Mysterty

[Redfox]

I have a 1997 ranger 3.0, 88000 miles. The truck started running low on coolant. The water pump is not leaking. No evidence of coolant on the floor after running the engine. No water in cab floor from heater core leak. No water in the oil. Compression checked OK. Checked radiator and replaced it. Replaced both radiator hoses and heter hoses. Still leaking and running low on coolant. No bubbles in water. Used a Lisle combustion leak detector on radiator and found no evidence of combustion in the coolant. Tempature never goes above normal range. The truck has not been subjected to ru use. Engine runs fine.

I would appreciate any comments and cures you could provide on this problem.

Thanks.

 

[Rearanger]

Small leak in overflow reservoir or hose to it? Rad cap not holding proper pressure?

 

[Original_Ranger84]

Get some UV dye and put it in the coolant then run the truck until it is a bit low again. They with a black light in the dark search your engine bay. My truck was leaking coolent and it was so slow that the motor evaporated it before I cold pop the hood. UV dye will stay and glow.

 

[Redfox]

Thank you for your suggestions

rearanger & original_ranger84,

Thanks for your suggestion. The probles was in the heater control unit. I had trouble with it before and the leak was obvious. This time I couldn't find a leak. I took it to my local mechanice and he swaped out the unit and it no longer leaks.