Thread: 3.9 V8 air conditioner causing overheating

Originally Posted by murramaiman

Hey Guy's...new to the site...wonderful place.

Any idea's why my 3.9 V8 Disco1 overheats when I turn the air conditioner on? took it to the man...pressure tested, new hoses and thermostat. He said maybe viscous hub is failing but couldn't test it... Thermo fan kicks in but doesn't seem to push much air...temp gauge rises quite quicly when I turn the air conditioner on.

With all these hot days we're having in good old vic...it's roastin my butt...

Welcome,
I'm not the most knowledgeable one on this topic, but suggest you should look through 'The Good Oils' Section of this forum. Aside from that my bet is rad blocked or blocking and the air con is just enough to tip it over the edge. Whack the heater on just to be safe or you may cook a head. At least you wont have to visit a sauna

I recently had a very similar problem with my '97 Disco V8.

Does the car overheat when you're going uphill? If it does, does the turning the heater on full blast for a while cool the engine down just as quickly as it heated up? If so (and you've got enough coolant etc) then it could be a problem with the viscous coupling as suspected as this is what the cuase of my problems turned out to be.

I hope this helps!

run it up again with a decently accurate thermometer in the (or on) the upper coolant hose OR the thermostat housing and run the aircon up again. you might just have gauge creep.

check that the fans are all pushing air in the same direction

can you rotate the center body of the aircon compressor by hand?

have you cleaned out the gap between and AROUND the condensor in front of the radiator?