TheSamba.com :: View topic - Sealing Plastic Radiator or Heater tanks to core

Sat Nov 27, 2021 2:23 pm

I remember when plastic radiators in new cars first came off the boats. We at the dealership laughed pointed and scoffed at the stupidity of plastic in the cooling system.
Well....... turns out we were right about the stupidity but wrong about its long term use in the industry!

So, I'm looking at a leaking heater core.
I can smell the sweet hot coolant with the warm air.

I'm going to pull the heater box shortly to fix the core, clean the box of mouse crap (I can lightly smell that too) reseal the flaps, install dhaavers Jeep resistor and a new blower fan.

I purchased a new heater core but am concerned about the new design with less cores and fins delivering less heat.

If I pull the core and see that it is a plastic tank leaking....... what do I seal it with?

I know they used gaskets but I imagine buying one would be a fruitless interweb search.

What can be used in this situation?
Wet suit rubber?
The Right Stuff?
Caulk Backer Rod?

I honestly have no idea and my searching so far has turning up absolutely nothing but some new radiator tank gaskets for unknown vehicles.

Anyone experienced in plastic tank radiator repair?

Dave

Sun Nov 28, 2021 7:22 am

i looked around the 'Net too as i want to return to an OEM core. not a lot of info but two things come to mind... all of course after testing at 40psi or so to actually confirm a leak.

some have just squeezed the crimps a skooch tighter all the way around without trying to take anything apart.

i'd like to try finding the leak, marking it, cleaning the core inside and out, drying it completely, and putting it under a strong vacuum. then dribble some form of epoxy or maybe even better a resilient compound into the leak area to get somewhat sucked in and let it cure. there's so much thermal expansion and contraction i'm not sure a hard epoxy is the proper sealant. RTV? TRS? PL2000?

or just buy a pressure tested used OEM core for $50.

Sun Nov 28, 2021 7:41 am

Dave--You just used the term, out of my wheelhouse which is where I am on this. I have a spare donor in my attic which I have been keeping "just in case", but even it may be leaking for all I know. Haven't looked at it recently so forget what it is like. If you are talking about reattaching a new plastic part which seems to be gasketed to the aluminum core, I would recommend 3M 5200. Unfortunately, it doesn't like to adhere long term to acrylic plastics. If the capping part is not acrylic, I don't see why this wouldn't work. It is a very strong adhesive, but also a sealant and so if it were to start to leak after 10 years or so, any mechanical connection should keep the coolant where it's supposed to be.

Just a shade tree guy, so wouldn't put this solution in a space shuttle with out some serious testing. Might be worth getting a part out of a junker and doing some investigating.

Also know Walker Radiator will custom make anything you want, but might be pretty pricy.

Duncan

Sun Nov 28, 2021 11:27 am

Guys;

I recall assisting on an '80s Jetta whose Heater Core had also become incontinent...when the old one (by Valeo) came out (after >2hours!), it too had plasdick endcaps held in place by folded over tabs which were part of the alu core...the seal appeared to be a closed cell foam...essentially some sort of fancy weatherstripping! ...I wasn't impressed by the modern quick and cheap construction either, but I guess the days of a soldered copper and brass HCs are long gone...but taking a lesson from this construction, I would recommend (thin, self-leveling) RTV as a sealer, over an epoxy, for its compliance (which will and is needed to accommodate the huge thermal operating range)...and I do like the idea of using a vacuum to draw it into the leak, instead of uncrimping the endcaps and essentially remanufacturing the entire thing. In the first place, those folded over tabs were never intended to be unfolded and refolded...in the second place, it would be difficult to get new (or make with the right material) the endcap seals.

Good Hunting!

Sun Nov 28, 2021 12:41 pm

DuncanS wrote: I would recommend 3M 5200. Unfortunately, it doesn't like to adhere long term to acrylic plastics. If the capping part is not acrylic, I don't see why this wouldn't work. It is a very strong adhesive, but also a sealant and so if it were to start to leak after 10 years or so, any mechanical connection should keep the coolant where it's supposed to be. Duncan

This was going to be my recommendation as well (5200 is awesome, especially the original slow cure variety) then looked it up to check temp range, and it's only spec'd to 198F.

If it were me, and I was trying to seal from the "outside" of the flange (i.e. not in contact with the water itself) I'd use it anyway if I couldn't replace the core. The original will take several days (3-5 IME) to cure unless the humidity is very high (never is here...). Misting with a spray bottle helps. Used this stuff many times, on my boat and elsewhere, and it's killer stuff, just allow time for full cure before stressing it. Thorough cleaning and scuffing to increase bonding surface area of the plastic (like 36 or 80 grit) helps as well.

Sun Nov 28, 2021 1:12 pm

"glass-filled Nylon 66" seems to be what many are made of... dunno the exact plastic on VW but it is definitely glass-filled as you can hear it crunch when scraped with a knife.
(tip to AvE for the win)

Sun Nov 28, 2021 1:17 pm

I resealed a Volvo plastic (same stuff) with epoxy - not the quick cure, but the slow cure - much better product. Car is still running 5 years later. I used the JB Weld two part clear epoxy product and crimped the aluminum to see the epoxy be extruded from the joint

I would not do it on any of my fleet of Ladies' Volvos, though.

Sun Nov 28, 2021 2:23 pm

I found this site but while interesting ….. doesn’t seem useful to me

https://www.thermprocesses.com/index.php?cPath=29_105

Dave

Sun Nov 28, 2021 4:16 pm

Now I see what you are up against. If it's leaking through the plastic, I'd try to patch that. If it's leaking at the mating of the two materials, I would remove the plastic and re seal it as i suggested with 5200. The plastic is not acrylic.

And the site https://www.thermprocesses.com/index.php?cPath=29_105 Shows some crimping strips which might be helpful.

Duncan

Thu Dec 02, 2021 3:16 pm

I'm going to add this link to a new thread dealing with resealing the OEM heater core.

https://www.thesamba.com/vw/forum/viewtopic.php?t=762484

I think I'll let this thread die a peaceful death..........

Dave