Question on testing heater core and temperature control valve.

[JamesR]

The other day I noticed some spattering of antifreeze on the floor mat of my old car - '61 Monterey - under the heater box. The heater box was damp, and when I wiped away the antifreeze from the heater box more antifreeze would appear. I figured a small leak was in either the heater core or the the related assembly (control valve or hose connecting it to the heater core.) When I blew through the heater core inlet (with the outlet plugged) I could NOT tell that there was a leak, but I removed the heater core from the heater box anyway, because there's a severely deteriorated fresh air duct that needs to be replaced anyway. Many thanks to Laughing Coyote for steering me towards replacement parts.

 

Once removed from the heater box I put the heater core and control valve assembly in a large bucket with clean water, then plugged the outlet and put air from my air compressor through the inlet with the inlet sealed so there was pressure in the heater core and control valve. BUT I got NO bubbles in the water indicating there was a leak (??) Shouldn't there be air escaping from my core or control valve if either or both are leaking antifreeze?

 

How could I get antifreeze coming out of my heater box if the heater core or control valve (or the hose that connects the two) aren't leaking?

[37_Roadmaster_C]

Short answer is: you couldn't.  I am not familiar with your car, but one thing you did not mention is if you tested everything with the control valve in different positions. Another possibility is as things heat up they expand. If testing cold, the leak may be self sealed. You may want to try the rest again with hot water. I would recommend boiling water or as close to it as you can get.

[JamesR]

I was almost wondering if the heater hoses had a poor seal at the inlet/outlet ports of the heater core assembly at the firewall, and maybe coolant was seeping into the heater box at that point, but the hoses and clamps are in newish condition and the clamps were tightened up pretty snug. Still might've happened, I suppose. If it was a readily available heater core I'd go ahead and replace it and be done with it, but they're not available and I'd have to send this one in to be re-cored. If it's not broken, I don't want to "fix" it, but I don't want it leaking again in a few weeks. I have noticed the coolant level gradually get lower a bit over time.

 

Good idea on putting the control valve in different positions 37_Roadmaster_C. I tried it and got no difference. I could also try the hot water idea.

 

What I may do when the replacement fresh air duct/boot comes in is reinstall everything and trim the heater hoses past the current clamp points. Maybe I over tightened the clamps and got slight leakage into the box through those connections...who knows. There was also some mouse bedding ahead of the core so all that needed to be cleaned out, too, so along with the duct it's not like it was wasted effort.  If I still have a slight leak, I may wait til it gets worse before addressing it so the problem will be more obvious. 

[Bloo]

Look for white powdery stuff that resembles calcium deposits wherever the core was leaking, probably along the edge where a tank or header attaches. The rot should show in this way, never mind the actual leak. The powdery spot is where the leak is. Similarly, the valve should show corrosion and probably a trail straight down if it is the culprit. Is this a Ranco valve? If so, it's usually easy to see the trail where the water came out of those.

 

If you have nice shiny new looking parts and there's no white powder and no trail, it probably was as you suspected coming from leaky hose connections outside and running in.

[JamesR]

To me, the core looks pretty decent for it's age, not really seeing calcium deposits. Tell me what you think though: Since core and valve are "FoMoCo" I'm presuming this assembly is all original. That would mean the connecting hose (between core and valve)  and clamps shown are original. A 60 year old hose is pretty old. Should I replace it before reinstalling do you think? Looks in good shape, but....

[Bloo]

Well, from that view I don't see anything wrong. If all sides look like that it is probably OK. I would look really closely at that valve though. No powder? No black trail of discolor going in the direction that would be straight down if mounted in the car?

 

I wouldn't trust that hose 10 feet. I don't like that design at all. I have two cars that I have preemptively removed the dashboards from just to replace underdash hoses like that before they broke. It's under the same pressure as the rest of the cooling system, and if it splits suddenly it could dump an unbelievable amount of almost boiling coolant in the footwell in a very short amount of time. I've not had that happen, but have seen cars roll into the shop like that. Slower leaks I have had years ago, where a hole opens in the side of the hose, typically making a mess and permanently injuring the carpet.

 

Edited March 30, 2023 by Bloo (see edit history)

[avgwarhawk]

Valve. It's the weakest link in the system. 

[John348]

31 minutes ago, avgwarhawk said:

Valve. It's the weakest link in the system. 

Depending on the vehicle it can be the hard part to find and needless to say expensive when you do. Hopefully this one is common. Regardless I would make every attempt to replace it if I had the heater core out in my hands now.

Edited March 30, 2023 by John348 (see edit history)

[JamesR]

2 minutes ago, John348 said:

Depending on the vehicle it can be the hard part to find and needless to say expensive when you do. Hopefully this one is common. 

I looked at the valve again from a different angle, and I actually AM seeing some of the white powdery residue that Bloo mentioned on it...more than I little in fact.

 

I found a replacement online thanks to Laughing Coyote, and I'm in the process of getting it shipped to me. It's NOS apparently. I hope that and a replacement hose will take care of the issue. Kind of glad it doesn't appear to be a heater core at this point.

 

I'll replace the hose, too. You wouldn't reuse those old spring clamps, would you? Or would they be better than standard hose clamps in this situation?

[Laughing Coyote]

Your heater core looks really good compared to what mine looked like. I think the temp control valve is the issue. If you look at the control valve it has a wavey capillary tubing that heats up and I think it open the valve inside along with the manual dash cable. Let me look in the service manual and see what it says.

[Laughing Coyote]

15 minutes ago, JamesR said:

I'll replace the hose, too. You wouldn't reuse those old spring clamps, would you? Or would they be better than standard hose clamps in this situation?

I replaced my hose and used hose clamps instead of the corbin clamps. Didn't want to have to get back in there.

[Laughing Coyote]

The manual doesn't go into great detail on the theory of operation on the control valve, but I'm sure that the capillary tube set up has something to do with opening the control valve in some way. 

2 hours ago, Bloo said:

Is this a Ranco valve?

It is.

[Bloo]

25 minutes ago, JamesR said:

I'll replace the hose, too. You wouldn't reuse those old spring clamps, would you? Or would they be better than standard hose clamps in this situation?

Under the hood, probably. Under the dash probably not but maybe if they fit good and are in good shape. They worked all these years. If you do re-use them, remove them carefully, and be sure the new hose is the same or slightly thicker than the old one without being way thicker. In my experience, black hose usually lasts longer than red even though red is marketed as premium. What's best is a fuel injection clamp (solid band with pull screw) or something similar that stays round as it tightens (worm clamps really don't). It's difficult to source big ones though. It will probably boil down to either the originals or what you can buy that fits. One thing about the originals is that they do stay round. You can only tighten the clamp so much on thin brass.

 

Oh one other thing, make sure the hose is just a wee bit undersize so it has to stretch a little to go over the nipples. It doesn't need much. If it's loose I'd get a different piece of hose.

[dodge28]

Over time it is naturally hot water in the form of steam will seep between the rubber and metal and will only show up when the system is at operating temperature in the form of steam. The solution is to once in a while remove the hose and clean metal and rubber and re install. Gasket glue helps but the trouble to remove the hose when needs be is not worth it. In cases where the outlet from rad  is plastic, the coolant will be visible so the owner will turn the clamp a little every time he sees some moisture until the pipe breaks off. The most common place   for this is the hose connection at the thermostat housing  

[avgwarhawk]

1 hour ago, John348 said:

Depending on the vehicle it can be the hard part to find and needless to say expensive when you do. Hopefully this one is common. Regardless I would make every attempt to replace it if I had the heater core out in my hands now.

Looks like a Harrison or Ranco. Fusicks can rebuild it I believe. Appears to be repair kits available. 

Edited March 30, 2023 by avgwarhawk (see edit history)

[dodge28]

Clean the pipes and inside the hoses before re installing, Under no circumstance put more than 18 lbs  air to test.