Rain Leak

skills4lou · December 3, 2007

98 K3500 crew cab.

I searched but haven't found anything yet on here. I have a rain leak that's coming in through the firewall/underdash area on the passenger side, through the HVAC blower area. I took the cowl apart, cleaned everything I could, removed the drain on the rightside firewall and made sure it's clean. Really didn't find much in any of these areas. I did find that the two screws on the far right of the plastic cowl piece must be right above the airbox, and siliconed them on reassembly. This leak is definitely not coming in around the windshield, it has to be coming in somewhere with the fresh air intake for the HVAC. Is there anything I can seal or should check before I start tearing out the blower/ductwork looking for this dang leak? It's driving me crazy.

sillyazz · December 4, 2007

Are you sure its a rain leak? Might be your A/C drain is pluged?

skills4lou · December 4, 2007

Are you sure its a rain leak? Might be your A/C drain is pluged?

Yup, it's rain. Haven't used the truck in two weeks. We just got over 1/2" of rain in the last 24hrs, and lots of it wound up inside the truck.

Is it possible the rain is going in a normal hole in the fresh air inlet, then not draining out the A/C drain and just backing up until it comes in the cab? I don't know where the A/C drain is, but if someone can point me in the right direction or post some pics I'll at least check it and rule that out before tearing the dash apart.

The only other thing I can think is there's a seam somewhere on the cowl that's leaking, but I'd have to remove the fender to get any farther down inside to look for that. I really like this truck, but the leak is starting to drive me nuts.

Zembonez · December 4, 2007

I really like this truck, but the leak is starting to drive me nuts.

Man, leaks are such a pain in the .....

I've had some success pulling the carpeting back as much as possible and having a helper run water (on low) over the cowl starting from one side and slowly working across. If it's a decent sized leak you should be able to at least narrow down the area it is coming in. Makes it a lot easier to do the detective work if your suspect area is smaller. As far as suggesting where it might leak I am afraid I am no help. Maybe somebody has had a similar problem and will chime in. Good luck with it.

skills4lou · December 4, 2007

Thanks Zembonez, but I'm past that stage. My wife's patience has run out with my "honey can you run the hose again, please?" I've got all the carpet pulled back, and even had to remove the front passenger seat to get it up and dry everything out. It's still coming in somewhere around the HVAC, but that big black monster under there is kinda hard to see around. I'll get this figgered out sometime, but for now my passenger side of the truck is dominated by towels to soak up the drips.

Zembonez · December 4, 2007

Thanks Zembonez, but I'm past that stage. My wife's patience has run out with my "honey can you run the hose again, please?" I've got all the carpet pulled back, and even had to remove the front passenger seat to get it up and dry everything out. It's still coming in somewhere around the HVAC, but that big black monster under there is kinda hard to see around. I'll get this figgered out sometime, but for now my passenger side of the truck is dominated by towels to soak up the drips.

Well sorry I'm no help then. Leaks are such a pain.

Anybody else have any suggestions?

skills4lou · December 11, 2007

TTT

Anyone have a pic of the A/C drain? I'm still trying to track down this stupid leak. Thanks!

EDIT:

I found the A/C drain, at least I'm pretty sure that's what it was. It's a small pipe with a rubber elbow on it just to the right of the heater core lines. I found that if I have the fan running there's a flow of air coming out the drain. I'm guessing that means that the drain is clear, since it was a nice strong flow of air.

So, I'm just gonna re-seal that whole piece where the two screws from the cowl go through above the heater box.

Deoncollins69 · December 15, 2007

This is actually a common problem. One of two issues. First the screws that hold the cowl cover down can actually let water leak into the cabin area and straight down into the ac housing. This gives the illusion that your a/c heater box is the issue. The other issue is also a cowling issue. it is more invloved. There is a seam ont he drivers and pasengers side on the top of the cowl. This is a spot welded and body putty sealed seem. It is likely that this body sealer is split and causing the same issue. If you are handy, and very Carefull!!!!! you can fix one or the other. I'd check the screws for the cowl cover first. Step one take off the wiper arms. Rom there you can pull all the screws from the cowl cover. Ther are 2 on the out edges for the end covers and them four to five more fore the actual cover. You'll need some good sealant to seal the screws. Don't you permaseal. If you do you'll have a hard time fixing the other issue if this does nto remedy the problem. Coat the screw and also dabbed soem on the hole. Reinstall and let is set for a bit. Then get the hose out and let it run directly onto the winshield. If you hear a leak it's the seam in the cowl. For that you'll have to dissasemble and pull the fender. Might be a job for a body shop. I have seen one case where the windshield was not set in place correctly from the factory. You be able to see that from the inside at the base of the winshield. Good luck. Feel free to contact me. My 97 did this and it drove me nuts for months.

skills4lou · December 16, 2007

Over 2" of rain in the last 2 days, and not a drop inside the truck. Wahoo!!

truckin-on · May 5, 2008

Over 2" of rain in the last 2 days, and not a drop inside the truck. Wahoo!!

I have the same problem - driving me nuts also. What eventually fixed the problem for you? I also have a problem of water dripping on the passenger side when the A/C is on so I suspect a clogged drain line...