Thread: disco 1 v8 running hot

Check for stuck thermostat and faulty pressure tank cap if water is escaping from expansion tank.

not sure about the D1 does it have viscous or electric fan, are they running when its hot? If its viscous is it engaging when warm?

thermostat is the most likely trouble, its unlikely your radiator would just deside not to cool one day and its still holding cooland.

Unless the thermostat is stuck, could be an air lock in the system. Take out the inspection plug on the radiator and check to see if you have flow. Do this when it is cold and let it warm up to op temp.
If you get flow OK, turn off the engine, remove the plug from the heater pipes and watch the radiator to see if the level changes.

To top it up, put the plug back into the rad, crack the cap on the expansion bottle and fill slowly thru the heater pipe fill point.
It helps if you have it facing up a slope too.

When you initially start it up, you should see flow coming from the plenum heater hose on the cold side of the tank.
If you have a probe type thermometer handy, drop it in the inspection plug into the water and see what temp is going back into the engine. Generally it should be around the 80ish degree mark give or take a few degrees.

as a side issue but related, honest. you mentioned normal running will be about 80C

What temps would these be at:

Normal running : 80C
OK for a short time but keep watching: ??C
Stop Now or Else! : ??C

The reason I ask is I am replacing my temp gauge with one that just has temperature numbers and no red part.

Originally Posted by HangOver

as a side issue but related, honest. you mentioned normal running will be about 80C

What temps would these be at:

Normal running : 80C
OK for a short time but keep watching: ??C
Stop Now or Else! : ??C

The reason I ask is I am replacing my temp gauge with one that just has temperature numbers and no red part.

The 80C is the rough inlet temp, not the running temp. You can get an idea if the problem is in the radiator by looking at the temperature drop. If it comes out from the thermostat at 90C and goes back into the engine at 88C, then you have a blocked radiator, providing the fan and viscous are working, as its not cooling it sufficiently.
If it moves even half way between its normal position on the guage and red, then can assume there is something wrong.
With an aluminium engine, there is really no "OK for a short time..". Its a "stop now or else!!!" Ask anyone who has slipped a liner!

Anything over about 95c I would be pulling over. As I run twin thermos on mine, the switch trips at 90C and shuts off at 80C. A standard thermostat opens at 82C for the EFI and 88C for carby 3.5
Cheers

Andrew

If you have not changed coolant lately i would be checking the Viscouse but if you have thermos and they are working sounds like thermostat

the fans are working, so i guess i put a new thermostat in it and drain the rad and fill up with new coolant, what do you guys reccomend coolant wise

Originally Posted by Dartybrian

Check for stuck thermostat and faulty pressure tank cap if water is escaping from expansion tank.

mate when we first got the truck it seemed to run like that to was really worried as you do ....but it did turn out to be a faulty over flow tank cap...brought a new one $20 form Anderson's in Hervey bay and the truck never had the problem agine.....so start there maybe ...you will be surprised how such a little thing can make a hell of a difference

cheers