Author Topic: A nasty rust surprise. A huge hole near the bonnet/hood release cable grommet.  (Read 14861 times)

littlefin

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Yep, that's a standard rust spot on RHD cars.

One has to be very lucky not to have a hole there.

Tim

I need to take a good look in that spot next time I'm under the bonnet  :o
110011 1967 230
108057 1972 280SE3.5
116024 1979 280SE
126037 1983 500SEL
124030 1989 300E

oversize

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Yep I think it's the major cause of death in most W116s.  I think many drains were blocked with sealant when they left the factory
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

TJ 450

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On all the cars I've seen, none of those drains have been clear, even though I know they are there. On rust free cars, it wouldn't hurt to make a new drain.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Rimas

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hi
I'm just after finding something just like that in mine , just under the bonnet release gromet.

I am just going to do what you did to repair it and hopfully keep it dry, did you repair the drain hole?

and if you did any tips ?  my car is lhd and the fuse box is next to that spot and any water build up goes under it,

I'll patch as best i can and later on in the year i have the rust sorted professionally

best of luck with your repairs

john

Hi John how bad is yours? Can we see a picture?

I found that I had to pull out the sound deadening in the floor wells, cut away the firewall insulation and 'dig' around underneath in the wheel arch to discover the true extents of the rust problem. I found that water was not only coming in through the gaping rust hole, it also created a smaller one just below it right behind the heater box. This was tricky to get to.





the first thing I did was vacuum the areas and pick away at the old rust with a screwdriver, wire brush and whatever else.

Then I applied these following products.



The first one on the left is a tar/fishoil blend that works really well in sealing rusted areas that you can't reach. I found it useful to get it up under the dash where the firewall rust had started. Also I've used this product in my doors. Initially I was going to make the rust kill blend with diesel, fish oil and thinners but this stuff did the job.

Any exposed rust I then treated with a rust converter. The next step was to use the 'Miracle Paint' stuff, it's like a really hard resin that binds to rust and moisture helps it set. This is what I was able to do the fibre glassing with. The KBS stuff underneath is the same, just a cheaper Ausssie alternative brand. I'm going to do my whole floors and firewall again with this stuff just to be sure.



I then finished over it with white enamel paint to try and seal it up.



Here is the same process done except with the floor/firewall.



Inside the wheel arch and under the floor I have sprayed under-body tar to make sure that the rust is sealed from BOTH sides.



Today I will be buidling up a silicone seal in lieu of the grommet, sealing it with the enamel paint and lathering the WHOLE of my floor in that rust seal stuff.

Tomorrow I will test for water leaks, drill a drain hole through the fibre glass and start putting this poor W116 back together and lay the dynamat to replace the old mouldy sound deadening (thanks Oversize for the product tip). Dynamat is expensive so I bought 4 sheets. One sheet fits PERFECTLY on the floor. Happy times. The other I have to do to the drivers side and I'll get up under the dash to replace the firewall insulation that I cut away.



Hope that helps!

PS, my work may look crude, but it's way more important to me to get this thing sealed and treated so that I can enjoy using the car again. This car is my go car, not my show car. I would love to delicately cut and replace rust with new welded metal but my budget/vision for this car doesn't allow me that luxury.

At this stage I'd prefer a mechanically perfect car with an 'honest' body/paintwork that I can enjoy rather than an immaculate car that I'm scared to park at shopping centres.

Rimas
73 350 SE

TJ 450

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Nice work for sure!

Yes, the main thing is to stop the water getting in there and making the problem worse.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

w116john

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hi Rimas

nice job I spent the last few days doing the same job, but i had put in some sealer earlier to see if that would stop it so i had to take that all out again, and then sand treat and fill both sides.

before i filled it i inserted a piece of tubing to recreate a drain hole , its about 6 inches too long , i will cut it at some stage and so far so good its working,  rain is never too far away so its easy to test.

next the boot, the rear light is letting in lots of water.

new to photo bucket so see if this works

ok so pics in next post
« Last Edit: 15 June 2013, 12:42 PM by w116john »


w116john

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hi

three posts where one would do, pics in last post

pic 1 is new drain tube, a little long but working
pic 2 is repair area beneath bonnet release
pic 3 original hole from inside

pics in this post

drain hole top and bottom






oversize

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Good to see these cars getting the attention they deserve!  Unfortunately many owners aren't aware they have blocked drains that're causing their cars to rust to the point where water comes inside.  The first time it gets noticed is when the carpets are wet and by then it's already a big problem to fix.

BTW you guys know that the inner wheel arches were originally painted in the body colour right?  With all the dirt they can look black, but they're not meant to be.....
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

Rimas

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BTW you guys know that the inner wheel arches were originally painted in the body colour right?  With all the dirt they can look black, but they're not meant to be.....
:o :o :o

Wow.

Hey John, yours isn't looking as bad as mine was however that hole looks like the rust could extend a fair bit further underneath the surface.

Guys I'm getting confused where the drain hole is actually supposed to be. Mine seemed to have no evidence of a drain hole at all?!

I assumed there wasn't one and was going to make one here so that it drains into the wheel arch:

I was thinking I'll put a pipe in so that it doesn't simply cascade over the wheelarch.

Cheers

Rimas
73 350 SE

oversize

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The hole should be at the lowest point to drain all the water away and keep it dry.  If you remove the deadener from the passenger side of the inner wheel arch, you should find a separation between the firewall and the wheel arch panels.  Probably the best way to do that would be bead blasting, but a scraper would do.  This is a very late W116 and I'm not sure if they're all the same or whether MB made a design change after identifying the problem.  Can you see the light?





1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

oversize

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Aussie driver's side:



1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

oversize

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Note that I can't see the opening for the hole on the RHS near the fusebox and it's obviously been blocked for years and I think it's rusted through.....





1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

oversize

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I might try to force through a screwdriver from underneath and see where it comes out up top.....  I'd say it'll be to the right of the fusebox
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

oversize

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Looks like Rimas car is the same looking back at the first pic.  Obviously the drain was totally blocked and the insulation kept it all damp.....
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P