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Well today I discovered why my windows have been misting up.  I always assumed it was a leak somewhere and it turns out that rear wheal arches on both sides rusted through just where the sunroof outlet drops in.

I assume although I have been clearing out the mud from behind the mud guard, the rot would have set in before I got the car (5 years ago). Actual holes once I started poking about (not a good idea) about as big as my fist (jsut stuffed some bin bags in there for now)

So off to garage this week to find out when they can do some welding and hopefully not too big a bill!!!

Still better than my Omega, which at 10 years was falling apart big time with rust in rear arches all the way around..

The old lady is due for her MOT in two weeks, so hoping nothing else major going to crop up.

Still apart from usual costs (cam belt, filters, oil change, tax etc) so far this car has worked out costing me just over £800 per year (that includes cost of a new spring, the odd UCA and tie rod) which is a darned bargain.  

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I have an OEM inner tie rod for Mk4 right hand side if you need it.

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Never nice to find. So you removed the side panels in the boot and found the holes? Right where the drain pipes go through the floor on the sides? Just checking so I can check!

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What’s the “sunroof outlet”? You mean a drain tube exit? Behind the rear wheel?

Not heard of this before (although my windows don’t list up either).

Good practice to keep the wheelarches clean, especially the bit in front of the rear wheels where they meet the sill - big mud trap there

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45 minutes ago, cornershop said:

What’s the “sunroof outlet”? You mean a drain tube exit? Behind the rear wheel?

Not heard of this before (although my windows don’t list up either).

Good practice to keep the wheelarches clean, especially the bit in front of the rear wheels where they meet the sill - big mud trap there

If you look in the boot, where the tool kit holder is on off-side and where the SatNav is on near-side, you have the two black drain pipes with their 'rubber' holder, and the wheel arch is right there.  I though these were leaking into the boot, or the seal had gone, but that all seems okay there.

I noticed that small amount of water had been buidling up, and when I looked last night, I could see rust bubbles for about 10cm running up the inside of the wheel arch (a bit harder to spot where the Satnav unit is.  So I poked it and my finger went right through.  I then poked from the wheel side, and the metal wall flexed and then hey presto a hole about the size of my fist. All done in the dark with head-torch, so not sure how bad it really is, but it is not good.  Not sure if it counts as MOT fail (though even if not needs to be sorted).

At the weekend I will have a good look, and decide if it will be good enough to use mesh and filler to sort it out.  My concern about welding is that where the Datnav is, that has to come out as you do not want to be melting the cables.  But I am no welding expert, and thought would prefer it welded, I assume it is not going to be cheap, and given it is hidden repair, not going to affect the look of the car.

Hopefully the weekend will be dry and I can get a good look at how bad it really is, and hopefully not end up with holes as big as my hand.

Also noticed some bubbling rust on the bottom of the arch sills where by the rear doors, so need to check out what is happening there as well.

Because the car needs some other paintwork done as some point, it is the quandry of whether the old lady is starting to fall apart elsewhere, and what that means for the next few years ownership. 

I am hoping to keep this one for another 4 to 5 years at least, but have the missus saying she does not want to me start throwing money at the car having just spend £300 getting LS handbrake sorted last week (says she who has had welding on her 12 year old X-type for last MOT)

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So it would seem that the drain pipes blocked at the exit end (from road crud?) and the water backed up in the wheel wells. Sunroofs, more trouble than they are worth on an older car.

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10 minutes ago, Newbie1 said:

So it would seem that the drain pipes blocked at the exit end (from road crud?) and the water backed up in the wheel wells. Sunroofs, more trouble than they are worth on an older car.

Not sure if it is problem with the drain pipe blocked which over the years has caused this.  Once I get a chance over weekend to jack the backend up and have a darned good poke about, I'll know if they are part of the problem. 

For sure a heck of a lot of mud collects in the arch, especially at this time of year, and when look at how the back of back end of the rear arch is, and the way the mudflap creates lovely storage area for that mud it seems like a little design fault to me. 

I also wonder whether the boot seal failure you get, creates a lovely humid air in the boot which start the arch to rust internally while the mud eats from the outside. 

I would think when I got this car, the boot seal had been leaking for well over a year looking at the state of the spare.

Maybe we should build cars out of all this spare plastic we keep chucking into the recycling bins, then all we would have is cars falling apart when the UV light finally breaks them down:wacko:

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Yes sunroofs are always a source of problems - I drove one of the earliest cars (the one Lexus themselves have bought back) and it didn't have a sunroof - never seen another.

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Well checked the roof drains, and they are not at all part of the problem.

The drain drops out under the skirt of the rear bumper, and outside of the bulkhead, so there is no mud trap there.

Just need to get some mesh, filler and decent weather to fill the holes on both sides.

On the subject of sunroofs, had them in many cars, and only ever had a problem once with a Cavalier.  Looking at the LS sunroof it is a really tight fit (ie: well designed), so there is very limited chance of crud getting into the channels and then being washed down the drain. 

I suspect if you open the sunroof a lot, then general dust will stand more chance of building up to eventually get sluiced out via drain. The LS is fairly airtight, and when you close door you should see the sunroof lift by about 1mm, indicating the car is well sealed as is the roof when closed.  (Unlike the early new generation VW Beetle which was so airtight you really had to slam the doors shut).

 

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I used fibre glass kit for some holes on an old LS400 - its cheap <£10 and much easier to use than you think if you haven't tried it before.

May take a bit longer to set in cold weather though - best of luck. 

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14 minutes ago, DaKa said:

I used fibre glass kit for some holes on an old LS400 - its cheap <£10 and much easier to use than you think if you haven't tried it before.

May take a bit longer to set in cold weather though - best of luck. 

I did think of FIbre glass, but just bought some alu mesh, Isopon filler (which sets well at cooler tempatures).

Just got to hope the weekend will be dry, and then get set to work on it.

The gashes in the arch are about 6inches long (15 cm in new money), and about 2inch wide, so bigger than expected, so this rot has been going on for a while.

It looks like where they roll the sheets together when making the car at the bottom of the arch there is a small channel which is a b*gger to clean out so I suspect that has not helped, even though I have been cleaning the arches in the past.

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The weekend is anything but dry around here - a few inches of snow outside - and I guess it may be the same where you are.

I have done repairs in the area you mention on both of my LS400s. I thought about welding in a repair section but ruled it out, as it is a difficult area in which to weld and I thought the metal was probably too thin anyway. I used PetroPatch to make the repairs. It is made for repairing fuel tanks but can be used for bodywork repairs as well. I have found it easy to work with and it seems to have done an effective repair job on both of the cars.

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14 minutes ago, Colin M said:

The weekend is anything but dry around here - a few inches of snow outside - and I guess it may be the same where you are.

 

Snowy as you like, though melting now.  I was hoping to have done a bit of prep yesterday, but wind so bad, kept blowing the boot lid down on me (not nice).

Like you I assumed it is a difficult weld, and I would not be sure the welder had actually done a full seal. 

In the past I have let welders do their thing in boot of an old Escort, and Vaux Cavalier.  They were never watertight, so do not want to spend a fortune to find I would still have to get some filling done.

 

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It can be difficult to get a watertight seal when welding. After welding in any repair sections, I have always covered the welded seams with seal sealer to prevent water ingress.

Good luck with the repair, Pete, when the weather gives you a chance to do it. 

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This scenario occurred on my Mark 1 the skins on the inside of the mudguards are very thin and the stone chips piercing the metal are not spotted because the factory applied underseal conceals them .On my Mark 1 rust bubbles appeared on the wheel arches next to the seat as early as the car being six years old.

We pumped in gallons of waxoyl and that cured it for the cavities in that location but eventually ten years later the cills rusted through on the bottom and end of the rear door location both sides this became a mot advisory and required welding.

I thought the issue had been resolved by the time the Mark 4 arrived , but from your experience looks like another good looking at is required.

There is a rubber bung just inside the line of the cill at the rear in the chassis which if removed gives access to the inside of the chassis cavity.

Rubbing about inside  with your finger will feel any damp and rust, it is also a good access point to pump in waxoyl although this process for the whole of the cill is easier done by removing tread plates on the door cill.

As for the sunroof drains causing rot in the ventilation wells it is a myth ,they are designed to drain from there.

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