Hi
Newbie question about my newly purchased 1997 xk8:
The manual states that coolant should be filled to the «bottom of the filler neck».
My tank has no neck as far as I can see, what is the length of the filler neck supposed to be, measured from top of tank opening?

 

Your tank is correct. Filling to the bottom of the neck just insures that you have the tank filled all the way.

 

The coolant expansion tank just needs to be filled up to where the cap fits onto the tank’s “neck.”

It’s an Hydraulic pressurised system so needs to be full.

If you look look closely at the cap, there’s a spring valve in the centre. This is to bleed pressure into the atmospheric recovery tank behind the front right wheel.

Look after the coolant system as overheating is an engine killer in our car. Whatever you do, don’t mix green and red types of coolant. They’ll gell and block the pipes.

 

Thanks a lot for the thorough anwers!
I am just finishing my installation of aluminium thermostat housing, and have not started the engine yet, so I will top it up before starting.
I have read somewhere that you should start the engine with the filler cap off to bleed off air, while others claim that the cap should be on before starting her up. Any opinions on that?

Best regards,

 

If you start it with the cap off be ready to replace it quickly or you'll likely have coolant overflowing as the temp increases. I always squeeze the upeer radiator hose several times with the cap off to remove air, then replace the cap. Run the engine up to temp. then shut off and top off the tank after it cools.

 

A photo is the easiest way to illustrate the correct level. This is the level I filled my XK8 4.0 Expansion Tank:





Half an inch below that isn't going to cause any trouble. It's not a chemistry laboratory exercise.

As the system warms up any excess is pushed out to the Atmospheric Recovery Bottle in the RH wheelarch. As the engine cools down, coolant is drawn back from the Bottle to maintain the correct level in the Expansion Tank.

Any fluid loss or requirement for topping up between services should be investigated. There's a lot of plastic and rubber in the XK8 cooling system and if something fails it can rapidly lead to serious trouble.

Graham