Please help

I am after some help please as I have recently bought my first discovery2 td5 2.5 td5 and it appears to have a slight issue with the coolant system pressurising, temperature rising and then dropping its coolant on the road.
This seems to happen after the heater in the truck goes cold even though the heat is on full and under load.
It has had a new rediator fitted by the last owner so ruled that out.
I've bled the system and all seems OK till you drive it than after about 10/15 miles it loses heat in the cab and the temperature slowly rises with the heat coming and going.
I have checked the other posts and will be checking the thermostat tomorrow as I don't know if this was changed when the rad was.
Next point of checking is the water pump but does anyone know if it could just be the head gasket that's causing all the problems??

After some much needed advice

Many thanks

Water pump?

I have been told that it could be an air lock, water pump, thermostat, or worst case head gasket but after as much help as I can get before I spend money on having the head done.

Rustycar said:

I have been told that it could be an air lock, water pump, thermostat, or worst case head gasket but after as much help as I can get before I spend money on having the head done.

Click to expand...

first thing to check is the water pump. look for the little weep-hole in the pump casing. if the seal has gone, you will see evidence of coolant leaking out of there. you might not see much, if anything, coming out at idle. it will come out under pressure. fill up the system, get someone to rev it to around 2000rpm while you look at the weep-hole and if thats the problem, it will be very obvious! it would likely show you if you had any leaks elsewhwere too. get it sorted asap. because if you haven't already warped the head, you soon will.

I will check it now and report back shortly

he must have drowned...

do a gas test as per here will rule out head or not
test fluid avail from sealey or get a local garage to do a test

http://www.sealey.co.uk/PLPageBuilder.asp?id=20&method=mViewProduct&productid=11248

Sorry only just got home been out all afternoon.
Bled the system properly... Got rid of all air in the system, which there was some of... And it's running g spot on now temp sits at half way, heaters blow red hot.
Been out driving it for 4hrs without any issues or problems.

Thank you everyone for your time and help it's much appreciated