Overheating problem. 2000 Disco. Car drives for 15 min. or so with temp gauge at normal then goes quickly to red light. Would idle for long time without overheating. Tried to bleed system but canont get heat out of any vents (occasionally some will come but only for a few minuets) put new thermostat on car, new water pump, head gastets w/ pressure testing and machining, and resovior cap. Check engine light on idles rough but excelerates smoothly. When overheats not alot of fluid comes out of overflow. Any suggestions? TWM

 

remember these blocks are aluminum, just one time in the red and you can warp your heads or drop a sleeve.

 

Blown head gasket.
The coolant coming out of the overflow bottle is from the cooling system being over pressurized by combustion gases.

 

TWMJ, sent you an e-mail

 

The heads gasgets have been changed twice, once by me and once by a mechanic, both times the heads were milled and pressure tested. I just can't understand why I'm not able to get heat out of the vents.

 

You cant get heat out of the vents because either you have a air pocket in the cooling system somewhere, that would account for it getting really hot.
Your heater is clogged (have you been using DexCool?)
Check out the pictures page...http://sancarlosradiator.com/dex-cool.htm
Your heater hoses are hooked up backwards.
Your thermostat is stuck open.
If they removed the heater lines to do the head gaskets it is very possible that they were hooked back up wrong.
If you have a big air bubble stuck in the heater you can try and force it out by bleeding the cooling system and revving the engine at 2,000 rpm for several min.
Follow the sticky on the top of the page, and remember that the radiator cap MUST be off to properly bleed the system.

 

I'll give that a look, is there away to tell if the heater hoses are connected incorrectly, and what is the best way to 'flush' the colling system?

 

I do not know how to check on a DII if the heater hoses are hooked up correctly.
All I can say would be to unhook them from the fire wall side, start the truck and see which one the coolant comes out of.
That will be the one that goes to the inlet side of the heater core, which will be the lower connection.

After you get that figured out then remove the lower radiator hose and drain the system.
Refill with water, leave the radiator cap off and turn on the heater to full HOT and start the truck.
Idle for 15 min, cool for 15 and then drain, repeat until all the water comes out clean.
Then refill with your favorite aluminum safe coolant.

 

Thanks, I'll give that a try. Do I have to use Dex Cool or can I use any Al save coolant? I'll let you know what happens.

 

DO NOT use DexCool, ANY aluminum safe coolant either 50/50 pre mixed or you buy it straight and mix it yourself will distilled water.