16lb rad. cap too much for heater core?

Rosco

Active Member
Joined
Jan 8, 2020
Messages
309
Reaction score
38
Location
Todos Santos
Well, that title is pretty much my question. Just bought a new aluminum radiator which is supplied with a 16lb. cap. My shop manual states, "7-12 psi". My concern is whether or not the 16 lbs. of pressure might cause a leak in my (original) heater core.
any thoughts?
 
And, believe it or not, we use the heater quite often down in Mexico- chop top gets a bit chilly at night.
 
Well, that title is pretty much my question. Just bought a new aluminum radiator which is supplied with a 16lb. cap. My shop manual states, "7-12 psi". My concern is whether or not the 16 lbs. of pressure might cause a leak in my (original) heater core.
any thoughts?

Use the cap that is correct for the application. A 16lb cap is going to put more stress on the hoses, heater core and freeze plugs. If any of those items are ready to go, throwing 16lbs at them will be a quick way to find out.

Dave
 
Well, that title is pretty much my question. Just bought a new aluminum radiator which is supplied with a 16lb. cap. My shop manual states, "7-12 psi". My concern is whether or not the 16 lbs. of pressure might cause a leak in my (original) heater core.
any thoughts?

A sixteen pound cap is usually used on cars with A/C. Without A/C, I think a fourteen pound cap is used . . .
 
Use the cap that is correct for the application. A 16lb cap is going to put more stress on the hoses, heater core and freeze plugs. If any of those items are ready to go, throwing 16lbs at them will be a quick way to find out.

Dave
Radiator supplier claims 10,000 sales w/out an issue using the 16lb. cap. The radiator is, I assume, rated for 16psi but my concern is mainly the heater core. I'll be replacing:
water pump
thermostat housing
all hoses (heater, upper/lower radiator, bypass)
Really the only original component is the heater core. I have no idea what the freeze plugs are rated at or what level pressure stresses them. I've never heard of one blowing out due to overheating (only freezing) but I have no idea. I know the higher pressure allows the coolant to get hotter before boiling and spewing out into the street but, again, worried about the [old] heater core not being able to withstand the higher pressure.
It gets HOT down in Mexico (where my car lives) and I'm definitely attracted to keeping the coolant in the vehicle if possible.
Do you think the rest of the new parts (mentioned earlier) are ok w/ the higher pressure?
 
Well,
It'd be nice to know what pressure the engine and components are rated for:
-heater core
-hoses and fittings
-water pump
-thermostat and housing
 
If the shop manual says 7-12lbs, you can assume that the components were rated for continuous operation at those pressures. They might well take 16lbs if they are in good condition. I personally hate changing heater cores, especially on A/C equipped cars. If your old radiator was corroded and leaking, you can also assume that the heater core is probably degraded as well. If you are having issues with coolant being forced out in hot weather, invest in a coolant overflow tank and run a stock pressure cap.

Dave
 
If the shop manual says 7-12lbs, you can assume that the components were rated for continuous operation at those pressures. They might well take 16lbs if they are in good condition. I personally hate changing heater cores, especially on A/C equipped cars. If your old radiator was corroded and leaking, you can also assume that the heater core is probably degraded as well. If you are having issues with coolant being forced out in hot weather, invest in a coolant overflow tank and run a stock pressure cap.

Dave
good point about the condition of the heater core. Maybe heater-core thirty here. I don't have A/C. I am hoping not to have coolant boiling out after these new parts are installed but don't generally know anything about the pressure rating of '68 Fury II heater cores. The heater does work fine w/out leaks at the moment and I wouldn't care to replace it unless needed.
It'd be easy to get a different cap (w/ lower pressure rating) but, if I can get away with a higher pressure unit, the better.
 
good point about the condition of the heater core. Maybe heater-core thirty here. I don't have A/C. I am hoping not to have coolant boiling out after these new parts are installed but don't generally know anything about the pressure rating of '68 Fury II heater cores. The heater does work fine w/out leaks at the moment and I wouldn't care to replace it unless needed.
It'd be easy to get a different cap (w/ lower pressure rating) but, if I can get away with a higher pressure unit, the better.
Like I mentioned earlier, the heater is really the only component of the heating system not being replaced. I didn't consider the freeze plugs though. Have you noticed f/p's springing leaks from overheating?
 
Like I mentioned earlier, the heater is really the only component of the heating system not being replaced. I didn't consider the freeze plugs though. Have you noticed f/p's springing leaks from overheating?
Sorry, make that "COOLING SYSTEM" not "HEATING SYSTEM."
 
Like I mentioned earlier, the heater is really the only component of the heating system not being replaced. I didn't consider the freeze plugs though. Have you noticed f/p's springing leaks from overheating?

Freeze plugs usually leak if they rust out, overheating usually will not cause them to leak. Look for rust spots on the plugs, they usually will rust from the inside out unless the vehicle is used where there is lots of road salt used. If the coolant is rusty, there is rust corrosion going in the block and heads, including the freeze plugs.

Dave
 
good point about the condition of the heater core. Maybe heater-core thirty here. I don't have A/C. I am hoping not to have coolant boiling out after these new parts are installed but don't generally know anything about the pressure rating of '68 Fury II heater cores. The heater does work fine w/out leaks at the moment and I wouldn't care to replace it unless needed.
It'd be easy to get a different cap (w/ lower pressure rating) but, if I can get away with a higher pressure unit, the better.
So, generally, can heater cores withstand 16 lbs of engine pressure? I hear your concerns regarding the age of the unit. But, assuming there are not any leaks presently is it your opinion that introducing 16 lbs would is going to kill that heater core?
 
So, generally, can heater cores withstand 16 lbs of engine pressure? I hear your concerns regarding the age of the unit. But, assuming there are not any leaks presently is it your opinion that introducing 16 lbs would is going to kill that heater core?

If it is in good shape, probably not.

Dave
 
If it is in good shape, probably not.

Dave
Appreciate your two cents. I'm tempted to roll with the 16 lb. cap but what I will do is see how it goes with a 12 lb cap. If it's spewing out all the time then I will throw in the 16 lber. I am also installing an aftermarket temp gauge so I should have a good idea on what's going on.
 
16lb caps were common on A/C equipped cars, but those use a different design heater core, so I think trying the 12lb cap first is a good choice.

Dave
 
Thanks for your input.
It's so funny, after re-reading this thread I can't help but notice that it looks like I am waiting for someone to give me the answer I want-namely, "you're fine with the existing heater core and the 16lb cap". It's the classic if-I-keep-posting-the-question-eventually-someone-out-there-will-give-me-the-answer-I-want-to-hear scenario.
However... not getting that feedback.
With the lack of overwhelming support to roll with the new 16lb cap, I agree, let's go with a lower pressure cap at first and see how the overheating situation goes.
 
A sixteen pound cap is usually used on cars with A/C. Without A/C, I think a fourteen pound cap is used . . .
hey Rip
gonna go with a 12 lb. cap to be safe. See how it goes and if I'm loosing coolant then I'll bump up the pressure (cheapest upgrade). Thanks for your input.
 
I started my work carreer for the company named Blactsone Corp. with Chrysler as its major customer, for decades.

To test units before shipment we typically tested at 20 psi air under water. Anything bigger than a champange bubble was a no go.

As others said well - will it take 16 psi ?...all depends on condition of the other items in the system.

Copper Brass Radiators use - Tin /lead solder and the solder corrodes. For heater cores - The type of tube used is folded - and the edges soldered. The machines that facedipped the cores in solder - we called the "big bertha" machines. Prior to 1986 they where all made in Jamestown, NY. After that in Mexico.

Aluminum rads - in aftermarket typically use welded tubes. These can withstand significant pressure. Hence the manufactures claims.

The higher pressure cap - will push the boiling point higher. Radiator systems typically have gone up in pressure, to gain in heat transfer performance.

I would start with the lower pressure cap and work up.
Coolant - use premixed coolant. I have spent 900 days in Mexico the last 5 years (Saltillo) ....I trust a what comes out of a bottle, not the municipal system.

Ideally - with an aluminum radiator, you would want an aluminum heater core. A mixed system (Alum rad and copper/brass heater core) a galvanic reaction could be set up in the coolant. Some risk .....but lots of folks have done this, without an issue.
 
Back
Top