Porsche Enthusiasts Club Forum

That is an impressive set of photos. Nobody could be left in any doubt about 'what lies beneath'!

I remember it well, but didn't take too many photos (shame), a lot of yours are almost identical to what I did. You certainly can see the repair to the suspension mounting point from inside. It also shows the gauge of the metal brackets as well, they are pretty robust, it's the thinner sheet stuff that is the real problem.

OK, managed to take some pics of the underside of the car. Couldn't get the camera in to the hole in the door but managed to get one shot through the offside door hole.











I suspect mine will be similar to the pics linked by EDDIE, although not sure the offside rear suspension mount area is that bad? Outside rust is only visible near the front and rear wing quarters. I'm planning to open up the sill myself at the weekend to see what's what inside. From looking through the door holes, it didn't look too bad, if I'm honest.

I understand that it's an instant MOT fail if there's visible rust/corrosion anywhere within a 30cm radius of the seat belt mount points, which there is in my car but I'm skeptical that there is rust actually affecting the seat belt mount points directly. All shall be revealed when I open up the sill on Sat.

Hi, good photos, but a bit confused about the first one, it is marked up as offside front, but looks like offside rear as I can see the front wheels (turned) at the far end of the shot? If that is the worst of the corrosion and your internal shot shows that some wax may have been sprayed in the sill at some point, I would think it might be in better condition inside than perhaps we think?

The suspension mounting area just looks a bit scabby. What I would do is get a rotary wire brush wheel on an electric drill and take off all the underseal to really assess what the condition of the metal is. Use goggles! It won't take long, then have a poke around with a screwdriver, etc.

The nearside sill looks a bit scabby at the front, so again I would remove all underseal and poke around, Surface rust displaces the underseal and makes it look bad, so it is always best to get down metal to see what's what.

Another thing you can do to help assess the problem is simply push on the outer sill panel to make it flex, if you hear it creak and crack and bits are falling off inside, you know you have a problem. If it all sounds fine it might be OK... Also, look for small pimples in the underseal coating on the face of the sill. If you have these it could be the rust inside is now eating through. Best to take off the underseal in those areas and poke around. If the screwdriver goes though - well it's not good!

If you are opening them up I would suggest that you cut a small area in the sill rear quarter panel, not the main sill under the door. As then you can see the end of the inner sill and look inside. It would be a shame to open it up to find it's not too bad and that it doesn't need too much work. Do not cut any higher than the underseal line on the body.

Best of luck, happy rust hunting!

Thanks for the tips! Pretty much a newbie so all your advice is very welcome! The first pic is a very close up shot of the area hidden by the jacking beam in the 2nd pic, it makes is look weird due to the close up...and yes, that area is the worst of the visible rust underneath and outside when poking about near there, the metal/paint crumbles.

Because this appears not that bad, I'm thinking may be it is a good idea for a proper body shop to do this. If the whole thing was rotten, then I wouldn't have minded doing some of the work myself. I will see tomorrow after assessing the extent of the issue.

Was quoted £1300 for just the offside sill repair not including cost of parts, from a body shop nearby.

It will be quite a labor intensive job but £1300 is way over the top. I would personally get stuck in, you'll find that once youve cut all the rot out it will looks much more achievable. The rust is a great creator of fear and when its gone the job seems much less of a handful.

Did you say this a daily driver? Or are you able to do it over a week or two?

Broady is right, £1300 for one sill does seem pretty excessive. At £50/hour that would be 3.25 days (26 hours)...When I got my sills done I admit that I did all the cutting out and prep work which did take a day for each side. But in my defense, I am not a bodywork technician, the car was only lifted on standard jacks, and I don't have too many tools...and I like long tea breaks!

Then I got a mobile welder guy in who charged £20/hour, each side was done in 4 hours tops. So, welding costs £80.

I was there every step of the way to ensure the job was done well, safe and strong. I certainly couldn't leave it and come back later, but then I kinda watch all my vehicles MOT tests too...weird?

Where you based?

You can pull the bung in rear that MIT give a slight insite.

Best off getting mobile phone in the though the vent in the door jab. Take quite a few pics with differnt angles to get it right.

If you can cut and drill out spot wields yourself and have weilder come to car oem sills would be cheaper.

You can remove the door and brace. However if you jack the car up and sit it on the wheels drive on to ramps or something. There's less movement.

However if the rear needs rebuilding then it could get pricy and quatily can vary.

Couple of pics of where I'm up to in the offside sill...





Seems to me, just the corners were affected and that some sill work must have been done previously, with the flaky top paint coat in the first pic?

Hi, the bottom of the wing is not a load-bearing structure and rust there will not (or should not) cause an MOT failure, so don't worry too much about that at the moment. The area between the door sill and the rear quarter is definitely what your MOT tester has failed the car on and I would suggest you cut around there to have a look inside:


You don't have to cut too much, see photo. You will then get a much better idea of the extent of the problem. It's going to have to come off at some point anyway...

With a mirror and a torch you should then be able to see most of the inner sill.

You could do a similar test cut at the front of the sill too, if required.

Post any further photos as you proceed..

That area will be much wider spread then that, looking at how flakey the bits are. Remove the paint till you see clean metal

More pics!





I opened up a little bit of the offside sill and noticed quite a bit of surface rust on the outside of the the inner sill and inside of the outer sill. Whilst cutting in the front wing area of the sill, noticed that it had quite a bit of filler. It has definitely been repaired previously. Am guessing its pretty recent. Anyway, I have decided to change both the outer sills and have ordered those along with the lower quarter of the rear arch from porkaparts. Now am hunting for a SH offside front wing as I might as well do this properly. Any ideas what causes this rusty sill problem on 944s? Just thinking about a design fault really and what can I do to prevent this from happening in the future? What is the actual design fault here?

Hi, yes plenty of surface rust there, but not too much going in deeper. The metal still appears quite thick where you have cut. However, you have elected for a complete refresh so all the rust will come out - and that's a good thing!

Not sure there are too many design faults here. The front wing lower section gets road crud building up as it is a natural shelf for it behind the plastic wheel arch liner. It is difficult to remove this build-up unless you pull back the liner and wash it out.

Sills (in general) will rust as water (such as condensation) tends to flow down to the lowest point. Porsche designed in many drain holes, but not all the water gets to them, and if they get bunged up they are useless.

Bear in mind that we are talking about cars that are 20 to 30 years old now, how many other models from this era are still on-the-road? Although the fully galvanised approach Porsche took has really helped, it does break down eventually - hence our problems today. But, if you get a car that was Dinitroled or Waxoyed from new (and maintained) the extent of the problem is much much less.

Ok, was very busy during the work week and so didn't get much work done, however had some time to work on it today, so thought I'd update this thread and ask for some advice.

The sills and rear quarter pieces arrived from porkaparts during the week, and I opened up the outer sill. Here are some pics!







First of all, how does the inner sill look? Do you guys think it needs to be replaced?

At the rear it looks a little rusty but haven't done anything to investigate yet to see if its just surface rust. May just need a patch in the rear area there where it looks particularly bad. Also, the marked area in the first pic appears to me like a weak point of these sills for rust...I noted quite a bit of moisture there. The way Eddie has tackled that area seems quite good!

Front wing is shot near where it joins the sill...loads of filler there! See below!



Next is nearside sill...

This is is not that bad at all! Phew!

Anyway, because I have the outer sill for both sides (and welding will be cheap!), I will change both the sides for future peace of mind. Unlike the offside, the front wing is clean and the rear of the sill looks manageable too. Now, I need some advice. I guess I need to sand the inner sill lightly (and get rid of the surface rust). What should I treat them with before welding the outer sills in place? Is there a paint or anything that I can do to preserve the inner sill's integrity? I would guess I need to do the same for the inside of the new outer sills.

One thing I noted was the outer sill metal was quite thick on both the sides compared to the porkapart sill?

Design fault... Could be where the sill over lap and are spot wielded. Wielding will often start to rust first.

Air flows though the door and sills but you Very rarely get rust in the doors.

Inner sill I would clean up and paint, replace what can't clean up. Heard the inner sills are desgin the way they are so they act a set way in a crash? so mit not be a simple as a flat sheet. im sure there was someone offering diy replacements. Try and paint both sides, and get some cavity wax inside behind the inner sill.

Paint the inside off the new sills then cavity wax them after.

Are you leaving the top off the sills in and placing up to the stone chip line?

The rear will be the worse section to do. There a small drain hole there as well

Best off luck looks like you got it under control