The coolant is always disappearing from the header tank in my AU3 Sedan (6 cylinder). I have replaced all of the hoses, new thermostat, new three core radiator, replaced the Welch plugs under the exhaust manifold, which I am lead to believe is the coolant side of the motor, new coolant (Nulon). When I done all of this work, I also installed a transmission cooler to keep the coolant and ATF fluid in separate systems.

I am at my wits end as to what is causing this problem, and I would really like to have it fix, once and for all.

The car doesn’t go into the red on the temperature gauge on the dash.

Please any help/information would be greatly appreciated.

Regards,

Holocaust
Peter

Have you checked your oil to see if the coolant is mixing in there? It may well be a head gasket.

How much are you losing?

how quick does it disapear???

When you fill it up with fluid, are there any bubble's?????

Could be that it's the Head Gasket/ Head Cracked, and it's cracked around the exhaust, and as that part is hot, it evaporates.

have you changed the cap??
same thing happened with my au3 ute.... it was the cap

Ah yes, good point there. Always start with the simple things

Damn it, I forgot to mention the cap has been changed int he past, the rubber appears to be in good condition right now.

If it is a blown head gasket, what sort of dollars would I be looking at??

Anywhere from a few hundred (DIY) to a couple of thousand in a workshop. Also depends if any repairs are required on the head. How many KM are on it?

I think the next logical step would be to get a compression test and see what the results are.