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internal mechanism I had to break the tabs off the cap to get this out... I'm replacing it anyway and wanted to see how this works and what was wrong
this is what it looks like taken apart... you can see the four tabs to release the outer housing
in this pic you can see the spring that regulates pressure 18 psi
broke down further the internals that allow the system to breathe
exploded view
this is the little rubber piece that was STUCK on my cap
it fits in this and was stuck to the seat and would not let air pass, you can see the whole in the bottom of the seat... the small tit on the rubber piece goes thru this whole and with the spring on top acts like a diaphragm/valve to Vent vacuum
with the "stopper" in it...this needs to be free to move...there is a very small spring that sits on top the stopper you can see it in the exploded view
the housing all those pieces go back in
so that is what the inside of the cap , in a nut shell
hope this helps someone else see how this little guy works
Last edited by 73Corvette; 03-07-2015 at 09:08 AM.
I am installing a vararam, the car is on jacks and the hood is up, just happened to see the upper radiator hose was collapsed ... which of course is caused by vacuum... but I wasn't sure why?
I had removed the radiator to clean it a couple of months ago and no doubt got some air in the system, which can and I think usually will work it's way out... but, because that tiny little stopper was stuck, my surge tank, could not breathe properly...Bill Curlee had suggest the cap was the issue and he suggest to take it off and wash and should free it up...but, I didn't have a clue what he was wanting me to get freed...
thus the take down of the cap... I ordered one from GM it's $21 a little more than some others but I want the OEM replacement.
Anyhow, now I have learned a LOT about the importance of what seemed to me, to be an insignificant part that is in reality a VERY important part of the whole coolant system, that working together can orchestrate an efficient way to maintain optimal operating temps. Sorry got a little long winded.
Last edited by 73Corvette; 03-05-2015 at 07:15 PM.
I am installing a vararam, the car is on jacks and the hood is up, just happened to see the upper radiator hose was collapsed ... which of course is caused by vacuum... but I wasn't sure why?
Ah, got it. I've never seen that one myself, then again, this is the first car I remember having that has a pressurized overflow/surge tank.
Now, are you saying that cap works a vent to release pressure? I've been chasing a slight coolant smell from the engine bay for a couple years after parking. Never low on coolant, never a drop anywhere, could this be the reason? Seems if it was venting you would smell it.
Now, are you saying that cap works a vent to release pressure? I've been chasing a slight coolant smell from the engine bay for a couple years after parking. Never low on coolant, never a drop anywhere, could this be the reason? Seems if it was venting you would smell it.
The cap is supposed to vent, based on what the larger spring pressure is, but like most things I suppose with age it could get weak and release pressure less than was intended... so yes, that is possible. 18psi i think
The cap valve also goes the other way to prevent Vacuum for one, this allows the air/steam/flashed coolant to work its way to the highest point in the system, which just happens to be ( by design) the coolant cap.
I would try a new cap...make sure you get the correct pressure from Napa or some other auto parts place or the OEM one is about $20
Your surge tank may have a small leak/weep
Let us know if this fixes that issue please
thanks
The cap is supposed to vent, based on what the larger spring pressure is, but like most things I suppose with age it could get weak and release pressure less than was intended... so yes, that is possible. 18psi i think
The cap valve also goes the other way to prevent Vacuum for one, this allows the air/steam/flashed coolant to work its way to the highest point in the system, which just happens to be ( by design) the coolant cap.
I would try a new cap...make sure you get the correct pressure from Napa or some other auto parts place or the OEM one is about $20
Your surge tank may have a small leak/weep
Let us know if this fixes that issue please
thanks
Guido, i too was chasing a coolant smell. Usually when it idled when i was jocking cars around the garage, found i had just a drip from the water pump, dripping on my new belt. Chirp cold got me looking in the first place.
Well you have eliminated the cap... if your still smelling it, there has to be a leak somewhere even if its very small sounds like you'll just have to seek till you find...good luck...let us know when you find it.
Thanks
I recently noticed a coolant smell from under the hood and it's appears strongest from the top of the tank. There are no leaks so I ordered a new oem cap to see if that works.
I think I should add that a proper fluid level is very important also... the fluid level mark is on the front of the reservoir tank right behind the passenger side headlight housing... they did a pretty good job of hiding it lol DO NOT OVERFILL
I think I should add that a proper fluid level is very important also... the fluid level mark is on the front of the reservoir tank right behind the passenger side headlight housing... they did a pretty good job of hiding it lol DO NOT OVERFILL
Yes, my fluid level is almost a half inch above the full mark. Been that way for years. Never need to add and pressure tested and still found no leak. I'm baffled, will keep an eye on water pump
internal mechanism I had to break the tabs off the cap to get this out... I'm replacing it anyway and wanted to see how this works and what was wrong
this is what it looks like taken apart... you can see the four tabs to release the outer housing
in this pic you can see the spring that regulates pressure
broke down further the internals that allow the system to breathe
exploded view
this is the little rubber piece that was STUCK on my cap
it fits in this and was stuck to the seat and would not let air pass, you can see the whole in the bottom of the seat... the small tit on the rubber piece goes thru this whole and with the spring on top acts like a diaphragm/valve to Vent vacuum
with the "stopper" in it...this needs to be free to move...there is a very small spring that sits on top the stopper you can see it in the exploded view
the housing all those pieces go back in
so that is what the inside of the cap , in a nut shell
hope this helps someone else see how this little guy works
Kids and their toys..........Taking things apart to see how they work......Been there, done that and still do that....... Thanks for posting. Never had one apart before.
03-05-2015, 12:55 PM
Your surge tank vent cap... how it works
...Taking things apart to see how they work...
...Been there, done that and still do that...