evansandwilkins · Jul 26, 2019

I have been struggling for a while with my L322 V8, its constantly leaking coolant - had head gaskets done, new radiator , pressure tested and UV light leak tested !!! nothing, my local mechanic has come to a conclusion that thermostat might not be working causing the water to overheat in the expansion tank and pressure being lost from the cap . last night we ran the engine until hot then took off the cap (got away with it ) resulting in a lot of coolant erupting out the top , we stopped the engine and allowed things to calm down then restarted the engine which again erupted more coolant out the top - he seems to think that the primary coolant circuit is working fine but once engine is up to heat its not opening the thermostat to allow coolant to circulate the whole engine ! Does any one have any ideas

Datatek · Jul 26, 2019

evansandwilkins said:
I have been struggling for a while with my L322 V8, its constantly leaking coolant - had head gaskets done, new radiator , pressure tested and UV light leak tested !!! nothing, my local mechanic has come to a conclusion that thermostat might not be working causing the water to overheat in the expansion tank and pressure being lost from the cap . last night we ran the engine until hot then took off the cap (got away with it ) resulting in a lot of coolant erupting out the top , we stopped the engine and allowed things to calm down then restarted the engine which again erupted more coolant out the top - he seems to think that the primary coolant circuit is working fine but once engine is up to heat its not opening the thermostat to allow coolant to circulate the whole engine ! Does any one have any ideas

De-pressurise the system and almost always the coolant will boil over.

discool · Jul 26, 2019

Ok quote” he seems to think that the primary coolant circuit is working fine but once engine is up to heat its not opening the thermostat to allow coolant to circulate”.
So the answer is simple... replace the thermostat, but if he wants to waste time, charge the same but doing less he could test the thermostat.

Excessive coolant pressure being lost from the cap proves the cap is functioning as it should.

Also your location might help, you never know there may another L322 V8 owner local to U, and give another view on your issue.

evansandwilkins · Jul 26, 2019

Thanks Discool - my Location is Carmarthen South West Wales - that was the next move, if it was faulty would loosing about 1/2 a pint of coolant on a 40 min trip (providing its blowing out of the cap) sound about right!!! my only concern is 1.has the head gasket gone again , 2 is the problem lower down in the engine - my reasoning to worry about this is no coolant to be seen on surface of expansion tank when i check after running the vehicle - but then this might be because its evaporated !!!

biketeacherdave · Jul 26, 2019

Find a new mechanic to start with change the stat for the uprated version you will find it on the bay then bleed it properly.
These stats are electronically controlled and known to fail at the electrical connection at the stat as well as the stat failing also
Good luck

discool · Jul 26, 2019

A symptom of an iffy head gasket is increased coolant pressure therefore coolant blowing out from the reservoir cap, also there’s no indication of the engine over heating, although it’s possibly would do eventually due to the lose of coolant.
So is the engine overheating ie indicated in the dash display?
Thermostats fail mechanically but not instantly... so I suggest you drain the coolant from the engine and radiator and refill “slowly” as per the workshop manual to the correct level in the expansion bottle to elevate any air locks within the cooling system.
If still issues then theres a simple well known test that would confirm that there’s a possibility of a head gasket failure...gasket failure again is not unknown unfortunately.

As for coolant indication a coolant colour stain would remain.

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