Windscreen scuttle advice please
Hi
Sorry all this is a bit of a long one - but life with a G is a bit of a never eneding story!!
I have had a significant amount of work done on my 85 300GD (many thanks for all teh advice greatfully recieved so far). Since a significant amount of body work and a full respray all done very well and to a high standard (not just my opinion - honestly) one area has remained a problem.
Despite having no previous rust on the panel, rust has developed along the joint seam under the windscreen. One attept to correct this has resulted in teh problem returing within 6 months. I was picking up a steering box from our frends at Malvern, and he commented that this was not an unusal problem on G's subjected to a lot of body work. Following his advice we drilled into teh scutlle from inside and drew a hot waxoil injector along it.
Whilst doing this a very limited visual inspection failed to see (endoscopic camera) any significant internal rust in this area (I assume this would not be the same area that the spindle go thorugh though as it has definately had wet carpet syndrome - cured ongoing with now 2 new sets of wiper spindles and parking down hill where possible!!
So where I am at is a choice. I want to get rid of the rust before we go trhough winter and have costed a proper screen out/ sand blast the rust out and seal the seam with correct flexible joint filler (to current merc authorised body shop standards (it looks like half the seem has no joint filler in it! currently). That's about £450.
Or to cut the offending panels off and replace with new as teh concern is (expressed by the body shop not me) is that the problem will just keep repeating. no my recollection is that whilst the outer panel aree relatively cheap £60-£90 each?? I am assuming if teh rust is that bad then the internal one will need doing and that one if north of £500 so we are looking at a potential £2k fix!!
So advice please. The original panel is solid - I know becuase I have worked on it and when it went if for teh second time and got acid stripped they confirmed only slight new surface rust. the windscreen revela is rust free, so that leaves potentially the area that the wiper spindles allow water ingress into, but there is no eveindence under the dash of rust or rust staining.
The waxoil will stop the water from leacing from the inside out, and flexible filler should stop it from the outside in, so even if the seam is rusting no water or oxygen means no more rust??
So put simply what would those with more experience do - believe me if I need to spend the dosh now and get it right I will, but I am not sure a full rip out and replace it is needed?
Thoughts??
Many thanks
Simon
I think you have answered your own question, there is only the two options, spot blast and epoxy prime, or replace the panel.
My G-wagen is just about the same and has the original paint on it, I have been doing some paintwork here and there as there were much worse areas. The screen surround was the least of my worries!
If it was my decision I would be cleaning the corrosion with spot blaster and MBX tool, epoxy prime the panel, then seal and painting over the top of that. I would be taking the window out as stated and cleaning up all the flange where the seal is, mines looks abit rusty inside as well. This could last for ever, or it could last a couple of years! but it would be my option as the other option f panel replacement would be scary, my old G needed that work carried out, so I sold it, to much for me to get involved in, financially and emotionally!
What I would be questioning is why has it rusted if it wasnt before! MB state when metal is exposed from the bodyshell you must prime it within 40 minutes or surface corrosion will set in. Or there maybe acid in the seam that has opened up the paint abit!
This is most likely due to windscreen seal failing, and thus corroding metal behind seal, unfortuately windscreen removal is the only way to check condition, though it may be a nasty sight there? Shouldn't cost that much for someone to remove screen they should be able to reuse old seal, if all ok?
Just make sure they use a spot blaster and mbx tool to clean it up and not a sander, sanding leaves the pitting in by only flatening over top of it, where as spot blasting and mbx hit the rust from above thus cleaning right into the pitted area.
Epoxy primer is the best, Mercedes research centre in Germany during the late unpleasantness with the 210 e-class carried out research into every product they could find in the marketplace to remedy the corrosion problems they were having and found that spot blasting and epoxy priming would last longer than anything else!
Epoxy primer can be sprayed direct onto the metal as it is an acid etch as well. If there is any pitting that needs body filled, it should be applied over the epoxy primer as this is the approved method. Not the "workshop" know how of fillering direct to metal as it will hold it back longer, thats hearsay! make sure they get epoxy on the metal no longer than 40 minutes after it is stripped out, i.e. not lying overnight in the paintshop waiting for someone to start it in the morning!!
Painters hate epoxy primer as its not easy to rub down, they are crafty at using two pack instead of epoxy as its an easier rub!! but thats not in your interest!
I hope this information helps, I have delt with rusty Mercs for the past decade and this is how we have delt with them!!
Rusty Mercs, not seen any of them......hahahahahaha ;)
LOL Gav, I think we have all tried to block them out of our memory, in fairness we are not getting any these days, 211 eclass onwards seems to be sorted!!
Oh, I also remebered, there was agreta post on here from Fixwin about how to deal with cleaning up and treating the windscreen seal for longevity and sealing purposes when putting it back in, it would be well worth finding out that info as well. Dont let them cut it out, my old G had a full missing front screen panel ecause autoglass had cut the seal/paintwork!
If it is acid dip still in there is can be neutralised with paint thinners so a good scrub out when exposed metal is there would be a good idea!!
Hi. Many thanks to you both on this. The screen seal is brand new and at nearly the cost of a screen your comment is spot on. Don't want them to get happy with a Stanley knife when a bit of para chord will do.
I have had a word with the body guy already and went in acting a bit dumb. He straight away suggested the spot blast as it removes all rust and emphasised the need to 'get it right' using correct sealers etc, which gave me some comfort. I will give him a bullet list of your combined advice under the guise of owners club best practice. He is taking 5 days over it, so the point about speed from bare metal to epoxy primer is a good one.
On the upside I can now fit my new rear view mirror and from the info Gavin sent me I can run to a new rubber roof strip and fittings as the owner before me has 'colorcoded' it and despite being sanded back it let's the front down.
The new body shop did a 420 SL for me 10 years ago. And when I last saw it a few years ago it was still spot on.
Here's hoping the shot blaster does not reveal a can of worms, but as I have said before given less than a year ago it was rust free, and the fact we have been able to internally expect the panel via the holes for wax oil injecting, I am hopefully!!
Thanks again guys for the advice
Simon
We are doing a stack of SL just now, we have had 4 in the past few months and one was a full restoration! we have just completed two older 1960 se as well. I think those SL would be a good investment if you had somewhere to store one!!
Quick update...
I am off to the body shop they have stripped the metal work back, but have found moisture coming from inside the seam - not sure how this fits with getting the epoxy primer (they mentioned this straight away as the only way to go!) on the bare metal within 40 mins - guess they will have to keep blasting??
Anyway they want me to have a look as they feel another pair of eyes will help them get to the bottom of the water source asap - and also give me a chance to agree to 'what next". My view is that either the top seal behind the roof rubber strip has issues - it's coming off anyway - or it's water that has worked its way in through the failed paint on the seam (needless to say it poured down for the 4 days prior to it going in) - Given we have seen into the panel via a camera when wax oiling it and there was no visible rust - and the screen is out and again no rust!
Fingers crossed and all that. If anyone has any other views on how water can get into this panel I will gladly hear them - for example as far as I aware it can't work its way back from the wiper spindles as that single skin Oh and there is no rust internall as we have had the glovebox and clocks out for a look.
Ta
Simon
Well pristine metal work (after a light sand/blast i.e. very surface) either side of the seam, but rust in the seam and it was/is damp.
They did not know for certain what sealer was in the seam, but it was damp, and coming away like putty (bondo??). Checked again and inside the panel is rust free - we drilled it to it from teh back to draw waxoil through - so the G is going in the oven for a day to dry it out.
Then they are going to reprep the area - i.e. attempt to get as far into the seam as they can with a fine blaster then epoxy primer it, seal with correct panel sealer and paint and then do more waxoil internally.
General view is we will be lucky to stop it re-occuring at some point as it is now in the seam.. The guys doing the job know their stuff though and are taking 5 days over it - fingers crossed and all that
Ta
Well thats good and bad news,
Is it coming in the seam at the screen where the inner and outer are spot welded together and running down into this. Or coming from a seam up where the screen panel to roof joins?
Hi Johnny
This has been a bit of a saga. My view is the original repair caused a known problem ref moisture penetrating the seam from the inside - The likely culprits just been the normal evaporation of wet carpets caused by general use and occasional dodgy wiper spindle seals - the repairers twice put metal washers on the outside despite being told to use fibre washers!!. Or perhaps they dropped one on this part of the repair as I saw it with the rest of the car prepped and this part had not been touched - so they may have rushed this bit
So we get a rust blister on a small (25mm) section of the seam. The first attempted repair confirms no other rust along the entire window scuttle - they acid stripped it and visually inspected all the seams/welds. They then did something in the repair that a) perhaps exasperated the mositure problem coming from inside - This is the bit Pete at Malvern G pointed out and resulted in the wax oil injection or b) cause the seam to fail (paint & joinnt sealer wise) along it's entire length.
So the bottom line now after restripping everything we needed to is no seam issues at the top of the screen. No issues on the internal part of the panel, just damage from water ingressing from the outside of the G through/into the open seam - which may have caused a permanent rust issue, or we may have caught it in time - something we will find out over the next 6-12 months.
Which is pretty much what I suspected all along!!
ta
Simon
I have attached a pic so you can see the extent of the first work - Overall they did an excellent job.. Just not sure they got after this 'fault' fast enough..
I really hope this elimates this as you have done some amount of work to this G, it would be terrible to see this wee bit being a constant nuisance!
I worst came to the worst could that full seam not be cut out and replaced with flat plate, therein removing the problem full stop? replacing those panels would be really invasive and expensive!
I have my wiper spindles etc just arrived, I plan to put them in the next couple of weeks, I ordered it as I have a water ingress in my passenger side footwell. The battery tray was the cause of most of it, but that got welded up and is sound and there is still a wee dribble coming in, so the spindle is next! here is hoping that solves it! as i have my fuse box ripped out to stay out of the way of the water.
I'll finish my oil servicing tomorrow and give the full underside a clean up, stonechip and wax coating, wirebrushing is fun!!
Just re-reading these posts, the soft putty like sealer taken from under the paint maybe key to finding the actual fault!
That is really strange that its soft! I wonder if it wasnt cured out right before overpainting! I wonder if it was a waterbased sealer!
Yep. Next time it will be a cut out.
Not sure if the seam contributes to the structural strength of this area to a significant level, but there one of the guys on here can get the outer skins anyway and they are not to bad expense wise, so I think if it comes back the full screen surround is coming off. Then it will just be the roof and bonnet that are original panels :-))
Here's hoping. On the 107 SL's it was the front bulkheads that had a habit of failing, often spectacularly apparently. Hope the ones you have in are sound!
Ta
Simon
Crossed reply..
Yep the feeling was something was definately wrong with the sealer - they were not even sure what it was. It was this that convinced them to stick the G in the oven for 24 hours!!. They have ground and blasted the joint as far as they can. Thier view was sealer should be hard, but not brittle and - as the name implies - seal the joint. From my point of view if water and air can't get it, rust can't form - afterall it is a chemical reaction (electolytic oxidisation??) and if you remove one of the reagents - no reaction.
It's like bleeding CSI :-)
If there is a lesson it's trust your instincts and act early!! As I have said a few times the original repairers did a good job, but got caught out on this bit.
Ta
Simon
The ones we had were ok, we have put a bulkhead in a 107 before it was a bit of a guddle as there was nothing to weld it to lol.
It sounds like these guys really know what they are doing which is peace of mind, your only issue is of course water coming from the other side of the seam under the sealer, I would get that waxed to death, especially after being in the oven, it tends to run abit with the heat!
I wouldnt think that skin wouldnt be structural, its probably the way they were designed to be assembled in sections which means that it could be plated. I would like to see a few pics of your G as it sounds like you have done loads to it!
Hi Johnny
Couple of pics of the car this summer and others during (the major) repair. I have asked the garage to sort out the defuct glow relay - stopped working on the day it went in) so not back til after a short trip to Wales otherwise cld have shot some of it as it looks now - but unless we have had a disaster it will look like it did in summer!!
Ta
Simon
PS On the repair pics we decided the back end was that bad we cut the whole thing off and replaced the entire rear end with one OEM supplied panel, and converted to internal wiring loom at the sametime to avoid the in/out loop on the back door - got a youtube video of how to do that!!
well done nice looking truck you've got there
That does look fantastic! and a pile of work has went into it for sure, there is not many cars get that much of an overhaul! So what do you use it for, do you ever get it dirty??
I want to find some side steps for mine at some point in time! where did you get them from?
Many thanks guys. I am pleased with it..
It is my daily driver and whilst I do look after it, it has to deal with whatever I am doing, including flogging up and down the motorway (all relative in a 300GD) being loaded up with building stuff.
I am not an experienced off roader, but would have no prods getting stuck into more than the limited green lanes and fields it has done. As long as the gearbox and transfer case hold up - the box already has already had a leak that seems to have healed. I reckon G's are built to last 30yrs - just a shame mine is 28yrs old :-))
So far it's a pretty even split expenditure wise between body work and mechanicals. Rear suspension is next on the list.... For the second time!
Ta
Simon
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Hi to both of you.
You have reinforced where I am at on this. Given the panel was not rusting before and having had the windscreen out myself I know the flange is ok as well, I think it is time for a repaint only option with as you say a lot of well informed chat about epoxy primers etc. so they step up to the mark.
I do think the fact they acid stripped it is, as you say, a big clue to why it has gone wrong. One bit of good news though, as the screen is coming out, I can put my new rear view mirror in :-))
Thanks again
Simon
Ps it's going to a different body shop for this attempt though!