Stat housing gizmo - what does it do?


Could you please tell me what this “valve” does in the stat housing that I am pointing to, and do I need it? The problem I have is the little tab that you see, like half a “T” is not allowing the other half to bolt up tightly.

Thanks, Pat

It’s a bleed valve to allow air to escape from the closed system. It should align with a hole on the mating housing so it’s free to move in and out.

No idea what its for unless there is a passage back to the water rail side to act as a bleed port. Is the valve in the correct way?
I think there has been discussions on another thread about this?

One of Jaguar’s embarrassing cooling system errors. When the S2 manifold was developed, the specified thermostat was a 75C Waxstat. It didn’t have a jiggle valve, so this ridiculously complex housing was created, with an air bleed passage. Then a jiggle valve was pressed into place while the casting was hot. This mated to an unduly complicated cover, which has a cast port and pressed-in nipple, interfacing to a small diameter hose, leading to a nipple soldered into the radiator top tank. Probably added $75-100 to the cost of the car when new. Looks awful and offers several unnecessary failure points.

Around the spring of 1969, Jaguar switched to an 82c Waxstat with an integral jiggle valve, making this whole mess an expensive redundancy. Nevertheless, it continued through end of production.

There should be enough room in the cover for the ‘t’. This may not be the case if you have an aftermarket cover. I would be inclined to ream the cover, as the jiggle valve can’t be replaced easily. If you remove it, be sure you plug the passage and use a vented thermostat.

The purpose? When you initially fill the system with coolant, a big air bubble would form behind the thermostat unless there’s an air bleed. Once the system is full, it has no further purpose.

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