Looking for tips on how to approach getting to the heater core on my '72 Z

[Stanley]

Once the evaporator is removed, it's possible (with contortion, a small extension mirror and/or a small camera) to see the core, valve and hose fittings well enough to see where the leaks are, by the corrosion and coolant stains. As mentioned above, maybe the core is OK.

If and when I get around to doing mine, I'll probably put a restrictor in the heater line, to reduce the chance of future problems. Got that from a Mustang site. Sounded like most Mustangs from certain years blew out the heater cores from too much water pressure at high rpm.

[bartsscooterservice]

My 1972 Z has the dealer installed AC. I know I can just start taking things apart, but if any of the forum members have some helpful tips on how to approach this I would be most thankful. I know I have a leak, but, at this time, don't know if it is the core or one of the hoses. As far as I know, this one owner car, before I bought it last year, has not had anyone try to get to the heater since the car was new.

Thanks,

Charlie

I removed the heater core last year. But in the end it wasn't the core that was leaking but the hoses and the valve that's on the passenger side. Like some other members said here, try to do a pressure test to the heater core first before removing it. I removed the core in a bout 1, 1/2 hours, you need patience and broken hands hehe. The front control panel needs to go out and remove the connecting cables, also remove the glovebox. After you removed a few hoses. The heater core is holded in place with a few screws. After that you can pull it out to the right, passenger side, with some wiggling. Don't know about the AC stuff though. I feel pulling the dash is far more of a hassle.

[Coastalman]

Here is an update on my leak. The background is that last winter, the first I had owned the car, I tried the heater and had the windows fog up and a strong smell of antifreeze. I shut the valve via the slide on the dash and everything cleared up. I knew there was a leak. Since I was working on other issues I did not work on the heater at that time. Now, with cooler weather coming, I wanted to be able to use my car in the winter. After getting the advice from the forum, I pulled out the glove box, pulled the vent hose off and was able to see the valve and hoses. I ran the car to get it warm and then engaged the heater valve with the slide control. After watching the hoses and valve for awhile, I could not see a leak. I drove the car for 20 miles with the heat working just fine. No smell and no leak. Heat was working fine. Since the car had been barely driven for 10 years before I bought it, could the valve have dried out and then when I first used it "re wetted" some kind of seal that then expanded and begin to function as it should have? I have left it all exposed so I can watch it, but for now it is working fine. Thoughts?

Charlie

[hr369]

If you're going to drive it then i'de get tool that crimps the heater hose leading into the heater core.

so if it pops while you're driving you can pinch it off. Then i'de get a gallon or 2 of water inside antifreeze

bottles and store them behind the seats. Mine popped under the dash one nite and it was a hellish nite

getting home. Now i carry 2 gallons in the car at all times.

Edited October 27, 2014 by hr369

[Coastalman]

Good advice!

[metalmonkey47]

Here is an update on my leak. The background is that last winter, the first I had owned the car, I tried the heater and had the windows fog up and a strong smell of antifreeze. I shut the valve via the slide on the dash and everything cleared up. I knew there was a leak. Since I was working on other issues I did not work on the heater at that time. Now, with cooler weather coming, I wanted to be able to use my car in the winter. After getting the advice from the forum, I pulled out the glove box, pulled the vent hose off and was able to see the valve and hoses. I ran the car to get it warm and then engaged the heater valve with the slide control. After watching the hoses and valve for awhile, I could not see a leak. I drove the car for 20 miles with the heat working just fine. No smell and no leak. Heat was working fine. Since the car had been barely driven for 10 years before I bought it, could the valve have dried out and then when I first used it "re wetted" some kind of seal that then expanded and begin to function as it should have? I have left it all exposed so I can watch it, but for now it is working fine. Thoughts?

Charlie

That tells you right there that there's a 90% chance the core is the issue. If the valve or hoses were leaking, it wouldn't get onto the core, meaning you wouldn't be fogging windows as you drive and blowing moist air through the vents.

it's possible the core corroded around the leak from seeping, and it's just a ticking time bomb. I had the exact same issue in my 620. I took it apart and found it leaking everywhere. Ended up un soldering the tanks and it was a mess. I couldn't get it soldered back together because it had a 2 piece tank, so I took it to a radiator shop and paid them $60 to soak the core/tank in solvent, and re-solder it. The results were good.

_DSC0074 by metalmonkey47, on Flickr

[siteunseen]

I've read where a guy put some type of valve in between the in and out at the engine bay fire wall right before it enters the cabin. He said it bypasses the heater core in the summer months to help cool the cabin. I can't find the thread right now but I will. It sounded like an idea I'd like to try.

[metalmonkey47]

I've read where a guy put some type of valve in between the in and out at the engine bay fire wall right before it enters the cabin. He said it bypasses the heater core in the summer months to help cool the cabin. I can't find the thread right now but I will. It sounded like an idea I'd like to try.

We actually had a pretty productive discussion on one of the Facebook pages last night (I think it was Datsun Parts and Needs) about overheating issues around the last two cylinders cause by bypassing the heater and feeding hot coolant back to the rear of the head. Apparently someone has measured the rear of the cylinder head at about 220 degrees under a 50hp (or so) load at somewhere around 3000rpm and 170 at the front with the heater bypassed straight to the rear of the head. I'd love to find those links again to reference.

[zKars]

This issue of bypassing the heater has come up many times. The correct way is to BLOCK/PLUG the heater hose connections at the head and lower rad hose fitting at the front. Do NOT just join these inlets/outlets effectively short circuiting the rad and putting hot water at the back of the head. I know it is super tempting to just connect the front and back heater hose fittings with a nice piece of hose as you don't have to find two big bolts or equivalent to use as plugs, but DO IT. It will save your engine or at the very least prolong its life.

That said, if you have to do it as an emergency on the road when you heater core or valve suddenly blows, do the jumper hose/short circuit thing, and get home safe, its not an instantaneous damage thing, but remember to fix it right SOON.