Cooling system oddity

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Active Member
Jun 12, 2004
East Sussex
W124 estate

'had the old W124's Rad changed out following a pressure test (whereby the old rad failed at the top header seam.)

This was done as precaution as we're touring abroad very soon :cool:

Occasionally the low coolant level warning light comes on the dash, ( the Temp gauge never goes high.)
when I quickly turn off & open the bonnet I see the Header tank level rising to the correct level. :eek:

I think it must be air entrapment or some such similar thing,

Any thoughts ? :confused:


the garage is very willing to take another look before we set off on tour, I'm just puzzled as to the cause and possible consequences !
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Almost certainly an airlock somewhere. Some cooling systems can be really troublesome and it can take ages to get all the air out. Quite often the air gets trapped in the heater circuit, so it can be worth playing with all the heater controls while the engine is running. There may even be a special filling technique for the car - only a workshop manual will tell you this.
It could be nothing worse than an air lock in the system. Check the heater hoses by disconnecting them. :)

This ones a stab in the dark but could it be an old water hose that is expanding like a balloon as the engine temp and water pressure rises? It may be the case that the pressure test caused some of the older hoses to lose their rigidity. :eek:

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