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Thread: Z20let cooling saga (its a long one)

  
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    Z20let cooling saga (its a long one)

    Ok Ive had my Astra gsi for nearly 5 years now, and I have done any work on the car myself, from cam belts, servicing, coolant changes, etc and up until last summer, my coolant temp has always been where it should be, around 82-83degrees on the gauge (this is with a Courtenay front mount fitted). It would only rise to 90ish when sat in traffic and the fans would soon bring it back down to normal.

    Then last year the mileage got to 90k so I decided to rebuild the cylinder head; new stem seals, skimmed, acid dipped, etc and get the turbo rebuilt. I also replaced the water pump and thermostat while I was at it. The problem I have is that since then, my coolant temp will not stay below 89-90 degrees, no matter what I have tried, and I have tried a lot of things!

    So far I replaced the thermostat 3 times (now running low temp stat from regal), brand new radiator, water wetter and I have flushed the system out a few times. Each occasion I have bled the system just like any other time previously over the years. Ive also just tried running pure water to see if it was the coolant mixture, but the problem still persists. The only thing left to change is the water pump, but it appears to be pumping water fine into the header tank. Im at a loss at the moment, as in this hot weather the fan is coming on all the time, even when driving along sometimes. So has anyone got any ideas about what my problem could be, or how to solve it, as Id like to get it sorted before I get the CS4 remap in July!

    Cheers people

    jimbo
    ASTRA MK4 GSI TURBO
    WAS CS3 268bhp & 282lb/ft
    NOW CS4 279bhp & 336lb/ft

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    buckle's Avatar
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    Seems normal to me. More surprised the car ran so cool with a FMIC fitted. If I have been giving the car some, then stop at traffic lights the temp will easily reach 93-94 in warm weather.

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    mines never gone above 90degrees on the gauge as the fans cut in straight away. has anyone else got any thoughts? cheers

    jimbo
    ASTRA MK4 GSI TURBO
    WAS CS3 268bhp & 282lb/ft
    NOW CS4 279bhp & 336lb/ft

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    Coupe John's Avatar
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    Mine sits at about 83ish when driving and then goes to around 90 when stood in traffic for a short time. I have a front mount on aswell. but as soon as I drive off it starts to drop again. its possible that the water pump fins maybe damaged or broken. vauxhall used to use metal ones but then changed to the plastic type. You could also check the electric aux water pump under the battery.

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    yeah i think ill have a go at changing the water pump, i cant see what else it can be. if anything the cooling system should be more efficent now with all the new parts! cheers for the input

    jimbo
    ASTRA MK4 GSI TURBO
    WAS CS3 268bhp & 282lb/ft
    NOW CS4 279bhp & 336lb/ft

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    montyfox's Avatar
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    You say that you have skimmed your head so that will have increased the compression which will in turn increase running temperature (unless you have fitted thicker/extra gaskets to retain the OE CR).

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    I dont see the problem if the cars not over heating or playing up, have you put into consideration outside temp is higher as we're supposed to be in summer lol.

    If you've got flow to the header tank then the waterpump's working!

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    The dash gauge is accurate till about 85 deg, then it stop rising, so when the water temp hits 99 and the fans cut in the dash gauge is showing just over 90. I assume this is so people don't panic, pressurised water boils above 100, but not every one knows this. I use my scan guage and on a hot day by ACT needs to travel at 45mph or higher to lower it's water temp back to the high 80s. I'm running a FMC and cool stat as you are. I'd say it's perfectly normal what you're seeing. I'm not sure the cool stat works inline with the cooling fans.
    Tell me what you've done, not what you're going to!

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