Stant Radiator Caps 102... or...

What I thought I knew and what I learned...

I am still having some cooling issues with my Vette when I thought they were all fixed. One area I hadn't been able to prove or disprove was my cap... because my Chinese Pressure Tester from HF could test every system known to man, but none of the traditional caps.

I now see that the Stant Testers on EBAY can be had for 30 to 80 bucks and they may not be able to test every system in the world, but they do not have a "gender-bender" adapter to test my cap.

A friend loaned me his and I got started testing my NEW 16 pound cap and found it would not hold but 13 pounds and still slowly dropped. I looked for leaks and submerged the entire thing in a sink under water and still no leaks!

I then took out my Chinese tester and used the Stant adapter with it and WHAA-LA... the exact same readings! I tested my OLD 16 pound cap and it was identical to the NEW one! I took the 13 pound cap off the FIAT and it was rock solid at 12 pounds and holding using BOTH testers...

My trip to Pep Boys resulted in the same findings. I was able to test several NEW caps still on their "hang-cards" with their "bottoms" exposed... and got the exact same readings! I purchased an 18 pound cap for the Vette and I'll see how that works as it indicates it will hold 16 pounds.

BTW...The 18 and 20 pound caps are $2 dollars LESS than the 13 and 16 pound caps... Supply and Demand at its finest!

Sooooo... I found the higher pressure caps were all 2 - 3 pounds LESS than their stated ratings... and their 13 pound cap just 1 pound less, which I've never had a problem with on the Fiat.

('74 X1/9s had about 7 pound caps and I3 pound caps work well on the others...)

I now wonder about what OEM caps actually worked at or work at... regardless of what was/is stamped on their covers. Do they too actually release pressure at 2 or 3 pounds LESS than what they are rated at?

I no longer have any OEM caps that I can test... Does anyone happen to know???

I recently tested my Stant 13# and 10# caps using the "rental" tool from O'Reilly's, both tested at their rated pressure. I don't think I tested my old stock cap, not sure if I have it.

I just tested my 13# cap which is approximately two years old. I tested it with the autozone loaner and it blew at precisely 13 pounds.

Tony, convert to Evans Waterless, and worrying about pressurized caps or their ratings will be a thing of the past.

You know that over the years I have learned that YOU...

are someone to be trusted, are an excellent fabricator, and an imaginative designer... BUT...

This statement appears to be too remarkable! I understand how and why Water Wetters work and agree they can be good stuff... but I find it difficult to believe they work that well!

Alas, my overheating issues have NOT been because the system didn't work as it should... but because of very small leaks that were difficult to see and find which would then cause me to loose much of the coolant over time.

I did not find the leak in my goose-neck on the aluminum intake until I pumped the system up to 25 pounds. There were no other leaks found and when this was fixed... the system held and ran COOL even on 95 degree days with the A/C on, thanks to replacing the thermostatic de-clutching fan with a twin shrouded electric unit.

Then I checked the level and found that my catch can had somehow come off its mount and dropped into the bay getting chewed up ans spit our by the crank pulley. It was this that caused me to start testing the stats...

I don't feel the need for the Water Wetter at this time but will keep the thought in mind. It takes a bit of time to come to operating temp as it is, around 4 miles, and its needed for this beast to run properly. It does run between 20 and 30 degrees hotter with the A/C on and maybe the Water Wetter could address some of that. Hmmmmm... I think I talked myself into trying it!

HA!

Thanks Greg and Greg... I cetainly trust what you say...

and do not doubt a word of it... I also find it equally amazing that I currently have in my possession TWO pressure testers that read wrong, exactly!

Hmmmmm... story of my life...

Black-Tooth said:

are someone to be trusted, are an excellent fabricator, and an imaginative designer... BUT...

This statement appears to be too remarkable! I understand how and why Water Wetters work and agree they can be good stuff... but I find it difficult to believe they work that well!

HA!

Click to expand...

Its not a water wetter. You have to prep the system to remove any and all traces of water/coolant prior to use. The main reason for switching (for me) was the higher boiling point & lack of localized hot spotting that typically occurs with any water based system. Volvo whiteblocks are known to split the bore liners when pushed far beyond the intended output - I just want to improve my odds of not splitting a liner when I get it over 500AWHP.

I mentioned it as a joke, really. I know how much you love to pressure test those caps :laugh:

HAHAHA... Yeah, when yur old and have these testers...

just lying around... ya just gotta get up and use them.

Don't get me started with the Laser Thermometers... HAHAHA!