Plugging and sealing a hole in a plastic evaporator case

[JHZR2]

I had been chasing water in the floorboard in my 1991 Mercedes 350sd.

I thought it was the typical foam condensate drain failure. That tube wasn’t in great shape.

But I wasn’t actually seeing a lot of moisture coming from the drain. I found it coming from the case. I probed around and found a small hole.

I suspect maybe at some time the clip holding the parking brake cable in place, which practically touches the evaporator box, was pushed up and broke the box.

There is some surface rust on the floor by the throttle. I thought it was from salty shoes, but I think it’s from this!!

So here’s the hole:

To drive home I used the only thing I had, blue painters tape. And naturally it started to seep. So I’d like to figure out the adhesives to do the repair.

I don’t know what’s in there, looks like some debris. But I won’t mess unless some day I need to change the evaporator or heater core. Until then I’d like to plug it.

I was seriously thinking of chewing gum to clog the hole, and then flex tape or gorilla tape to seal it. Maybe that’s the best bet or perhaps with some low energy plastics adhesive mix jammed in there then some tape or other covering.

It’s very tight and uncomfortable to access.

Any suggestions?

 

[SHOZ]

If you can get it dry some black gasket maker silcone would work.

 

[dnewton3]

Some possible solutions come to mind

- JB Weld makes a plastic sealer: https://www.jbweld.com/products

- Flexseal: www.flexsealproducts.com

- RV roof tape "Eternabond": https://www.hbfuller.com/en/north-america/products-and-technologies/brands/eternabond
(available at several sources)

 

[HowAboutThis]

I'd look into epoxy type things they have at home improvement or auto stores. As long as it isn't a hole that's supposed to be draining (I didn't look closely) epoxy putty type things have worked well for me in random things.

 

[brianl703]

JB Weld Plastic bonder (a 2-part polyurethane adhesive) with a patch made of ABS plastic sheet. Could also use sheet metal but it might rust.

 

[JHZR2]

The main considerations I have are that it is:

-extremely tight there. The clip for the parking brake cable is bolted in there and removal under the dash is near impossible

- probably a low surface energy plastic that will have bonding issues. I’ve worked with these before but it’s still a big consideration.

 

[brianl703]

- probably a low surface energy plastic that will have bonding issues. I’ve worked with these before but it’s still a big consideration.

Do you have any PVC pipe primer? Apply some in an inconspicuous place and see if it melts the plastic. I think it's probably made of ABS.

 

[Astro14]

PLASTEX, PLASTIC REPAIR KITS, FIX CRACKS, REPAIR PLASTIC

Manufacturer of plastic repair kits. Plastex easily glues, fills gaps, repairs stripped threads and can remake tabs or small parts in just minutes.

www.plastex.net

Works very well. Bonds to all sorts of plastic.

 

[Rand]

Plastex looks good.
I have also used underwater type tape for a similar repair... but that would be second option for me.

https://www.amazon.com/Gorilla-4612502-Waterproof-Patch-Black/dp/B07HSKRYQW

 

[Chris142]

This stuff

 

[JHZR2]

Plastex looks good.
I have also used underwater type tape for a similar repair... but that would be second option for me.

https://www.amazon.com/Gorilla-4612502-Waterproof-Patch-Black/dp/B07HSKRYQW

I think I’d use something like that over whatever I apply in the hole.

 

[clinebarger]

Sure it's not Fiberglass? GM/Harrison used fiberglass evaporator housings for decades.

 

[Nukeman7]

I'd cut out a thin aluminum square patch from a soda can and slather regular JB Weld into and around the crack. Then apply the aluminum patch and secure it with blue painter's tape until it cures overnight. Or you can just use epoxy putty to seal up the hole.

 

[2strokeNorthstar]

Butyl tape would be a fast effective patch I think.

 

[doitmyself]

Is there room to drill the hole round and then insert some type of screw plug?

A foam ear plug??

 

[JHZR2]

Sure it's not Fiberglass? GM/Harrison used fiberglass evaporator housings for decades.

Could be. But it would be the GF PP or PE then, no? It’s not fiberglass like the body of a corvette or a boat or a ladder, right???

 

[vavavroom]

I'd patch this with duct seal/sealing putty (Dum-Dum). It sticks and seals well, it is water-resistant, and it ages well. A 1lbs brick looks like dark grey plasticine/C4. Pinch off a quantity, knead it, shape it, and apply it. That stuff has many uses around the house, car, boat, etc. Great for eliminating noise from rattling and chafing parts that rub or vibrate.

https://www.amazon.com/Gardner-Bender-DS-110N-Duct-Seal/dp/B00689V41G

 

[joegreen]

Devcon plastic welder. Its two parts but its not an epoxy. Its smells horrible so you know its good. It’s supposed to melt the plastic a little and bond with it. Its some type of resin and it does have a shortish shelf life so get a small container of it.

 

[Dave9]

Seems like due to the location, ncluding that it's on the bottom, you will either need a patch applied to the outer surface, or need something very viscous. If there are cracks extending away from the hole, it will be difficult to get putty to work unless you cover the entire area.

I think I'd go with some RTV sealant like Chris142 suggested, clean the area around the hole, fill the hole then around the hole on the outer surface, and scrounge up a scrap of plastic to bond to the outer surface. However the sealant you put into the hole, may take a very long time to set up, days without using the A/C, while an epoxy can set in minutes to hours.

If it were out of the vehicle, I'd use epoxy instead, but not necessarily JBWeld as its main virtue is being more hard and brittle than most, which aren't beneficial in this application. If applied to a material that can flex like thin plastic, and subject to temperature fluctuations, a more flexible epoxy usually works better.

 

[JHZR2]

Seems like due to the location, ncluding that it's on the bottom, you will either need a patch applied to the outer surface, or need something very viscous. If there are cracks extending away from the hole, it will be difficult to get putty to work unless you cover the entire area.

I think I'd go with some RTV sealant like Chris142 suggested, clean the area around the hole, fill the hole then around the hole on the outer surface, and scrounge up a scrap of plastic to bond to the outer surface. However the sealant you put into the hole, may take a very long time to set up, days without using the A/C, while an epoxy can set in minutes to hours.

If it were out of the vehicle, I'd use epoxy instead, but not necessarily JBWeld as its main virtue is being more hard and brittle than most, which aren't beneficial in this application. If applied to a material that can flex like thin plastic, and subject to temperature fluctuations, a more flexible epoxy usually works better.

That’s why I do generally think something like dum dum as @vavavroom mentioned, then covered with a very tenacious waterproof tape, might be best. Any adhesive would need to be very viscous. Being able to press a plug in upward seems beneficial.