Water leak from under dash
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Lead Driver
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From: Ohio
Water leak from under dash
I've had a random leak that would leave a damp spot on my floor mats. I've poked around and just couldn't figure it out.......til this weekend. It rained real good Sunday morning so I went out and looked and saw the damp spot running down the floor mat(rubber mat over my carpet) and it was coming from up near the dash. I stuck my head under there and noticed a small drip from my brake rod. Huh? A couple times through the winter time I would have a frozen(stiff/stuck) brake pedal in the morning. Never figured that out, and have replaced the booster years ago thinking it might have problems.
Apparently the seal between the booster and the firewall is allowing moisture to seep through and drip down on the mat. I know I put a touch of silicone on the booster mounting surface when I installed it, but it seems it didn't take care of it. This time I took a finger full of clear silicone and ran it around the top of the booster mounting surface so that any moisture running down the firewall could not get into the brake rod area. Time will tell if it stays dry and when there is another freeze it will tell if it doesn't make the brake pedal stiff to push the first time.
Apparently the seal between the booster and the firewall is allowing moisture to seep through and drip down on the mat. I know I put a touch of silicone on the booster mounting surface when I installed it, but it seems it didn't take care of it. This time I took a finger full of clear silicone and ran it around the top of the booster mounting surface so that any moisture running down the firewall could not get into the brake rod area. Time will tell if it stays dry and when there is another freeze it will tell if it doesn't make the brake pedal stiff to push the first time.
Tuned
Joined: Dec 2018
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From: SE WI
I've been chasing that leak all year on my 89. I resealed the gutters on the top of the cab, every seam I could get to, sprayed a few cans of rustoleum bedliner spray in the cowl because I didn't want to try digging out that old seam sealer, the only thing really left is my windshield.
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From: Mi'kma'ki
Yeah there shouldn't be any water running down inside the firewall like that at all. You'll have issues far worse than just a damp floor. Your wiper motor will eventually rust and seize up and you'll get all kinds of corroded electrical connection issues. You really should replace your cowl seal.
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Joined: Feb 2012
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take the wipers off and then the cowl plate (whatever it's called) there should be two rubber gaskets under there that seal another possible leak area. And get a cowl to hood seal, there is a huge amount of water that will enter that area.
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From: Mi'kma'ki
Yeah but that doesn't mean it hasn't dried out and no longer seals properly. Try running a hose over the trucks cowl and hood area. Pop the hood first to make sure it's all dry, the soak it and keep checking for leaking past the seal. You'll probably see water passing by in several spots.
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Lead Driver
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From: Ohio
I did notice water getting by the hood seal and running down the firewall, thus I figured that was the issue. I'll get some water and pour down the cowl vent and see if it leaks from there. I didn't know there was a way to get water inside the truck from that area, especially just at the brake pedal rod.
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From: Mi'kma'ki
Yeah, your drains could be plugged up. That would hold water inside the cowl but I'm not sure, I guess it would or could seep out around seams from there but that would take a lot of water probably. Anyway, that's easy to check too. Try to fill the cowl right up with the hose. If you can't, then you'll see the water running right out from the drains, located inside the fender area. If they're plugged, you can just get under there and you'll see the drain tubes and just shove a screwdriver up in it until the water can flush it out. My guess is though, your cowl seal is old and dried out and just not sealing anymore and it's dripping from there.
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From: Central Mississippi
Both boosters I replaced had thick hard plastic OE seals tween the booster & firewall. (cracked)
Replacements came with the rebuilt units, but I could not imagine them sealing well, but so far so good.
Replacements came with the rebuilt units, but I could not imagine them sealing well, but so far so good.
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From: Ohio
That is why I replaced the booster at first. It would get stiff when damp/cold. I couldn't really figure why, so I replaced it. I siliconed it to the firewall and the master cylinder to help alleviate any change of moisture getting inside and freezing as once I pulled it I noticed rust building up on the pushrod. All summer it still would get random water on the floor mat but never could really investigate it why raining. I finally got the chance and saw the drip on the pushrod hooked to the brake pedal.
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From: Ohio
The water is not coming from above the dash area, like the window. It is on the brake rod. No roof lights on my truck.
A previous '95 I had dripped from the top center of the windshield. Again, rust free truck, but apparently the factory sealer got loose in one spot, dead center and if it rained I had to put a rag on the dash to keep it from building up water. Local glass shop wanted to do a day long "test". I just wanted them to pull the window and reseal it. Nope. Unfortunately a rogue minivan ran a red light and bent that truck in half so I didn't have to worry about the window anymore.
A previous '95 I had dripped from the top center of the windshield. Again, rust free truck, but apparently the factory sealer got loose in one spot, dead center and if it rained I had to put a rag on the dash to keep it from building up water. Local glass shop wanted to do a day long "test". I just wanted them to pull the window and reseal it. Nope. Unfortunately a rogue minivan ran a red light and bent that truck in half so I didn't have to worry about the window anymore.
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