VT random temporary overheating issue

[snicklefritz]

Hey guys,

A few months back I was driving my V6 VT and approx 15 minutes into the drive (city driving) the temp gauge rapidly shot up to hot, a weird chime played and the dash said hot. As I was slowing down to pull over there was a rather loud clunk that came from the engine bay and the temperature quickly went back to normal.

I assumed that it was a sticking thermostat and the clunk was it releasing so I replaced the thermostat, thermostat housing, radiator cap and flushed the cooling system. Everything seemed fine after that and for the past few months I haven't had any issues until today.

Whilst I was waiting at the traffic lights after having driven about 10km the same sort of thing happened again, the temperature rapidly rose, the chime played and the dash said hot. The light having just gone green I decided to turn the corner and pull over. Pretty much as soon as I came to a stop and before I could shut off the engine, the temperature quickly dropped back to normal. There was a lot of traffic, so I couldn't hear if it made any clunking noise etc.

Any ideas on what may be failing/has failed or what I should be looking at?

Cheers

 

[dirty hands]

check again

water in oil

faulty temp sender on the block

leaks at the lower inlet manifold gaskets

bleed the air out at the thermostat housing nut

heater valve on when hot

water pump

serp belt tension

the engine cooling fan not coming on (works through the ECU )

or not spinning fast enough (age )

 

[Tree cutter]

I would say it is getting air into the cooling system over time until the coolant is lower than the thermostat, which will cause it to stay closed. You must have a slight leak somewhere.

 

[snicklefritz]

I had to drop something off in the postbox so I decided to take the car out to see if I could hear anything and If I listen very carefully I can hear a sloshing sound, almost like running water. I had a look over everything and it doesn't appear to be leaking or weeping from anywhere and coolant isn't getting into the fuel or oil. I haven't checked the coolant level yet because the radiator is still hot. It just occurred to me though that when I filled it full of coolant it only took about 7L. How much water would be left in the block after flushing? Is it possible that there was an air pocket that wasn't bled out properly?

Edit: I found a new water pump and gasket for this thing in the shed so I might as well install that tomorrow and I'll make sure to bleed the system properly afterwards and see if the problem persists.

 

[dirty hands]

to hear sloshing around inside

would be the heater core under the dash ..so air is in there

you may have a faulty heater valve ..not opening fully

also if the hoses are old and soft --they collapse when hot- restricting coolant flow



repair manual if needed page 3
http://forums.justcommodores.com.au...en-factory-service-manual-located-online.html

 

[devilly]

when you changed the thermostat did you also install new hoses and ring clamps ?

best way of bleeding and checking the system is hold mode and up arrow start car then press mode and get the temp gauge up.

take off cap undo the little screw on top of the thermostat housing,put heaters on full blast,
when temp gets to 90 thermostat should open and fluid in radiator will go down and a stream should come out of the top screw.

close top screw as its steaming out put cap back on.

if it over heats and your trying to pull over and cant put heaters on full blast until you can safely pull over.this will pull the heat away from the engine.

also check the heater tap and lines going up to the firewall

 

[snicklefritz]

Just a quick update, I replaced the water pump, top and bottom radiator hoses and clamps as well as the heater thingo and it's 4 hoses and clamps. I tried bleeding the system with the heater on full but I couldn't get the car to go over 83c but it was spurting little bits of coolant out of the top of the thermostat housing so I put the needle back in. Is that correct I should I have waited for a constant stream of coolant?

I took the car for a fairly spirited drive and the temperature stayed under half and the water noise has gone.

 

[dirty hands]

sounds like you fixed it

bleeding question .I dont know for sure ..

 

[snicklefritz]

Thanks for your help guys :spot on:

 

[devilly]

well done, just check the tightness of the clamps,then redo the air bleeding if it doesn't stream then turn heaters off ,then it will stream

and only refill via the top up bottle or air will get back in the system,check out the picture on the bottle it explains alot

quote :
it was spurting little bits of coolant out of the top of the thermostat housing.
this is totally normal it's pushing out all the air from your whole system then it streams