I read in a recent post that some people are removing the jiggle valve from their thermostats and possibly drilling the hole a little bigger. The reason given was to help keep air out of the cooling system. Can some one explain how this helps and what the jiggle valve's original purpose is?
Removing the jiggle valve from the thermostat?
- Thread starter Gman87t
- Start date
It's to let air bubbles that can collect behind the thermostat pass when the thermostat is closed. On Supras I don't drill it out but I often cut it off. Course, unless it's mounted at 12 o'clock none of that does any good.
Why do I cut it off? I dunno really, other than it's an old habit from dealing with cars where they hung up or the hole needed to be opened up for one reason or another ie; no bypass path in the system. Never had it happen on a Supra though. Ran jiggle valves for years on mine without a problem before I started snipping them. On this car it doesn't seem to be a big deal either way.
I do wonder how many cooling systems suffering trapped air are a result of leaks combined with the valve not being installed at the top though. I've seen many a thermostat that was put in wrong. The valve is there to prevent air locking of the thermostat ie; if a large enough bubble builds up behind it, it won't sense coolant temp and may not open until much later, if at all. If the system has leaks it'll draw in air every time it cools off. That usually involves the overflow plumbing because since it doesn't operate under pressure people tend to neglect it. The path from the radiator neck fitting to the little strainer in the overflow tank must be airtight.
For noobs here's a bit about cooling system basics: http://tinyurl.com/yvhn9l
I do wonder how many cooling systems suffering trapped air are a result of leaks combined with the valve not being installed at the top though. I've seen many a thermostat that was put in wrong. The valve is there to prevent air locking of the thermostat ie; if a large enough bubble builds up behind it, it won't sense coolant temp and may not open until much later, if at all. If the system has leaks it'll draw in air every time it cools off. That usually involves the overflow plumbing because since it doesn't operate under pressure people tend to neglect it. The path from the radiator neck fitting to the little strainer in the overflow tank must be airtight.
For noobs here's a bit about cooling system basics: http://tinyurl.com/yvhn9l
Yeah, kind of how I feel. Better to do it than not. There shouldn't be any air in the system but if some gets in there I want it to find an easy path out.
A bit more relatively useless knowledge: The vacuum valve in radiator caps comes in two flavors. One is spring loaded closed while the other is weighted ie; it's free to move and normally hangs down in the open position. Either kind works fine but the weighted type stays open until enough pressure builds in the cooling system to close it. This allows the system to run zero pressure until it heats up and also allows any air that gets moved to the radiator neck to be expelled before the main pressure relief valve in the cap opens. Otherwise it's a toss up which type is used. Every OEM cap I've seen employs the spring loaded valve.
A bit more relatively useless knowledge: The vacuum valve in radiator caps comes in two flavors. One is spring loaded closed while the other is weighted ie; it's free to move and normally hangs down in the open position. Either kind works fine but the weighted type stays open until enough pressure builds in the cooling system to close it. This allows the system to run zero pressure until it heats up and also allows any air that gets moved to the radiator neck to be expelled before the main pressure relief valve in the cap opens. Otherwise it's a toss up which type is used. Every OEM cap I've seen employs the spring loaded valve.
^ Just to add to that, at some point Toyota did switch over to the weighted type. I know you understand that, but to many what you posted will read "Supras use the spring type".
Colin: Thanks, didn't know that. Fwiw the OEM cap I bought a few weeks ago is spring loaded.
Nomad: Yeah, just like the TSRM says
Nomad: Yeah, just like the TSRM says
The T STats I use don't have a jiggle valve at all just a simple notch that you place at 12 o'clock.
wow for some reason i am feeling very dumb... umm.. wtf are we talkin' about.. i THINK i know.. but i have no other clue. :1zhelp: can someone clue me in as to what the "jiggle valve" is as i have NEVEr heard that term before.
C
cnewingham
Guest
its the fail safe vale on the thermostat which allows the coolant to still flow a little when the tstat is closed