I know the answer is somewhere on the forum, I have seen it, but I have just spent the last 45 minutes trying to find it with no success!

Does anyone know what size hex wrench (Allen key) is required to undo the top cap of the thermostat housing?

Thanks


Malcolm

 

You will need a 10mm hex for the plastic thermostat housing cap.

 

Malcolm,

I was wondering why you needed to remove the Thermostat Housing Cap.

If it's to refill the cooling system then the Jaguar procedure was revised a while back to fill through the Expansion Tank. This avoids having to remove the Thermostat Housing Cap:

(Refill the cooling system with a 50% solution of water and Jaguar Antifreeze / Corrosion Inhibitor ESD - M97B49 - A)

1. Fill the cooling system at the header tank until the level stabilises at the top of the breather neck.

2. Allow at least 2 minutes for air to purge from the system.

3. Top up the header tank as required and fit the pressure cap.

4. Switch on the ignition, switch off the climate control system and start the engine.

5. Run the engine at between 1500 and 2000 rpm until the cooling fans operate.

6. Switch on the A/C system, set to maximum heat, and check that heat is coming from the heater at the fascia vents or the footwell outlets.

7. Switch off the engine and allow it to cool down.

8. When cool, remove the pressure cap and top up the system as necessary at the header tank.

If you're removing it to fix a leak, then just ignore me!

Graham

 

It is my belief that the Allen socket is intended only for the initial installation of the cap.

Having broken one may I suggest that it is not a proper way to remove the plastic cap that has been there for years. Got a 'rubber band' wrench?

 

Thanks for the Info. It is an aluminum body, and is leaking from the top cap, so I need to open it and sort it out.

malcolm

 

Either a worn O-Ring or a hairline crack in the aluminum cap - but I would think the O-Ring is te issue. Ensure you tighten the cap on with the 10MM hex wrench to 9Nm (6.7 ft lbs - round to 7)