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Re: Cooloing System Inquiry (archive)

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Posted by John A on December 09, 2001 at 20:33:49:

In Reply to: Re: Cooloing System Inquiry posted by jej on December 09, 2001 at 18:32:14:

...... "Since I can see the fluid discharging through the overflow tube, (the uppermost one pointing towards the front of the car on the coolant reservour tank), it would appear that a blown head gasket is unlikely. Further, I am not seeing any coolant either on the coolant tank or underneath it".......
The condition I described did cause the coolant to be discharged from the tube. This is because there are two seals on the to seal the top and the bottom one, which establishes the blowoff pressure. The pressure that the cap is rated (in our case, 1.4 bar) is established by two things; the area of the opening and the spring pressure. As I explained, distortion of the lip reduced the spring pressure, reducing the blowoff pressure. Since the overflow tube is connected BELOW the top of the cap AND is open to the atmosphere, of course the coolant will be expelled through the tube.

...."What is baffling, is that the thermostat would need to be sticking in the closed position during the warm weather conditions, but then in the open position during the cold weather conditions"....
Your assumption infers that there is one opening for the thermostat for the required 80 degree C operation, regardless of ambient conditions. Nothing could be further from the truth. The thermostat MUST be opened further in hot weather than when it`s cold. That`s the whole function of the thermostat. It is reasonable that your thermostat could be too open for cold conditions and too closed for hot conditions. It`s not an on/off switch, but continuously variable (when it`s working).

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