Offside Inner Wheel Arch corrosion Hole

[Guest]

When I got the LS in Autum 2018 I had the car dinitrolled. I was told at the time when I asked what her general condition was underneath (even though I had seen a lot of the  underneath with a fine toothcomb and noted she was very good) I was told on the inner offside wheel arch there was a pin hole in one of the seams that was sealed by seam sealant. In fairness I took that at face value and duly cleaned up the minor stain on the boot inside, cure rust treated it and them hammerited it. All was tickerty boo until I was encouraged to give the sunroof drains a clear out as a result of another helpful post on here. I checked in the rear boot for the pipe work and found a bit of stain in the offending area, then with blunt screw driver pulled out a blob of sealant and exposed the hole and surrounding corrosion. I was not best pleased, if same had been brought tp my attention at the time, the requisite work would have been carried out. Now by chance I can save that location by the offending rotten  metal being removed and replaced by welding a plate and then anti corrosion treating it. It is booked in for this work tomorrow at a different garage. OK the rot has not been caused by the original garage but their lack of care/common sense could have eventually LED this car to be written off prematurely.

BTW those buggers are paying for the work.

[ambermarine]

Hi Simon

This was a common fault on the early Mark 1 and both of my inner wheel arches rotted from the inside out when the car was less than five years old .The rust showed itself on the rear door enclosures at the top facing edge and was very difficult to access ,I eventually flooded the compartment from the oblong bung at the bottom of the wheel arch on the chassis.

This did the job in stopping further rot ,I think the problem occurred because the  metal on the wheel arch was so thin it was penetrated by stones and the rot set in beneath the underseal  as water got though the holes and collected in the inner cavities.

I have had no issues with my mark 4 I think that they improved the areas that were suspect. 

[Cotswold Pete]

Simon,

I had way worse on  my Mk4, both rear arches, and on both sides, ended up with holes the size of my fist.

Mainly caused by lack of the latex like coating used on the arch.

I would prod the whole of wheel arch with a bradawl it will let you know where the rust has really got to, as I only picked up on the problem when I noticed a small (and I mean small) amount of water near the SATNAv disk holder.

This was my posting with the horror show photos MOT Pass and Swiss Cheese. I had four holes this size once I had poked every part for the wheel arch.

The metal was not that thin, but seems like little punctures all over the arch were just eating away in many places, and so best to be brutal cutting back to clean metal.

[runsgrateasanut]

I put this link in a thread a few years back. Didn't try it myslf but may be a good idea for the doors although there is no sign of rotting out - yet.  Not like on all my previous Mercedes which were terrible for this.  Fact is that the rubber by the rear Windows is getting rather old and cracking thereby letting perhaps more than a little water to enter.   Daresay can buy new rubber but at what cost and haivng to remvoe the door cards etc is a pain.  Offside rear door handle is a bit stiff and can't lower the window completely to apply any oil. Spring/Summer - another maybe!

https://www.youtube.com/watch?v=uHMpJebGx_g&utm_source=LexusOwnersClubUK&utm_medium=ForumLinks

[Guest]

Peter, I will take your advice thankyou. What a shame these brill cars can have such a basic achilles heel that would cost bugger all on the production line to prevent. Was your holey issue in danger of going into failed MOT land. For me I have had the hole above sorted by use of removal, plating and welding. I will at the same time make sure all areas of both wheel arches are checked and sorted if required. This LS is so mint inside and runs so fantastically it would be a shame to let it go because of this weakness. 

[Cotswold Pete]

14 hours ago, Wisemonkey said:

 Was your holey issue in danger of going into failed MOT land.

I had a level of water ingress in the boot for about 12 months, and one day after driving for 4 hours in driving rain, thought, 'This is not right' as a lake had appeared.  So this was about two weeks before MOT, I decided to have a look, thinking a few small holes and a bit of Isopon and I would be sorted.

Problem was that - as you can see from photos on my Cheese post, I ended up with a big job.  I did consider a plate weld, but Isopon is good and strong enough for even a larger repair in the arches, as it does not impact any structural integrity.

If you look at the thickness of the rubbery coating Lexus put on it seems that it is about twice as thick on the inner side of the arch, compared to the thickness near the arch rim.  That is just a robot (or something), programmmed a little oddly.

Once I had repaired the gashes, plenty of rust proof primer, then a grey top coat (or two), and then a good going over with Waxoyl. 

The problem that will (IMHO) alway lurk is where the boot floor meets the arch, as this is where the mud a crud gathers behind the read mud flap, so I overlayed the external surface with a bit of extra Isopon, but I will be jacking the car some time this year (2 years since I did the job), so give it a clean and re-waxoyl.

MOT due soon, only thing I know about is front side light bulb has failed (though they are as dim as can be), so hopefully car will be fine for its 20th birthday.

I do take a view that 99% of cars over 20 years old will have rust somewhere, at least with the LS400 it's weak spot is easy to get to and sort, unlike my wifes Jag (since scrapped) that need the sills re-welded for the last 3 years of its mere 13 year existence. My Omega in days of old, at 10 years was beginning to rust like a Steam Engine at Barry Island Scrap Yard, and every now and again I see Omegas that look fine, until you look carefully at their rear arches for that sign of bubbling, which means the rust has already done a lot of damage.