Alloytec cooling system essues

[Alons]

Hey people,
Own a commodore 2004 vz 3.6 v6 alloytec for a few months and can't stop it from over heating. It coused after long drive on the highway (more then an hour), when I'm going into a city or facing with traffic the cooling system is not getting air, can't hold it and overheating - the coolent is bubbeling and then start to overflow.

Steps that have been taken:
1. First mechanic told me the thermostat is faulty so he replaces it and the housings. (was very expensive due to the location of the termostat). Flushed the rad as well.
2. After that noticed that the radiator fan not working (just when I'm turning on the heat AC it's kicking in). Second mechanic replaced the thermo fan switch. Now the rad fan is working when the engine reaches working temp. Although when the car switched off the rad fan stops working. (Coolent temp was 117 at one time, it should keep working even when the engine turned off!!)

When the heat is turned on the car controls the heat, therefor thought that fixing the rad fan will solve the problem but it seems that even if the fan works, the car will keep overheating unless I'll use the heat A.C and let the air in the angine circulate.

After mechanics checks here some more info about my cooling system:
Cooling system pressure is ok, no air in the system, water pump bit noisy but seems to work well (no leaking).
Used to fill 100% red coolent, now mixed with rain water due to constant refill (After coolent got out from the overflow.
System lid looks fine.
Most important thing - No coolent in the oil or oil in the coolent.

Saw some similar essues with the alloytec engine in this forum, but couldn't figuer out what is the next step that should be considered.

Sort of lost with it, will glad to get some help.

Cheers

 

[rambunctious]

water pump bit noisy but seems to work well (no leaking). [Quote

I would be replacing water pump, then next step, replace radiator.
Is the heater tap ok ??

 

[Alons]

water pump bit noisy but seems to work well (no leaking). [Quote

I would be replacing water pump, then next step, replace radiator.
Is the heater tap ok ??

If to be honest neither of the mechanics told me something about the heater tap, so i guess it's alright (or that it's worth inspection? Can I check it by myself without mechanisem exp or should I go to a mechanic with that?)

Thought about replacing the water pump, but the car has been looked after preaty good ("above expected", according to the mechanic). Therefor hard to me to believe that thermostat, fan and water pump were all faulty.

Anyway, spent hips on money on that and trying not to keep the trying and failure game. Want to replace the water pump just after I'll have enough confident that it is really the essue. can't be 100% sure but what with other options? Electricity or ACU?

 

[greenacc]

I would go and buy a radiator cap from a Holden dealer just to eliminate a simple likely cause. Do not buy from other parts shop as they are rubbish and don't seal.
Sounds like your mechanic isn't too good.

 

[Bonus]

Yeah I second a new genuine cap, and to be honest still sounds like there is air in the system somewhere.

Have you tried undoing the bleed screw on the top left of the radiator under the shroud?

 

[Immortality]

^^^ Agreed, mechanics tested the cooling system is holding pressure but not the coolant system pressure cap. Coolant boiling and coming out of the overflow is a classic symptom of a faulty pressure cap.

Noisy water pump, replace it before it fails because it is only a matter of time.

 

[Alons]

I would go and buy a radiator cap from a Holden dealer just to eliminate a simple likely cause. Do not buy from other parts shop as they are rubbish and don't seal.
Sounds like your mechanic isn't too good.

The essue is that i went to see 3 different mechanics so it bit wired.

Regards the rad cap - pressure is good so it sort of eliminate this option isn't it?

 

[Immortality]

Not necessarily, They remove the radiator cap to pressure test the system so the pressure test tests the whole cooling system except the radiator cap.

Radiator caps are cheap and certainly don't last forever.

 

[greenacc]

Depends If the mechanic is right about the pressure or if they are wrong about that too,
Have you felt the pressure in the hose yourself?

 

[Alons]

Depends If the mechanic is right about the pressure or if they are wrong about that too,
Have you felt the pressure in the hose yourself?

No mate didn't check it by myself.
Will go tomorrow to buy a genuine rad cap, after that will consider to replace the water pump.
Rough Idea how much water pump replacement should cost me?