i should of known better 
i think the reason that my pinto is over heating is that the header tank cap is not sealing properly and not pressurising the system correctly, thus allowing water to freely leave the coolant system when the water expands, i constantly have a rusty stained headertank after a drive and im always filling up the header tank with more water, could this be th reason for my over-heating problem?
yes, it could be one possible reason
Defiantly a possibility, changed the headgasket on the wife's MGF last year to eventually find out the overheating was caused by a £2.50 header
tank cap i should of known better
Is your tank like this if so it dose let air in & out are you over filling the tank i only fill to half way up
engine 2
am i correct in thinking there should be a constant flow of water through the header tank?
The cap isn't supposed to seal completely it is a pressure relief valve.
The rusty stains left in te header tank make me think something else is wrong ----- ie head gasket.
But before we jump to conclusions have you got a by-pass hose fitted ?
this is my coolant routing,
1)bottom outlet of header tank goes to inlet on water pump
2)heather hose outlet on intake side of the engine is t-pieced back into (1) (this section has temp sensor in it)
3)outlet of water pump goes to bottom pipe on rad.
4)thermostat outlet goes to top hose of rad,
5)breather from rad goes back to header tank,
can anyone see anything wrong with this? could it be that the thermostat might not be opening or the water pump may be knackered?
my honda used to regularly overheat.
new radiator cap fixed it 
on my bmw, it had the header tank built into the radiator itself. there is not a constant flow of water through it. well, only when you rev the engine
above idle, so i assume there is a constant flow when you're driving...
anyway, start with a new cap before looking at bigger more expensive fixes
quote:
Originally posted by omega0684
this is my coolant routing,
1)bottom outlet of header tank goes to inlet on water pump
2)heather hose outlet on intake side of the engine is t-pieced back into (1) (this section has temp sensor in it)
3)outlet of water pump goes to bottom pipe on rad.
4)thermostat outlet goes to top hose of rad,
5)breather from rad goes back to header tank,
can anyone see anything wrong with this? could it be that the thermostat might not be opening or the water pump may be knackered?
Plumbing sounds a bit odd to me, or maybe its the way its written, but this is how I would do it.
1. Header tank bottom pipe into midway on the bottom radiator hose, (cooled water return to engine).
2. Heater pipe from inlet side, if you haven't got a heater, I would blank this of.
3. Top hose as is, but fit the temp sensor into this.
4. Rad air blead into top of header tank.
Just how I feel it would work best, as most tin tops are set up in this manner, and they seem to work quite well, :-) Cheers Ray
quote:
Originally posted by Chippy
Plumbing sounds a bit odd to me, or maybe its the way its written, but this is how I would do it.
1. Header tank bottom pipe into midway on the bottom radiator hose, (cooled water return to engine).
2. Heater pipe from inlet side, if you haven't got a heater, I would blank this of.
3. Top hose as is, but fit the temp sensor into this.
4. Rad air blead into top of header tank.
Just how I feel it would work best, as most tin tops are set up in this manner, and they seem to work quite well, :-) Cheers Ray
Hi, may have got confused here, are you talking about the fan temperature sensor, or the one that goes to the dash clock. I assumed that it was the fan sensor, if its the other then yes you are correct, should in fact be a place already to screw the sensor into. Cheers Ray