Panamera coolant cap details
 

Anyone have an image of the under side of coolant cap on panamera? I looked on mine the other day, and I could swear there is no rubber seal under the cap. Could that be wrong?
mine is 2011 PTT. Removed the cap, looked under, and see nothing but the plastic cap.
could swear other cars have a robber seal that helps keep pressure in system. if you have a picture, it will be awesome.

Here's one (aftermarket but looks pretty much/exactly the same) with a oversize red silicone o-ring. Coolant is leaking past the cap in ours for some reason...
https://cimg4.ibsrv.net/gimg/www.6sp...6758fb4422.jpg

my factory replacement has a black O-ring, but otherwise looks like the picture JZChen posted

Cool. Yeah, mine has that orange, but I thought there was another one inside the blue plastic. There isn't one in this one, so I guess I am not missing any seals.

If your seal leaks, try to rotate it, so when seal is made, it will be against different part of rubber and plastic. If that doesn't help, it's because seal is old and lost its elasticity. I am starting to suspect my cap, smell some coolant in engine bay, but don't see leaks. Will have to test the cap and maybe buy new one. Thanks again.

Sorry if I wasn't clear. Instead of replacing the whole reservoir with cap I've been buying various larger o-rings from Grainger and fitting them on a genuine Porsche (dealer bought cap).
https://cimg7.ibsrv.net/gimg/www.6sp...6620e59d17.jpg
There's just that one seal even with the massive o-ring it still bleeds out when I turn off the car. I suspect the coolant change kits enlarge the hole so the original o-ring doesn't seal well anymore.

Viteon o-ring on left, super oversize silicone o-ring on right:
https://cimg2.ibsrv.net/gimg/www.6sp...cbae429860.jpg
If not clear left part # 41KY31 right # 41UV37. The 41KY31 is a nice fit the 41UV37 is very (extremely) tight.

Same (Generic) cap is readily available all over the place I believe it is shared with VW, and possibly Audi. Hard to tell the difference among different aftermarket and even genuine Porsche I have to keep track of which is which. (Maybe I'll mark the original Porsche with a marker).

Lol, that's a lot of seals you got there. Do you go through many due to the leaking? Do you keep the coolant level at 0 (middle mark)?

Well, it felt like the original o-ring is not pressing against the wall to create a good seal, so I searched for a slightly larger o-ring. If you go to Grainger.com they come in packages and many I pick are the wrong size. (I'm actually more proficient at it so less packages with the Porsche, which is good because the Viteon rings were somewhat on the expensive side). The silicone one in that size is the smallest quantity package I could buy...

​But no I don't destroy them they just came in large quantities for the size/coolant compatible/temp range I needed...

Yes I add coolant every few driving days sometimes to above the mark a little.

Can you tell me where you got these multi packs of 41KY31?
trying to find a good decent price place to get a package of each, can't seem to locate. Thanks.

To update the red silicone one ended up warping it was just too big and I was opening and closing a few times each week to top off. I got them from www.grainger.com but not sure what you consider reasonable price. (I picked them up from the somewhat local store to save on shipping):

https://www.grainger.com/product/FABORY-O-Ring-41KY31

So you ended up using only one kind then? Cool. I'll check that out. Thanks.

I went back to the black ones because new red silicone ones were so big it was EXTREMELY HARD to fully close the cap. Then it would be similarly HARD to open. You can temporarily make sure coolant is not seeping past the o-ring if you are still concerned after trying the bigger black viteon ones. Eventually the red warped out of shape. Didn't want to start over forcing a new red one down....

I have two new aftermarket caps in stock. The Stant cap never came in, (I had ordered 3 different ones for free Amazon shipping, but they kept giving me a MotoRad cap instead of the Stant). MotoRad has 20 lbs pressure relief and the Gates has 22 lbs pressure release. I will try the cap as is and then switch to the viteon o-ring if I still notice a leak. Do you think 22 lbs is going to be too much pressure? I guess I'll be testing my JB Weld soda can strip holding power....

EDIT-. Disappointed with the Gates cap and viteon o-ring fit, (it fits loose vs Original Porsche), I stuck a new red silicone o-ring on and cranked it down. (41UV37 purchased from Grainger.com).

Well, I'm finally giving up on the idea that I can find an o-ring of just the right size to stop it leaking from the cap. I just placed an order at my local dealer for a new reservoir and new cap. I'm pretty sure it's leaking past all the options I listed, even the really thick one that was difficult to twist closed completely....

Just out of curiosity, how did you determine its the Cao that's leaking? Do you smell coolant? See seepage at cap? Thanks.