Heater core swap or repair?

[Pengineer1]

My '86 has started smelling like coolant inside the cab when I run the heater and even the inside of my windshield kinda fogs up with I assume coolant. Anybody here ever had to remove your heater core from a Gen 1 truck?? How difficult of a job? I'm assuming the heater core is leaking and I'm hoping I can resolder/ repair but I may have to try to find a new heater core? Any suggestions / experiences welcome, thanks in advance. Bill

[geezer101]

They are 'easy' enough to remove. You have to drain coolant, disconnect the heater hoses and remove the entire heater assembly with the control levers intact. There are only 4 flare nuts holding it in place - 2 mounting the upper half of the case to the dash frame and 2 on the firewall. The ducts are only press fitted to the heater casing and slip right off. Be prepared to do some mechanics' yoga to take it out. The issue will be the heater core. If it has failed on an end tank, there's a good chance you will be able to solder the holes up. If it's the cores it'll be harder. AFAIK there are no compatible heater cores and there are no OEM style replacement units*. Gen 2 HVAC isn't an option as an alternative either. Might only be a bad heater valve or hose. I've chemically flushed one using citric acid powder to dissolve all of the sediment built up inside of the core. Also a good opportunity to completely disassemble the heater and clean it out.

*I've thought about this and considered that an aftermarket 100/125cc 4 stroke radiator core 'might' be a plausible core replacement. There are different sizes available and can be bought relatively cheap. Issues are hose connection diameter and how much you will be prepared to modify the heater case to make it work...

[geezer101]

Just an example - https://www.aliexpress.com/item/4001...d=3sUWgWfzaICK

M12 thread should be adequate for barb fittings

[SubGothius]

First try using Bar's Leaks Radiator Stop Leak Tablets. They're cheap and fairly effective for minor leaks, and don't have any sodium silicate that could lock up your engine if you have any coolant leaking into the oil system.

[Pengineer1]

Thanks Geezer! That's just the info I was looking for... but I've never heard it called mechanics yoga!! I've done my share of that and don't mind having to do it again especially on old vehicles like these that actually use screws and are meant to come apart and go back together. Most modern crap with rivets and spot welds could never be thought of as yoga!

[geezer101]

The heater case halves are held together with steel spring clips. Expect them to be rusty as hell - and don't lose them or you are toast. All of the air seals on the control flaps will have decayed. I used a roll of self adhesive foam seal (2mm thick by 10mm wide) to make new seals. The main flap has a big vinyl cover on it that isn't necessary. Just run the foam tape on the edges that make contact with the heater case.

...and, you're welcome

[xboxrox]

Heater control valve thread: http://www.mightyram50.net/vbulletin...+control+valve

Aliexpress ? Might they have em ?

[ostlar]

I had the same problem as you, except mine got so bad that coolant started seeping out of the heater assembly.

Getting the heater core out wasn't a terrible task, the worst part of it was removing the hoses as they were stuck there pretty good. Use your hands and twist them while you pull the hose off. Do not use a pipe wrench like I did at first, ended up tearing a hole in the hose and slightly bending the pipe. It was all fixable afterwards though.

I located the leak to some crusty old solder joints, luckily they were on the outside part of the tubes.
Cleaned them up with a brass brush and some brake cleaner, and soldered them with a tiny butane torch and regular solder.

It was not easy, and it doesn't look good, but it helped.

I can see by inspecting the heater core while the car is running with full heater and fan turned off that there is a slight amount of sweating still. At least it was better than it was originally, and is a placeholder until I can find a better (or hopefully a new) unit to replace it with. Alternative would be to remove my three leaking tubes and seal those completely, but I bet there are other bad solder joints too.

[geezer101]

If you want to really clean the core out, fill it with a solution made from citric acid powder. It will break up the scale and calcification and get it flowing. I made a flushing rig out of a pressure cleaner that had a bad pressure regulator and simply filled a bucket with a warm mix and let it cycle through the core until there wasn't any more junk or discolouration coming out of it.

[ostlar]

If you want to really clean the core out, fill it with a solution made from citric acid powder.

I've used 35% vinegar acid, that also works well, although it smells a bit under the process.

[ostlar]

Update: I have yet to find any heater core replacement, and my core leaks worse than ever before now. Last resort is removing it and doing a bypass, driving in the freezing cold in winter with the windows down.

I had my hopes up when I ordered one from mitsubishidirectparts, but they cancelled it afterwards and sent an e-mail that it's discontinued and out of stock. There are none of these left on the wreckers in Norway, so I need to keep searching abroad.

Hit me up if anyone here knows about a heater core available (MB123852).

[Pengineer1]

Finally got the time to pull my heater core unit. The core actually seems to be fine! I'll pressure check it before I reinstall it but I think all the leaking was coming from one of the hose connections at the heater core! I'm going to replace the heater hoses and use multiple hose clamps and hopefully slide the hoses further onto the brass heater core pipes to hopefully make a leakproof connection. I'll try to post photos of where mine was leaking...hold your breath and cross your fingers!
Bill