W123 Water in Driver's Side Rear Floor
 

hey all,

the 82 300D has some water in the rear floor pan. front area looks fine and is dry.

the rear door seal looks good and I have replaced it with MB OE ~7 years ago

what could i be missing here?

it's gone on long enough that there's some rust that needs welding :mad::mad::mad::mad: so I want to kill this dead before fixing.

cheers,
dd

Usually that is from a bad windshield seal. Its the low point so all water that gets into the passenger area settles there.

I dont have any specific knowledge of this, certainly someone here does. But, I have disassembled two cars rear seat area and seen consistent issues. The lower left rear window seal collects water and possibly rust. And both cars have the rear seat, back padding pretty much gone, along with the springs/frame rusted. I assume water is entering around the rear window and causing the damage.

You might remove the rear seats (easy) and look around.

One place that 123's always rust out is in the wells where the hood hinges live when the hood is closed. They get trash in them and the drain holes clog up. After they rust out the rain water runs under the dash into the front floor and then runs under the mats to the back and remains there. Few 123's are not rusted out here.

I fixed mine with roofers asphalt and fiberglass cloth. It's not elegant, but it holds up and keeps the water out.

Richard

Sunroof seals. Had same issue but I sealed the sunroof with silicon until I can find the replacement seals and felt (the felts NLA). No issue since. major rains and dry as a bone. Before this, I had 2 inches of standing water in there after a rain!!

There are many causes but the result is the same. The lowest point in the interior is the rear floor. Any interior leak will cause the water to end up there. The water seeps under the coating and rots the steel from the inside out. There is a pinch weld running right through this region, and the water goes to the V and settles there.

You may have to remove some interior bits (floor mats and carpeting, lower dash cover) and have a friend try to incite a leak with a hose while you look around with a flashlight.

The sunroof is intended to leak. There is a catch pan that is supposed to drain out in 4 places (behind the front tires, and at the trim where the c-pillar meets the rear fender). If your drains are clogged then the pan fills up and floods the interior.

see pic and arrow.

i tore the interior out completely. water collects right at the back of the driver's side rear floor pan. i cannot figure out where it's coming from for the life of me.

trunk is dry. front floor pan and pathway back to that spot is dry.it's not coming down any of the wires.

any further thoughts?

it may be time to peek under the headliner.

Look in your trunk. Remove the driver side inner trunk liner and look for water/rust. If you see it there my bet is on the rear windshield seal. That's where my problem was. Get someone you love and trust to close you in the trunk with a flashlight and run a hose around the rear windshield and trunk door seal areas.

The trunk seal is an easy DIY. The rear windshield seal may require a repair to the channel that seats the seal. If so it is a fairly inexpensive job that can be done by any competent body shop. Total with a new seal should be in the $300 range.

sounds crazy but do try the front sunroof drain clean out. Weed trimmer line and a bit of air followed with some water.

At the risk of being a pain in the neck, I will reiterate. The major sources of water in the rear floor pan are from three places. The hood hinge wells (or whatever they are called) are rusted out, the area under the grill around the windshield wipers is rusted out, or the battery box, which is always rusted out in these old cars. In your case the battery box is probably ruled out, since it is on the passenger side of the car.

The water from the hood hinge wells will pass under things in the front floor pan so you never see it. This is the most likely source of water in the rear floor pan. They are always rusted out, even in cities where there is no road salt, because people never clean the accumulated leaves out of them.

Richard

evaporator drain hose?
 

Although you're probably not running the a/c in Boston this time of year, just for future readers of the thread for whom this may be applicable:

I had water collecting in the same location (driver's side rear floor) and the culprit turned out to be a leaking evaporator drain hose for the air conditioning system. The hose had simply deteriorated over time (it was some sort of odd foam-like material). Replaced the drain hose and no more water. I was surprised at the volume of water generated...

I'll second looking at the hood hinge wells as it happened to me, for as much water that comes off the hood, the hinge well holes are small and clog easily, putting water toward the firewall and, yes, it travels to the rear floor pans.

Oh Goody ,ive got all 3 ,do we win a prize.A shop vac would be nice.Ironically I have a parts car ,zero rust .

How do I to clean out the sunroof drains?
 

Was searching for info on why I have water collecting in my rear passenger side floor in my 85 300D and found this helpful thread. My hood hinge drains are clean so I do not think they are the source of the problem. I opened the sunroof and looked for access to the drains but do not see anything. Can someone give me some guidance as to how I find and clean out these drains? This car has no rust and the windshield seals are tight.