Disco Not warming up

A duff thermostat is the most likely culprit - and changing it is one of the easier jobs to do.

On or around Tue, 22 Nov 2005 19:03:46 +0000 (UTC), "Andrew Cooke" enlightened us thusly:

very likely and no. make sure you get the right one...

did the heater get hot or only tepid? If hot, then suspect the gauge sender unit instead.

housing on the front of the head, comes off easily IIRC. When you've fitted it, remove (*carefully*) the black plastic plug from the top of the housing (21mm socket is the best bet) and refill through there, keeping an eye on the level in the header tank.

I've not found that TDis fill very well by filling the header tank - the water level in the tank appears to be below the top of the engine - and it's important to make sure there's water in the head. On V8s, there's mostly a little chminey on the water pipe with a plug in the top for filling it through.

...and Austin Shackles spake unto the tribes of Usenet, saying...

Yup - anti-freeze all over unless you watch it. BTDT. Fill so that the header tank is 1/2 to 3/4 full, refit the header tank cap, and then completely fill from the top of the engine. Start, check for leaks, run until warm, allow to cool, check levels, there you go. Keep an eye on levels for the next few days, as a leak and the consequent overheating can wreck the engine very quickly.

The weird thing is I have just been out in it again and this time the temp gauge went to the normal mid position but the heater blew icy cold. Then on the return journey the gauge again went to the middle but the heater blew warm, what the h*ll is going on with it????

Airlocked? Have you checked the coolant level?

Air lock in the heater possibly?

On or around Tue, 22 Nov 2005 20:07:22 +0000 (UTC), "Andrew Cooke" enlightened us thusly:

Check the coolant level before driving it again. You've got classic low-coolant level symptoms there.

IME if the coolant gets low (only takes about 2" missing from the header tank, so it don't LOOK very low) it will airlock the heater. Top it up and get it hot and run it uphill at medium revs seems to cure it. But watch the coolant level carefully to make sure it's not leaking.

Possible coolant leak points include the P gasket between the water pump body and the block and the one on the front of the head behind the thermostat housing. Both of these are hard to spot.

worth doing a pressure test on the cooling system if you suspect a leak. Connect a T-piece and a bit of hose on the end of the small pipe that goes to the corner of the rad, then you can connect a pipe from there to a partly-inflated spare tyre or other source of pressure.