Rad cap for system with expansion bottle???

[gr_diver]

Hello friends!

I was digging inside a box with previously replaced but known good stuff, and I came upon this radiator cap I replaced 3 years ago. Back then I knew almost nothing about working on cars, and I changed it as a safety matter...

So today, staring at it, I noticed it has two rubber gaskets, and by playing with it I discovered there is a small spring loaded valve at the bottom, that controls a small passage to the center cylinder shaped tube that the cap's main spring is around. I posted some photos of it...

Now solely from descriptions I have read in the forum, that 2 gasket/ valve combination sounds much like a rad cap for a fluid recovery system (I've never seen one closely...). Is it one of these? If so, it came in right on time, because I am already preparing the expansion bottle and I would go buy a rad cap on monday!!!!

Can you guys confirm if it is such a radiator cap?

Thank you in advance!!!

[ddoyle]

Yes it is, fluid recovery cap will always have 2 rubber seals on it.

Dan

[opelnut10]

All the Opels imported to the US with expansion tanks had a plastic cap on the tank. I think what you have there is a regular radiator cap with a "pop off" valve that allows pressure to escape above a certain temp. in order to prevent blowing a hose or the radiator.

[gr_diver]

Originally Posted by opelnut10 All the Opels imported to the US with expansion tanks had a plastic cap on the tank. I think what you have there is a regular radiator cap with a "pop off" valve that allows pressure to escape above a certain temp. in order to prevent blowing a hose or the radiator.

This is a radiator cap though, not a expansion tank cap. It has the common strong spring that lifts the entire assembly for the coolant to escape towards the overflow tube (what I think you mean by "pop off" valve), and the smaller also spring loaded valve that opens towards the radiator's top tank (from it's function, I assume it would open only if there was vacuum inside the radiator).

[ddoyle]

Thats right, as engine warms up, coolant expands. Once the pressure rating on the cap is exceeded, coolant goes out thru the overflow. If a recovery tank is used, as the engine and coolant cool down, a vacuum is created in the cooling system, this pulls the small valve open and draws the coolant back into the radiator. This will only work right if there are no leaks in the cooling system. The benefit is to keep all air out of the cooling system, better cooling efficiency.

Dan

[gr_diver]

And if I understand correctly, in open cooling systems, there would be no upper rubber gasket, since no fluid moves through, and the small valve would allow air back in the radiator when cooling to avoid hoses collapsing, right?

But since it has two rubber gaskets, it is made for coolant flow to a external tank... Again right?

Nice, I will prevent summer spils on the floor (not exactly environment friendly) plus increase efficiencly!!! I like it!!!!!