Hey guys, I got an 02 disco with overheating problems. Pulled the t/stat and it ran fine. Just flushed everything and put the t/stat back and it's overheating again. No leaks anywhere. Brand new t/stat. Any ideas? Thanks ahead of time..

 

Did you purge the air out of the cooling system & did you put the right hose on the right thermostat port. Top hose goes to middle port of the t/stat.
Easy mistake to make!
T/V

 

^What he said! My oldest daughter has a '98 Subaru Outback, and it's pretty specific how you have to add coolant. Need to pour it in SLOWLY, then when it gets to the top, you need to squeeze the radiator hoses to "burp" the air out of the system. Once you squeeze the hose and there are no more bubbles coming up, SLOWLY top it off. Drive for a few miles, to get up to operating temp and get the t-stat to open, come back, let it cool down, then repeat the "add slowly / burp" process, until it's topped off again, then that should do it. Also a good idea to make sure all the hoses are connected correctly. From what you describe, it definitely sounds t-stat related (internal / external), especially if it doesn't overheat without it.

 

Wow ok no I didn't do all that, but with that and putting the right hose to the right port, hopefully that'll fix the problem.. Thanks for the help, I'll update..

 

when you say overheat, would it be correct to say the gauge has swung above 50%? The gauge is built to point at 50% over a very wide range, and once it sneaks high you have been overheating for some time. A scanner with live data function can show you the real temps. This pix shows around 183, with the low temp thermostat. Others have posted 221 with same gauge reading with a stock unit. Point is don't trust that gauge.

 

This is important to avoid possible engine damage.
The thermostat cools on the return to the engine on a D2.
When the thermostat module is removed there is a total loss of coolant from the not only the radiator but the block cooling jacket.

It is essential that the block is refilled before start up. That means the block must be filled by using the upper hose as a funnel. Detached at the thermostat use the hose as a funnel to pre-fill the block. Then reconnect it.

Then follow by filling the expansion tank; the connecting pipe work will fill the radiator and allow air to vent back to the tank. Expect the level to drop as the fluid fills every void in the system then top up.

In a pro shop environment the usual practice is to use a tool called an "air lift" which creates a vacuum in the whole system, then auto fills the system full.
Without such a tool the above procedure will avoid drastic overheat of the block and head/gasket damage.
T/V

 

NJ
How many miles on the engine, have you pressure tested the engine, how about a chemical block test?