Ford Fiesta Finesse 1.3, Year 2000 (W-reg) - Boiling coolant in expansion tank

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Wed 25 Jul 2012 17:47
Ford Fiesta Finesse 1.3, Year 2000 (W-reg) - Boiling coolant in expansion tank - Mikeymike33

Hi guys,

I'm at a miss as to what is causing the coolant to boil in my Fiestas Coolant expansion tank. The level is at the appropriate level - and there appears to be no loss of coolant. After engine shutoff, I can hear "hissing", the sound of pressure escaping from the Expansion tank cap?

Only a few days ago I've had

  • Headgasket replaced
  • Manifold gasket replaced
  • Rocker gasket replaced
  • New water pump
  • New thermostat
  • New fan switch
  • Engine flush & cooling system flush
  • New coolant (50/50 mix of Anti-freeze and distilled water)
  • New heater matrix
  • New heater control valve

When bring the engine up to temperture, the fan kicks in as it should momentarily. The entire radiator gets hot, so suggests that the radiator isn't blocked? Althought the mechanic suggested that the radiator would need replacing at some point (i'm not sure why?) The heater in the car works normally (hot when on hot, cold on cold but still a tad warm...)

Could this possibly be an airlock or something worse? Theres no temperture gauge within the car (poor design, i know!) only a warning light -- but I don't want the engine overheating (if the coolant is boiling after prolonged usage then i'm assuming it will be?)

Any help appriciated.

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Wed 25 Jul 2012 21:27
Ford Fiesta Finesse 1.3, Year 2000 (W-reg) - Boiling coolant in expansion tank - Peter.N.
Have you replaced the filler cap? Could be yours is leaking. It could be that the coolant is boiling after you stop as the water is not then circulating through the radiator. Can you actually hear it boiling or just the hissing?
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Thu 26 Jul 2012 01:27
Ford Fiesta Finesse 1.3, Year 2000 (W-reg) - Boiling coolant in expansion tank - Mikeymike33
Haven't replaced the filler cap - how would I know it's bad? Also any recommended sites to buy from new? And the boiling sounds like a gurgling sound. It isn't aggressive boiling - as the coolant isn't spilling out of the cap.

You can hear an occasional hiss -- sounds like pressure being released.
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Thu 26 Jul 2012 01:40
Ford Fiesta Finesse 1.3, Year 2000 (W-reg) - Boiling coolant in expansion tank - unthrottled
It is normal for the coolant to boil after the engine has been switched off. This raises the pressure in the cooling system, which raises the boiling point of the coolant until an equilibrium is reached. If there is a slight pressure leak, then the boiling will be noticeable because the pressure won't rise.
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Thu 26 Jul 2012 01:41
Ford Fiesta Finesse 1.3, Year 2000 (W-reg) - Boiling coolant in expansion tank - Mikeymike33
I wondered this as there was never any coolant loss... The gurgling / heat of the expansion tank just didn't seem right to me...
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