Wheel Arch Rust

banjo · May 9, 2015

Last weekend while I was cleaning my 1995 LS400 (after I had the cambelt, plugs/leads, drivebelt and water pump changed) I noticed some rust at the bottom of the driver's side rear wheel leading edge where it meets up with the cill. After I prodded it with a screwdriver a hole appeared. Filled the space behind the hole with Waxoyl then as a temporary measure epoxyed a piece of metal over the hole to stop water entering and covered that with some solid Waxoyl. I obviously looked at the rest of the wheel arch and there is some similar rusting at the bottom of the trailing edge of the wheel arch. I didn't prod this time as looks like the same symptoms.

I looked at the other back wheel arch and yes, exactly the same rusting. So do you get new arches or partial arches fabricated? or can you buy these items? The car has done 115,000 miles, I have had the car for more than 4 years and waxoyled yearly although it's impossible to keep any kind of covering under the wheel arches for long as it gets blasted off.

The car is completely rust free elsewhere and I love it to bits, best car I've ever had.

is200 Newbie · May 9, 2015

Rust .... Lexus .... naaa, must be mud!

Never seen one with rust before ...

Bluesman · May 9, 2015

One of the reasons can be because of previous accident damage that wasn't repaired correctly.

banjo · May 9, 2015

Accident damage, in both wheel arches? Don't think so! I'm the second owner, the first one had the car from '95 till he died in 2011 and I have all service records and work done. He was very meticulous and I'm sure it would have been recorded if there was any damage.

plexus914 · May 9, 2015

Same here - rust in the rear of the rear wheel arch ....both sides.......behind the mud guards (real "dirt trap")..........on the right side is a little hole already..........I choose the cheapest way for the repair, so I am gonna get rid of rust and get me some poor15 or Hammerite Rostblocker + fibre glass for the hole and after that I put some Hammerite Underbody Seal with Waxoyl on the whole wheel arch. To seal it up from the inner side (via trunk) I'm gonna get some Fluid Film (best stuff ever for cavities....=;o)...).

Bluesman · May 9, 2015

Accident damage, in both wheel arches? Don't think so! I'm the second owner, the first one had the car from '95 till he died in 2011 and I have all service records and work done. He was very meticulous and I'm sure it would have been recorded if there was any damage.

It was just an idea. Mike.

cilgwynbaby · May 9, 2015

My 1996 Ls400 has started to develop rust bubble on the passenger side rear wheel arch.I've owned the car for about 3 years.I'm wondering how much it would cost to get it done professionally,as I'm colour blind & cack handed.Any idea of costs involved?

Steve

Colin M · May 9, 2015

I have had rust just inside the rear arches on both sides on both my LS400s.

The worst areas were on the front section of the rear arches about half way up. When I removed the rust here there were holes that needed to be repaired. I used Petropatch, which is used to repair holes in petrol tanks, to repair the holes. It is easy to work with and can be used on rusty metal.

Once I had repaired the holes and removed as much rust as I could, I gave the area a couple of coats of Bonda Rust Primer (not easy to get hold of but really good in my experience and I have been using it for over 25 years now). This was followed by a coat of black Hammerite, the following day. A few days later, I put on a thin (4-5mm thickness) coat of Hammerite Underbody Seal, which I left for about a week so that it hardened up as much as it was going to do. It always seems to remain a bit tacky. Finally, I put another coat of black Hammerite on, so the tacky feel disappears and there is a shiny surface which makes it easier to remove any mud etc.

Once I had done the above repair work, I then got hold of a pair of LS400 front wing liners which I adapted to fit inside the rear arches. The rear arches are now well protected and I am not anticipating having to do any further work there.

If anyone is interested in fitting front wing liners in the rear arches, I did do a post and write up on the Forum on how to do this.

plexus914 · May 10, 2015

Banjo: "So do you get new arches or partial arches fabricated? or can you buy these items?"

There is no repair sheet metal for the LS400 available.

Some nice rear wheel arch pic I found that shows pretty good where to put the Fluid Film:

banjo · May 10, 2015

Thanks very much Colin, Plexus914 and Mike for your responses and info.

I'll go the Petropatch route with some metal. Will post on the club when I've completed.

I'm rather anal when it comes to stopping rust on my cars with a yearly Waxoyl and now Dynax S-50 spraying that I will repair this damage and attempt to stop any further corrosion.

Mybikes a cx500 · May 10, 2015

Banjo: "So do you get new arches or partial arches fabricated? or can you buy these items?"

There is no repair sheet metal for the LS400 available.

Some nice rear wheel arch pic I found that shows pretty good where to put the Fluid Film:

Seems a bit drastic, just to get some rust killer in place....

ambermarine · May 10, 2015

Banjo

The waxoyl also needs to go into the area that forms the cill, this area is accessed via an oblong rubber bung just forward of the start of the cill under the rear door arch.

Water that as penetrated the wheel arch runs down and settles in that area and the cill rots from the inside out.

I had to have both my cills patch welded though this problem on my Mark 1.

I halted the rust within the arch after its initial discovery when the car was 6 years old by flooding the wheel arch cavities with two gallons of waxoyl.

That treatment did not get into the cill area unfortuanatly and ten years later the cills rusted through.

If you remove the bung and feel around with your finger you will soon get the rust on your fingertip if it is present.

The cause of this problem was stone chips to the wheel arch that the underseal hid, the stone chips then rusted away undetected.

I patched mine with epoxy resin impregnated into fibreglass weave then undersealed.

Waxoyl within these cavities is a preventative measure and after the experience with the Mark 1 My Mark 4 got it straight away although it as to be said that the paint job within those hidden away areas is much better now.

ROYT · May 10, 2015

I recklessly drilled holes in the front of the wheel arch inside.

Then removed the 'kick' trim on top the sill and drilled a few more.

Plenty squirting of Waxoyl, then flat grommets to neatly cover the holes.

banjo · May 10, 2015

Thanks Ambermarine and Roy, will get to these areas now. I had a Vauxhall Senator back in '94 and I did this same as you did Ambermarine and flooded the wheel arches with Waxoyl from inside the boot which was fairly easy on that car which had a bad reputation for rusting wheel arches. They never rusted in all the 8 years I had that car. Should've been a bit more diligent when I first got the Lexus back in 2011, will correct that now.

steve2006 · May 11, 2015

I may have posted this before but here goes.

Every year after the winter I remove the black plastic arch trims and them clean them and the exposed arch, smear a good coat of grease on the trim and refit it.

I also ensure all the mud build up on the lip of the arch is removed.

Never had a sign of rust.

Malc · May 13, 2015

... seems to be rather too much worrying here guys .... our cars are 20 years old and the rust problem is just simply tiny tiny tiny .... any other car would have gone to the knackers yard by now with the rust mouse prevalent and taken over

Malc

SHELLDRAKE · May 13, 2015

They are good cars but remember--R.N.S.

lordturns · May 31, 2015

Hey guys,

have been reading this post with a great deal of interest - my NSR inner wheel arch is crumbling, there are now a few holes plus the subframe is in a poor state. The OSR rear wheel arch is not as bad although will still need work. The subframe was going to be addressed this year and never for one moment did I think that the wheel arches were in such poor condition.

Question is, can this be repaired/welded effectively or should I just cut my losses? car has done 86k miles, generally good panels, mint interior and mechanically strong (serviced by Japex). What do you all think?

Malc · May 31, 2015

............. any MOT Advisories about rust ?

Generally I would say repair it all ... 86k miles is insignificant in the life of a Mk3

Malc

ROYT · May 31, 2015

If the chassis is corroded through, unless it's localised and minor i would abandon it.

The wheel arches can be repaired, but if the inner arch is rotten as well it becomes a

big job.

Get a body man to see how extensive and widespread the corrosion is.

I broke up a series one with no corrosion anywhere, better than my series two and looks like

better than later models

ambermarine · May 31, 2015

Jeremy

If the inner arches are rotten its a lost cause,the cost of taking off the rear wing to get in there is prohibitive, you can bodge them from the outside face but they will continue to rot were you can't see.Thats not to say that the car will fail its ticket and may take ages to get riddled but its not something I could live with.

banjo · May 31, 2015

If the car is going okay then it's worth fixing the rust and your mileage is quite low for this car.

I bought some 1mm thick steel sheet on eBay (about £12), used some cardboard for a a template, and cut the metal to the template for both wheel arches. You can't do it in one piece for the whole wheel arch, so I've done in several sections. I haven't done the trailing edges yet. I've just painted them with Hammerite. My idea is to stick the metal to wheel arches and rivet in place, then paint using waxoyl underseal.

ambermarine · May 31, 2015

That will work for a time and will give the car a longer life ,if you are happy with knowing the rot is still going on and keep an eye on the cills it should be ok.

Colin M · May 31, 2015

It is difficult to make welded repairs to the inner arch partly because of limited access but also because the metal may well be too thin and/or too rusty to weld.

It is OK to cut metal sections to cover any holes by sticking/riveting them in place or using self-tapping screws. The holes I had were quite small so I used Petropatch to cover them (see earlier post). If they had been larger, I would have cut some metal to cover them.

Repairs like this are fine in the wheel arches because they are not structural but this should not be done on the sills/cills. These areas are structural and only welding repairs should be done here, preferably with the rusty section cut out and new metal welded in. If you just weld a patch over the rust, the area will continue to rust from the inside.

steve2006 · June 1, 2015

Prevention is better than the cure, I've mentioned this many times before but will again.

I clean out my wheel arches every year since I owned the car, the 1st time I did it there was a pile of crud all over the floor and now there is very little.

When the car is dry remove the black arch trims ( 4 self tappers) then feel around the arches loosening any built up crud with your fingers (take care here not to snag your fingers or use a stiff toothbrush),using a hosepipe wash the remaining crud from the arches and clean the area where the black trim fits over.

Allow to dry then apply a good coat of underseal behind the arch,apply a good layer of grease to the back of the arch trims and refit wiping off any excess grease.

I also take the car to one of those car wash places where it also washes the underside after winter to remove the salt.

I've no rust issues with the arches or anywhere else on my 21 year old car, the arches rust due to the build up of crud which contains plenty of corrosive road salt and when left causes the problems especially when it gets damp.