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Black 308 over heating

Discussion in 'VB - VK Holden Commodore (1978 - 1985)' started by Stephenvk, Oct 12, 2017.

  1. Stephenvk

    Stephenvk New Member

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    In need of help guys
    Got a black 308 in my vk. Seems to over heat in traffic. Then when i try and fill the radiator even when its cold the thermostat opens and shoots water back out at me. Or even if i hold it at a certain rev it sucks water down the let it go and it shoots a fair bit back up. Has new radiator, thermostat, fans, head gasket just done, head where also shaved and tested. Im thinking water pump but just want some advice
     
  2. Stephenvk

    Stephenvk New Member

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    Ive also done the timing and the is no water in my oil
     
  3. rambunctious

    rambunctious Active Member

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    Try an earlier opening/lower temp thermostat.
     
  4. Stephenvk

    Stephenvk New Member

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    Im more looking for an answer to the water spitting out. Its puzzled me
     
  5. Lacksballs

    Lacksballs Active Member

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    To me it appears to be an air lock or the water pump is not working. Just to eliminate the thermostat take it out and run it up again, check the condition of the radiator cap (seal) & radiator neck.

    You don't say what sort of cooling fans you have & if it overheated at any time on the initial road test?????
     
  6. Stephenvk

    Stephenvk New Member

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    Brand new radiator and two
    10in fans
     
  7. Lacksballs

    Lacksballs Active Member

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    Did you have the heater tap open initially to bleed the coolant through the heater core???? Also did the thermo-switch kick in @ 85-90 deg C for the fans???? Or just switch the fans on manually/constantly & take it for another spin.

    Another thought: just check the bottom hose when you are holding it up in the rev's as I've seen the hose collapse (so can't circulate)????? Some bottom hoses have coiled wire in them to eliminate this from happening..
     
  8. Stephenvk

    Stephenvk New Member

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    The fans are constantly on.heater is no longer connected either
     
  9. Lacksballs

    Lacksballs Active Member

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    Check the rotation of the fans to ensure they are "sucking" & not trying to blow through the radiator! Make sure the water pump belt is tensioned correctly.

    Fill the system tomorrow, top off the overflow bottle. Take it for a run, keeping an eye on the temp, if it starts to over heat, pull over open the bonnet and feel (IT WILL BE HOT SO BE CAREFUL) the radiator to see if the temperature is hot across it (i.e. top is slightly hotter than the bottom). Check the overflow that it is still within the prescribed limits, if coolant is blowing into etc... Don't just go a open the cap, as this will drop the pressure & could cause the coolant to boil. Remember to check the bottom hose.

    If you have access to a infrared thermometer, take that with you as that will help with the readings.

    You didn't have a rag anywhere near or in the radiator, thermostat, water pump outlets while you had the heads off????? Did you check ALL the gaskets where the same as those that came off so your not blocking off any water galleries??????
     
  10. Ponza

    Ponza Member

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    Did you fit your manifold gaskets the right way?
    Have read that they can go on two ways, one way partially blocks the water crossover apparently.
     
  11. gtrboyy

    gtrboyy Active Member

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    Go back the factory clutchfan & shroud it will most likely stop overheating.

    Twin aftermarket 10's are crap unless mondeo setup or au fans get wedged in there.

    Even vn-vs single will do better job but you'll still need correct thermostat,85a vn-vs alternator & working thermofan switch.
     
  12. EYY

    EYY Well-Known Member

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    This is your problem. I agree that a single 16" fan is the go. But not an aftermarket one. Good twin fans draw heaps of current so you end up needing to replace your alternator too.

    The fact that the fans are on constantly means that they can't move enough air to bring the temp down. It's the dead giveaway.

    See here: https://forums.justcommodores.com.a...eo-bf-fg-plus-120a-alternator-upgrade.263089/

    I was at a car show over the weekend where a guy had a 245 Hemi with a big turbo and all the fruit which made 270ish rwkw. I overheard him saying he's made many phone calls to Davies Craig wondering why the 16" single thermo he purchased wouldn't keep it cool and was constantly overheating even in cool weather. He did have a big 5 core alloy radiator which should've been complete overkill, but the puny fan (shrouded) let it down.
     
    Last edited: Oct 13, 2017
  13. jandjmc

    jandjmc Member

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    I think you have an airlock, 308's don't normally have issues but My blue 308 used to do the same thing. It was caused by a large airlock in the cooling system and cheap water pump which changes the way the water is circulated in the cooling system. The only way I could bleed the system was to add a bucket to the filler neck to allow the air to escape without pushing all the water out. The bucket would have at least 2 litres of coolant until the air bubble would escape . (you can check youtube to see how this is done ) Interesting I've just rebuilt the engine and replaced the water pump with a genuine one from Holden with a cast impellor and didn't have any problems with bleeding the system.


    Pressed.JPG cast.JPG
     
  14. DerekP

    DerekP Member

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    Old 308's are notorious over-heaters. I spent years and $$$ trying to sort out my blue 308's cooling issues, it seemed nothing worked. Eventually returned to the factory clutch fan set up and a three core radiator, regular flush outs with good quality coolant. In addition I have a large electric fan that is only operational when the A/C is on. You should never fill your radiator by removing the radiator cap, even when it is cold, this will not help the trapped air issues. Bit late but you may also not have the gaskets installed properly.
     

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