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Old 27th February 2021, 13:06   #21
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Originally Posted by Gigagator View Post
Out of interest, if one does overfill the expansion tank above the 'Max' mark when viewed through the filling neck, where would the coolant get ejected to? Or do you mean it will find the weakest point in the system (i.e. a seal, hose or gasket) and make its way out.
If the coolant is over-filled to leave insufficient space to expand, it will be ejected out from under the filler cap, which has vent holes underneath. The hydraulic pressure generated will open the pressure relief valve on the cap. This is set to about 22psi. The tank design and the recommended MAX marker provide more than adequate space for expension. You can over-fill by a couple of centimetres or so and still leave enough space. However, filling it to above the fins will probably push it too far, especially if the running temperature goes above normal. Interestingly, I did a calculation for the required expansion volume in the header tank and the standard fill level provides several times the minimum.


Last edited by T-Cut; 27th February 2021 at 13:09..
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