VZ Overheating Mystery

[Sean880]

I would also have some tests run to see if you have engine gasses blowing into your cooling system via the head gasket.

Don't delay having it looked at by a competent mechanic as you don't want to cook your engine. The good ones will do a proper diagnosis before they recommend solutions. The alsorans will guess and want to start replacing this and that in the hope they stumble on the solution.

 

[bigdaddycool]

Make sure there's no blockages in your exhaust etc.... cats etc. I had my temps going up and down wildly at one stage, was a blocked resonator on one side....

 

[jaisvz]

Blocked resonator? .. WTF. Talk about throwing him right off course!

Aussie Dark: it will be either your water pump (classic symptoms) or thermostat.

I would most likely be inclined to say water pump, as I have had mine replaced
with the same symptoms - and fixed all problems instantly.

 

[bigdaddycool]

tru that...... happened to me tho. but yeh, waterpump most likely then thermostat.

 

[Aussie_Dark]

Wow... water pump. What issues did people have with the water pump? It would be great if it was the water pump as I think that this would be the easiest thing to replace.

 

[Torquative]

simple answer is they leak, and leak big time!!!

But VZ's are known for having both issues, thermostat and waterpump

 

[calay]

my WP was leaking and has been replaced, although i'm 100% sure it's working properly as the temp still goes above that 25% mark more often than it used to...

 

[Aussie_Dark]

My water pump is not leaking... does that point me back to the thermostat?

 

[sssmechanicholdenbrisb]

too know if thermostat
drain coolant (bung under radiator)
fill and (in vz only vt is on thero housing under eng cover)
bleed BEFORE starting at bleedr top right hand side of radiator,
then hold revs at two thousand until fans come on this is SUPPOSED to be when the thermostat opens (this takes five ten minutes)
when fans come on level in fill port (where cap is) should drop significantly,
fill and when fans turn off bleed via screw rh top of radiator again.
if level doesnt drop or fans dont come on WHEN fans work when driving only! then thermostat is shagged,
will not set any codes and most holden dalers sadly will miss this point. if not bled as above eventually will destroy thermostat anyway!!!! very "common"
also dont mix coolant colours fork out the cash and get genuine coolant can make a 10-40 degree difference in temp reading!!!
by the way qhwen doing above blleed procedure have the overflow tank hose (where you can top it up yellow cap) pushed into where radiator cap was or block it off.
hope this helps if not msg me!~
by the way thermostats also have THREE o-rings on them in vz/ve that must also be replaced at the same time!2 for heater lines and one for lower radiator hose connection

also if not bled properly will resemble a blown headgasket ONLY vz/ve i have had head blown on is lpg taxis/limos at around 250,000km's with wrong coolant so take the hint!@~

 

[Aussie_Dark]

Thanks SSSMechanicHoldenBrisb.
Sounds like I have something to do this weekend.
I can confirm that the fans do not come on unless I drive the car, however the cooling system would not have been bled as you indicated. The level does drop, but then fluctuates up and down a lot.
I'm going to cross my fingers that this positively identifies the thermostat as the problem. Will post on the weekend after I do the test.