Thermostat housing cap, which is the proper one? (Page 2/4)
Blacktree JAN 31, 12:05 PM

quote
Originally posted by theogre: Not Quite right...


I described a problem I had with the cooling system in my Fiero, and how I fixed it. I offered that story, because Cliff's problem sounds familiar. He can easily test his car, to see if it has the same problem.

If you want to nit-pick minutiae, that's up to you. Have a nice day.
Cliff Pennock FEB 05, 06:59 AM
I just received the new radiator cap:



It's quite different from the old cap. The old cap seals 100%, it has no pressure release valve or anything:





The new cap however, has a middle part that moves up and down. Meaning it doesn't seal at all. It is indeed a 0psi cap. So it is a vented cap. Also, since the thermostat pushes up on the cap, the middle part is always open.

So which cap is the proper one? My old or the new cap?
Steel FEB 05, 07:20 AM
The one you just received is the Thermostat housing cap, in the engine compartment. Your old cap you pictured is a radiator cap in the front of the car.
Cliff Pennock FEB 05, 07:22 AM
No the old cap I showed is the thermostat housing cap. The radiator cap is vented (15psi) and is quite a bit smaller.
Steel FEB 05, 08:05 AM
Oh shoot my apologies I was looking at it on my TV across the room and wasn't paying close attention. The one you ordered with the spring is a 'non-vented' cap and the correct radiator cap. The one you're replacing without the spring is a vented radiator cap and not the correct cap.
Cliff Pennock FEB 05, 08:37 AM
I just looked it up in the official Fiero parts list, and the RC40 (my old cap) is the car´s original cap. my new cap (Stant 10232) is an open vent cap.
Cliff Pennock FEB 05, 08:42 AM
I also looked up several threads here on PFF about the cap and just about everyone is using the Stant 10232 which is the wrong cap. I'm guessing that if you use the open vent cap, you're losing a lot of coolant as steam and the radiator cap never opens.
Steel FEB 05, 09:15 AM
Okay if your new cap is a 10232, doesn't have a spring, then it isn't the correct cap to my knowledge.

The caps I buy for restoration Fiero's that I flip for resale are #10230 caps (i believe is original P/N # and are hard to find these days) and also #10409635 (which is current last I checked) and I never have issues. These caps have a noticeable spring installed on the underside, but are considered 'non-vented' caps.
Cliff Pennock FEB 05, 09:26 AM
I think you're talking about the radiator cap, since the 10230 is a radiator cap and not a thermostat housing cap. The thermostat housing cap doesn't have a spring so it's either a closed cap, or an open vent cap. A closed cap is what is required, an open vent cap is the incorrect one. The Stant 10232 is an open vent cap.

I probably need something like the Gates 31313 since that looks like a closed cap.
cvxjet FEB 05, 11:43 AM
The Thermo cap should not vent at all- that central rivet should be TIGHT. You may have a bad one (Defective) There would be NO reason for any cooling system cap to vent at 0 psi- you want the cooling system under pressure. Send that cap back and have them send you another.

I want to add that the Gates 31313 is the correct diameter; 2.86" as stated on the Jegs website, and I measured mine (Stant)

[This message has been edited by cvxjet (edited 02-05-2022).]