Header tank needs topping up

All my older cars used to need a top up after being worked harder than usual. I believe the mechanism was that the header tank simply wasn't large enough to accomodate the expansion of the coolant so it blew some out under pressure . It definitely sucked air in when taking the cap off and took most of a pint to top up to the mark. More modern systems tend to use a remote header with a little more volume. Maybe that's the way to go? If you put a hose onto the overflow pipe and take it to a remote tank, with a plain cap on the original neck to allow coolant to pass through to the new tank which should be fitted with the original pressure cap.

I believe that a number of Volvo engines with this system suffer losses due to the pressure cap leaking due to vibration (the tank is mounted on the engine). Owners have found the cure to be to take the expansion tank off the engine and mount it on a nearby bulkhead to isolate it from engine vibration.

May not be the cause or cure for you, but all I could think of straight off.

Rob.
 
ferroboat said:
My header tank has started to need topping up. It's a perkins 4236, i have spent half an hour with all the engine running and covers off looking for leaks with a powerful torch and couldn't find any. The oil is not milky. Any ideas please ? We Have done a lot of motor sailing last month.
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Maybe the heat exchanger is leaking and coolant is being lost into the seawater ??
 
ferroboat said:
My header tank has started to need topping up. It's a perkins 4236, i have spent half an hour with all the engine running and covers off looking for leaks with a powerful torch and couldn't find any. The oil is not milky. Any ideas please ? We Have done a lot of motor sailing last month.
Click to expand...

I would go for heat exchanger too. Try running with no pressure cap so no pressure to force the coolant into the seawater and see if the loss is the same.

David Berry
 
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