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startech47
Jedi Knight
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Looking for a source for coolant recovery radiator cap for a 1958 TR3. The radiator neck on these cars is 1" deep vs. the more common 3/4" deep necks. Thanks,
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TR2/3/3A tr3 radiator cap
- Thread starter startech47
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Try the NAPA # 703-1411 cap. It has top & bottom seals & is the correct length, diameter, & is a 7 psi cap.
D
D
MGTF1250Dave
Jedi Knight
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Aloha,
The NAPA part # for the 4 lb cap is NBK 703-1410. It has the correct length for the TR3 radiator filler neck.
Safety fast,
Dave
The NAPA part # for the 4 lb cap is NBK 703-1410. It has the correct length for the TR3 radiator filler neck.
Safety fast,
Dave
OP
startech47
Jedi Knight
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Thanks for all of the information. My local NAPA dealer did not have the cap in stock, but had it from the warehouse in 4 hours. I'll install it this weekend. I bought the 7 PSI cap. I want to try and raise the coolant boiling point. If I have trouble I'll try the 4 PSI cap. I'm also installing an expansion tank off of a 79 Midget to serve as the overflow tank. It looks more period than a plastic tank. I'll install a 0 PSI cap on it or defeat the pressure seal in a standard cap. When I'm done I'll post pictures and report on improvements in cooling.
Don Elliott
Obi Wan
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Water boils at 212 deg. F. A 50/50 mix of antifreeze and water will boil at about 245 deg. F. A 4 psi cap will take the B.P. up to about 260 and a 7 psi cap will move the B.P. up to about 280 deg. F.
How hot do you want to go ? Heat transfer will only be remarkable reduced when the mix has turned to steam and it can't transfer the heat when there is only steam in the system.
Going too high on the rad cap can cause an overpressure of the system and the oval cooling tubes in the rad will become rounder with the pressure depending on the age and/or contition of the rad. Round tubes cannot transfer the heat to the cooling fins because the fins are no longer contacting the flat portions of the tubes.
Don Elliott, Original Owner
https://www.britishcarforum.com/ubbthread...e=&sortdir=
How hot do you want to go ? Heat transfer will only be remarkable reduced when the mix has turned to steam and it can't transfer the heat when there is only steam in the system.
Going too high on the rad cap can cause an overpressure of the system and the oval cooling tubes in the rad will become rounder with the pressure depending on the age and/or contition of the rad. Round tubes cannot transfer the heat to the cooling fins because the fins are no longer contacting the flat portions of the tubes.
Don Elliott, Original Owner
https://www.britishcarforum.com/ubbthread...e=&sortdir=
Alan_Myers
Luke Skywalker
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Hi,
A couple quick comments in addition to Don's excellent points.
First, always measure the radiator neck. This is a commonly replaced item, if/when a radiator is rebuilt. It's not uncommon to find a 3/4" neck on an older car that should have 1". Just measure from the inner flange to the top of the outer flange.
Next, TR3 used 4 lb. caps primarily to keep from bursting the core in the heater. The TR4 and later cars using increased pressure caps have different heater cores. Even so, I've seen those "bulging" threateningly.
*Be very careful putting a higher pressure cap on an earlier car!* There is a possibility you'll get wet feet (and carpets, etc).
It might be wise to temporarily disconnect the heater while testing the cap to see if the higher pressure makes much improvement cooling.
There is also a possiblity of head gasket or water pump seal problems. But, both are generally up to spec with later cars that used higher pressure in the cooling system.
Higher pressure caps are used on race cars, to raise the boiling point, just as has been described. But, most race cars don't have heaters.
Overall, I think there are better solutions to cooling problems and would not recommend a higher pressure rad cap. It's a risky experiment.
Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
A couple quick comments in addition to Don's excellent points.
First, always measure the radiator neck. This is a commonly replaced item, if/when a radiator is rebuilt. It's not uncommon to find a 3/4" neck on an older car that should have 1". Just measure from the inner flange to the top of the outer flange.
Next, TR3 used 4 lb. caps primarily to keep from bursting the core in the heater. The TR4 and later cars using increased pressure caps have different heater cores. Even so, I've seen those "bulging" threateningly.
*Be very careful putting a higher pressure cap on an earlier car!* There is a possibility you'll get wet feet (and carpets, etc).
It might be wise to temporarily disconnect the heater while testing the cap to see if the higher pressure makes much improvement cooling.
There is also a possiblity of head gasket or water pump seal problems. But, both are generally up to spec with later cars that used higher pressure in the cooling system.
Higher pressure caps are used on race cars, to raise the boiling point, just as has been described. But, most race cars don't have heaters.
Overall, I think there are better solutions to cooling problems and would not recommend a higher pressure rad cap. It's a risky experiment.
Alan Myers
San Jose, Calif.
'62 TR4 CT17602L
Don Elliott
Obi Wan
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I agree with Alan. Having a higher pressure cap will increase the temperature that it will begin to boil - but it won't keep the radiator any cooler.
[ QUOTE ]
Having a higher pressure cap will increase the temperature that it will begin to boil - but it won't keep the radiator any cooler.
[/ QUOTE ]
This is true the rad will not be any cooler at the input, however if I remember thermodynamics correctly, the rate of heat flow (from high temperature to lower temperature) is a function of the temperature difference. Therefore if you raise the temperature in the rad (by raising the boiling temperature via higher pressure), and the air temperature around the rad is the same, then you will get more energy out of the rad per unit time (given the same surface area of rad). This is why modern cars have been designed to run at higher pressures.
Again this is memory form 23 years ago, when I last took thermodynamics, so I am willing to be corrected if my memory was wrong (again).
All that being as it is, I would not try and solve an overheating problem with a higher pressure rad cap. There are several things in the "system" that all assumed the coolant pressure was as per the design spec. As others have said, it is better to solve the problem with something other then the higher pressure cap.
Having a higher pressure cap will increase the temperature that it will begin to boil - but it won't keep the radiator any cooler.
[/ QUOTE ]
This is true the rad will not be any cooler at the input, however if I remember thermodynamics correctly, the rate of heat flow (from high temperature to lower temperature) is a function of the temperature difference. Therefore if you raise the temperature in the rad (by raising the boiling temperature via higher pressure), and the air temperature around the rad is the same, then you will get more energy out of the rad per unit time (given the same surface area of rad). This is why modern cars have been designed to run at higher pressures.
Again this is memory form 23 years ago, when I last took thermodynamics, so I am willing to be corrected if my memory was wrong (again).
All that being as it is, I would not try and solve an overheating problem with a higher pressure rad cap. There are several things in the "system" that all assumed the coolant pressure was as per the design spec. As others have said, it is better to solve the problem with something other then the higher pressure cap.
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Adrio,
I think you are pretty much correct. Temperature differential is what causes heat flow.
Another thing to consider is that the dynamic/localized water pressure against a top mounted cap with down flow radiator, can be quite high. High enough to unseat a low pressure cap. The water pump is forcing the coolant against the restriction of the radiator core. This actually pressurizes the water jackets considerably above the average system pressure which is good. The thermostat restriction also helps here.
At higher pump outputs this local pressure can unseat a low pressure cap. Even though the "average" system pressure may be below the cap setting. If the cap were located in a lower pressure location, this would not happen. Note that the cap on a crossflow radiator is located on the lower pressure side.
D
I think you are pretty much correct. Temperature differential is what causes heat flow.
Another thing to consider is that the dynamic/localized water pressure against a top mounted cap with down flow radiator, can be quite high. High enough to unseat a low pressure cap. The water pump is forcing the coolant against the restriction of the radiator core. This actually pressurizes the water jackets considerably above the average system pressure which is good. The thermostat restriction also helps here.
At higher pump outputs this local pressure can unseat a low pressure cap. Even though the "average" system pressure may be below the cap setting. If the cap were located in a lower pressure location, this would not happen. Note that the cap on a crossflow radiator is located on the lower pressure side.
D
Geo Hahn
Yoda
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Maybe the first question I should have asked is "Is your TR3A overheating?".
Living where I do and driving as I do I have taken some (7) steps to improve the cooling on the TR3A but a higher pressure cap and an overflow tank are not among them nor would they be the next thing I'd try if I had an overheating problem.
There is nothing inherently wrong with adding an overflow (I added one on my late-TR4 (no header tank)) but that big header tank on the '3 holds so much coolant during expansion that I'm not sure and additional expansion container really gains you much cooling capacity.
Living where I do and driving as I do I have taken some (7) steps to improve the cooling on the TR3A but a higher pressure cap and an overflow tank are not among them nor would they be the next thing I'd try if I had an overheating problem.
There is nothing inherently wrong with adding an overflow (I added one on my late-TR4 (no header tank)) but that big header tank on the '3 holds so much coolant during expansion that I'm not sure and additional expansion container really gains you much cooling capacity.
The idea of an overflow bottle is an interesting one. I have one on my TR4A but not on my TR3A. I think I will add one on the TR3A, no so much for any cooling needs but I figure it will stop the noise I hear coming from the right seat area that sounds something like "I smell coolant" /ubbthreads/images/graemlins/nonono.gif