MGB Rain water getting inside behind dash

[RickB]

I have been trying to figure out how the rain gets inside and drips down into both footwells from behind the dashboard.
I have a heater vent cover in place when it's raining, however this provides no relief.
RTV added to the windshield seal, still water collects unabated. I keep a pan in the footwells to collect water, it's that bad.
In the northwest where I live I can collect a couple inches of rainwater in a day.
I can see water inside where the dash and windshield meet from around 10 inches inside all the way over to the corner.
I just can't figure out how this water is getting in, so if anyone has any great ideas of what I can do to figure this out I'd be grateful.

 

[princetn1]

All I can offer is my (similar) experience. I had water coming in after being caught in one of those notorious Florida afternoon downpours. I figured dripping water onto Lucas wiring behind and under the dash is a dangerous combination!! So I got small rubber washers for the windows sprayers. I also lined the top of my windshield frame with insulation that meets the new top seal. And lastly I replaced my 45 year old, hard, and cracked windshield seal (NOT fun). No issues since. You might also check under the bonnet to see if all the rubber grommets are in place. Hope this helps.

As a last suggestion, moving from the NW (I grew up in Renton) might also be considered.

 

[RickB]

Thanks, yeah maybe I could move to Arizona!
Nah too much family here in the PNW, going to have to get the leaks fixed.
I will look at the wiper plinths and see if that's where its coming in, also I will need to get my windshield replaced some time so that might fix it.

 

[RickB]

Is the plinth gasket this:

Moss #282-820 PAD, finisher

Described elsewhere as:
PAD, WIPER BEZEL

 

[Joe Reed]

Is the plinth gasket this:

Moss #282-820 PAD, finisher

Described elsewhere as:
PAD, WIPER BEZEL

Yep, that's it. I don't think that'll solve your problem though (at least not completely) based on your comment "I can see water inside where the dash and windshield meet from around 10 inches inside all the way over to the corner." That indicates that water is encroaching either between the cowl and the windshield seal, or (less likely) between the glass and the glazing rubber.

 

[RickB]

I'll keep looking, replacing the windshield and seals is on the short list.

 

[princetn1]

I have polished windshield frames, all 4 pieces, to a mirror finish and offer this service to others...$275 which includes $75 core. If you're going to replace your windshield, you'll need to disassemble the frame so make it look stunning (for you, others, and judges).

 

[RickB]

Found a John Twist video about this.

https://www.youtube.com/watch?v=gVxhtGU7N-I

 

[NC Mike]

With all the talk of windshield frames, I'm assuming you're talking "B" specific. As a GT owner, I don't have the frame troubles, but do know of a source for a "behind the dash" leak into the footwells. Even with the cowl inlet covered, rainwater still gathers inside that plenum. (neither the magnetic cover nor the cowl "grille" are water-tight) That said, the drain tube that is supposed to direct water underneath the car will occasionally clog. When it does, it is evidenced by water "dripping" into the foot wells. Actually, it's more like "splashing" into the foot well, especially during turns. Maybe not a "B" problem, but possibly a source if all else checks out okay.
-Mike

 

[RickB]

Yes it effects both the GT and the Convertible.
I've cleaned that tube out on all the GT's I've owned so I know what that is like.
I can see that water can get in around the fresh air vent grille, I do need to make sure the tube is open and can freely remove water from that area so that I'm sure.
All that being said, I have seen water inside where the windshield meets the top of the dash and over from the corner out to 7 or 8 inches inward.
That can't come from the fresh air vent.
This is not to say I didn't have several places that water was getting in, the things I've done have reduced the amount of water so I'm just going to have to go through every possibility and fix them.

 

[NC Mike]

Yes it effects both the GT and the Convertible.

. . . I have seen water inside where the windshield meets the top of the dash and over from the corner out to 7 or 8 inches inward.
That can't come from the fresh air vent.

Unless you know a secret, and if you do, please share, water doesn't run uphill, so no, the fresh air plenum is not the source of the leak you're seeing where the windshield meets the dash.

In the early 80's I was turning wrenches in a local Chrysler dealership. It was the days of the New Yorker model with the rear half of the roof covered in padded vinyl. I spent many hours inside the trunk of various New Yorkers with another guy directing the stream from a water hose onto the car in search of a trunk leak. Contrary to initial thought, it wasn't the vinyl roof. It turned out to be the sealant used to waterproof the seam between the roof and door frames near the front of the car. Water was entering the "gutters" at the front, getting into the framework and following it rearward until it dropped down into the trunk.

Having said that, dry the car of visible water as well as you can. Strategically position pieces of toilet paper where you are seeing water. From your description, I get the impression that you will be able to see them from outside the car. With "papers" in place, put your garden hose to work. Start low, where the window frame meets the body and start watering the car. If your paper gets wet, you've found a leak. If not, work your way up. Next step up in my book would be the bottom of the window seal within the frame.

Limiting the areas that are being watered and keeping your eyes on your paper "evidence" should help you find the source.

Happy Hunting!

Mike

 

[RickB]

Here's what I got this afternoon.

 

[NC Mike]

Aww, you're dash light dimmer switch is crying. Have you not been paying it any attention lately?

Sorry, Rick, couldn't resist.

I know what a pain it is for me to keep my dimmer (rheostat/ whatever you want to call it) happy enough and willing to rotate. I can only imagine how temperamental it would be if it experienced wet and dry cycles. Not to mention that wet and dry cycles on electrical components are the things that perpetuate the legacy of Lucas lighting, King of Darkness.

I'm in the process of prepping my car for some in-patient care at a local body shop. My windshield will have to come out to facilitate a repair near the bottom corner of the glass on the left side. I'm taking the opportunity to swap the fogged original windshield out for one from a parts car that is not fogged. I'm assuming that a new rubber will be required to maintain a proper seal and to increase the chances for a successful re-installation of an old windshield.

A little light bulb just lit up over my head. It has just dawned on me that we're talking about your B, as in roadster B, making my comment about being able to see the toilet paper from outside the car seem fairly ridiculous. I guess the mind goes where it "knows," and mine apparently only "knows" that Bs are GTs. It's definitely time for bed!

 

[Mickey Richaud]

Here's what I got this afternoon.

Based solely on that picture, my money's on Joe Reed's suggestion above.

Also, check the joint at the top of the windshield frame where the stanchions meet the top of the frame.

 

[RickB]

Thanks Mickey, I will do that today - IT'S NOT RAINING!!!!!!
(until tonight anyway)

 

[RickB]

I just got back in from doing it up like John Twist recommends.
When I pried up the bottom corner seals guess what came out?????
WATER!

So I stuck paper towels in there and dried it up and then squirted clear silicone sealant under there up to around 10" inward and also under the post gasket / seals.
Then I took the top loose and put the flowable silicone on up there wherever it looked like water could get in and seep down.
I sure hope this reduces the floodwaters inside the car!!

 

[NC Mike]

Hey Rick, I'm feeling your pain.

I've been prepping my car for a trip to the body shop. I managed to get the seats and original rubber mats off of the floor this weekend only to find that water had been getting into the car.
Long story short, now I need to replace a floor pan.

Nuts!

 

[RickB]

I've got the passenger side fixed (it's only getting as wet as any British car now, not big pools like before).
The drivers side is still getting wet, water still coming out of the dimmer switch.
I have done as everyone suggested, I suppose I should get a new tube of silicon and try it again in case I missed a spot.
There is less water now, so I may be on the right track.
I have an 11x18 by 4inch deep pan I put in the footwell when it's parked so the water isn't just sitting in the car, there used to be 2 to 3 inches of water collected overnight after a good rain and now there's barely an inch.
:highly_amused: