Sill blister

[DavidL]

So I'm happily preparing my new wheels to go on and then spot a 10p sized blister on the drivers sill by the rear jacking point.
Bugger I thought, Didn't think I had rusty sills, they were treated to some S50 a year ago and there has been some remedial work to the front wings and a little to the passenger sill last summer. The rest looked fine.
Anyway I poked under the car a bit and that looks quite solid but when I poked the blister itself it weeped water which seemed a bit odd.
So what have I got - terminal rust (ok something that needs a bit of attention) or slightly dodgy paint prep (the lower panel was resprayed last year) or something else?
And what to do about it?

 

[sawood12]

Doesn't the sill stop short of the jack point? Like at the rear of the door line? If so it might just be the front of the rear wheel arch.

 

[cococola]

Ive had mine tidied up and it appears to look damp at the rear sill when the car is drying after rain (if that makes sense)I see the rear arch repair kits on ebay and wonder if they are worth a go maybe?

 

[Diver944]

ORIGINAL: DavidL

So what have I got - terminal rust (ok something that needs a bit of attention)

Unfortunately you won't know for sure until it's rubbed down and you can see [&o]

A blister that weeps water means the paint and stoneguard paint has come away from the metal, allowing water to get trapped behind. This could be a very early sign of corrosion coming through the sill and if you ignore it will only get worse. Best thing is to get it attended to asap whilst its still very localised and therefore very cheap

 

[rav]

David, My Dads Sierra had a blister that would weep. Once rubbed down it turned out to be bad paint prep.

Easy fix, no hassle. Wait until the warmer weather and get it sorted.

 

[peanut]

if like me you might not be able to attend to it soon ,you could brush a little sump oil/ grease mix onto the inside of the cill to kill the existing rust and prevent any further spread.

You can get access to the outer cill via the door jamb vent grille. To the inner cill via the rubber gromets along the inside cill under the carpet.

 

[pauljmcnulty]

It's not unheard of for water to get under the very thick stone chip paint on the sills, causing the same effect as rust coming through from the inside. It's not common though.

The simple way to tell is to take a look: pop the door pillar vent out and shine a torch down, or take a camera phone picture. If there's nothing bot a tiny bit of surface corrosion and lots of waxoyl, you're fine. If you can see daylight then you've not had your sills treated with waxoyl every year, and you need to panic. Most cars will have significant rust, but not through to the inner sills. At this point you can postpone the inevitable and get it fixed, or waxoyl like hell and hope it doesn't get worse whilst you save up.

If the area was painted last year, I'd have thought they would have advised you of any corrosion, and the options for treating it? You could go from new sills and proper paint on a fairly far-gone car for about a grand a side, to a few quid to paint over a few stonechips for cash. I'd want to know more about what work was done, why it was done and what you thought of the inside of the sills, before guessing what the cause of a small blister could be.

As I've posted here recently, RPM had two cars in when I was there. One looked pretty good from a few feet away, but once I saw under it on a ramp I got out very quickly. The structural parts were totally gone, and that on a car that sold for a pretty high price. The other has rust visible on every panel, it's visually the worst I've every seen. Yet, it's passed an MOT and will be run in to the ground over the next year or two.

944s corrode to a pattern, usually. If you're not treating the inside of the sills every year, or if you haven't even looked inside the sills through the very large and convenient hole Porsche fitted, then you will very possibly be getting a shock. If you don't keep on top of the very minor corrosion, compared to other cars of the same age, you will find an MOT failure and a very large bill.

 

[DavidL]

On reflection I would be able to see this from the door pillar vent - I'll have a look.
When I last put S50 in (about a year ago) the areas I could see (which would include this bit) looked fine but I'll have a poke about and see what there is.
Both sides were stripped and repainted last summer with minor issues corrected. They were under instruction to cut well around any rust they found before offering in new metal and I was happy with what they had done.
Ah well it isn't terminal and may be nothing at all - I'll get the body shop to have a look when I get the car back down on its wheels. Due a Bilthamber order soon so I'll include some rust stopper in it methinks.

 

[pauljmcnulty]

When I last put S50 in (about a year ago) the areas I could see (which would include this bit) looked fine but I'll have a poke about and see what there is.
Both sides were stripped and repainted last summer with minor issues corrected. They were under instruction to cut well around any rust they found before offering in new metal and I was happy with what they had done.

In that case it's surely only going to be paint on the outside bubbling up with water getting behind?

I can't see how a well-protected area of metal would have corroded significantly. In fact, there are people her ewith pretty rusty sills who've chosen not to cut metal out and replace, but rather to kill the corrosion and treat it every year. Assuming the strip, treat, and repaint was thorough, you should be in far better shape than most of us!

 

[colin944]

This sounds like a water blister to me. Can be caused by bad prep or even a tiny stone chip that lets water under the paint.It is a simple enough fix for a good body shop. You have to remember that the paint and stone guard in that area end up being more like a plastic coating than paint it's that thick.So a tiny hole in the paint will end up looking like bubble wrap.


see post below! He is 100% correct

 

[chrishak]

Whatever the cause of the trapped water - either rust or lifting paint, it is essential that you remove the paint, dry it off, remove any surface rust and put some neutraliser on it as soon as possible. If it's not rusty yet, it soon will be!