Cowl to firewall leak/rust

[Hstrymkrs]

I mentioned this in the WHYDTYTT. I noticed a leak coming from the firewall area, and I traced it back to directly above the clutch master cylinder in cowl area. Below are the pictures. I am open to suggestions. I have seen images from trucks far worse that’s mine. Do I clean it up really well and PQR15 in and seal it afterwards. There does look to be some integrity issues, and I am unsure if welding it up is the answer. I don’t know how to weld.

Thanks,

William

[Gary Lewis]

I wouldn't try to weld it, and I can sorta weld. The issue is that the metal is very thin and you'll surely burn through every time you strike an arc.

On the floors of Big Blue I had some rust and I brazed most of them shut, which worked pretty well. But it was still fairly easy even with a MAPP gas torch to get the metal so hot that it would melt, and I had to be fairly careful.

For the most part it worked, but there were some perforations I missed, and when I painted the floor with POR-15 I had a few spots where the paint oozed through. But that wasn't a problem as it didn't really drip and I smoothed it with a brush from the back side.

However, since then I've learned that there is something called POR-15 Patch, and it looks like the right stuff to fill holes in rusty metal.

Here's a description of it, and I think it is what I'd try in your bigger holes. And then I'd coat all of the rust with two coats of POR-15 paint. And, while that is tacky top-coat it with some standard paint that is UV-stable to protect the POR-15.

[Hstrymkrs]

I wouldn't try to weld it, and I can sorta weld. The issue is that the metal is very thin and you'll surely burn through every time you strike an arc.

On the floors of Big Blue I had some rust and I brazed most of them shut, which worked pretty well. But it was still fairly easy even with a MAPP gas torch to get the metal so hot that it would melt, and I had to be fairly careful.

For the most part it worked, but there were some perforations I missed, and when I painted the floor with POR-15 I had a few spots where the paint oozed through. But that wasn't a problem as it didn't really drip and I smoothed it with a brush from the back side.

However, since then I've learned that there is something called POR-15 Patch, and it looks like the right stuff to fill holes in rusty metal.

Here's a description of it, and I think it is what I'd try in your bigger holes. And then I'd coat all of the rust with two coats of POR-15 paint. And, while that is tacky top-coat it with some standard paint that is UV-stable to protect the POR-15.

Thanks, Gary. I remember you talking about welding the floor and the risk/probability of burning through. Glad to see the above mentioned filler. It seems way more reasonable for this situation. I will look it up and start reading about it.

Here are some more pics after a brass wire brush and better access.

Not sure why the above picture is upside down.

The firewall does not appear to have any integrity issues and the reinforcement where the master cylinders mount appears to be strong and solid when tapping on them. It seems logical that the above mentioned stuff should work perfectly.

William

[Gary Lewis]

Thanks, Gary. I remember you talking about welding the floor and the risk/probability of burning through. Glad to see the above mentioned filler. It seems way more reasonable for this situation. I will look it up and start reading about it.

Here are some more pics after a brass wire brush and better access.

Not sure why the above picture is upside down.

The firewall does not appear to have any integrity issues and the reinforcement where the master cylinders mount appears to be strong and solid when tapping on them. It seems logical that the above mentioned stuff should work perfectly.

William

The pic is upside down 'cause you turned the camera over. Cameras encode the orientation in the metadata in the picture's file. Smart devices read that data and reorient the pic before displaying it. Our forum isn't smart and doesn't read the data. You have to reorient the pic before posting by using an app.

Anyway, I'd want to use the POR-15 paint everywhere I could and only use the putty where needed. That's because the paint will run into cracks and crevices and seal them, but I don't think the putty will. The paint sticks so well that if you put the lid back on the can w/o using something like wax paper or Saran Wrap to keep any paint in the groove from hitting both the can and the lid you'll never get the lid back off. DAHIK.

And since the paint is rather thick it won't run through little pin holes. So I'd just use the putty where you are sure the paint will run through and then let the paint fill and seal the little holes and cracks.

Also, once POR-15 cures it is HARD and the only way to get another coat to adhere is to sand it. You don't want to have to do that down in the cracks and crevices of the cowl. So paint everything with one coat, go back and hit it with another coat while it is still tacky to ensure full coverage, and then coat that with the top coat while everything is still tacky.

I usually use a brush for the POR-15 coats and then use a spray can for the top coat as when everything is sticky it is no fun brushing another coat on. But down in the cowl it may be hard to spray so you'll have to decide what to do there.

[Hstrymkrs]

The pic is upside down 'cause you turned the camera over. Cameras encode the orientation in the metadata in the picture's file. Smart devices read that data and reorient the pic before displaying it. Our forum isn't smart and doesn't read the data. You have to reorient the pic before posting by using an app.

Anyway, I'd want to use the POR-15 paint everywhere I could and only use the putty where needed. That's because the paint will run into cracks and crevices and seal them, but I don't think the putty will. The paint sticks so well that if you put the lid back on the can w/o using something like wax paper or Saran Wrap to keep any paint in the groove from hitting both the can and the lid you'll never get the lid back off. DAHIK.

And since the paint is rather thick it won't run through little pin holes. So I'd just use the putty where you are sure the paint will run through and then let the paint fill and seal the little holes and cracks.

Also, once POR-15 cures it is HARD and the only way to get another coat to adhere is to sand it. You don't want to have to do that down in the cracks and crevices of the cowl. So paint everything with one coat, go back and hit it with another coat while it is still tacky to ensure full coverage, and then coat that with the top coat while everything is still tacky.

I usually use a brush for the POR-15 coats and then use a spray can for the top coat as when everything is sticky it is no fun brushing another coat on. But down in the cowl it may be hard to spray so you'll have to decide what to do there.

I used the POR-15 once when I moved the radius arm brackets back for the lift kit. It worked very well and you are right in how it hardens/cures. I was very impressed with it. It sounds like the biggest challenge will be the clean/prep to ensure the best adhesion possible. I will start looking at the pint/quart cans and spray cans and the filler/sealer so I can plan how much to buy as it isn’t cheap if I remember.

I am sure I didn’t seal the small can I had the wax or cling wrap and it will be useless.

I will know next time. Thanks for the heads up.

William

[kramttocs]

I used the POR-15 once when I moved the radius arm brackets back for the lift kit. It worked very well and you are right in how it hardens/cures. I was very impressed with it. It sounds like the biggest challenge will be the clean/prep to ensure the best adhesion possible. I will start looking at the pint/quart cans and spray cans and the filler/sealer so I can plan how much to buy as it isn’t cheap if I remember.

I am sure I didn’t seal the small can I had the wax or cling wrap and it will be useless.

I will know next time. Thanks for the heads up.

William

Fixing this by cutting it all out and replacing is a big job so if it works for the usage/purpose of the truck - the solution outlined sounds valid. It's similar to what I did on my 80 and it will likely outlast the rest of the truck.

I'd also consider spraying in bedliner or flex seal after the por15 has taken care of the active rust.

[Gary Lewis]

Fixing this by cutting it all out and replacing is a big job so if it works for the usage/purpose of the truck - the solution outlined sounds valid. It's similar to what I did on my 80 and it will likely outlast the rest of the truck.

I'd also consider spraying in bedliner or flex seal after the por15 has taken care of the active rust.

I like the bed liner or flex seal idea! That will shield the POR from UV as well as provide even more leak stoppage.

[Hstrymkrs]

Fixing this by cutting it all out and replacing is a big job so if it works for the usage/purpose of the truck - the solution outlined sounds valid. It's similar to what I did on my 80 and it will likely outlast the rest of the truck.

I'd also consider spraying in bedliner or flex seal after the por15 has taken care of the active rust.

Thanks, Scott. I will add that to the shopping list as well. It looks like the local advance auto stocks the POR stuff so I will go look at it today and start planning.

[FuzzFace2]

Thanks, Scott. I will add that to the shopping list as well. It looks like the local advance auto stocks the POR stuff so I will go look at it today and start planning.

Dig out as much of the old seam sealer you can so you can get what ever you use down in there.

The hard part for me, I did not have holes, was working through the cowl opening as you need to do that side also.

Mine only had the seam sealer flaking off so I got the loose stuff off and got some brushable seam sealer to get it sealed like factory.

I then used the spray Flex Seal (clear) to go over that. I used a plastic straw from carb cleaner on the can so I could get it in areas that needed it.

I cant remember if I painted in the cowl area but think I did when I painted the firewall.

Dave ----

[Hstrymkrs]

Dig out as much of the old seam sealer you can so you can get what ever you use down in there.

The hard part for me, I did not have holes, was working through the cowl opening as you need to do that side also.

Mine only had the seam sealer flaking off so I got the loose stuff off and got some brushable seam sealer to get it sealed like factory.

I then used the spray Flex Seal (clear) to go over that. I used a plastic straw from carb cleaner on the can so I could get it in areas that needed it.

I cant remember if I painted in the cowl area but think I did when I painted the firewall.

Dave ----

Thanks, Dave. That is exactly what I spent the day doing.

I cleaned out the old seam sealer as most of it was coming up on one side and I figured there could be some integrity issues underneath it. I did find more holes. I also finished tearing out the duct work for the heat/air so that I could assess the passengers side more. Glad I did as there are some small holes there as well. Here is a look at the process as I went along.

I am thinking I can get into the cowl with the small angle grinder with a wire wheel and get the seam cleaned up well and then put the POR patch/filler, then POR paint, and finish it with the paintable bed liner as mentioned above.

I plan on going slow and easy so I don’t damage any of the thin metal, but leave as much in to support the POR as it sets up and hardens.

I was able to get all the old outer layer of seam sealer off, and it left a small “filler” in the seam to close the gap. I think if I get the metal clean enough it will bind and ultimately do well at sealing it. I am feeling confident about the process and it working.

William