A/C converted car - questions

[tony-muscle]

To tryed to slow down the rust in my vert I took POR 15 and taped an extension on the handle of a paint brush and went inside the cowl and brushed it on the top of the cowl and bottom and went up through the vent holes and put around the Hat. I had also removed the wiper arms and wiper motor to give more room. Of course I cleaned it the best I could before applying the POR. I actually poured some in and let it run out both sides of the drain holes in the cowl that are under the front fenders. Just trying to seal up any cracks I could. I then sprayed some undercoat inside the cowl similar to what Ford did during the assembly.

Okay, I was able to get in the cowl with my cellphone camera. Here are some pictures. There is some rust that appears surface rust. You can see the paint peeling. I actually peeled it more to inspect. Based on your recommendation, I will clean the area as much as possible, probably use some rust converter as far as I can reach, some POR15 or epoxy primer, maybe use some sealer, and spray some undercoat. It is a very difficult to reach area so I will get as far as I can. I think the area between the hat and fender is almost impossible to reach so maybe I can use some of that Eastwood frame spray that has the long tube extension. Also, will epoxy primer work similar to POR15, any preferences?

The first 3 pictures are the passenger's side, the next 2 are the driver's side and the last one is a view of the evaporator. How bad do you think it looks?

 

[Carolina_Mountain_Mustangs]

Now you know why the floor rust when the water pours in from the cowl. Bad design for sure but was not meant to last just a few years.

David

 

[tony-muscle]

Now you know why the floor rust when the water pours in from the cowl. Bad design for sure but was not meant to last just a few years.

David

From what you have seen, is that surface rust or do i have to worry about more? Will a layer of POR15 and some sprayed encapsulator do it?

Also, I think i would like to access the hat from the inside, do i have to disassemble the A/C box in the passenger side? I think it will make sense so the evaporator doesnt get clogged with debris from peeling and cleaning the area.

1971 M-code Mach 1

 

[Mister 4x4]

There are a couple of things you can try. You'll want to pull the A/C and heater core out for the best results. Finish scraping as much of the loose 'undercoating'/factory sealer you can from inside the cowl - moisture will accumulate under the loose stuff (the passenger air hat on mine, all that was left was the factory seal coat in the shape of the hat)

First, take a drop light and stuff it into the cowl - turn it on, and look for any light showing through from under the dash (if you see pin holes, they'll only get bigger). You'll need to repair pinholes and whatnot accordingly, then seal after.

Another test would be to take a hose (or bucket of water) and gently "flood" the cowl from the outside by pouring onto the windshield and letting it run into the cowl. Not a lot of pressure, and don't dump the bucket all at once - just enough for a good flow to make its way to the drain openings on the sides. Be inside the car with some good lights inspecting the underside of the cowl while someone waters the car for you.

If nothing leaks in, then dry it all out, apply some rust converter/encapsulator, coat with an epoxy sealer/primer (POR-15 or Rust Bullet), and apply seam sealer to all metal 'joints' (where panels meet, around the base of the air hats, etc.). This is a quick -n- dirty way to do it, and won't last forever. The right way is to open it all up and repair whatever damage is there and reseal. It's a lot of work, but worth it in the end by never having to revisit the cowl.

 

[tony-muscle]

There are a couple of things you can try. You'll want to pull the A/C and heater core out for the best results. Finish scraping as much of the loose 'undercoating'/factory sealer you can from inside the cowl - moisture will accumulate under the loose stuff (the passenger air hat on mine, all that was left was the factory seal coat in the shape of the hat)

First, take a drop light and stuff it into the cowl - turn it on, and look for any light showing through from under the dash (if you see pin holes, they'll only get bigger). You'll need to repair pinholes and whatnot accordingly, then seal after.

Another test would be to take a hose (or bucket of water) and gently "flood" the cowl from the outside by pouring onto the windshield and letting it run into the cowl. Not a lot of pressure, and don't dump the bucket all at once - just enough for a good flow to make its way to the drain openings on the sides. Be inside the car with some good lights inspecting the underside of the cowl while someone waters the car for you.

If nothing leaks in, then dry it all out, apply some rust converter/encapsulator, coat with an epoxy sealer/primer (POR-15 or Rust Bullet), and apply seam sealer to all metal 'joints' (where panels meet, around the base of the air hats, etc.). This is a quick -n- dirty way to do it, and won't last forever. The right way is to open it all up and repair whatever damage is there and reseal. It's a lot of work, but worth it in the end by never having to revisit the cowl.

I am afraid of tackling the task of removing the heater core and evaporator. Can I have limited access to the cowl hole through the air bypass (air recirculation) opening? I have not seen an A/C box out of the car so i don't know how easy would it be to remove the bypass flapper and the metal grill. I can't see what's on the firewall side that holds the flapper. Also, to remove the bypass opening grill how do I remove those buttons that hold it in place. I won't have space to drill them out. Since the A/C is not original to the car I am not worried about modifying it to have access to the cowl.

 

[Mister 4x4]

Well, the whole point is to find out if any of that rust you see in the cowl has holes to pass moisture through to rust out your floor pans. With the HVAC system in the way, it's going to be awful hard to see where it's coming from if you have a leak.

Something caused the rust on the floor pans - and the overwhelmingly most common cause is leaks in the cowl caused by rust.

You could get lucky with the rust converter/encapsulator, POR-15, and reseal with things how they are. I had no choice with mine, since it was so far gone.

Good luck with it - I hope you do get lucky and it's an easy fix.

 

[tony-muscle]

Well, the whole point is to find out if any of that rust you see in the cowl has holes to pass moisture through to rust out your floor pans. With the HVAC system in the way, it's going to be awful hard to see where it's coming from if you have a leak.

Something caused the rust on the floor pans - and the overwhelmingly most common cause is leaks in the cowl caused by rust.

You could get lucky with the rust converter/encapsulator, POR-15, and reseal with things how they are. I had no choice with mine, since it was so far gone.

Good luck with it - I hope you do get lucky and it's an easy fix.

I will definitely try the water method you suggested. I will try using cameras in hard to reach areas to check for wetness. I will also extend this water experiment to other areas of the car. While I don't have plans to purposely use the car when it rains I want to be ready in case an unexpected pour down occurs if driving out of town.

It is still one of those mysteries with my car on why the floors were as bad compared to the rest of the sheetmetal. The rust I see in the cowl appears to be just a little surface rust on the vertical wall of the hat, but not on the bottom piece of the cowl. The inside-of-the-car half of the cowl looks in great shape and sounds solid. I am afraid that this car may have been left abandoned at some time in its life and water may have leaked through the window or maybe it flooded, who knows. Or maybe they did a great restoration work throughout but crapped out when it came to the floors. It is those times when you really would like to know the car story.

 

[Sydneydrumdr]

My '71 vert that I am just disassembling has the driver side cowl blocked off and the passenger side cowl is open to the A/C box. How do I know this? I just cleaned out a 4" deep mouse nest that was tucked just below the open cowl and resting up against the A/C evaporator in the box. The opening/closing of the cowl is controlled by a vacuum operator damper that can allow fresh air or block off completely. Unfortunately for me, it appears that when there is no vacuum applied, the flapper is in the normally open position, should have been the other way from the factory around to prevent unwanted entry...

Rats and mice love this hide-e-hole. Here's my version from some Sydney rats.

 

[Carolina_Mountain_Mustangs]

My '71 vert that I am just disassembling has the driver side cowl blocked off and the passenger side cowl is open to the A/C box. How do I know this? I just cleaned out a 4" deep mouse nest that was tucked just below the open cowl and resting up against the A/C evaporator in the box. The opening/closing of the cowl is controlled by a vacuum operator damper that can allow fresh air or block off completely. Unfortunately for me, it appears that when there is no vacuum applied, the flapper is in the normally open position, should have been the other way from the factory around to prevent unwanted entry...

I put the 1/4" mesh wire right where the nest is sticking out along with behind the plastic cowl covers to keep most of them out.

David

Rats and mice love this hide-e-hole. Here's my version from some Sydney rats.

 

[72Q]

I have a question along the same line....I have a 72 mach 1 factory a/c that has the usual lower cowl rust. I can buy a new upper and lower but only for non a/c cars...what are the differences? Would I be easy to modify the lower cowl to fit my factory a/c?.

 

[MikeGriese]

I have a question along the same line....I have a 72 mach 1 factory a/c that has the usual lower cowl rust. I can buy a new upper and lower but only for non a/c cars...what are the differences? Would I be easy to modify the lower cowl to fit my factory a/c?.

The differences are many - best advice is to have your body shop disassemble things piece by piece so they can keep track of the differences. At the least, the vent opening on the drivers side will need to be filled, and the brackets for the blower motor housing will need to be swapped over. If you have to get into replacing the firewall, those are non-air as well.

 

[72Q]

I have a question along the same line....I have a 72 mach 1 factory a/c that has the usual lower cowl rust. I can buy a new upper and lower but only for non a/c cars...what are the differences? Would I be easy to modify the lower cowl to fit my factory a/c?.

The differences are many - best advice is to have your body shop disassemble things piece by piece so they can keep track of the differences. At the least, the vent opening on the drivers side will need to be filled, and the brackets for the blower motor housing will need to be swapped over. If you have to get into replacing the firewall, those are non-air as well.

Fire wall is solid it just rusted out the the entire a/c vent to include the heater box bolt (clip thingy) and where the driver side vent would be