Magic water ???

[Colin S]

My water level is dropping ok, however when I release pressure cap water runs back into tank back up to full level, can someone explain please???

[missfixit70]

My water level is dropping ok, however when I release pressure cap water runs back into tank back up to full level, can someone explain please???

A bit more detail may help. How much is it dropping by? Under what circumstances is it dropping?
Any other symptoms?
As it's a pressurised system, the level in the header will rise slightly with a hot engine if you take of the header cap (do this carefully, I know of at least one person that ended up with serious facial scalding taking the header cap off with a hot engine & buggered head gasket).

[g8dhe]

Could be a pipe expanding, and about to burst, when under pressure. When the pressure is released pipe contracts and water flows back up to the tank ?

[321Away]

depends how much it drops? do you get a big pressure release when you undo the cap

Julian

[rita]

Could be a pipe expanding, and about to burst, when under pressure. When the pressure is released pipe contracts and water flows back up to the tank ?

Good thinking

[Colin S]

Ok thanks for that, in answer to a couple of points water drops down to low level and then refills tank when cap taken off. Obviously cap is not removed until the van has cooled down a bit, no great release of pressure just a lot of bubbling and then water flows back in. Pipe expanding seems a good theory. Just to throw a spanner in works though on Friday van left with full tank of water over night in morning tank empty 2 pints to refill but no wet patch on floor, in fact no sign of any leak. We have had the head gasket replaced in last month along with radiator and oh a new auto gearbox. Also changed thermostat we are now thinking of scrapping the van as its cost us so much and we only bought it in Jan and had it converted into a camper in March. So any suggestions gratefully accepted.

Very dissapointed Bongo owner

Colin

[Colin S]

Should also say vehicle has lost about a pint of water a week ever since we have owned it....but no sign of where its going thats why the head gasket was changed...no white smoke though...mystery eh...........

[missfixit70]

Has the coolant system been pressure tested to trace the coolant leak? could be water pump or a pinhole somewhere, but as is said so frequently, there's a good chance the head may be cracked, especially if it's been off & back on again to replace a head gasket, not often you get away with it just being a head gasket. Was the block checked for level & was the head pressure tested at working temp (not that that really tells you a lot)? Was the work done by someone who knows & understands the bongo cooling system? Was the thermostat replaced with a new one & if so, what brand?
Bongos don't always show "traditional" head/gasket failure symptoms such as white smoke, margarine in the oil filler cap, oil in the water or even showing up exhaust gases in the coolant. After a run are the coolant hoses very firm & do you get big fart of pressure when you release the pressure cap? (be careful opening it due to scalding risk especially if there are head/gasket issues)