Sill Corrosion

[jonm]

Hi

My 2001 IS200 has rust bubbling on the rear part of the near side sill, just in front of the rear wheelarch. I've owned the car from new, and it has never been damaged in this area.

I was surprised and relieved that it got through the MOT recently with no advisories.

Before I start trying to eliminate this rust, has anybody else experienced this and how did you deal with it? I am guessing that I remove the plastic shield in the front of the wheel arch, but do I need to inject the sill with rustproofer once I have dealt with it from the outside.

Looking at the workshop manual, it seems there is a big box section just inboard of this area, and the suspension trading arm locates on this. So is the sill corrosion just cosmetic?

Any thoughts or advice great fully received.

[ChrisIS200SportTTE]

It's very common and normally it's rusting from the inside out. It's a poor design, the area in the rear wheel arch just in front of the wheel just collects water. Ive had the same problem on both my IS's.

[ChrisIS200SportTTE]

Not my pics but saw this on FB the other day. Might give you some idea of what's going on and how to fix it.

[jonm]

Chris

This is very helpful. The pictures seem to confirm that the structural member is actually the beam behind, as I suspected.

Now that the weather is improving I'll remove the wheel and plastic shield, and do some digging. Does the water come from the rear wheel, or is it draining from the main sill or another area? The car is normally parked on a slope with the nose higher, so water may be draining back into this area.

I am rather surprised that if this is a common problem that there is not more about it on the forum. Because this area has a rubberised finish under the paint (to stop paint chips and corrosion from the outside), corrosion from the inside can be hidden until it is quite advanced. I noticed a slight bubbling, about the size of a 10p coin, a couple of years ago but thought it was just a paint chip. Now I wish I had investigated it and dealt with it before it spread.

But - the car is 14 years old, and this is the first significant thing I have had to deal with. And I am old enough to remember how fast cars rotted in the 1970s.

I'll let you all know how I get on with my repairs, but in the meantime any more comments on how to deal with it would be much appreciated.

[chazzito]

I had this identical problem, and I too wish I got to it sooner than I did before it got quite big. My problem was about the same width as in the picture but lower down and underneath a bit.

I ended up grinding the surface down to bare metal to uncover how far the rust spread, then literally pulled all the rusted metal away just with my hands until it got tougher, then cut away with a dremel a little further beyond the rusted metal to make sure I got everything. I painted it with kurust just incase, then cut a new piece of metal larger than the size of the hole that I cut into the sill. Drilled a hole in the centre of the new piece of metal and screwed in a self tapper so that I could use that as a handle and (very fiddly) angle it and slide it inside the sill through the hole. I then took it to a garage and got it welded for £20 (you have to remove ALL rust otherwise when they weld it will just chase it further and further and wont be a clean edge, nor will your cut piece of metal fit anymore). All I did then was angle grind the weld joints flat and flush with the body, fill it with P38 body filler, Sand, Prime, sprayed stone guard underneath (the soft protection paint), Colour matched spray paint over the top then lacquer on the top of that and looks brand new. I plan on spraying water proofing wax on the inside of the sill through a hole ill make in the rear wheel arch to protect it further in the future.

Sounds like a lot but overall it took me about 10 hours and cost about £50 so cant complain.

[gdh300]

A job for the summer on my old girl, this.

Oh, hang on; it is summer!

[Wootty]

yep very common design fault.

mines has this done on both sides and my mates blue is200 which is 3 years newer than mine has also had a plate welded in exactly same area.

luckily mines black and doesn't show up that badly.ive waxoyled all the sub frame and upper shock mounts too as they were looking a bit sad.

get it done before our lovely lovely winter approaches, (which is normally about 7 months of ******* weather).

[istanbul05]

Mines got a few small bubbles only looked today after reading this thread,dark grey so hardly noticable.I'm pretty sure I read somewhere that best way of preventing this to drill a small drain hole underneath each sill.. Makes sense if it's a hazard for gathering water.

Think I might try this and pp it with some waxoyl to slow the process.

[gdh300]

I've just had my man (thanks Richard) cut out and repair my rotten bits, back for it's respray next week. Which means I guess I'm committed to the old girl for a bit longer, but that's no hardship! Next job will be cambelt and I think auxiliary belts...

[jonm]

Thanks for all the comments. Really useful to find out that other people have had similar problems.

As a result I decided to tackle the two 10p sized bubbles on the nearside sill. The corrosion had spread under the stone chip paint, and I ended up with a 7cm long hole in the bottom of the sill. Fortunately the damage was quite localised, and the rest of the sill appeared sound.

The hole was big enough for me to investigate inside. It seems that there is a design problem, with any moisture in the sill or in the C-post behind the rear door collecting in this area, with no obvious drain hole. The problem is made worse because I park on a slope, with the rear of the car lower than the front. It also appears that there is inadequate rustproofing in this area, with little if any wax inside this part of the sill. There is wax further towards the front of the car, and I think that when the car was manufactured the wax was injected through the hole sealed with a rubber plug below the front edge of the front door. So the wax may not have reached the rear of the sill.

(There is another rubber plug inside the rear wheel arch (hidden behind the rubber dirt shield) but this appears to give access to another box section, which is an inner upper sill rather than the lower outer sill.)

My local bodyshop welded up the sill and painted it for £200. They reported that the damage was very localised, and the rest of the sill was sound. My first spend on the car in 14 years apart from routine maintenance - amazing! I then rustproofed the area (see below).

So - here are my recommendations for IS200 owners.

1 - inspect the rear of the sills for signs of rust bubbling under the paint. Look about 10 cm in front of the rear wheel arch.

2 - if you find any bubbling, don't touch it until you have checked your anti-corrosion warranty. Mine had a 6-year warranty, but someone on this website said they thought they had a 12-year warranty. If you are covered, take it to your local Lexus dealer for inspection. If you do investigate it yourself you may invalidate any warranty.

3 - if you are not covered and you have more than minor bubbling, the sill may be corroded and need welding. It may still get through the MOT because the stone chip paint masks the extent of the corrosion. But the area is close to the rear jacking point.

4 - I would recommend ALL IS200 owners rustproof this area, either after welding or for prevention. I drilled two holes in the bottom of the sill about 50cm apart (can be done with the car jacked up and supported), and also used the hole with a rubber plug below the front of the sill. Drill the holes just outside the flange. No point in drilling the other side of the flange as well, because it is the same box section. I used Dynax rust treatment, because it comes in a 750ml jumbo aerosol with a 60cm probe to get into box sections. Dynax came out well in a survey a few years ago, and I have used it a lot on my classic car. The probe makes it much easier to apply than Waxoyl, and the fluid seems to be more effective.

While you are at it, lift the spare wheel cover in the boot, remove the rubber plugs in the bottom of the wells behind the rear wheels, and spray the area with Dynax.

It took me less than an hour to treat both sills, bot a bad investment to extend the life of an amazingly reliable car.

[cskelton86]

Does anyone know if replacement sills are available? I spoke to Lexus and they told me the entire rear quarter panels, but are there any other specialist suppliers?

[ColinBarber]

1 hour ago, cskelton86 said:

Does anyone know if replacement sills are available? I spoke to Lexus and they told me the entire rear quarter panels, but are there any other specialist suppliers?

I don't believe so. You either need to purchase the quarter panel and cut off the bit you need, or fabricate from sheet steel.

[whiteman]

I can say that once the bubbling has started the rot has already set in, I did a repair a year ago on a 03 IS200, didn't look to bad with a few bubbles.. the sill is covered in stoneguard so it takes for ever for it to bubble but when it does it will definitely need the rot cutting out and plating up.. there is a thread on here somewhere about this problem,  Every IS I have seen needs this doing after a good few years. when they inject the sill with protection it seems it does not go all the to the rear of the sill.. 

[cskelton86]

22 hours ago, ColinBarber said:

I don't believe so. You either need to purchase the quarter panel and cut off the bit you need, or fabricate from sheet steel.

That's a shame considering how common it is nowadays. I may look at fabricating some as I need to do both of mine anyway.