As my X300 is running cool even on motorway journeys, I intend to replace the thermostat to see if that's the problem. I'm used to cars having a clearly visible one situated on top of the radiator but on my car this is not the case. I can see a large hose at the front of the engine near to the fan which connects to a housing near the top of the engine block. Is the thermostat in there?
I don't want to dismantle something unnecessarily.
If it is in there, is a gasket replacement necessary at the same time?
Apologies if this appears to some to be a rather simplistic question!
Thanks.

 

You're closing in on it!

The Part Catalogue diagram makes it clearer:



Thermostat (item 4) and Gasket (item3).

Graham

 

Wonderful. Thanks so much.

 

Be VERY careful when replacing it.

Some parts listing call for a gasket between the cover and the cylinder head, some call for an o/ring.

I have never seen the o/ring style, but I have seen many, many cracked covers from o/ring being fitted to a gasket style cover.

Ensure the groove in the cylinder head is CLEAN prior to refitting the thermostat.

I also use a "dob" of RTV on the new thermostat to keep it in place in the groove, coz if it drops out as the cover is positioned, you possibly will not notice it, and the cover will be cracked when tightened.

 

Thanks for that, good advice I'm sure, but what is RTV? Is it a form of liquid gasket available in tubes?
Thanks again.

 

It is also known as "silastic", or "form a gasket". Made by Dow Corning and many others.

Nasty stuff if used in excess, it blocks radiators.

All you need is about the size of a match head.

Down here it comes in 150gram tubes, like toothpaste tubes.

 

Understand Grant, thanks again.

 

RTV = Room Temperature Vulcanising

Once you know what an acronym means, you never forget!

Graham

 

Slightly off topic....

Gasket #8 in the illustration has been known to cause minor (and *hard to trace*) coolant leaks. A few of us have been there, done that over the years.

Just a little tidbit to store away for possible future reference.

Cheers
DD

 

Hi folks, my original thermostat had a little poppet valve installed in it. The new stat does not. Shall I go to Jaguar and get one with the little valve in it? Will the stat w/o the valve work satisfactorily? For the record, what is the valve designed to do? Thanks much. Rendo.

 

Rendo,

The poppet is to bleed air, and installed at the 12 o'clock position.

If no poppet, simply drill a small hole, 3/32" diameter is OK, in the outer disc, and is what I did to mine. Install the stat with that hole at 12 o'clock.

If that is not to your liking, return to the supplier and get a poppet stat.

 

It's called a 'jiggle pin' and, as Grant says, it's to allow air to bleed and therefore must be fitted at the 12 o'clock position.

Graham

 

Thanks for the reply and the advice about simply drilling the little hole.