1984 300TD water in back seat footwells - PeachParts Mercedes-Benz Forum

chrisgt · #1 08-08-2022, 01:10 PM

My 84 300TD has had this problem for a while so I've just parked it under cover, but I want to start driving it again.
When I wash the car or it rains, I end up with water in the back seat footwells. Sometimes on the driver side, but a ridiculous amount on the passenger side.

I know that it's a common problem for the water to leak in under the windshield or somewhere up front, but this appears not to be that. If I pull up the mats, etc. in the front seats, the floor is completely dry. I had the windshield and gasket (oem MB gasket) replaced several years ago and they said there is absolutely no rust up there. This car is in very good shape with no rust.

Would this be broke sunroof drain tubes? Leaks where the roof rails bolt up?
I'd like to know if it's anything common before I have to go remove the headliner, that doesn't look like very much fun.

Sugar Bear · #2 08-08-2022, 03:38 PM

Chris,

Common problem areas:

Hood hinge pocket drains plugged,
Sunroof drains rotted away or plugged,
Holes rotted behind and under battery from a not connected battery vent tube,
Plugged drains in the wiper wells and the two scuppers on the firewall,
Plugged gaps in the drain openings on the rocker panels,
Rear quarter glass...look for moldy spots on the seals. Rust forms between the seal and the body, and door seals.

Rig up a shower head or garden shower on a pole so that the elevation of the sprayer can be raised up/down. Start low and watch for leaks. Move upward until water enters.

Can probably rule out the sunroof by taping it off with blue painters tape for a day or so. Make dams in the corners of the sunroof and pour water into each of the 4 corners individually and watch for leaks.

If it is the rear sunroof drains on a wagon it's a bear!

Good luck!!!

chrisgt · #3 08-10-2022, 03:58 PM

I found the passenger side issue, mouse nest behind the inner fender liner caused rust, and rust under the battery tray went through to the passenger footwell. Paint is drying there, hopefully that's it.

I can't pin down the driver side issue, though. I dumped a ton of water through the sunroof on that side and it all came out.
I'll wait until the paint on my passenger side repairs is all dry, then i'll do as you suggest by working my way up from the bottom until i get water ingress.

Diesel911 · #4 08-11-2022, 01:12 AM

There is rubber plugs in the floors you can pull to allow the water to drain.

vwnate1 · #5 08-11-2022, 02:45 PM

Subscribed to learn the leak's location .

I miss the Summers in Maine in the late 1950's ~ mid 1960's .

Good times .

vstech · #6 08-12-2022, 06:41 PM

Lift the rear trunk cover (third row seat footwell)and check there, also in each rear side bay sections...
Often the rear hatch drains clog and let water into the areas.
If the sunroof drains are clogged, or the rubber tunes have failed, you will get water in the footwells, rust in the sunroof areas also can drain down the b pillars causing it.
.95 string timer line works great to clear the sunroof drains.

chrisgt · #7 08-16-2022, 06:53 PM

I dumped a lot of water into the sunroof rails, and I don't think that's the problem.
I had checked under the third row seats, and that was dry.

I still do not know how water got into the driver side front floor (and drained back), but there was some dirt behind the front fender liner, maybe that was backing water up into the holes through the body where the fender liner screws in?? Not sure.

The passenger side, however, was REALLY obvious...

It's hard to see what you're looking at here, the hole in the bottom right in the front of the fender, basically. That fender liner is cracked and there was a huge mouse nest in there, caused this damage

I'll be finding a new liner.

Up top right, you can see some light, that's the grommet for the wiring harness that comes out behind the battery, there was also some rust through to inside the car in that area that I fixed.

Finally the hole in the center left was really unexpected and completely hidden.
On the outside of the car, it was hidden under the undercoating, inside the car it was fully hidden under the black sound deadening stuff.
I only found it because there was a tiny crack in the undercoating in the wheel well, i gave it a poke and my poke tool went right through. I hope no more of this kind of rust is lurking in the car, it's scary how well it can hide!

I have cleaned all this up and fixed it. Paint has been drying for a week and i finally took it outside for a bath. I only hosed it off from the windows down, everything I removed from the interior is still sitting on the roof, so I'll have to clear that off and give the car a good proper wash and cross my fingers I have solved the problem, or if i haven't, it's easy to find.
So far no water in the car so fingers crossed.

t walgamuth · #8 08-17-2022, 07:32 AM

Congratulations on your persistence!

silver · #9 08-18-2022, 10:23 PM

Check the bottom of the heater rubber from box to the trainsmission tunnel that’s where mine was getting the water from so check it silver

vstech · #10 08-20-2022, 09:50 PM

Quote:

Originally Posted by silver

Check the bottom of the heater rubber from box to the trainsmission tunnel that’s where mine was getting the water from so check it silver

It’s posts like this where I REALLY wish this forum had a like feature!

chrisgt · #11 08-21-2022, 10:53 AM

Quote:

Originally Posted by vstech

It’s posts like this where I REALLY wish this forum had a like feature!

Yes, A+ post. I was about to lose my **** when I remembered this post and went looking for that drain. I still don't know the proper fix for it, but I did something that works ok enough and at long, long last, my car is back in order.

chrisgt · #12 08-20-2022, 09:06 PM

I hosed the piss out of the car and no water got in. I was super excited about that. Put the interior all back together and took it for a drive. Today was hot and humid. Got home and the car was full of water again.

I had no idea what you were talking about the drain hose over the transmission but omg thank you for saying that. I went looking and found that it was missing.... The insulation was still there so it wasn't obvious the hose was gone until I reached up in there.

WHAT A PAINFUL PLACE TO REACH!!!

I got some hose in there temporarily and it seems to have fixed the last of my water issues. But my question is, what is supposed to be there? The nipple coming out of the HVAC box has a weird barb on just one side and it's at a strange angle, not pointing right at the hole. I have some ideas on how to fix it, but what's the actual correct fix here?