Changing a VT Commodore 6 cylinder thermostat.
Hey everyone, new to the forum just bought my first commodore a couple of months ago, loving it so far. I noticed this Friday I was driving back from a mates place it was about a 20 minute drive and I was heading up a hill after being stopped at traffic lights and my car made a noise and said 'hot' so I looked over at the temperature gauge and sure enough it was it the maximum hot position anyway so I kept driving home and it went back down to normal temperature and when I pulled over to park my car it happened and again so I turned the engine off and the radiator fan was still running and it did this for about 3 minutes after I had taken the key out. I have no idea why it was doing this as I checked the engine it was regular temperature when I put my hand on it and also the radiator hoses where not even that hot so I could touch them.
I checked my coolant and the liquid was between the arrows on the indicator and is fluro green so its not dirty or anything, I had had the car serviced 3000 km's ago. It is not like I have neglected the car or anything so the only thing I can think of doing first is to change the thermo stat as its the cheapest thing to fix.
That brings me to my question of how do I change the thermostat. I have just bought a Tridon HIGH FLOW THERMOSTAT TT2003-195 of ebay. And I checked on their website to make sure it was the right part for my car. What else will I need to do this, gasket? gasket goo?
Anyway help would be much appreciated. Thanks Ed
SYMPTOM
Engine overheats very quickly i.e within 10 -20 minutes from cold.
DIAGNOSIS
Firstly, use the diagnostics function in your Commodore. This is NOT Police mode that I see written elsewhere. That’s rubbish. Only genuine police cars are fitted with additional speedo features like smaller speed graduations and surveillance mode where interior lights are disabled.
All Commodores have a diagnostic mode where you can read engine information.
a) Make sure ignition is off.
b) Press and hold “up” arrow and “mode” button simultaneously
c) Turn ignition from Off to On. You can start the car if you wish.
d) Release both buttons
e) The LCD enters diagnostic display.
f) Step through the diagnostics with the mode button.
(Note this disables the normal display temporarily like the odometer trip and speed alerts.)
This function is available on all VT, VX, VY, VZ Commodores.
On VE/VF, hold down the left control button on the steering wheel whilst starting engine, release. VE gives slightly more functions like transmission temp etc.
There is an annoying calibration mode that gives a high pitched sound. Don’t panic, just step through it.
g) Once you reach “T” you will see the engine temperature in degrees.
This diagnostic mode will also give, litres per hour, volts, litres in tank, digital speedo, digital tacho and a few other useless functions.
You can drive the car like this but as soon as you turn the ignition to OFF the display resets to its normal operation.
Checking for failed thermostat....
1.Feel the top of the radiator, if it is still cold and the engine has overheated there is a very good chance that the thermostat has not opened and allowed water to enter the engine when the engine has warmed sufficiently. The thermostat usually opens to let radiator water in when the engine temperature gets between 90 and 95C.
2.The engine temperature should then fall back to around 85 then as the radiator warms it stabilises to around 87-92C during normal operation.
3.If the engine is idling the temperature will creep up to 104C over 10 – 20 mins in normal operation then one radiator fan will start to cool the radiator and the temp will fall back to about 99C. The fan will then switch off. It will keep cycling normally like this whilst idling.
4.With the engine off, squeeze the top radiator hose and if it can be squeezed the radiator can be opened and inspected for coolant. If the hose is rigid it is pressurised and the radiator cap should not be removed until cool and the hose can be squeezed i.e it is relieved of pressure.
5.If the radiator is full of coolant and the coolant is still cold or only luke warm then most likely the thermostat is not opening. It could be corroded shut or stuck with deposits from the coolant.
Firstly, go to your Holden dealer and get the exact part for your car. If you are smart, you will pay no more for the genuine article that fits perfectly than any aftermarket place. I paid $15 for mine incl gasket. Also buy a new radiator cap. The genuine one is about $6. But even list price is still better than aftermarket. It will fit your car perfectly and it has a warranty.
Also purchase the genuine coolant for your car. 5Ltrs is about $25 and makes 10 litres of ready mixed coolant.
Gasket cement is not required as the gasket should seal the joint perfectly on the thermostat cover.
Radiator caps like thermostats have a spring that releases on temperature so renew both especially if you are having cooling problems and if the cooling system is not pressurising. Sometimes the cheapest solution is all that is required to fix the cooling.
“Note most VT Commodores water pumps corrode around 100,000kms and the impeller does not push the water properly. This is usually evident by a small leak behind the water pump where the seal has given way.” BUT you will also be losing coolant…."
Find somewhere level. There is NO NEED to drain the cooling system.
Remove the plastic engine cover four chromed nuts and put the cover out of harm’s way.
Make sure you draw a diagram of how the belt is fitted around the pulleys as it will be useful in putting the belt back on again or buy a Gregory's manual.
REMOVE the drive belt (fan belt). If you don’t and it gets coolant on it ,it will squeal and you will have to renew it to get rid of the squeal.
Remove the drive belt (fan belt) by placing a socket on the left upper idler pulley and push towards the left. It is spring loaded and will release the tension on the belt so that it can be removed. Put the belt out of harm’s way.
Next, get some old rags and pack them around and under the thermostat housing to catch any spilt coolant and keep coolant off the pulleys.
Unscrew the hose clamp on the upper radiator hose and remove the hose from the thermostat end housing. A little coolant will spill (not much). Just place the end up on the alternator to keep it from dripping coolant.
Undo the two bolts on the thermostat housing and lift off. It might need a slight tap with a screwdriver to release the stuck gasket.
Lift the old thermostat out and put aside. Then you can throw it away.
Stuff a clean rag into the coolant inside the thermostat housing then scrape with a knife or screwdriver, the excess gasket away. The rag will stop this going inside the thermostat housing. Use a bit of emery paper to make the surface smooth. Remove the rag and clean the face so that it is dry.
Do the same with the thermostat top cover and remove all old gasket so that the face of the join is clean.
Fit the thermostat snug into place, put the new gasket over the top of all the holes and replace the thermostat top. Use a little screwdriver to make sure the bolt holes and gasket are aligned. Tighten both bolts.
Refit the radiator hose and clamp in it’s original spot.
Top up the radiator with GREEN coolant mix. 50/50 coolant and water.
Pack some more rags around the thermostat housing then unscrew the bleed screw on the thermostat housing top one and a half turns.
Tip coolant into the radiator until it just starts coming out of the bleed screw then tighten the bleed screw back one and a half turns until tight. Put the new radiator cap on. This should ensure all air is out of the cooling system. VTs, VXs, VYs are notorious for having random over heating if ANY air is in the system even when the radiator appears full. VZs whilst they look like the VT shape they are actually have a VE Commodore engine and have a self repairing bleed (or supposedly) system to get rid of air locks.
Start the engine using the diagnostic function again and observe the engine temperature rise.
You can go for a drive to speed this up. When the temperature gets to 95C+ the engine temp will then drop back to around 85C then stabilise back to around 92C. This proves that the thermostat has opened and radiator water has entered the engine. The temp should stay around 87-92 whilst driving normally and start to rise whilst idling.
Return and refit the plastic engine cover.
Once you have replaced the thermostat and radiator cap you will notice that the engine is running smoother as everything is back in balance.
If you still have problems then go to the Holden Dealer and buy a new water pump. These are also really easy to fit.
