308 THUMPING NOISE

  • Tiny
  • azzaand
  • 1977 Holden HX
  • V8
  • 2WD
  • automatic
  • 250,000 miles

I have a blue 308 that if left to idle for a few minutes it starts to make a popping or cluncking noise from the thermostat i've just replaced the thermostat because of this noise but still have the same problem. Any ideas would be great

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Tuesday, July 12th, 2011 AT 5:42 AM

9 Replies

  • Tiny
  • mhpautos
  • Expert
  • 30,561 posts

I would say it is boiling in the block, make sure that the thermostat is working and it is a quality unit with a bleed hole, cheap thermostats with out bleed holes can caused these problems.

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Tuesday, July 12th, 2011 AT 7:48 AM
  • Tiny
  • azzaand
  • Member

Ok so i've put a new thermostat in with bleed hole. Still having the same problem not quite so bad but still making a noise like the thermostat is opening then slamming shut if that makes any sense.

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Friday, July 15th, 2011 AT 2:07 AM
  • Tiny
  • mhpautos
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  • 30,561 posts

You may have air trapped in the heater system, take off a heater hose and allow coolant to flow from bothy directions, plug the hose with your finger and get coolant flowing out of the heater and visea versa.

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Friday, July 15th, 2011 AT 2:47 AM
  • Tiny
  • mhpautos
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  • 30,561 posts

Also ensure radiator is not part blockerd as well.

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Friday, July 15th, 2011 AT 2:48 AM
  • Tiny
  • azzaand
  • Member

I disconected the heater hoses altogether as it's on gas i've tried bleeding it through the hoses that go to the converter. As far as I can tell the radiater is clear as I can run water through it from both ends. I'm at a loss as to what else it can be.

Thanks for taken the time to try help me out.

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Friday, July 15th, 2011 AT 4:29 AM
  • Tiny
  • mhpautos
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  • 30,561 posts

Radiator can still be part blocked, garden hose pressure will not dislodge muck that may be blocking core tubes, you may have over 1/2 the core tubes blocked and still have flow the way you tested, are the top and bottom hoses getting hot? Converter hoses hot and heater hoses both hot? Try running with out a thermostat and see if it still knocks.

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Friday, July 15th, 2011 AT 7:45 AM
  • Tiny
  • mhpautos
  • Expert
  • 30,561 posts

Also With the thermostat out look at the flow in the radiator, just fill to above tubes and watch for strong flow with no thermostat, if not the water pump is faulty.

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Friday, July 15th, 2011 AT 7:47 AM
  • Tiny
  • azzaand
  • Member

I've put a brand new pump in it just the other day I thought that was the original problem. How can I test the radiator cores the top and bottom hoses all feel the same temp.

Cheers
Aaron

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Friday, July 15th, 2011 AT 9:04 AM
  • Tiny
  • mhpautos
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The core will have to be flow tested by a radiator repairer.

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Friday, July 15th, 2011 AT 1:45 PM

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