (quarter sized) oil leak

I have a new pan gasket and I'm prepped to replace it this weekend. I've been told (at a local AAMCO) it was the pan gasket (I had it in for other work and they did a list of recommended repairs).

Before I go through the hassle of lifting the engine and unbolting the mounts etc, I want to make sure I'm not dealing with a leaking rear main seal.

I've been under the car, and the pan itself is soaked (all the way around). I've checked as well as I can with an inspection mirror to see if it's coming from the valve covers or somewhere else, but I don't see anything (major) above the pan gasket.

I've also added UV dye to the car, and it's hard to tell the source of the leak.

Anyway - any advice on how to differentiate between a seal leak and a pan leak?

get brake clean. (or engine shampoo)

clean everything off so that it looks dry.

run engine.

inspect for leaks.

I've taken the flex plate cover off and the flex plate is bone dry. Plus, the inside of the cover is dry too.

The pan was soaked. I've cleaned it off as well as I can - all the bolts are now pristine. I still don't see any leaks or any new oil. I put about an 1/8th of a turn on one pan bolt under the flex plate in the corner - it looked a little loose and was indeed looser than all the rest.

What are some other sources of oil leaks that I could be missing? I've been underneath my car for about 1/2 hour and just can't track it down

was the car running while you were under it?

You may have very well slowed the leak by tightening the pan bolt.

I've been under the car running and off - I see no leaks in either condition.

The side of the block above the pan gasket on the firewall side is wet - but I don't know if this is just old dirt or new leakage. I can't see any leaks below the lip of the valve cover (where I can look). I can see toward the corners and it looks "clean". I can't see in the middle due to a heater hose assembly being in the way.

There are sensors screwed into the sides of the block right above the oil pan - I presume these are knock sensors, but I have no idea. This sensor had oil covering it (the wire plug end had a drop or so on it). I've been presuming that the oil has been migrating up (like wicking or just splashing more or less), but it seems to be a lot to migrate up.

My car has had the recall fix - it leaked before and after this. Speaking of which - does this recall affect the front, rear or both valve covers?

One last thing: I keep my GTP in the driveway. It's a very sloped driveway (the steepest driveway I've ever seen). I've tried to mimic this condition when checking for leaks - I think it may be contributing the the condition.

I'm going to tighten the back valve cover (I can tell for sure the front one is fine) to see if I can reproduce a leak.

Originally Posted by 01GTP

Replace both of your valve cover gaskets and gromets.

This.

my rear gasket was leaking down onto the exhaust mani's.

Originally Posted by matt5112

This.

my rear gasket was leaking down onto the exhaust mani's.

While I can't say that the pan gasket is leaking, I can say that the firewall side valve cover is. Directly above the O2 sensor, the block is wet. Also, the valley near the intake is also wet. It looks to be leaking on both sides. Plus, the bottom of the cat has signs of oil on it (more VC leak evidence).

I have a new gasket and will replace this weekend. My guess (and hope) is that the pan gasket was never leaking and it's been the VC the whole time.

Worst case, I fixed one of >1 leaks.

I've replaced the back valve cover and grommets with a new Fel Pro setup. I can say for sure that the old setup was leaking - the old gasket was not sealing The gasket sealing surface was flat and compressed and didn't project onto the head surface like the new round one does. I venture to say that the new gasket is about 3/32" taller than the old one - the old one was more or less flush with the valve cover and the new one sticks out as it should (to seal against the head).

I'm going to replace the front valve cover gasket tomorrow - after the back one, this will be a piece of cake. Plus, I know that the front one isn't leaking (but I will replace it anyway).

Now that I see the setup I can also say that replacing the gasket without the grommets is worthless. The grommets provide the sealing force (they act a springs more or less that presses the gasket against the head). Without new grommets, the new gasket will be much less effective.

I don't know if the oil pan is or was leaking. But I know the valve cover was.

Thanks for the help guys!

My car got the recall fix and the front gasket and not the rear was replaced at the dealer. In addition, each of the VC bolts and corners of the replacement and different VC gasket was soaked in RTV.

The back gasket was original and orange. The sealing face was flattened and wasn't doing squat. The front gasket was new and black. It was a lot taller than the back one and also the same as the new Fel Pro (except it was black and the Fel Pro was orange like tha back one).

When I replaced the front VC gasket I didn't use any RTV and it's not leaking at all.

Once you take it apart and see how the sealing is accomplished, you can see that the grommets are what provide the spring sealing force and not the valve cover bolts (the steel collars prevent you from applying sealing force to the gasket with the valve cover bolts - the sealing force is ONLY applied by the elastic spring-like properties of the grommets).

Personally, I think they should be called something other than grommets as grommets imply little more than anti-chafing whereas these are integral to the functionality of the seal.

I did ZZP VC gaskets and reused grommets and they started leaking in less than 6 months.

I agree 100% with what you're saying.

Now I have felpro's with new grommets and refuse to buy ZZP VC gaskets for the two reasons you mentioned.