VZ Cooling System Thermo Fans

[super coach]

So I have abit of a concern with my VZ V8 cooling system.

The engine temp needle is fine and doesn’t show anything abnormal (it sits on the second line down from half way mark)

I recently had the system flushed with new coolant put in and put in a new thermostat but soon put the original one back in as I thought it was the problem.

What seems to happen is the fans kick in all the time and they take forever to switch off. I checked the pipe that runs from the radiator to the thermostat and you can touch it, but the heater hoses and the block itself are very hot to touch and you cant keep your hands on them.

Like I said the needle doesn’t move any higher then second line from half way mark.

The fan settings are Fan 1 to come on at 95 and switch off at 92, Fan 2 to come on at 98 and switch off at 96. I checked my mates VZ Monaro which is the same and his fans come on at 99 and all his hoses are hot including the one from the bottom of the radiator running to the thermostat. His fan switches off at 92 but only stay on for about a minute as the fans are able to drop the temperature down from 99 to 92 very quickly.

As for me mine stays on for about 4 minutes or more and the temp takes forever to come down from 95 to 92. I know this as we had engineering mode on and watched the coolant temp.

I also plugged in the Tech 2 and checked for codes and checked relays and everything seems to be working fine.

Later on I went for a drive, this is at night time with the air temp outside being about 15/16 and the coolant temp was reading from 91 to 93. is this normal for a VZ V8?

So im abit lost and puzzled as to where next, as im abit concerned the engine is operating at a higher temp then it should be even though all systems say its ok.

[white lie]

Sounds normal to me, they run on the warmer side but there's nothing wrong with that. It's certainly not running hot at 91-93 or even 95.

Temp needle won't start going up till around 100 generally.

Do you have an OTR and/or additional coolers in front of your radiator?

I think there was mention of the fan setups/settings being slightly different between VZ and previous, not sure what the Monaro would run.

[IJ.]

AC will also turn them on/off

[Micks]

Had both VY2 LS1 & now the VZ 6L & find the Z setup in general runs a little cooler!

[super coach]

the car is stock standard nothing in front. Haven't been using the AC at all it's just normal driving. Maybe its a good thing my fans come on earlier but why does mine take longer to cool down meaning the fans stay on longer? Yet my mates whose was built 3 months before mine cools down quicker?

[Micks]

the car is stock standard nothing in front. Haven't been using the AC at all it's just normal driving. Maybe its a good thing my fans come on earlier but why does mine take longer to cool down meaning the fans stay on longer? Yet my mates whose was built 3 months before mine cools down quicker?
How long ago was the recent work done with Stat & Coolant change? A slight possibility there could be air in the Cooling system?

[super coach]

it was done about a week ago but i took it back the other day and we swapped the thermostat back to original one as we thought the new one wasnt opening up, but the same thing was still happening. im a little worried that maybe the thermostat isnt opening up fully.

exactly when does the thermostat open up? when the fans come on or before the fans? like i mentioned i can touch the pipe leading to the thermostat but everything else is bloody hot and mates monaro everything is hot including the pipe leading to his thermostat

[Toddler78]

Im wondering if they purged all the air out the system when they flushed your coolant? if they didn't turn on the heater in the car to purge the air out of the heater coil then it could have lower coolant. This would/could also effect your sensor and thermostat as it could only be reading the temp of the air not the actual coolant.

I had this problem on my old ecotech, engine was flushed but the air wasn't purged out the system, it built up enough pressure that it popped the hoses off and dumped all the coolant on the ground. temp gauge showed perfect operating temp then entire time even when the engine ground to a halt once it had cooked the block

[super coach]

Toddler78 what temp do i put the heater on (obviously dont put the AC on) and how long should I drive around with the heater on? I dont want to be causing more problems with the block heating up too much

[Micks]

Im wondering if they purged all the air out the system when they flushed your coolant? if they didn't turn on the heater in the car to purge the air out of the heater coil then it could have lower coolant. This would/could also effect your sensor and thermostat as it could only be reading the temp of the air not the actual coolant.

I had this problem on my old ecotech, engine was flushed but the air wasn't purged out the system, it built up enough pressure that it popped the hoses off and dumped all the coolant on the ground. temp gauge showed perfect operating temp then entire time even when the engine ground to a halt once it had cooked the block

The Eco's were renowned for same is what I was eluding to in post #6 also!!

[white lie]

Put the heater on full and leave the cap off.
Wait for it to fully come up to temp. You may need run thru the process a couple of times to bleed it properly.

Stock thermostat should be 180F which is 82C. You can put it in a pot of water and boil it to check if it's opening but I would bleed it a couple of times first as it's much easier to do.

[white lie]

Btw, don't drive it with the cap off just let it idle up to temp. I assume you would have gathered that but you know what they say about assumptions ;)

[Toddler78]

As a couple of the other boys have said just let the car sit and idle with the heater on full bore wit the radiator cap off and stand and watch it bubble. As the water level starts to go down top up with more coolant until it doesn't go down anymore. Then put cap back on. Go for a drive. Then let car cool down open up the cap and check the lecel one last time

[IJ.]

So I have abit of a concern with my VZ V8 cooling system.

The engine temp needle is fine and doesn’t show anything abnormal (it sits on the second line down from half way mark)
I recently had the system flushed with new coolant put in and put in a new thermostat but soon put the original one back in as I thought it was the problem.

What seems to happen is the fans kick in all the time and they take forever to switch off. I checked the pipe that runs from the radiator to the thermostat and you can touch it, but the heater hoses and the block itself are very hot to touch and you cant keep your hands on them.

Like I said the needle doesn’t move any higher then second line from half way mark.

The fan settings are Fan 1 to come on at 95 and switch off at 92, Fan 2 to come on at 98 and switch off at 96. I checked my mates VZ Monaro which is the same and his fans come on at 99 and all his hoses are hot including the one from the bottom of the radiator running to the thermostat. His fan switches off at 92 but only stay on for about a minute as the fans are able to drop the temperature down from 99 to 92 very quickly.

As for me mine stays on for about 4 minutes or more and the temp takes forever to come down from 95 to 92. I know this as we had engineering mode on and watched the coolant temp.

I also plugged in the Tech 2 and checked for codes and checked relays and everything seems to be working fine.

Later on I went for a drive, this is at night time with the air temp outside being about 15/16 and the coolant temp was reading from 91 to 93. is this normal for a VZ V8?

So im abit lost and puzzled as to where next, as im abit concerned the engine is operating at a higher temp then it should be even though all systems say its ok.

Put an OBDI reader on it or put the Dash into engineering mode and find out exactly what temps it's running at, the stock gauge has a bit of a vague zone around "normal" but these engines aren't like an old SBC, I've ran mine at 114c with 0 effects other than the gauge moving, I used to freak out if it went anywhere near 100c.

[Toddler78]

Put an OBDI reader on it or put the Dash into engineering mode and find out exactly what temps it's running at, the stock gauge has a bit of a vague zone around "normal" but these engines aren't like an old SBC, I've ran mine at 114c with 0 effects other than the gauge moving, I used to freak out if it went anywhere near 100c.

I think he did do that. As I said through if the sensor is reading air and not coolant it isn't going to give a reading.

Personally I would start at the collant making sure that is full and then look at things like thermostat, fans, electrical relays after that. Some time coincidences do happen but rarely, it would have to relate back to the recent work - and extremely unlikely two thermostats are faulty.

[IJ.]

If the coolant is low enough that it's below the Sensor the Engine is dead....

[super coach]

Checked this morning no coolant registering on the dipstick at all undid the cap and there was full of coolant. Will give it a go at bleeding the system and see what happens.

I checked what my V2 Monaro temp runs at and its between 88-90 the VZ is a little higher which is in the range of the fans hence why they keep coming on all the time

[IJ.]

Checked this morning no coolant registering on the dipstick at all undid the cap and there was full of coolant. Will give it a go at bleeding the system and see what happens.

I checked what my V2 Monaro temp runs at and its between 88-90 the VZ is a little higher which is in the range of the fans hence why they keep coming on all the time

Just fill the Reservoir, it's doing it's job if the Radiator is full, eventually it'll bleed all of the air out, The coolant that's missing from the reservoir is now replacing air in the engine....

My VZ will run at 100 ish in traffic, no cause for concern.

[super coach]

So just top it up & not worry? How will it bleed itself? Should I still run the heater when driving it?

[white lie]

The radiator cap is the highest point in the system, air will rise in water and end up at the cap. As long as the cap is off, it can't pressurise so the air can escape. Watch it while it's warming up and see if you can see any air bubbles at the cap. If you can, then there was air in the system

[IJ.]

So just top it up & not worry? How will it bleed itself? Should I still run the heater when driving it?


The radiator cap is the highest point in the system, air will rise in water and end up at the cap. As long as the cap is off, it can't pressurise so the air can escape. Watch it while it's warming up and see if you can see any air bubbles at the cap. If you can, then there was air in the system

As White mentioned the Cap is the Highest point, as the engine heats up any air in the system eventually ends up there and the coolant expands forcing the air and some coolant into the tank, as the motor cools the coolant contracts causing a partial vacuum and sucks the coolant from the bottom of the tank back into the radiator keeping it full and free of air.

The Heater tap never closes 100% so this action covers it as well, the bleeding procedure is more for the first fill of a near empty system, I've found the VZ is pretty good in this regard, 5 minutes of idling cap off usually does the trick then just add to the tank as needed.

[bozodos]

I just replaced the radiator in my VZ (while changing the cam sensor) and idled it with the heater on for the 2 minutes or so before it would cut out of its own accord, only needed to do that twice and the radiator was full. I also squeezed on the hoses etc when the engine was off.

[super coach]

So I just topped up the reservoir went for a drive fans came on, checked all pipes & they were all hot including the one that runs to thermostat. So that makes me happy knowing coolant is moving around.

The next question I have is what is the standard holden setting temp for when the fans should come on? As I have had a tune & am thinking maybe he changed them to come on abit earlier than normal!

[white lie]

VZ may be slightly different but my reference says
Low speed on - 98, off - 95
High speed on - 108, off - 102

AC on/off, AC system pressure and road speed also has an effect on them.

Don't think i'd like waiting to 108 degrees before they kick in to high gear!

[Micks]

So I just topped up the reservoir went for a drive fans came on, checked all pipes & they were all hot including the one that runs to thermostat. So that makes me happy knowing coolant is moving around.

The next question I have is what is the standard holden setting temp for when the fans should come on? As I have had a tune & am thinking maybe he changed them to come on abit earlier than normal!

I wouldn't be getting excited about fan hi/lo on/off settings as this will only come into play when the Vehicle is slow moving or idling! The cut of the fans self propel @ speed & generally the air passing over Rad. keeps the engine cool.