Access to Inside of Sills for Rust Protection

Hi Team, I have spent the past few weekends with the car quite high on stands so I could clean everything up and apply some Lanoguard grease/motorspray. In the process I managed to successfully plastic weld a couple of undertray cracks, strip/treat/paint the rear diagonals, replace the front diagonals and replace all fittings/rubbers/clips etc Where I got stuck was with the sill cavities. I pulled a rubber bung out from the rear wheel arch looking towards the front of the car and stuck my borescope down for a look inside the sill section, the first couple of feet towards the door were perfectly clean and looked new, then I spotted a brace/bracket so had to fiddle to navigate the camera past that and pushed it another few inches down, then I could see patches of rust staining. Couldn't see how bad it was (or even which way up my camera was to know if it was bottom or top of sill!), but figured it was probably located somewhere between the mid-point of the door and the end of the sill at the front wheel arch. I went to the front wheel arch and found another grommet/bung, but this one wasn't looking straight down in line with the inside the sill, it was at 90 degrees so parallel to the sill so wasn't sure... anyway I put my camera around the bend and pushed it into what I thought must be the sill trying to find the rust patches from the 'other end' but couldn't see them.. then I had another problem... the borescope camera was stuck fast!! Anyway, I have lost my borescope camera and 10" of the wire inside what I think is the still! In the end the wire snapped and its toast. Whilst underneath I have spotted 3 or 4 circles that look like bungs/grommets along the length of the car underneath the factory underseal... Is that what they are? Can I prise them out and get a view inside the sills, possibly treat the rust inside with something like Jenolite converter spray to delay progress, and maybe even retrieve my knackered borescope camera? Anyone removed those bungs? Is it a good idea? What can you get to if you do? What did you use to reseal them after breaking the factory underseal to get to them? Cheers, Simon

Modern cars (I'm including the 996 in that) often have multiple sections to the sill area, they are no longer just a single box, you may have been in a different part of the sill. If the circles are bungs not sure which bit of sill they'd look in to. Might be worth searching for pics of 996 shells to see if you can work out the construction, found pic of Skoda which shows multiple sill voids.

Ps I'm pretty sure you can look down in to the sill area if the rear side trims are removed

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Thanks yes I expect its a bit more complex than one long box section with internal supports, so my challenge is figuring out where the rust patches so I can inspect further and see if there is anything I can do. It may be that ultimately the only fix is to cut them out and replace, or they may be very minor so may as well try and get some converter/eater/sealer product on there to delay any of that being necessary. I looked at the 996 body manual and it does appear the grommets lead into the sill, but don't know which section or whether it will give me access to what I need to see (let alone what, if anything I can do about it!) Hopefully someone has actually done it so I can benefit from their experiences before I take a chance!

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I have .2 aero skirts on mine so perhaps I will get more access once I remove them in the new year, I'm planning on getting them off and checking a bit deeper but given the short days and holiday period I figured I would leave that till spring and probably get them off, see what is lurking and get it all fixed, resprayed and sort a few stone chips etc.

Couple of pics of sill areas!

Of the few cars I've seen which need welding it's been the front or rearmost 12 inches. Never seen one go rusty half way along. If the ends are in good shape I think it's very unlikely anything sinister is going on in the middle. Probably a tiny bit of surface rust where the sill mountings penetrate the sill

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Thanks for the pictures, it looks like there are two skins so the view from the rear arch bung looked like the bigger main section, and the one from the front where I lost my borescope camera looked more like that thinner outer channel. I'll probably be able to see more with the skirts off, there was definitely some patches I could see but hard to tell whether its just surface rust patches on the inside, or whether its gone through from the outside and needs a bit more work.

Seat out carpet back and you will see bungs as per picture above.

One of my sill ends has seen better days but looking inside it’s all galvanised grey and solid

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Great thanks, so bungs on the inside, sounds much better to remove them then disturb decent factory underseal under the body. I'll get the carpet out as is sometime smells a bit musty if left for ages so I bet I've had s clogged sunroof drain or minor water ingress in the past so something else to check and rectify whilst I am in there! Cheers.

A good thread here on the subject T Thread 'rusty sills' 6 Nov 2017 Hi guys, first post here been lurking for a while. bought myself a '98 c2 coupe in August as a bit of a project and something fun, shortly after purchase I took to my local trusted garage to have it looked over and get a heads up on any mot issues that would need looking at before it's test at the end of November so I could sort them in advance. One of the few issues my tester flagged was corrosion around the n/s rear sill that need investigating. this weekend I decided to have a proper look at it so I got the car up on ramps and removed the rear sill trims and the rear undertray and... Thomp1983 Replies: 55 Forum: Porsche 911 996 (1997-2005)