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6 cyl Bristol cars Type 400 to 406 - restoration, repair, maintenance etc

Radiator relief valve setting.

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Old 13-08-17, 02:39 AM
Join Date: Jun 2010
Posts: 2
Default Radiator relief valve setting.

The radiator relief valve on my 400 is allowing coolant to dribble out, and at times to run out, when the engine is run up to operating temperature (observed whilst the car is stationary). The radiator has recently had a new core fitted and I have cleaned the ball-bearing (it is brass), cleaned its seat in the top tank and checked the spring. The workshop manual does not offer much advice regarding the spring rating and my spring seems to offer very little pressure on the ball bearing. Any suggestions?
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Old 13-08-17, 04:53 AM
Join Date: Jul 2008
Location: Sydney, Australia
Posts: 384

the ball and spring should both be brass .
the spring is VERY light as it only produces around 2 psi pressure in the cooling system when working correctly .

How did you clean the seat in the top tank ?
If you damaged the seat it will not hold pressure .
But regardless of the pressure or whether the seat is damaged, it should not be leaking coolant from the pressure overflow .
How high are you filling the top tank ??
If it is overfull the coolant will expand once it is to temperate and the only place to exit is past the ball .
I fill my radiator to about 1/2 down from the bottom of the filler neck , which is below the ball and spring and very rarely ever have to top it up.

Where are you located and can you please give me details of your 400 .

Geoff Dowdle
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Old 13-08-17, 10:09 AM
Join Date: Jun 2010
Posts: 2

Thanks for the info Geoff - the valve seat has been very lightly cleaned with emery cloth, just to reveal some colour, and the header tank is filled to just above its bottom level. Located in Melbourne and a BOCA Member.
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