Propensity For Ls400S To Rust

[Newbie1]

Hi all,

I'm on my LS400 hunt and being patient, having checked out a few cars. I inspected a 1995 UCF20 with 150k odd recently and was surprised to find rust at the rear of the sills at the base of the wheel arch and a bit of crustiness along the sills generally. Looking into the engine bay and I noted surface rust on the trumpets and a few other places. Otherwise, this car looked very well cared for with good service history. The point of this is to ask my learned friends what their experiences have been on rust in the LS400. Was this just an unusual example? Or do the LS400s rust like any other 1990s Japanese car?

Thank you.

[ambermarine]

The mark1 was the worst model for rust I suffered the problem when mine was just six years old it started to come through the wheel arch's shoulders where the back door closes and had started behind the plastic insert that runs down to the cill,The plastic peice was siliconed on and had chattered away the paint this then quietly rusted away from the inside out.We remided it about three times in the 16 years I had the car by flooding the cavity with waxoyl.The other problem area was the forward part of the rear wheel arche's ,they are very thin and the metal is easily penetrated with stones coming off the wheels the rubber compound hides the corrosion and water gets into the cills from this area and rots the cills from the inside out.I had the last 6 inches of cill welded in the last couple of years I owned the car and she was 22 years old then. The top of the rear wheel arches where the protective plastic strip fastens was another area that needed regular maintanence because of rust ,basically because it was a water and mud trap ,the protective embellishments have been improved upon in these areas through the development of the car and by the time the Mark 4 arrived they had virtually eliminated the problem areas.I went under my Mark 4 as soon as I could after buying it and sprayed Dinitrol on every area that could be a potential problem I used 4 cans ,so that was virtually the whole of the underside from the start of the rear subframe including the subframe and the area where the metal meets plastic around the rear Bumper.If you spray all leading metal edges on the extremes of the body it will protect the welded joints and flanges from rust .

[Newbie1]

Thank you for an informative post. The plastic guards/inserts seem to be a double-edged sword, being a good protector for the first few years and then being the devil incarnate if not removed and regularly cleaned.

This helps to confirm my view that I will look for a Mk 4, helped by my dear wife extending the budget a little! I would be interested to hear from anyone who has experience of rust issues with a Mark 4. I do appreciate it depends on many things i.e. care, the locality of the car, whether rust protection was applied (interestingly I've not yet seen an LS400 where someone has taken the time to waxoyl the car, unlike many other older cars I've seen or owned.)

[Cotswold Pete]

The mark1 was the worst model for rust I suffered the problem when mine was just six years old it started to come through the wheel arch's shoulders where the back door closes and had started behind the plastic insert that runs down to the cill,The plastic peice was siliconed on and had chattered away the paint this then quietly rusted away from the inside out.We remided it about three times in the 16 years I had the car by flooding the cavity with waxoyl.The other problem area was the forward part of the rear wheel arche's ,they are very thin and the metal is easily penetrated with stones coming off the wheels the rubber compound hides the corrosion and water gets into the cills from this area and rots the cills from the inside out.I had the last 6 inches of cill welded in the last couple of years I owned the car and she was 22 years old then. The top of the rear wheel arches where the protective plastic strip fastens was another area that needed regular maintanence because of rust ,basically because it was a water and mud trap ,the protective embellishments have been improved upon in these areas through the development of the car and by the time the Mark 4 arrived they had virtually eliminated the problem areas.I went under my Mark 4 as soon as I could after buying it and sprayed Dinitrol on every area that could be a potential problem I used 4 cans ,so that was virtually the whole of the underside from the start of the rear subframe including the subframe and the area where the metal meets plastic around the rear Bumper.If you spray all leading metal edges on the extremes of the body it will protect the welded joints and flanges from rust .

Did you give things a good clean down first.

On the web site I found seems like for just over £30 for 4 spray cans - a worthwhile spend.

My Mk4 looks okay but I may have a look see behind the plastic strips - but certainly seems to me that the undercoat protection on the Mk4 is way better than even my old Mk2 (which has only a few small bits of rust around indicators (stone chips I guess)

[ambermarine]

Cotswold Pete

I was fortunate that my Mark 4 had only done 19k when I got it but it had been steam cleaned underneath as it does not take long to mess them up with road filth. The important areas are the body itself and the fastenings from subframe to body and that immediate area any where that dirt and moisture might collect. The subframe on the later Lexus LS400 went tubular and consequently there were fewer webs for muck and the likes to dwell in.One area that is suspect on the Mark 4 (which was pointed out by my friendly MOT inspector who is also a petrolhead and loves classic cars)is the chassis just in from the front subframe fixing point going out to the cill ,this area seems to get missed when the car is undersealed and only as the block colour of the car as paint protection ,the weld spots were just showing rust, the area was quickly treated and sprayed with Dinitrol.Trust me, it will be the best £30 Quid you've ever spent.

[lordturns]

My MK3 has a very badly corroded (dry rust) rear subframe and associated suspension components - it would suggest that the car had been stood for a long time seeing little use and this may explain the low mileage when I bought it at around 65k miles and now on 72k. Also there is some rust on one of the front wings and also a little on the rear quarters that will need repair. I would also be curious to remove the plastic sill covers that run the length of the car including the wheel arches to see what is going on behind them. Other than that the condition of the panels is very good with no rust whatsoever.

Having owned many BMWs with the aforementioned plastic sill covers, upon removal they have often yielded many a surprise with rust and fortunately this has been superficial, therefore easily treated and protected.

[Cotswold Pete]

Cotswold Pete

I was fortunate that my Mark 4 had only done 19k when I got it but it had been steam cleaned underneath as it does not take long to mess them up with road filth. The important areas are the body itself and the fastenings from subframe to body and that immediate area any where that dirt and moisture might collect. The subframe on the later Lexus LS400 went tubular and consequently there were fewer webs for muck and the likes to dwell in.One area that is suspect on the Mark 4 (which was pointed out by my friendly MOT inspector who is also a petrolhead and loves classic cars)is the chassis just in from the front subframe fixing point going out to the cill ,this area seems to get missed when the car is undersealed and only as the block colour of the car as paint protection ,the weld spots were just showing rust, the area was quickly treated and sprayed with Dinitrol.Trust me, it will be the best £30 Quid you've ever spent.

I would had a look this weekend has been dire.

So when I am sorting out my washer bottle float, I'll be having a good look about.

[Ruud]

I have also seen quite a few ls400's, mk2, 3, and 4 with rust near the top windscreen rubber. Not sure what causes that, apart from something hitting that area and not being treated.

[plastic orange]

Mine has some rust in both top corners of the window area - no idea why as the rest of the car is rust free.

I may bite the bullet and replace the screen and get it fixed next year.

Pete

[Parrot of Doom]

My mk4 has rust in the top corners of the front windscreen and on the offside rear wheel arch. There's also quite a bit of rust around the rear diff, where the brake pipes run. None of it is particularly serious, it's a 15-year-old car and I'm not all that concerned about keeping it cosmetically perfect. As long as it's mechanically ok.

One thing I have found is that any nuts and bolts under the car, if they haven't been treated beforehand, will be completely seized. The front strut rods had to be heated up and cut off they were that bad.

[ROYT]

Other places to check are just under the outside mirrors where the fix to the body and behind the steel trim around the windows.

This trim is held by welded studs which rust away and are not replaceable.

The complete steel edge and window surround are all one piece and will cost a fortune.

Try to get some Waxoyl or similar behind it.

When they rust through the trim becomes loose and a poor solution is silicone sealant to try and stick it.

[Newbie1]

Interesting that people are getting rust around the windscreen. Having restored a few older cars, I've always found that visible rust around the windscreen usually hides some ugly stuff beneath. Perhaps not so much with bonded windscreens but it would make me nervous if it was rust near the A pillar.

It looks like the same story with any car on British roads: get it cleaned and coated/injected with with waxoyl (or Dinitrol, which has lasted much longer on my old cars and tends not to crack and gather hidden muck like waxoyl can.)

Oh for a car lift. Axle stands on a beast like the 400 does not sound like fun.