Overheating Disco TD5

[manxman]

Under load my 99 TD5 auto looses all heat from the heater, immediately followed by the temperature gauge going into the red. Water is then being lost out of the header tank over flow.

It's only done this twice. I've stopped the car immediately both times, and once it cools down it's fine, but to be honest I haven't had the bottle to use it since.

The symptoms to me sound like the head gasket has gone. But my local dealer + others tell me they have never heard of this on a TD5.

Has anyone else? Also I have read that if the head gasket is blowing, you can't replace it, or skim the head. Is this true? If so why?

As an aside at it's recent service a faulty water pump was replaced, and since then the thermostat as well (just in case).

[Mantamad]

Has this problem started since the water pump was replaced?

[madmole]

Sounds like they fitted the wrong pump. The tdi and TD5 pumps look physically the same but they are designed to spin the opposite directions (or so I've heard on another board)

So you probably got a little water flow that copes with low heat output but not with full load

Could also be a duff thermosat (does the radiator get hot?) I've seen brand new ones that are duff plenty of times

Or a head gasket, blowing when hot (PS you can skim and replace gasket as long as you chaneg the plastic dowels). Does it loose power at this point. There is a problem with the head moving on the block with a range of TD5's as the palstic locating dowels dont hold the head and it can move about

do you get water flow back into the expansion tank when at idle, that indicates the pump is running

[Hightower]

I've had this problem twice on my TD5.
First time was down to a leaky radiator. The second time was down to a head gasket. This was replaced a fortnight ago (and the head didn't need a skim) and all is now running well.
I have heard the stories that earlier TD5's had nylon head locating pins which shear and allow the head to shift, resulting in gasket failure.
Either way I would have the gasket looked at. The longer it goes on for the more chance you'll do some lasting damage to the head.

[manxman]

Thanks for your ideas guys,

I've checked the water pump and it is definately the right one.

The problem, or rather some minor symptoms had started before the water pump was replaced (the engine would briefly loose power which I am told is down to the ECU stepping in to stop me cooking the engine)

The head is coming off this week, so I will find out either way then!

One final thing, and this could be me being stupid (probably) The fluid in the header tank is a pinky colour, but the fluid that comes out of the bleed screw in the top hose is green which is also the colour of the fluid being forced out of the overflow pipe.

I have worked on and rebuild dozens of petrol engines over the years, but the disco is my ever diesel, and this is a new one on me, Any ideas?

Thanks again. I will post the findings once the head is off