Heat mark on rear bumper?

Hi all, I've recently purchased at 2001 silver C2 (with GT3 bodykit) and have come across a bit of a problem which I'm not sure whats causing it. Following a recent longish trip (250miles to the lake district) I noticed a yellowish discolouration on the bumper about four inches above the exhaust (passenger side), its sort of circular in shape, and another patch just to the left of the number plate. At first I thought it might have been from the exhaust fumes etc, but on a closer inspection this doesn't seem to be the case. The bumper feels really hot on this point so I assuming there is either an exhaust or engine issue which has caused the bumper to overheat and discolour from the inside Has anyone ever heard of this of have thoughts on what might be causing it. Ive tried using a T cut to see if that removes it but to no avail, I'm a bit worried that it might need a respray but don't want to consider that until ive rooted out the problem?

Heat shield missing maybe? I had a fabspeed exhaust fitted recently and the box on one side fouled the heat shield very slightly. The guys at PCT who fitted it were concerned it may discolour the paint but never has and doesnt get that hot. Not sure it helps you though ... Regards Neil

Only hot item under the rear bumper is the cat's, the exhaust sit in the 'wings' rather than the bumper - they must have got very hot to penetrate the bumber metal itself and then the painwork. Suggest getting them looked at ASAP - potential fire hazard there IMO ... The cat's will also be destroyed if they got that hot, is the car running ok ? - a lean mixture will produce this effect as the cats are the first 'resistance' after the main exhaust headers/manifolds....

The car is running fine to be honest although ive only actually owned it for a couple of weeks and just use it to 'run around the doors' so to speak, I certianly havnt noticed any difference in driving/performance etc since this happened last weekend.. The pre inspection didnt come up with anything except slightly corroded exhuast support so im surprised anything going wrong,.There is no warning light on the dash either to indicate and cat problem! All I have done is put petrol in and drive it. Im going to the porsche dealer on saturday to get them to check it out for me, so are replacement cats an expensive repair?

Was that a Porsche PPI prior to putting on a Porsche Warranty ? Exhausts (incl the cats) are not covered by warranty anyway BUT if they have failed so soon after you getting the inspection done, then I see a strong case for them doing them FOC as good will ... Of course it may not be the cats at all, but I can't see what else it could be ... PS - can you post a pic of the discoluration - 'may' have a few other ideas depending what it looks like ...

thanks for the advice Richard, I will try and post a picture later on tonight, As i said in my original post is sort of a faded yellow, looks like a roundish water mark on blotting paper, just above (about four iches) above the passenger side exhaust, the second mark is to the right of this adjacent to the left side of the number plate which almost rectangular in shape but the same colour. Its not dead noticeable, but if you squat down and look its definitely there, the colour becomes more noticeable at the circumference of the mark. Its got to be heat related as i had just got back from a round trip to the lakes which was around 250 miles (almost a constant 4hrs of driving), and the bumper was really hot, especially where the patches had developed. On the down side it wasnt a porsche inspection but an 116 point essentials plus RAC one, before you laugh...the engineer was a porsche specialist who only inspects porsche models for the RAC and used to work for a porsche main dealer so i had every confidence, the catalytics were part of the check and came back okay. The only problem is that the inspection is only a guarantee of quality at the time of the inspection and does not mean you have any comeback with them if something subsequently fails after the inspection has been done. The warranty is the dealers own 1 year warranty (small independent dealership), but saying that a failure only one week after purchase would mean I have statutory rights under the sale of goods act and automatically expect a free repair regardless of any warranty or whether it was a consumable item.....or so I would expect...fingers crossed.

here are some pictures of the damage

and another

and another

Ah no - not's that the cats - it's in the wrong place - the cats are in the middle bottom of the bumper, not where the main stain in. Have you looked in the engine bay for a split water tank - the bumber is actaully plastic and it may be that the expansion bottle has split and leaked badly onto the bumper staining it - it's in the correct place for this - but I have NEVER seen this before I must confess. Also can't see how the water can get through the inner body shell and paintwork, it usiually just leaks into the floor if it has split ? I feel this may be an external blemish and has nothing to do with the internal workings / heat from the car ... Weird one ... :-(

ah there's one that side too - that rules out the water bottle ... ?! Let have another think !

Has the bumper cover perhaps been re-painted? May be bad preperation by the bodyshop.

strange I know! it seems kind of weird that the two stains are next to each other but i cant help but think its heat related after my long run last weeked, might give the t cut another go but the marks seem to deep to t cut out. Mark, thats a possibility, I remeber the guy who did the PPI mentioning about a bumper respray being done, but i assumed he meant the front one..nice bit of help there mate. I'll still get it checked out tommorrow at the porsche dealership as i need to get it booked in for a major service in anycase

ok - just checked for my own sanity where the cats are and they are where I though they were - last think to check which the first poster alluded to - check the cats have a heatshield on them each - look under the number plate and you will see the cats, feeling 'behind' the cats there should be a heatshield, a bobbly thin sheet of metal. If it's not there, then there is a possibility that heat is radiating up the 'inside' of the bumper and causing the heat spot... but it's a long shot. Unfortunately I think it's a surface paint problem - caused by a bodged repair I would imagine (not good to hear I know..) - I would take it back to the dealer and ask them to get it sorted using a Porsche approved repairer and get them to check everything else too (cat's etc) while they are there ...

The heat shield is intact as that was one of the first things i checked when i found the marks, you can feel it under the bumper and it seems intact where the 'stains' are, so i think its got to be the paint job which may have reacted with the high temperatures from the engine....what a bummer....then again, would rather it be a paint job than an engine fault[ ]