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2009 Gen 2 C4S with 49,000 miles with a cherished history. Literally everyone told me not to worry about rust proofing and to do nothing as Porsche treatment from factory was good enough. This week, I've removed under trays etc with a view to inspecting and treating, and, well, there's rust everywhere, even in the bottom of the sills. Its all treatable, but not if i'd left it another year...
This looks like it was a DD in the winter. My 07 C4s with 67k on it has some build up on the block and the oil pump was a rusty mess but had nothing like this on the under carriage. My Indy said what they saw on mine is typical of being stored in a garage they gets some moisture.
Wow where do you live? When the layers of steel start to delaminate, that's a real problem.
I just had my undertrays off recently and other than some collected dirt and gravel, there was no rust at all. I guess your pics are a good lesson to other owners who live in the rust belt to remove the trays and rinse the bottom of the car occasionally if they're going to drive on salted roads.
Good news from the (wonderful) guy that is doing the work :
Don’t worry, I would say if I thought if wasn’t OK! It probably looks worse than it is. The rusty thing on the left hand side of the photo is a sill tray retaining fastener, all of which are very rusty but there functional strength isn’t impaired. The blistering is just the blanket sprayed seam sealer coating that the water has got behind which is being pushed out. To rectify this we will locally remove the coating around the failed areas, you will find just outside of this the condition will be perfect. We will then prep the corroded bits, apply a rust converter/epoxy product (Dinitrol RC900) then along with all the other bits will brush apply a specialist black epoxy resin paint, which is an exceptionally good primer in these situations. Once dry we will seal the area with a brush-able seam sealer. Followed by the various Dinitrol waxes. Also shining a light inside the sill through one of the vent holes and peering down another reveals the internal condition to be excellent. We will of course wax inside these cavities. (Some of these may indirectly vent internally behind the carpet etc so some wax solvent/vapour may be able to be smelt inside the car for a period of time but given the potential vulnerability to corrosion i would recommend treating them)
Have you stripped the plastic undertrays and sill covers off yours though...? More looked perfect before those came off...
The trays have come off for various work... suspension, clutch, and a front end accident many years ago. While I personally didn't inspect.... I would have hoped the shops would have said something to me. Anywho.... I have taken the wheel wells out for suspension work.... rear bumper and side panels off for three plug changes..... everything that I could see looks totally fine. I put 197K on my 2000 Boxster S.... only had a rotted heat shield. The next owner replaced the blown engine and heavily modified it for track use.... we kept in touch as he wanted to know how new etc... parts were... and he had no issues.
While I will admit Philadelphia area is not a heavy snow climate, our roads are constantly salted during the winter as the temps almost always drop below freezing... with preemptive brine applied before rain/snow low temp events.
Maybe car stayed a while on sea side with previous owner ? Or was partially flooded with salty water or driven on salty roads and never cleaned.
Mine is 200k kms daily driven in Germany and no rust at all... to be on this state of rustyness with fairly low mileage on a modern premium car, something wrong probably happened ^^
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997.2 Underbody Corrosion
