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-   1958 To 1960 Squarebirds - General Technical Discussion (http://squarebirds.org/vbulletin/forumdisplay.php?f=14)
-   -   Radiator cap pressure rating??? (http://squarebirds.org/vbulletin/showthread.php?t=5913)

KULTULZ 01-27-2009 02:07 PM


Originally Posted by bcomo (Post 28135)

I wanted to add something about the purpose of a radiator cap.

The purpose of a radiator cap is to raise the boiling point of the water/antifreeze mix.

This is 100% correct. If one is concerned that the correct pressure cap will blow out the cooling system, it is time to perform a little service.

Additionally, the purpose of 7# caps was in the days of using either water or an alcohol based coolant. On this time period systems, it will not only cause spitting but will ingest air on the intake, creating air pockets and creating even more problems.

The AC radiator cap being correct for this period is interesting. I always cringed from anything not marked FOMOCO.

tbirds8 01-27-2009 06:42 PM

I know the 7lb isn't going to work in the summer. It will start spitin up. but I bought this car on flebay with a stuck motor and everybody gave up on it. From a ford dealer no less. Has 80000 on it and runs FINE. Been sitting since 1977. Took a little playin with it but you wouldn't believe how this car runs and everything works. (no clock). It's a 66. I think my 60 will run it down. But then I have figure out how to stop.

Patreer 06-04-2018 11:02 AM

Good day from Montreal,

I had to change my heater core recently and since I noticed the coolant tempature is higher then before (I have a gauge, a 180F thermostat and a 13# radiator cap).
Temperature used to be at 180F point all the time, but now I see that thermostat opens when engine warms up and after running for 20 minutes or so temperature climbs in the 195-210F range.
Yesterday we had 75F oustide and my coolant temp was more than 200F.

Even on the highway it does the same as if themostat was not operating.

I'm worried about overheating.
Should I change my radiator cap to a 15#?

Forgot to mention I switched to Shell Rotella T4, 15W40, if it may have an impact.
(1960 Tbird, 352)

Thanks for your help

jopizz 06-04-2018 11:26 AM

Changing the heater core should not cause your temps to be higher than before. My thought is that you have air in your system. Make sure you run the car with the radiator cap off and the heater control on hot to bleed any air out. I would not go to a 15 lb cap. The higher pressure will only put stress on your engine and radiator. Stay with 13 lbs. I've used the same oil many times and I haven't noticed higher temperatures.


Patreer 06-04-2018 11:42 AM

OK Thanks John
I'll do this and see if it helps.


simplyconnected 06-04-2018 01:31 PM

Did you ever do any canning? Canning produces a vacuum all by itself. Your radiator uses the same technique; first coolant is heated but when it cools down, the air inside contracts into a vacuum (provided your radiator cap has a good seal).

Cars with radiators LOWER than the engine (like Corvette and Escort) have used this technique for decades. It's important for those cars to have coolant in the aluminum heads at all times or they crack.

Over a few heat/cool cycles, your heater core should displace the air bubble with coolant. This is evidenced by finding a lower coolant level when the system is cool enough to check. Modern cars use the overflow to pull liquid back into the system. That's why their systems are always 'to the top'. - Dave

Patreer 06-04-2018 01:51 PM

I just did the test and clearly heard the thermostat pop while opening. I'm now waiting for the coolant to cool down. leaving the cap open.

Patreer 06-11-2018 11:35 AM

OK, I have been testing the bird several time now and it's still runiing at 210. Should I worry?

Patreer 06-22-2018 02:45 PM

Hi All,
Please let me know if ok.

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