I decided to change my thermostat in my 2005 XK8. Got the old one out, but have not been able to stuff the new one into the housing. No matter how much pressure I apply (even using a vice) I cannot get the thing to compress enough to rotate the little wings into their slots. Any thoughts appreciated.

 

If we are talking about the coolant thermostat something went wrong, it's an easy fit, no force or compression necessary to stick that thing into the housing.
And as far as i remember there are no wings to rotate into slots. Maybe you like to post a pic of both, the removed one and the spare part.

Fritz

 

There have been reports over the years that folks have installed their new thermostats upside-down, but I do not recall reading about a new thermostat that would not fit into its housing. Are you certain that you purchased the proper replacement thermostat?

 

It should go together without any force like this:





The "giggle" pin (1) at the top and rubber ring (2) around the perimeter of the thermostat.

Graham

 

Generally, the standard advice is to replace the entire assembly of plastic pipes, o-rings, thermostat and temp sensor. It is not as expensive as one would think ($120?) and gets these old brittle plastic pipes out of there. As you know, our 4.2 do not have that nice Aluminum tower option. Consider this more comprehensive replacement for reliability alone.

Part#:AJ89486




Best of luck, keep us posted.

 

I guess the 4.2 has a different thermostat. This is the style my car has.

 

I did replace the main housing, including the thermostat. I got a message that my thermostat was not operating properly, so I pulled it. It is held by a spring in the connector part. Once it's out it is impossible to get back in. I have seen the thermostat and just its connector part sold as an assembly. Now I know why.

 

Your car is presumably an XK (X150) and not a XK8 (X100). Although i have an 4.2 XK8 i have never seen a thermostat like this, it ist very different.

 

Looks like it was designed by Rube himself. Weirdest stat I ever saw, but evidently correct for the late MY.

Terrys Jaguar website shows it assembled in two different ways
https://www.terrysjag.com/product/AJ82697.html

 

In the photo, they reversed the bottom part. The pointy end should be pointing down.

 

My first encounter with this style, also.

 

That looks nothing like my thermostat, and mine's an 04'.

 

Don't know why they had to change it. Just complicates a simple job.

 

I finally figured out how to get the thermostat back into its housing. With the style thermostat used in the later VINs, there are two metal "wings" that need to be rotated and locked down under a couple of lugs inside the housing, This is not an easy thing to do, given the spring you're working against does not want to compress. My natural inclination was to push down on the metal disk, which in turn would push down on the wing area, so I could try to rotate the wings to the locked position. No matter how much pressure I applied, even utilizing a vice, I could not compress the spring enough to get the wings below the lugs so they could be rotated. Then it dawned on me that I needed to apply the pressure directly to the wing area, not the disk, as the disk would not push the wings down low enough. I solved this by inserting a wrench end in between the metal disk and the wings, which did push the wings down farther so they could rotate and lock under the lugs.

I also learned that running my car without the thermostat in causes it to quickly overheat. This surprised me as my experience has always been that cars ran cooler without a thermostat. I guess newer cooling systems are more demanding of precision temperatures.

 

I think the actual reason for overheating without thermostat is that the cooling system needs 1 to 1.2 bar pressure to handle temperatures obove 100 degrees celsius. Without thermostat the system wont be able to achieve the neccesary pressure.

 

Thank you, John - I am doing a cooling system job on my '03 XK8 and was running into the same problem you did in removing and replacing the thermostat in the plastic housing. Not only am I proactively replacing the thermostat (though it was replaced six years ago along with a new housing and it still looks clean as a whistle) but also top and bottom main hoses, serpentine belt (since access is now easy) and -of course- the coolant itself. I will try the procedure with the wrench for the t-stat and expect that will work great. Thanks again.