Does this look like the correct unit?
I recall it’s more complicated than just buying any old unit-bypass no bypass, etc?
The one that was in my car disintegrated upon removal but it looked like a normal unit. But It’s long since disappeared.
I’m looking for things to buy since all I need at the moment is ball joint shims at .048 each. Shipping minimum and what not.
Was there supposed to be a link or a pic?
funny you should ask…
This is SNG’s pic
I just put this exact unit in my ‘63 OTS. Beware…the lip on this stat is thicker than stock. You’ll have to use a significantly thicker gasket (very easy to make), or you can always grind down the lip of the stat (I cant imagine that would be much fun). I went with a thicker gasket. Works fine, no leaks.
you have a bypass set up, yes?
Indeed. The new stat seems to work fine. But the 3.8L by-pass is different from the 4.2L I think. I remember seeing a thread on this. Try searching for “thermostat bypass” or something like that.
Looking at XKs site the one you picture would seem to be for the 3.8L engine:
Whereas the 4.2L uses this one (what I have in my S2):
Note that that one also comes in a 190° version.
Geo, the earlier, i.e. Series 1 4.2’s, use the thermostat with the sleeve which closes off the bypass port when the engine heats up. The first one that you show is the correct one for his '66. The later one without the sleeve will fit, but will contribute to overheating problems because some of the coolant will continue to flow through the bypass once the engine is warmed up.
Both the S1 3.8 and 4.2 engines used a sleeved thermostat albeit of different designs: This is because the by-pass side port is in a different position on the two engines. Neither used the vertical poppet thermostat.
The sleeved thermostat is designed to force water through the bypass during warm up but as the thermostat opens to allow coolant to flow through the radiator it closes off the side by-pass slot. Fitting a thermostat without a sleeve, such as the one in the second link in Geo’s post will only accomplish one of those functions - it will open and close the radiator inlet but coolant will always be allowed to flow through the by-pass.
This is what happens with a poppet thermostat fitted. A sleeved thermostat would close the by-pass when the poppet opens:
This is the double poppet thermostat fitted to the S2 cars, useless on the S1 cars as they have the by-pass is on the side not at the bottom:
SNGB sell the correct version for the S1 as part C3731/1*, same one as Bill posted a photo of.
Now you can argue that leaving the by-pass permanently open makes no difference but Jaguar thought it did. They adopted the vertical poppet style thermostat for the S2 because that style was becoming the industry standard and was more reliable - the sleeved type could jam with debris.
David
That is probably the best explanation I’ve seen on how these thermostats work. Thanks David.
