Thread: Choosing a radiator cap?

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Seems my new hot rod likes to puke coolant out of the overflow tube after driving for more than 30 minutes in the Florida sun

It has a 160* T-Stat and I recently flushed the system out and added an 80/20 mix of water and green plus a bottle of Purple Ice

The temp gauge doesn't get higher than 180*, but she'll piss A LOT of coolant if I let her

Turns out the radiator cap is only rated @ 10lbs.

Went to my local speed shop to get one with a higher rating and all they had were 20-22lbs. caps

I was hoping to get one with a 16lbs. rating since that's what I have on my old T/A, but they said they didn't stock any lower than the ones they had

My question is how do I go about choosing the right cap for my engine?

The dude behind the counter was clueless and said he only deals with imports

I didn't want to chance going too high, so I figured I'd do some research first....





Rick

Your cap pressure is going to be limited by your radiator. If you're running one of the aluminum core units like PRC or Walker I believe 15 to 16 pounds is your limit - PRC sells 16# and Walker sells 7# & 15#. You may need to check with your radiator supplier to see what they recommend as an upper limit. Do you have a coolant recovery tank? I would think one would be necessary in your FL heat.

and if you overfill you rad it will puke out a bit .. about 4 inches from the top is normal

Originally Posted by rspears

Your cap pressure is going to be limited by your radiator. If you're running one of the aluminum core units like PRC or Walker I believe 15 to 16 pounds is your limit - PRC sells 16# and Walker sells 7# & 15#. You may need to check with your radiator supplier to see what they recommend as an upper limit. Do you have a coolant recovery tank? I would think one would be necessary in your FL heat.

I don't have a clue what radiator it is, but I'll check when I get back to the shop in the morning.

It has a small overflow tank on the side (I think 2"x15")

I was thinking about getting one of these thermometer caps since I'm not quite sure about the accuracy of my temp gauge

http://www.jegs.com/p/Mr-Gasket/Mr-G...74786/10002/-1

Debating between the 16 and the 20

Originally Posted by 98 SNAKE EATER

I don't have a clue what radiator it is, but I'll check when I get back to the shop in the morning.

It has a small overflow tank on the side (I think 2"x15")

I was thinking about getting one of these thermometer caps since I'm not quite sure about the accuracy of my temp gauge

http://www.jegs.com/p/Mr-Gasket/Mr-G...74786/10002/-1

Debating between the 16 and the 20

Another way is to use an infra red temperature gun to shoot your block, heads, radiator, etc when at operating temperature to see what you really have through the system. On the cap, you really need to know what your radiator is good for before you boost the pressure over 16psig, IMO.