Stants cap FYI..

ecohen2

ecohen2

True Classic
Over the weekend I discovered that not all Stants caps seal equally well. Here is what happened...

During the past year, I swapped out my plastic stock tank for a stainless steel tank. The first tank had a leak, so I returned it but I kept the cap that I purchased with it. The second replacement tank has the same depth neck as the plastic tank and came with a 13 PSI Stants cap. This gave me 3 caps to play with although one of them was a 7PSI. Ever since I replaced the tank, I noticed that it never made a hissing noise when I removed the cap and that my temps would run higher than I expected. Yesterday I was thinking about how could the system lose pressure but not leak any coolant? What I discovered was that both of the Stants caps seal properly on the cap part, but one of them didn't seal against the inside of the neck. The result was the coolant would boil and I would eventually get air bubbles in the system without ever losing a measurable amount of coolant. I even did a pressure test and never found a leak in the system, but couldn't figure out why I had no pressure.

The two 13PSI Stants caps are both new, identical part numbers, appear to measure the same but the spring on the bad one seems to be cut a little short which is why it doesn't seal properly. My guess is that it is 1/8th of an inch difference. You don't feel any spring resistance at all with the bad one until the cap is almost tight. On the good one, you can feel the resistance as soon as you start turning the cap.

Just a seriously weird problem...
Ed
 

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I don't remember fully, but didn't C. Obert mention something here at one time about aftermarket coolant caps and how important it was to use a specific replacement model? Perhaps drop him an email. chohen2, if you ever want to sell that gem please drop me a note.
 
There is always a price!! However it is spring and everything works really well, so it might not be the best time for you to negotiate :)
 
Why not use the factory equivalent sold by vendors? I never trusted a Stant on a fiat, they always caused overflow problems on my FIATs
 
Just out of curiosity, how much difference does .2 bar or 3PSI make in the performance of the cooling system?
 
I have watching quietly this thread waiting for the Stant cap numbers everyone is using, but no one is posting the model number. Please post the numbers so I can buy some for my cars.
 
Radiator Cap-OE Type GATES 31527

http://www.gates.com/

Specifications
Cap Depth (in) 1.25
Filler Neck Depth (in) .75
Filler Neck Inside Diameter (in) 1.61
Filler Neck Outside Diameter (in) 2.13
Shell Diameter (in) 2.33
Weight
Weight (Lbs.) .19
Working Pressure
Pressure Rating (psi) 13
SAE Pressure Range (psi) 12-16
 
Thanks for the information. I thought I had saved the information from a few years ago. I like to change the cap every 3 to 4 years.
 
Hmmm replace every 3-4 years. I have never replaced a cap. The one on my 850 is getting pretty close to fifty and the 124 is nearly the same age. Never had a problem with an old cap as long as the rubber seal was good.
 
OK... Comments here from another old-guy...

I took my PRESSURE tester with me to the store (and Auto Zone will usually let you use theirs...) and took a handful of their Stant 10229 caps and tested them right there. I tested the first 3 caps and they blew at 8, 10, and 12 pounds and I retested to be sure. I took the 12 pound cap.

I've also used them for DECADES with no issues but I must agree there is some QUALITY CONTROL missing. Lately, I have purchased a few Brand X T-Stats that were made in ISRAEL. I have usually used Stant's but these were all that were available at the time I needed them. No problems also.

I always test my T-Stat's in boiling water and Mama's Baking thermometer in a clear coffee pot. (Coffee never tasted so good!)

HTH
 
Both of mine were made in Mexico and are visibly different... I ordered a cap from Vicks which is not Stant and am going to give that a try... Random question to go along with the cap conversation. How much room do you leave at the top of the tank? I am running a stainless steel tank and leave about 5 inches from the cap. I occasionally will get a dribble out the vent tube, but otherwise it seems to be happy...

Ed
 
Yeah Ed... the tank holds about a gallon and I fill mine to about 3/4 full. Usually no problem and if it does puke a little at first, it'll kinda "heal itself" and you'll have no further worries.

I IMPLORE you thought to TEST the caps... as usually your pressure and temperature gauges do not lie. Every pound of pressure RAISES the boiling point by about 3 degrees. Do the math,
use a laser thermometer, and calculate all that into your temperature gauge and how it reads, and I'm pretty sure you'll wanna have a 13 pound cap.
 
I am in total agreement.. I have to tools to test my system, but not the cap itself... Going to find someone to do that...
 
Yesterday, when I was playing around with fitting my aluminum tank, I realized that my cap(s) are all incorrect for both my stock plastic tank & my new tank, which match the 3/4" depth mentioned earlier. The caps I have on hand are all closer to 1/2, which means no contact with the seat. Not a major issue with Evans, since you can run with zero pressure, but that does explain why I always smell coolant. I'll have to get the 10228 7psi max version.

EDIT - I was mistaken, I mis-measured my caps - they are in fact 3/4" offset from the inner lid seat to base of the seal.
 
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