Thread: Radiator problems (Coolant refill) Discovery 1 (300 Tdi 97)

It seems like an airlock with the exception that the temperature guage is reading ok. It sometimes takes a while for all the coolant to replace the air pockets so it might take a few attempts to purge the system.

Did you remove both the plugs on the radiator and the thermostat housing whilst filling?

Did you run the engine after "filling" and check the levels topping up as necessary?

Did you squeeze the top hose?

Edit: I recollect that turning the heater on also helps as it opens part of the system that can hold air. If your heater does not run hot then that indicates that there is an airlock.

yep......do as mahn says.......
turn the heater on......remove both plugs....from the radiator and the expansion tank.....

and fill from the expansion tank till it starts to come out the top of the radiator....
then plug up the radiator and continue to fill up to the correct level......

fit the radiator cap and start the engine and run it at about 2000 rpm till its up to normal temp.......
this will get the coolant flowing through faster as soon as the thermostat opens....which should flush out any air and push it up to the expansion tank......

then shut it down......and allow a few minutes for it to cool down enough for the pressure to drop in the cooling system........so you can safely remove the radiator cap.......

top up the level if it has gone down......go for a drive to get the engine up to temp again.......then switch off and allow to cool back down again......
then recheck the level again......

recheck it once more after it cools down again the next day......just incase there was any more air trapped.......

the coke bottle method works well..

fill the cooling system at the tank with the radiator plug out.
when it flows out there install the plug and add more coolant
invert a coke bottle (2l) full of coolant into the neck of the header tank then start it up and maintain high idle untill the coolant in the coke bottle begins to heat up or the coke bottle purges down into the cooling system (squeezing it can help)

if the bottle empties repeat the process.

Hi thanks to all, I have had fitted a coolant level monitor in the expansion tank , it operates a light & buzzer, all good now, no coolant loss. Thermostat opens after 3km on level road from cold with gauge then getting quickly to normal running temp, them very constant. I am thinking of adding an extra temp sensor ( in the top hose) operating light. can someone tell me what normal running temp should be in the 300tdi ?? as i would like an early warning ( towing) when temp goes well beyond normal but before boiling ??? thanks in advance.

T/stat starts to open at 88*C.

BTW, is the Disco heater different to a Defender ?

On a Defender the heater always circulates water, there is no water valve only air flow across the core is opened/closed/modulated

Disco is the same system as the Defender.The Engine Watchdog is a digital temperature gauge with a sensor that is mounted under a bolt in the vicinty of where you want the temperature monitored.I have mine on the back of the 300tdi head.......the display is fitted above the ashtray in the Disco...works well.

I got my sensor on the block, think under the bolt that holds the dipstick tube - after monitoring it for a while and not getting any reading above 90, I set it to 95 deg to give me plenty of time to assess the situation in case something does happen, however I only installed it in early autumn this year so might have to adjust for the big summer heat.
(From memory people consider it normal temp up to 114 deg under hot cond/towing etc (assuming you've got proper coolant since it is meant to raise the boiling point))

On 300TDi's that I've worked on I've found the black plastic "joiner" for the bleed hoses to the header tank is often blocked. The feed from the thermo housing has a small orifice that forms a jet pump to remove air bubbles from the top radiator tank. I assume it wouldn't do that if it is blocked. I replace it with a brass tee piece as I need the full flow for my d-gas conversions.