C3 water leak and vacuum feedback

[Tony Roussos]

Greetings Vette fans!

I'm including two questions for the price of one. The car is a 1971 350 4-sp coupe.

Q1: I've resolved water infiltration from the tops and firewall seam, however, after heavy rain, both floor panels behind the seats are soaked! Where is it coming from now!!? I had the weather seals replaced last year.

Q2: Both the headlamp buckets and the wiper door pop up when I shut off the ignition. I have to restart the car briefly and quickly shut the ignition off again to get everything to settle down. What is causing this to happen?? Vacuum feedback? A bad valve?? Which one and where?

Thank you for your advice.

Tony

[Dick W.]

Re: C3 water leak and vacuum feedback

Tony, I would remove the wiper grille and look at the sealer in the area underneath. You will see a lot of sealer spread in this area. I would clean all the trash out, go to Lowes, Home Depot, etc and get some black roofing sealer. Take a 2" putty knife and spread a generous amount of the sealer in this area. This usually takes care of most of the mysterious water leaks in C-3's. Works on 68-82 cars.

I would start with the vacuum check valve to solve your headlamp problem. If the engine has ever backfired, the valve is probably "toast". Try this first. It is the cheapest? component that could go bad.

[Tony Roussos]

Re: C3 water leak and vacuum feedback

I already took care of all the seams under the wiper grill. Besides the carpet from the dash back to the seat is BONE dry. The water is definitly behind the seats on both sides. I'm thinking its getting in from the door seals. Just a note, I replaced the rear grill drain tubes and plates. The reardeck area is also BONE dry. It's just the floor behind the seats.

Where is this check valve? I don't recall the engine backfiring, but I'll check it if I can find it. You mentioned the headlamp, but its the headlamp and the wiper door that come up when the engine is turned off.

Thank you for the help.

Tony

[Harmon C.]

Re: C3 water leak and vacuum feedback

Troy Do you had a strip near the bottom of the door jam rear side to help guide water out? Lyle

[Roger S.]

Re: C3 water leak and vacuum feedback

I had a problem with the seat belts getting wet. It appearred to me that the water was leaking in between the door and the body. I never could get the seals to work so I installed the water diverters at the back edge of the door sill plate. I got diverters for a 1974 model. I also put a small dab of silicone at the edge of the diverters where they touch the body. The diverters fit under the rear edge if the sill plates and are suppose to be held down with two rivets, I just let the sill plates hold them down.
Roger

[Jim T.]

Re: C3 water leak and vacuum feedback

I did the same as Roger with my 68 and 70 back in 75 when I saw what GM had done to change the way they were diverting water on the 68-73 Corvettes. The factory installed water diverter strip on the 68-73 Corvettes just was not efficient enough. I also did not rivet the diverters and let the sill plates hold them down.

[Harmon C.]

Re:Best way to stop C-3 water leaks

Park Corvette in garage and wait for sunshine. Lyle

[Tony Roussos]

Re: C3 water leak and vacuum feedback

Yes. There are rivited strips on a diagonal on both sides.

Tony

[Tony Roussos]

Re: C3 water leak and vacuum feedback

Yes, I believe I have those. There are two narrow strips, one on each rear door sil on a diagonal held in place by two rivits.

Tony

[Tony Roussos]

Re: C3 water leak and vacuum feedback

OK. Did GM have the angle wrong? Where can I see a pic or diagram? Can you e-mail a picture of your diverter for reference?

Thank you.

Tony

[Tony Roussos]

Re:Best way to stop C-3 water leaks

No Garage. Bad weather the last two years has contractors backlogged!!
My wife is scared. I told her I will run the heavy machinery and break ground myself!!!

Tony

[Harmon C.]

Re: C3 water leak

Tony Starting in 74 GM used a small metal piece with a rubber lip on the back of the sill plate. You have the older style rails on your corvette so I don't think the newer type will help but you could have both if you want. Lyle

[Klaus Friedrich #33362]

Re: C3 water leak and vacuum feedback

Tony,

try this: Take a hair dryer and switch it to cold. Sit inside the car and let someone other blow in the door gap and all other places where water is possible coming from. If the side window is closed, you'll hear the leak by whispering.

Wish you success

Klaus Friedrich
#33362

[David W.]

Re: C3 water leak and vacuum feedback

When your neighbors see you taking a hair dryer to your car, they'll know you are definitely in love with it! Sounds like a great idea though.

[Tony Roussos]

Re: C3 water leak and vacuum feedback

You don't suppose the tender kisses has given me away yet??

So, how about the vacuum operated doors all coming up when I shut off the engine??

Anyone??