66 Heater Core failed

[Rob M.]

Well it looks like replacing the carpet just moved up on the time line a little. The heater core in my 66 SB failed today.

Question: Last year I replaced the radiator with a new DeWitts, flushed the engine etc., and replaced the green coolant with Dexcool. I read in the archives that if there's any green coolant left in the system and it gets mixed with the dexcool it will cause problems. Could the the switch to dexcool have anything to do with the heater core failing?

Second, how much of a headache is it going to be to replace the heater core?

Thanks in advance,
Rob

[Rob A.]

Re: 66 Heater Core failed

Can't speak with regard to the anti-freeze, but I've replaced several heater cores. You'll be surprised at how much is involved, like removing the glove box, the "Y" duct, radio side panels, and of course, the entire inner heater box assembly and outside cover. When you reassemble it, look at the diagram carefully that comes with the gaskets. Some aren't very clear where the lighter, foam one goes. Be careful when you re-attach the hoses to the new heater core, it's not that hard to break off the hose outlet and/or inlet, which you certainly don't want to do after all the work installing it. I think they are just soldered on. When you put the inner heater box assembly back in, as per the assembly manual, attach the nut that holds the "U" shaped bracket on the upper, left corner first. The chassis service manual is very helpful in this procedure.

[Don H.]

Re: 66 Heater Core failed

I doubt that the coolant change had anything to do with the core going bad. It is not too tough of job (a little harder with AC). I think it is described in the service manual. Don H.

[Jim Baxter]

Re: 66 Heater Core failed

I have to do the same procedure. Who has the best gasket and heater core deal?

[Duke W.]

Re: 66 Heater Core failed

There is some question as to whether Dexcool provides proper protection to some solders, but I doubt if one year would cause problems. I've been using Dexcool since 1996 with no problems. Anything can happen to a forty year old heater core.

Just the same, I've backed away from my Dexcool recommendation and now recommend Zerex G-05 which has a hybrid organic acid technology (HOAT) corrosion inhibitor package. The industry consensus appears to be than HOAT types are best for cars with soldered brass components that originally had "green stuff".

Can you describe the heater core "failure" in more detail.

Duke

[Joe C.]

Re: 66 Heater Core failed

Rob:

The cooling system flush probably removed any deposits that were "sealing" the old core. Same thing happened to my '85, which is also a nightmare job to replace the core.
Be sure to fully rebuild your heater box with fresh seals while you've got it out of there.

Joe

[Rob M.]

Re: 66 Heater Core failed

Duke et al.,

First thanks for the advice from everyone.

The failure was as follows. Last weekend I was under the car bolting on my starter that I had rebuilt. I noticed a very small amount of coolant on the firewall and dust shield. No big streams of water or puddles under the car. There wasn't any water (that I could see) in the car either. I thought it could be one of the repo hose clamps leaking. Yesterday, after about a 20 mile cruise, I pulled into the house and could see and hear water dripping out of the heater box onto the passanger floor mat and carpet. I popped the hood and could see plenty of water coming out of the heater core houseing onto the dust shield and floor of the garage. I went for some rags and a beer after some choice language left my lips.

Thanks again for the help.

[Duke W.]

Re: 66 Heater Core failed

I take it you have not removed it yet, but I'd be interested in knowing more about the failure.

A common failure is cracking of the solder joint that holds the inlet and outlet nipples. This can be occur during removal of old heater hoses.

Once it's out a radiator shop will usually test the core for free and they may let you watch so you can determine where the actual failure occurred and whether it's a solder joint or a tube.

Duke

[Jim T.]

Re: 66 Heater Core failed

Jim I have bought 3 heater cores from GM and they did not come with gaskets. Dr. Rebuild has the gaskets and heater cores.

[Jim Baxter]

Re: 66 Heater Core failed

Thanks Jim, was that gm restoration parts.com? Do you have a part number?

[Rob M.]

Re: 66 Heater Core failed

Duke,

I'll let you know when I get it done (a couple of weeks I'm guessing).

Rob

[Jim T.]

Re: 66 Heater Core failed

Jim I bought my GM heater core parts mail order from a mail order business that no longer responds. The heater cores came in unopened GM boxes and the cores were very nicely sealed prevent movement in the GM box, strong box also. This was several years ago. When the heater core started leaking in my 70, I already had the heater core. I don't know if your heater core is available from GM now. There was a post awhile back about buying a US made heater core or one made off shore and a price difference between the two. Some posters use GM parts direct, I don't have any information about gm restoration parts. The Last Detail has a online catalog as well as others you could check.

[Jim T.]

Re: 66 Heater Core failed

Jim just checked Dr. Rebuild's on line catalog. Only Delco heater cores are sold by Dr. Rebuild. However a statement more or less says at the top that all Delco heater cores are made in Mexico. I am going to check my heater core boxes since I stored the old leaking cores in the original boxes. Your year of heater core is available.

[Jim Baxter]

Re: 66 Heater Core failed

Just went to gmpartsdirect.com and GM part number 52484057 works for the heater core, Al at corvette corner gave me the part number.

[Eugene B.]

Two Questions

Gentlemen,
Interesting thread to read about anti-freeze and heater cores. I'll be there with the '65 by spring. The thread raises two questions:

1) Can a good radiator repair shop clean, repair, pressure test, etc. an original heater core so that we can return it to service?

2) Why should we change to new technology anti-freezes? Why not just put back ethylene glycol base?

Thanks for your input.

Best regards,
Gene