Pressurised coolant header tank.

[piman]

Hello all,

my X Type 2.5 petrol is using a little coolant but what I find peculiar is that even if the car has stood for a few days, opening the header tank releases air and coolant flows back into the tank. I find it difficult to understand how that pressure is retained?

Alec

[RichardSEL]

Check whether there's any exhaust gases getting into your coolant.
See: https://itstillruns.com/test-exhaust-ga ... 85485.html
for more info

Otherwise what you're releasing is a partial vacuum that the coolant in the system moves to fill

[piman]

Hello Richard,

thanks for the reply, I suspect that your second suggestion is correct and I have assumed it is pressurised not de pressurised. That and the slight coolant loss would reinforce that diagnoses I think.

Alec

[piman]

hello all,

further top ups have confirmed my intial diagnoses that the header tank is pressurised. Quite why that pressure does not bleed away over time is what I don't understand? There also is no leaks that I can see but there may well be areas not visible without dismantling some of the engine?

Alec

[ng4xjs]

Hi Alec

I've a similar problem with my wife's 2005 2.5 Sport. I've plugged various leaks which I believe in sequence were caused by excessive pressure building up and the system merely finding the next weakest point. I think I can smell exhaust gasses in the coolant but will need to get that checked at some point. There is no oil in the water or water in the oil, but something is not right. My own view is a cracked block or head causing a pressure build up but will continue to eliminate possible causes.

In the meantime we went out and bought a 2009 2.2 diesel. Immediately halving of the insurance, road tax and fuel costs. It's a good deal less of a performer, but in truth not really a big issue (still nave the XJS to play with ).

Nick