VT Supercharged - should I run a colder thermostat in a stock engine?

[Hatz]

Hi guys,
I've had an overheating issue with my VT Supercharged Calais for the first time yesterday. The temp normally sits between 1/4 and 1/2, however yesterday for the first time, the temperature would creep up to over a 1/2 and then move back to the normal operating spot. It was like the thermostat was getting stuck closed and then opening and letting the coolant through the thermostat.

The car is stock with 160,000kms and has never had any overheating issues before.

I have a water pressure tester and the car holds pressure without any leaks so I'm assuming it's the thermostat.

I know it's a pain to replace the thermostat on a supercharged engine cause I've read through the threads in the forum so I know I'll be "having fun" this weekend!!

The question I have is what thermostat temp should I run? Shoudl I run the 91 degree stardard thermostat or a cooler one at 82 degrees?

Thanks.......

 

[Decicrate]

Most of us run the 81deg C thermostat, but you will not see much of a difference in the temps when in traffic as the thermo fans are set to come on a a certain temp.

If the temps are coming up, especially at this time of year you may have a blocked radiator and the cooling system may need to be flushed.

 

[Bowen]

Bet the sender unit is cactus pay no attention to the dash displayed temp unless its 12 months or newer, 81 degrees is perfect stock is 91

 

[Hatz]

Thanks guys. I will run the 81 degree thermostat. As an aside, where abouts is the temp sender unit on the supercharged engine?

Cheers.

 

[chargedvx6]

Is the overheating random or just within the 1st 10 mins or so of driving when cold? If it is that would say certainly a sticky thermostat.

These cars, similar to ecotec are reknowned for failing the intake manifold gaskets too. An easy way to check is by torquing the intake to head bolts and you may find they're only finger tight. A sign of perished gaskets right there.

I'd suggest alloy replacements if you end up going that way

 

[Hatz]

Thanks. I'll look at the intake bolts as well. I will change the thermostat regardless - the Calais has been in the family since new and thermostat never replaced.

I'm sure I'll live to regret the thermostat decision but I'll give it a go!!

 

[gm1961]

Hi All

I have a VT SS 5.0 and a WH V6SC

Both do well in the cooling area but here is the history


WH was bought from a work mate who bought it new and always pampered and servied the car, at about 180k on the clock the radiator developed pin holes on the side tank ,easy to fix
Later at 190k the temp guage would creep up more than normal , the car was always a fast warm up car , but noticingit going a few hairs past the 1/2 was unusual but it coolled back as the thermos kicked in for a few minutes.


One day i noticed some small amount of water on the garage floor, i had actually started the car , noticed i left the mobile phone in the house and went looking for it , as i reversed out of the garage i saw the water, as i had not turned the air con on
i got out had a look and it was green. The engine temp was just coming out of the blue so it was still coldish, i took the radiator cap of and noticed it was low in water, it took 2 or 3 litres , definitely unusuall as the car will go 12 months without needing any top up

The problem was the thermostat housing was slightly corroded and the hose swollen and soft.
There are 2 problems, the thermostat is in the back of the engine on supercharged cars and the hose is hard to find as it is no longer made by holden and both ends are 2 different sizes !!

That got fixed and touch wood still good.


The SS i bought this year, always ran cool, takes 15 mins to get out of the blue and about 30 mins before it gets close to 1/2 way mark and the thermo fan comes on, ordinarily i would say this is ok, but as winter came, guess what, no hot air from the heater for 30 mins on a cold morning, and the engine temp is between cold and 1/4 , when i got to work i popped the bonnet and yes the top of the radiator is not hot, the guage is correct and the engine is cold.

In summer running cool is good, but overall the car is not at operating temperature

The problem was a simple fix, i suspected the car had not thermostat, i took the hose and thermostat cover and it had one, i then say ok its stuck open, , plucked it out and not its shut , then i noticed the 3 or 4 nice 1/8 holes drilled around the edge of the thermostat, now at this stage it clicked, i have on some cars that run over 1/2 and toward 70/80% warm done this mod and drilled 1 small hole in the thermostat plate , and another car drilled 2 , what this does is allow some water to flow when the thermostat is closed.

The car was a datsun 200B , 2 thermostat changed and still runs close to 3/4 hot all the time , after the radiator was cleaned and rodded out and found ok i was advised to make the mod, water flows in case the thermostat is stuck shut , some water will get past, the car will take much longer to boil and you should notice it on the guage ,it is like a 10% chance or extention of time.

The only draw back on start up or winter, that water escapes and gets cooled int he radiator and returns cooler to the engine so the engine does not warm up , this s the thermostats job, close when cold wait untill it warms up then open up to release the hot water to cool down - perfect in theory if every thing works 100 %

So i replaced it with a new trident and i noticed it was a 90 or 91deg unit , now it is middle of winter, it warms up in3 to 5 mins out of the blue and heater works, takes about 30 mins to reach 1/2 and the thermo fan cuts in and cools it , so overall the car is running fine, it starts, warms up in average time and the thermostat is not restrictive as the car does not go past 1/2 way

PS with all the stuffing around on the V6 supercharge get wither genuine or top quality stuff, at least on the early normal V6 and 5.0 it is a simple 5 to 10 minute job as it is in front of the engine - easy access

regards
george