Hi I have a 99 disco I. Sometimes when at idle coolant will blow past coolant bottle cap and leak. Truck never overheats or looses coolant any other time. Has good heat. Happens every couple of months. Doesn't matter if its 100 or 0 outside. sometimes after 5nim of driving or hours. It looses about a half gallon. I shut it of for a couple min than start it back up and no problems. Get home and top it back up with coolant then good to go for a couple months till it happens again. Has anybody ever had this problem before???? Only thing I can notice is the cap is a pain in the *** to get on and off.

 

The cap should be easy to screw on and off. Replace the cap and you should be good.

 

re: Truck never overheats

If you depend on the factory temp gauge you won't know until it is too late. It points at 50% from about 130 - 240F. Get a scanner that can read live data like an ultra gauge. Here are two pix that show some of the spread.

I do agree that a new cap is a good first step.