passenger side firewall rust source - identifying

[nathan]

Plodding through the silver 6.9 chain of events, i arranged to have my window replaced whilst the dash is out so it doesnt need to be done for 10-60 years.
as noted in other threads, the cars is stripped on the interior after the engine rebuild led to me deciding to fit a new dash and finding some rust on the passenger front floor panels. i had previously (15 years ago) had some rust repaired on the passenger front footwell/firewall (low).  at the time, i didnt really think about what caused the rust, but in retrospect, it was probably the same source as the floor pan rust i found when my exhaust was dropped recently.

so to my horror, i found a small amount of water in the same repaired footwell after a recent downpour (dads garage has one leaking spot - it drips very slowly).

i talked to the usual WA 116ers who thought it would be the plenum under the chrome grill.  I wondered whether it was a poor window seal on the passenger corner despite it being soft and supple.

So i removed the chrome grill today and ran the hose in there, nothing happened after a few minutes. i got the hose and sprayed a bit around the area and sure enough the water came in. it seems its the rubber grommet where the heater box hose goes in. it was cooked. it certainly didnt let in a torrent, but for a car that gets washed every couple of months after a drive and then put into storage, i can see how this is a problem.

ill get onto the parts and though i should even replace the hoses that feed the heater box, although the EPC shows some wacky numbers.

67 - grommet 107 997 01 81 (X2)
469 -seal 116 835 01 98
---hose 116 831 16 94
502 - hose 116 831 14 94
510 - heater case? 116 830 31 62 (R)

[nathan]

oops, the EPC diagram

[rumb]

Yes, it's always best to just replace every bit of rubber when you are in there.

[daantjie]

Grommet is  NLA last I checked.

[UTn_boy]

Food for thought.....it's much easier and less damaging to the dash to be installed while the windshield is out.  The windshield is perfectly able to be installed with the dash in. 

[nathan]

Dan, I dont wanna hear this!

UTN, I got paranoid a few years back after the window guy said it didnt seal perfectly and then I found that rust.  thats why I thought if I had him put it in with the dash out he could put 8litres (gallons) of sealant in there to ensure there is no leakage. now I know where the water is coming from though, I feel a bit more comfortable with the way you describe. I certainly appreciate they dont take out dashes to put windows in 

[TJ 450]

Yes, any water entering up the front will definitely rust out the floor. The worst culprit is rust holes in the firewall (RHD cars, in the corner behind the blower unit), as well as those grommets etc.

I've tried removing a dash with the screen out and it made no difference, but maybe this differs with RHD cars, I would doubt this though? You can't lift it up without pulling it forward in which case you might as well leave the screen in. The angle of the a pillars also compounds the situation.

Tim

[Peter]

Hi Nathan, nice work. The slshop is showing these grommets as available for about AUD $15 each. I have dealt with them before.
https://www.theslshop.com/mercedes-benz-107-sl-slc-bulkhead-grommet-1079970181.html

[nathan]

thanks PQ, I just ordered from them.
9 pounds a piece,
postage 53 pounds!
again, thanks for the heads up.
regards
Nathan

[UTn_boy]

BY the way, don't forget to clean all of your evaporator drains out, too.  Those will also rust the floor out. 

[nathan]

so I ordered from the SL shop in the UK with 4 grommets costing a whopping 50 pounds of postage!! however, before I could say crikey, they had turned up in two days so I won't complain too much as now I can work on the car this weekend. admittedly, the classic centre got back to me and noted they had them in plentiful stock at 15US ea. attached is a pic pf the SL shop ones which didnt have part numbers on them.

[nathan]

and the window seal also arrived. amazing, its a 1/3 the price to buy from MB overseas delivered to your door cf our Australian dealers. actually, its bloody outrageous and MB Australia needs a kick up the backside

[nathan]

I forgot to add, does anyone know what the correct colour is of the body underneath the chrome grill above all this externally ie the bodywork below that chrome grill where the wipers attach.  mine looks like a combo of silver and black but which is the wrong one. I cant imagine they would put silver on it if they didnt have to, but perhaps the black wore off the bits exposed to the sun to expose the underlying silver body paint?
regards
Nathan

[daantjie]

thanks PQ, I just ordered from them.
9 pounds a piece,
postage 53 pounds!
again, thanks for the heads up.
regards
Nathan

Nathan, did you check availability from the Classic Centre on these?  Seems like a ton of money, but if they are NLA from Benz as I suspect then I guess you have to pony up for these babies

[nathan]

Yeah Dan,
they emailed and said they had them in stock, lots of them!
but after you said they were NLA I couldn't be bothered waiting for their reply as Tom H is away, and they other guy dragged his feet.
then after id paid for the grommets with the SL Shop, the CC got back to me and said they had them!