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Question on cooling system of VZ 6cyl.

malbaby

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The recovery tank dipstick shows adequate coolant, but when I undo the filler cap on top of the engine, there is no coolant to be seen in the pipe.
Is this normal.????
 

vr_owner

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no its not, if its a v6 there is a bleeder screw at the top of the radiator near the battery, open the bleeder and listen for any sounds,
take the coolant filler cap off, turn your heater to full and low fan speed with no AC and start the car and let it heat up until the thermostat opens.
then fill until the coolant comes out of the bleed screw and close the screw and put the coolant filler cap back on
 

stick3

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just top it up with water see how it goes you may have a leak and its not overheating so check it daily by unscrewing the cap and don t rely on the dip stick coolant bottle
 

Fu Manchu

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There’s no bleed screw.
I’d be getting a new cap. 140kPa.
The VE and VZ use a self bleeding system (to bleed small amounts). Sounds like the fluid is going out but not back in again.


Properly bleed the air using either a vacuum set up with a compressor or using a reservoir tank in the top of the filler and run the motor through a few thermostat cycles to correctly bleed out the air.
 

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How was it solved?
 

Fu Manchu

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The air bleed won’t remove the air though. It removes a tiny bit and leaves a large volume in there. The only way to remove the air so the system is working properly is to either vacuum fill or to bleed using a reservoir.

The system will continue to self bleed small/tiny amounts of air through the coolant bottle.
 

shane_3800

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90% of alloytecs have a air pocket at the top near the cap and run fine.
 

Fu Manchu

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The system bleeds it out.

This kind of shows why I have used this method for decades and it has time and time again resolved issues that annoy me when it's not done properly. Noisy coolant flow through dash is one thing in some cars. Temperature fluctuations another. Anyway.
Eric The Car Guy knows what he is doing enough as a qualified mechanic, to use as a reference.
Bleed screw is used, but not sufficient to fully do the job. He only shows at the end, for a second, how much air was still in the system after a service on it.

I fill further and run the car through until all the large air bubbles are out and it only gets fine air bubbles every now and then. The system will continue to bleed that trapped air without drawing in significant volumes of coolant leaving it in a deficit or letting air back into the system.


The bleed screw on the VZ is on the top right corner, on the back of the radiator. I don't even use it. I did use it on the VP but only as a guide to know it was tight enough and leak free.

To quote Holden: "Under normal operating conditions, the cooling system should not be topped up at the coolant filler cap"

Also, Holden description of the Alloytec system:

Coolant Recovery System


The coolant recovery system consists of a plastic coolant recovery reservoir and overflow hose. The recovery reservoir provides an air space in the cooling system that allows the coolant to expand and contract. The coolant recovery system provides a coolant fill point and a central air bleed location. It is partially filled with coolant and is connected to the radiator fill neck with the overflow tube. Coolant can flow back and forth between the radiator and the reservoir.

In effect, a cooling system with a coolant recovery reservoir is a closed system. When the pressure in the cooling system gets too high, it will open the pressure valve in the pressure cap. This allows the coolant, which has expanded due to being heated, to flow through the overflow hose and into the recovery reservoir. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum opens the vacuum valve in the pressure cap, allowing some of the coolant in the reservoir to be siphoned back into the radiator. Under normal operating conditions, no coolant is lost. Although the coolant level in the recovery reservoir goes up and down, the radiator and cooling system are kept full. During vehicle use, the coolant heats and expands. The increased coolant volume flows into the recovery reservoir. As the coolant circulates, any air that is present in the cooling system will accumulate at the pressure cap as this is the highest point. When the pressure cap releases it is the air which is expelled first. When the systems goes into vacuum it will suck coolant back in."
 
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