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Old 14th August 2019, 08:15   #9
SD1too
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Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model.

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Quote:
Originally Posted by Mr Toad View Post
It is looking increasingly like HGF ...
It isn't Martin. Where's the evidence? What event would have caused the alleged head gasket failure? No, it's a variation in coolant level, the cause of which hasn't been found yet.

300 ml of coolant is not a lot. If it's seeping out of a failing thermostat housing 'O' ring it can evaporate quickly leaving little or no trace. You could leave your engine acoustic cover off for a while and check frequently for coolant with a powerful torch both when the engine is running, hot and cold, and when it's not.

On the straight pipe, are the two plastic clips pushed fully outwards in their channels?

But I'd say that the most likely reason is unintentional errors made during the refilling and bleeding process:
  • The Haynes manual can be misinterpreted. The small bore air bleed hose entering the expansion tank neck should not be disconnected.
  • It is essential that the expansion tank is raised during the refilling process.
  • The bleed screw should be refitted before starting the engine.
  • The engine should not be run with the bleed screw removed under any circumstances.

Another common cause of slight coolant loss is worn seals on the expansion tank cap. They can be obtained separately, there's no need to buy a new cap.

Simon
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