xbcoupe

This may well be a stupid question, but here goes....

I have just fitted a replacement radiator (Aussie Desert Cooler) to my XB. The last one gave up and was replaced under warranty. It was suggested that I replace thermostat and radiator cap in case they were in part to blame for the apparent "pressurising" that led to the original radiators demise.......which I have.

Anyhow, when the engine was up to normal operating temps (with the original radiator) a substantial amount of coolant would flow from the radiator into the return reservoir. When the car was switched off and cooled down, that fluid would flow back into the radiator. I'm talking perhaps a third of the capacity of the return reservoir... maybe 500ml ??

Now I have fitted the new radiator, thermostat (170degree high flow) and cap, this no longer occurs.

Is this normal or is something amiss ??

Thanks in advance.

atec77

It is . the big question is is it bled correctly ?
is it running cool ?

UCNTRY

first thing standard thermostat is a 180 degree one part number st21-180 or you can run chev ones in them which come in at a couple of different temps first thing would be to make sure you have a recovery radiator cap as you can buy them as non recovery thats what i would be checkin

xbcoupe

Thanks for the replies.

I haven't driven the car with the new radiator as yet, only had it running for long enough to get it to where the temp guage normally sits. It quite happily maintains its "cool" at exactly where it did with the previous setup.

I was told to use a 170 thermostat, but can't imagine that there would be any real drama there (of course I may be wrong), but the radiator cap is the one that Aussie Desert Cooler recommended, which is identical to the one for an XF falcon - CPC issue.

How do I check (visually) if I have a recovery radiator cap ? I may well have been supplied the wrong cap from the local.

Finally.............. is the flow of coolant to the reservoir normal upon the engine warming up ? (Neither my ED nor BA do it.)

Thanks again.

russxr67

if your rad cap is the same as an xf cap then it will be correct for coolant recovery.

beetfeet

Your old radiator cap was getting weak. These caps are pressure activated - which means once your system reaches a certain pressure the cap opens to let coolant flow to the overflow tank. When the system cools down, it actually develops a vacuum in the system which draws the overflown coolant from the resevoir back into the radiator.

The caps are spring activated and over time the springs wear out. Your old one must have opened at say 10 psi instead of the normal 16 psi. That is why you had so much coolant in the overflow tank with the old cap. Thermostats play a role in this also because a 190 degree thermo will have higher pressure in the cooling system than a 170 degree one would. Higher temps = Higher pressure.

NOTE: I was just guessing on the pressure figures. Most cars seem to run from 15-18 psi but I have heard of some going as high as 24 psi.

xbcoupe

Thanks beetfeet. I changed the cap again and all seems to be well. What you said about the old cap makes a lot of sense.

Thanks again