Has the Windshield/Cowl Leak Issue Ever Been Solved?

[zac]

I assume most people know what I’m talking about. I’ve tried most things people have suggested here, even some of the crazy stuff. My ‘72 burb had the problem, my ‘70 does too....

[LockDoc]

Originally Posted by zac

I assume most people know what I’m talking about. I’ve tried most things people have suggested here, even some of the crazy stuff. My ‘72 burb had the problem, my ‘70 does too....

It has been solved by many people. There are a couple of different scenarios so what exactly are your symptoms?

LockDoc

[HO455]

If the are no holes rusted through the cowl area (common problem) and the seal is a good quality pliable rubber unit. Then most likely it is poor fitment of the panels when the cab was built. My Burban was pretty clearly built on a Monday or Friday as the fit up on the roof and window frame is terrible. (The circled gap in the 2nd photo is 1/8") I'd bet it had problems from day one. I put about ten hours into making sure the seal had a nice flat surface to press against hoping to keep the water out. Not that here in Oregon it would be an issue but just in case I travel somewhere wet.

Man I tell you, LockDoc has the fast fingers on the forum as well as instant recall.

[LockDoc]

-
Here is where my '67 Panel Truck was rusted. You couldn't see it from the outside but you could see it from the inside with a good light.


Also where HO455 shows at the top, and the drip rail above it, which would cause the water to run down through the "A" pillar.

HO455: I guess that is because I spend WAY too much time on here....

LockDoc

[HO455]

My theory is water gets in at the top and is trapped at the bottom in the gaps inside the seal and eventually rots its way through. This in some part based on the factory manual saying that the upper corners of the glass may have to have sealant injected under the seal if leaks occur. I bet the dealerships just loved dealing with that. I would bet that none these trucks left the factory with sealant in the corners. Well maybe in the later years if the dealers rebelled.

[Hutch]

zac
I don’t think it was ever completely solved
Here is an old link to some insight from way back in the day
http://67-72chevytrucks.com/vboard/s...ad.php?t=74670

[LockDoc]

Originally Posted by Hutch

zac
I don’t think it was ever completely solved
Here is an old link to some insight from way back in the day
http://67-72chevytrucks.com/vboard/s...ad.php?t=74670

I stand by my statement that it has been solved by many people. All that thread proves is that the problem has been around for a long time. A couple of things you have to remember is that everyone's situation will be a little different, and that 90% of the people that cure the problem never report back and post exactly what cured the problem for them. I cured mine on a couple of different trucks by using sealant from the top corner of the gasket over 6" and from the top corners down 3" and I have posted that statement many times.

LockDoc

[zac]

Ok guys, good stuff. I have been awake all night at work and probably can’t generate a coherent response right now. But here goes. My ‘72 was a rust bucket, so that very likely was the culprit. Even after going over everything literally with a tube of caulk more than once, it still leaked like a sieve. I was sure I tried LockDoc’s idea, but now I actually think I sealed the bottom of the seal, which likely aggravated the problem. My ‘70 is actually pretty decent. Cowl area been disassembled more than once. Tried various things, but never saw any issues there. Has a new windshield and seal installed by PO, but I’ve had the truck 8 years. I have never thought of the body fitment angle. I will investigate that. What “sealer” are we talking about in the upper corners of the windshield seal? Just to be clear, this is the water running down the inside next to the cowl vents, both sides. Little puddles in the corners of the front floorboard. Starts raining, it leaks. Rain stops, leak stops.

[LockDoc]

Originally Posted by zac

Ok guys, good stuff. I have been awake all night at work and probably can’t generate a coherent response right now. But here goes. My ‘72 was a rust bucket, so that very likely was the culprit. Even after going over everything literally with a tube of caulk more than once, it still leaked like a sieve. I was sure I tried LockDoc’s idea, but now I actually think I sealed the bottom of the seal, which likely aggravated the problem. My ‘70 is actually pretty decent. Cowl area been disassembled more than once. Tried various things, but never saw any issues there. Has a new windshield and seal installed by PO, but I’ve had the truck 8 years. I have never thought of the body fitment angle. I will investigate that. What “sealer” are we talking about in the upper corners of the windshield seal? Just to be clear, this is the water running down the inside next to the cowl vents, both sides. Little puddles in the corners of the front floorboard. Starts raining, it leaks. Rain stops, leak stops.

I just used Black RTV sealant on mine. That leak would most likely be top of gasket or drip rail corners.....

LockDoc


LockDoc

[HO455]

I would get a friend and a hose then dive under the dash with a good light. I would bet there are holes in the cowl that are the culprits. So have the friend slowly move the hose around the cowl vent area while you watch for water. It can come in from the top or the side. The driver side is easier view unless you pull the jockey box. The link below has good cut away photos showing the common problem areas.
Good luck. Been through this myself.

http://67-72chevytrucks.com/vboard/s...d.php?t=721974

[Southpaw69]

These are all different on how far along the rust damage is. It doesn't take much of a rust hole letting water in to rot out the floors
On mine there was leaves and dirt packed inside the cowl where it curves down. This caused rust right on that seam. I removed the glove box(oddly, they had a new one in there when I bought it lol) and found a small hole up next to where the antenna hole is. I used a wire wheel then steel epoxy putty on it. Dabbed some silicone on the antenna hole and finally sprayed the inside of the cowl area with rust encapsulator. It's water tight at this point, hopefully it lasts.

the toughest part is finding exactly where the water is getting in, once you do, you can fix the source. Now to patch the kick panel and inner and outer rocker...

[davischevy]

I have never had one leak twice. As Locdoc said, RTV 6" to 10" in from the corner at the top and a few inches down the side and it will more than likely be sealed.

IIRC, the assembly manual shows the sealant at the top corners.

[HO455]

So to answer the original question. Only on a case by case basis. Although I hear there are still some folks pushing for the GM recall settlement.

[StingRay]

Silicone is the worst possible choice to seal around a window. It's actually not waterproof. It will absorb moisture and let it through trapping it behind the silicone. This will accelerate corrosion. There are two kinds of silicone, acetoxy and methyloxy based. Acetoxy based smells like vinegar or acetic acid. It will start a corrosion process. Methyloxy is less of a problem. If you are going to seal the area with a permanent sealant use urethane and clean an prep to the tech instructions. Butyl is best as a removable product and is recommended in the factory assembly manual around the window opening when the windshield is installed. It used to be very common for glass shops to pump butyl into the void of the windshield gasket after the windshield was in.

[zac]

Ok, I've had some sleep and a couple minutes of free time, and I see some problem areas, both above the upper windshield corners. Something tells me the design of the rain gutters maybe directs water into these areas in certain situations. The area with the pinhole is the driver's side and it has the worse leak. Apparently all the focus I put on the cowl area somehow made me miss this, although I'm sure I looked at this area and I don't remember it looking like this. The truck has been sitting indoors more or less abandoned for the last 3 years since I even thought about this. But sitting indoors in Kentucky for 3 years is like sitting outdoors for 30 in Colorado from a corrosion standpoint. I'm looking for a reasonable short term plan here to get me through to the part where the windshield comes out and repairs are made. I promise to report back what happens.

[Bowler1]

Hey guys all of you are on right track as a former autoglass installer I have seen leaks on every make and model car and truck. GM had some of the worst leaders of all. 67 to 72 being the worst as I mentioned the firewall was one, down through the cowl the heater opening, the lower windshield corners which was usually caused by no sealant at top corners. Remember when checking for water leaks always start at lowest point and work up.

[zac]

Update: I sealed the upper corners of the windshield. My truck has that stainless trim, I'm glad I did a search on this board before I tried to pry it out. I pulled the cowl vent piece off and realized I obviously had an issue with the antenna lead. So I sealed that up. I also found a gap in the cowl area, more on the passenger side than the driver's, so I sealed both of those also. Then I left the truck outside to get rained on while I did the rockers and cab corners on my '79. Of course it didn't rain until the last couple days.

The passenger side has a leak, but not in the usual spot like before. I think it's the door seal and was related to the way the wind was blowing while it was storming. The driver's side was dry for most of the day, but after a while it started seeping a bit. No puddle, just dampness on the floor mat. It would appear that I made at least some progress. Looking under the dash I see absolutely no leak on the passenger side. And it's literally impossible to see under the driver's side. Steering wheel, stick for the 4 speed and the '70 transfer case stick that bends over that way. I will probably try more windshield sealing and see what happens.

[toolboxchev]

Originally Posted by HO455

I would get a friend and a hose then dive under the dash with a good light. I would bet there are holes in the cowl that are the culprits. So have the friend slowly move the hose around the cowl vent area while you watch for water. It can come in from the top or the side. The driver side is easier view unless you pull the jockey box. The link below has good cut away photos showing the common problem areas.
Good luck. Been through this myself.

http://67-72chevytrucks.com/vboard/s...d.php?t=721974

Someone hopefully will come out with the patch panels to recover those areas in the future. After reading through the link I have re thought my goals for the current cab.

[HO455]

Originally Posted by zac

Update: I sealed the upper corners of the windshield. My truck has that stainless trim, I'm glad I did a search on this board before I tried to pry it out. I pulled the cowl vent piece off and realized I obviously had an issue with the antenna lead. So I sealed that up. I also found a gap in the cowl area, more on the passenger side than the driver's, so I sealed both of those also. Then I left the truck outside to get rained on while I did the rockers and cab corners on my '79. Of course it didn't rain until the last couple days.

The passenger side has a leak, but not in the usual spot like before. I think it's the door seal and was related to the way the wind was blowing while it was storming. The driver's side was dry for most of the day, but after a while it started seeping a bit. No puddle, just dampness on the floor mat. It would appear that I made at least some progress. Looking under the dash I see absolutely no leak on the passenger side. And it's literally impossible to see under the driver's side. Steering wheel, stick for the 4 speed and the '70 transfer case stick that bends over that way. I will probably try more windshield sealing and see what happens.

If you have the cowl off still you could also try putting a big light (like a 300 watt quartz) under the dash and after dark inspect the cowl for light leaks. It may not show really small holes but you may get lucky.

[mike16]

its even a problem here in southern AZ where to tourist brochures claim we dont have any rain... I pulled off the cowl panel and discovered a few seams where the seal has all but dried and pulled away from the seam. white window seal calking will sort that right out. 3.99 at Ace and a 35 year guarentee.

[Bearhawg]

I know, I'm resurrecting and old-ish thread..

Overwhelmed, discouraged, despondent, you pick the word, brother I got it. Started the install of my new Vintage Air and found it, cowl rust. Pretty bad. Got the kick panels and the floor to toe kick seam. I can go two ways, 1) stabilize the rust, patch it up as best we can with auto-body epoxy, close it up and keep it dry OR do it right and go broke. I say broke because I wont do body work for a number of reasons. Trust me, I've tried and it did not go well. Body work is best left to the craftsman. Anyway, just had to vent, no pun intended. This has not been a good day.

[HO455]

How about sharing some pictures so we can better help you with your decision.

[custom10nut]

Originally Posted by zac

Ok, I've had some sleep and a couple minutes of free time, and I see some problem areas, both above the upper windshield corners. Something tells me the design of the rain gutters maybe directs water into these areas in certain situations. The area with the pinhole is the driver's side and it has the worse leak. Apparently all the focus I put on the cowl area somehow made me miss this, although I'm sure I looked at this area and I don't remember it looking like this. The truck has been sitting indoors more or less abandoned for the last 3 years since I even thought about this. But sitting indoors in Kentucky for 3 years is like sitting outdoors for 30 in Colorado from a corrosion standpoint. I'm looking for a reasonable short term plan here to get me through to the part where the windshield comes out and repairs are made. I promise to report back what happens.

A sure way to stop it is to get all the rust out of the seam, and the go old school. Lead in the seams. I know it’s very uncommon nowadays, but still effective.

[Bearhawg]

Originally Posted by HO455

How about sharing some pictures so we can better help you with your decision.

Will do. I took it to a local Restomods shop that has done some work for me before. I hope to post some pictures tomorrow. Thanks

[toolboxchev]

I have the same issue and doing a windshield very soon. Looking like something similar to the light brown rig posted above. I would like to see those pics also.