16lb rad. cap too much for heater core?

[Rosco]

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.

wow, super info!! Sounds like 20 psi is the benchmark. Yes, I agree, the most suited component in the system for withstanding 16psi will be the new aluminum radiator. I am on board with starting with lower pressure and working my way up. If we're not overheating then done. It'll be interesting to see how the temperature changes with driving conditions due to the new gauge. I'm pretty hopeful that the new radiator and high-flow water pump (I sprung for a 'FlowKooler' model) will handle the temps. I am in southern Baja and mostly during the winter so we don't really see too hot of temps. But I have overheated in the past and want to put that issue to bed and not be fighting it,hence the new parts.
I did also buy a "consumable anode" from the radiator company which screws in where the petcock valve is. My local mechanic thought that aluminum radiators are fine but that I should change the coolant every two years or according to what it says on the bottle and he mentioned that with the cast iron block and aluminum radiator that "I was creating a battery". I don't know how the galvanic reaction takes place or why but hopefully the anode will help mitigate the effects.

 

[Rosco]

And, I will swap out the coolant on a regular basis- every other year or so.

 

[Davea Lux]

wow, super info!! Sounds like 20 psi is the benchmark. Yes, I agree, the most suited component in the system for withstanding 16psi will be the new aluminum radiator. I am on board with starting with lower pressure and working my way up. If we're not overheating then done. It'll be interesting to see how the temperature changes with driving conditions due to the new gauge. I'm pretty hopeful that the new radiator and high-flow water pump (I sprung for a 'FlowKooler' model) will handle the temps. I am in southern Baja and mostly during the winter so we don't really see too hot of temps. But I have overheated in the past and want to put that issue to bed and not be fighting it,hence the new parts.
I did also buy a "consumable anode" from the radiator company which screws in where the petcock valve is. My local mechanic thought that aluminum radiators are fine but that I should change the coolant every two years or according to what it says on the bottle and he mentioned that with the cast iron block and aluminum radiator that "I was creating a battery". I don't know how the galvanic reaction takes place or why but hopefully the anode will help mitigate the effects.

The short version is that the copper in the brass heater core is an anode, the aluminum in the radiator is a cathode. Ions are transferred from the aluminum resulting in oxidation of the radiator, left unchecked this will eventually cause the radiator to fail. Modern cooling systems eliminate the copper in the heater (anode) core so that the ion transfer can not take place. Keeping the coolant fresh prevents it from becoming acidic which also prevents the ion transfer (galvanic action).

Dave

 

[Rosco]

The short version is that the copper in the brass heater core is an anode, the aluminum in the radiator is a cathode. Ions are transferred from the aluminum resulting in oxidation of the radiator, left unchecked this will eventually cause the radiator to fail. Modern cooling systems eliminate the copper in the heater (anode) core so that the ion transfer can not take place. Keeping the coolant fresh prevents it from becoming acidic which also prevents the ion transfer (galvanic action).

Dave

Thanks for the explanation. Do you think the "consumable anode" is necessary?

 

[Rosco]

That is if I am replacing the coolant regularly?

 

[Davea Lux]

Thanks for the explanation. Do you think the "consumable anode" is necessary?

It is added insurance, so yes.

Dave

 

[Rosco]

It is added insurance, so yes.

Dave

10-4

 

[Rosco]

Found this online.
16 shmixteen!!!
Just an 8 degree difference from a 12 psi system.
-They did state on this site,"(Pressures are calculated values and should not be interpreted as actual data)"
Still, feeling pretty good about a ~255-260 degree boiling point!!

 

[fjr]

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?

The radiator cap's job is to limit the maximum pressure that the cooling system can develop. The actual pressure within the cooling system continuously varies and is determined by the composition of the coolant and its temperature. The temperature of the system is controlled by the thermostat and it will be fully open about 15-20°F above its rated temperature. That is, if you have a 195°F thermostat, it will maintain a minimum temperature of 195°F and will be fully open by 210-215°F. If your cooling system has enough capacity, it will remain within this range. The greater the temperature difference between the coolant and the air, the better is the system at transferring heat.

If you maintain your cooling system and your engine always remains within the control range of the thermostat, you will not need to worry about its pressure. If your service manual recommends a 7-12 psi rad cap, I would go with a 7 psi cap to avoid unnecessarily straining a potentially weak heater core. I would also use a a 50% solution because water has a higher heat capacity than ethylene glycol. See Cooling System.

 

[Rosco]

The radiator cap's job is to limit the maximum pressure that the cooling system can develop. The actual pressure within the cooling system continuously varies and is determined by the composition of the coolant and its temperature. The temperature of the system is controlled by the thermostat and it will be fully open about 15-20°F above the its rated temperature. That is, if you have a 195°F thermostat, it will maintain a minimum temperature of 195°F and will be fully open by 210-215°F. If your cooling system has enough capacity, it will remain within this range. The greater the temperature difference between the coolant and the air, the better is the system at transferring heat.

If you maintain your cooling system and your engine always remains within the control range of the thermostat, you will not need to worry about its pressure. If your service manual recommends a 7-12 psi rad cap, I would go with a 7 psi cap to unnecessarily strain a potentially weak heater core. I would also use a a 50% solution because water has a higher heat capacity than ethylene glycol. See Cooling System.

Thanks for the great info. I am hoping for the best. I'll be replacing the water pump, radiator and thermostat. I'm also going to install a water temp. gauge which will be fun to watch and determine how things are working under different conditions. I'm going to start with a 12 psi cap and take it from there. Hopefully, as you mentioned, we maintain a low enough temp that we never build high enough pressure to effect the heater core.

 

[livininharrow]

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?

any reason why you didn't have the original rad recored to original specs? as in copper / brass? I have had a few done in the past thereby avoiding the issues of an aluminum rad ******* up my cooling system.

 

[70bigblockdodge]

If it won't hold 16lbs. it needs replacing anyway. The above thoughts are like running a tire low on air because your worried if the rim can take the pressure. 16 is industry standard now, might as well have your car on par with new cars/trucks.

 

[Rosco]

any reason why you didn't have the original rad recored to original specs? as in copper / brass? I have had a few done in the past thereby avoiding the issues of an aluminum rad ******* up my cooling system.

What are the issues with an aluminum radiator?

 

[70bigblockdodge]

What are the issues with an aluminum radiator?

Nothing, just use the new orange coolant like new Mopars have in them. It works better with dissimilar metals.

 

[Rosco]

If it won't hold 16lbs. it needs replacing anyway. The above thoughts are like running a tire low on air because your worried if the rim can take the pressure. 16 is industry standard now, might as well have your car on par with new cars/trucks.

I guess my thoughts are if it aint broke you don't have to fix it. If it's happy w/ a 12psi cap (not overheating) then why go 16. We'll see how it performs. Maybe the whole fear of the heater core springing a leak w/ a 16lb cap is paranoia anyway, I don't know. I've yet to consult an actual mechanic. I prefer instead to rely on guys who drive and work on old mopars themselves. Seems like the general consensus is to start out low (PSI) and if need be bump it up.
So far my Fury has never seen anything more than a 7lb radiator cap. I've got a brand spanking new aluminum radiator (which I know can handle the pressure), water pump, hoses, t-stat. So I guess the only weak link would be the original heater core. It's a ***** to replace. If it won't hold 16 psi but will hold 12 then we're good as long as I don't need 16 psi pressure to keep from overheating.

 

[70bigblockdodge]

I guess my thoughts are if it aint broke you don't have to fix it. If it's happy w/ a 12psi cap (not overheating) then why go 16.

Yep, if it works at 12 and you own the cap I would just use it. I would not be afraid of 16 in a good system, new hoses are much more durable than ones from 50 years ago. 16lbs will give you a higher boiling point and resist the formation of localized steam formation in the heads, providing a more stable temperature to resist detonation.

 

[swinger69]

Advice from one of the best mechanics I've ever known was "put a 13 lb. cap on" whenever you got a used car with lots of mileage on it. I've always followed that rule since the 1970's with great results. Never overheated as a result of the cap change, never blew a head gasket, and it extended life of old radiators, etc. Never tried on a "modern" car (1996)? and up

 

[Rosco]

My Fury has never seen anything over 7psi. Turns out 12 lb caps are not readily available (they have 13 all day long) so instead I will throw on a 10 lb.er and see how things go. I have high hopes since I have a new radiator, water pump and t-stat. I don't think there is any need to go 16psi.
50 years with a 7psi cap and mild overheating (original radiator). With all the new parts we should be good to go!!

 

[1966newport]

all my c bodies use a 16 lb cap

 

[Dr. Dodge]

Thank you for schooling me. I'll have to check the 65 when i start to rebuild it in the spring. Pretty sure I slapped a spare good cap on it when I added a over flow bottle 1980s good.