I have looked all over to see if there was a similar problem and i have not found one so here is my question. I have a 97 Disco 1 with the 4.0. it over heated so i replaced the T-stat and drained all the coolenet by removing the bottom water pump bolt and replaced with fresh 50/50. City driving it runs fine and on the highway doing about 75 MPH it get a little warmer. the kicker is when i turn on the A/C the temp spikes but returns back to normal after turning the A/C back off. any ideas?

thanks for reading.

 

If the radiator is the original one, it needs to be replaced. I just had the same issue on my 98. When replacing the radiator, go ahead and replace the coolant expansion tank as well. I didn't on mine and when I took it to get the coolant system flushed, the expansion tank split at the seam.

Edit: I didn't add those hyperlinks into the text.

 

Did you bleed the system with the rt front raised, like on a curb or a few planks ? If the answer is yes, check for combustion gasses in the coolant. Have you been able to determine what caused it to overheat in the first place ?

X2 on the expansion tank, if you have the black one it is just waiting for the right time to screw you. The translucent Allmakes tank from AB works great for the money

Another question, are you going by the dash temp gauge, which is nothing more than an ornament, or do you have a real time scanner ? My guess is if you are watching the dash gauge, the actual temp is spiking much higher

 

have you checked to see if the condenser fan is coming ON?
The purpose of the condenser fan is to remove the extra load created by the AC.

 

Location?

 

I had the same problem but a new viscous fan clutch fixed it.

 

does it spike as soon as the a/c is turned on? then turn off a/c and it drops immediatly ?if so mine did that had a ground problem, was shorting the gauge i guess but the ug read correctly

 

Might be the start of a failed hg...

 

Which leads me to think, does anyone make a good thick hd hg that wont fail as much as the current ones on the market? Has anyone tried doubling up hg's, one stacked on top of the other, would it work? Just seems crazy to me that these rigs have so many cooling issues with a bad hg being the end result of everything else failing.

 

guess you can go with the metal ones that stack and get indian head shellak on them