Water leak when it rains?

Leaks can be very deceptive and difficult to track. Thankfully this is a truck so there is a smaller area to work with. First thing would be to look at where the water collects. Say it's the drivers side footwell, you would start on that side. I tend to start by using a good light and work my way around the area looking for washed areas or water marks. Using the footwell example I would look at the door opening, any marks where water passed? Then under the dash to look at the A pillar area and up under the dash at the firewall and cowl area. Any marks or stains? Then look at the area around the windshield, are there any rusted areas, is the glass still bonded to the cab? Check the rear window as well. There are a few common locations for leaks on vehicles, especially older ones, The glass is essentially glued in, rust or paint issues can cause the bond to fail and water can get in. Then the body seam where the firewall, cowl panel and pillars all join up, there are a lot of seams and the seam sealer can fail. The HVAC has opening under the cowl for air into the body, they can leak. There is a drain line from the HVAC case to handle some water and any condensation that comes from the cores, they can get plugged. Door seals can get torn or pulled free. The rear glass and the third brake light seals can leak. You know it only leaks in the rain, so ask yourself a few questions, Does it have to be a hard rain? Does it matter if the truck is moving or stationary? Where does it get the wettest? Then for testing the quickest way for a DIY is a water bottle or watering can. First look for signs and stains. Next look above those for seams or parts that can be loose. Not really seeing anything? Time for the next step apply water to one section of the vehicle, like the center to left side of the windshield. Any water inside? No, apply water to the other side. Still nothing, go around each door and window on the drivers side. Keep going to the rear glass, CHMSL and then to the other side. It might take a few times around to check everything. Another way to find leaks is to use a smoke machine, for that you use the fan inside the truck, turn it on high with outside air, then you move the smoke machines nozzle around the different areas and look for the smoke to blow away from the area of the leak. This is handy for glass and seam leaks but can be difficult if you don't have good access. If the truck needs to be in motion it gets trickier as those could be coming from water spray against things that don't get wet under falling rain. That is when you have to look at the firewall, up under the cab at drains, the floor panels themselves and the seams around those panels. It can take a while to find them, and depending on the location the repairs can be difficult.

The truck has been parked and I just bought it. I have marked the spots that I have seen wet runs while it's raining. I'll take a video and try to upload it

Are the spots all in one area or are they spread out? Will wait for the video, but if they are spread out I would start with the glass, gently push on it and see if it flexes from the body of the truck. Also look at the cab mounted light(s) they only seal with a thin foam that degrades. For testing a quick thing is to use painters tape and apply it around the area to stop water, then dump water over it, still have leaks? Likely not the places you applied the tape.

The black marker marks are where I have seen water runs but you can see other spots that have water runs around it all. It's been sitting 10 years without the trim on lol

Those all look like the glass seals are bad. Not surprising given the year of the vehicle. The roof though is likely the rear brake light or if someone added marker lights on the roof. For the glass seals, open them and clean the lip of the seals and with them open apply some silicone spray by putting it on a rag and wiping it into the seal. Do that a few times and gently try to reform the seal so it sets tighter to the glass frames. Look at the hinges as well as the pins can wear and the glass doesn't fully seal.

I'm limited on what I can do being that someone else is funding this project and I'm on his timeline for working on things. He's planning on removing the rear window and resealing it. He's an experienced body man so I presume he knows what he's doing. I'll keep you posted

Please let us know. Rear glass seals can fail so that could be some of it, but gravity pulls water down, so leaks above the glass are probably not the glass. But you can tape plastic over it and wet the cab down and see where the water enters. However I understand the limits of others. Some of the things that I'm told "No that has been that way for a while, it doesn't need to be repaired" would make you scratch your head.

I will try out taping it up bit by bit and hold the hose on it. We already sprayed the outside with soapy water and blew air from the inside out with no luck of bubbles

Water leaks can be a pear sometimes. If you get some of the cheap plastic "drop cloth" roll they sell you could tape it around the entire vehicle. Then cut out an area, like the rear glass. Apply tape so that the water cannot get under the plastic and hit the area around the glass with a water hose. Leaks? Yes = reseal the rear glass and test some more. No = Tape the cut out area back into place, then cut out a door. Hit that with the water hose. It allows you to isolate each possible area for leaks. Don't overlook body seams or lights. Basically you put a raincoat over the cab and then tear holes in areas that could leak one at a time. The hard areas are usually the cowl and firewall because you have to get creative with the testing.

I haven't had a chance to work on the truck yet and I'm sorry for keeping you waiting. I do have the water hose pulled out beside the truck and a big sheet of drop cloth roll right here waiting for me to get to it. I've just been feeling really overwhelmed right now with everything that's going on and it's destroyed all of my senses of purpose and order on everything. I'm trying to pull myself together and I shall SUCCEED!!!!

Not a problem. We are not going anywhere so take your time.

Ok so my friend came out to help me figure out the leaks with a garden hose sprayer set to the jet setting and I sat inside while he started from the bottom of the seams and worked his way around those and then the windows and the brake light. The back cab seams have multiple leaks on both sides. He said he's going to get some kind of seam sealer or something to fix it. I'm going to send you a quick picture of both of those seams and you'll probably see what he is talking about

Not uncommon. If they are cracked on the exterior you can go after them with a wire wheel and remove the old sealer and treat any rust in the seam with Ospho, then use a flowable seam sealer and reseal them. Most body shop supply places will have the correct stuff. If you mask off the areas around the seams in a nice even size you can clean out the sealer, put in some black replacement and make them into a "feature".

I guess my pops being a 50 year body man will hopefully help alot

I'm betting he could be very helpful.

He is

Good to hear :)

Lol just as highly adha as me. We have tried getting started on rounding up the sealant and other possible tools and then we something shiny lol. I'm sending a picture of the yard so that you get the idea of how easily it is to get distracted ?

See ADHD FunPark!!!

Looks like fun to me. Reminds me of my uncles place years ago, he bought damaged auction cars as well as repairing other odd vehicles. Wasn't uncommon to look out and see a 50's Jaguar parked next to am MG with a Camaro or a Vega setting there.

Lol it's definitely never a dull moment

lol nope!