My '91 W250 has a '98 12 valve in it. I'm having troubles keeping it cool. It's all stock except for the fuel turned up and exhaust. Normal driving say 0-50 mph it runs about 198 degrees. If I run it hard or do highway running 75 mph it goes right up to 215-220 degrees. What could be wrong?

 

id put a new theromostat, and all new coolant, antifreezw, oil,oil filter,and fuel filter you should never see 190 on the gauge crushing the only time your should see 190 is when your waiting for the thermostat to open the first time

 

Thats what I was thinking. How about the water pump? I heard that this year sometimes has issues with them.

 

i havent heard nothing about that but with how easy they are to put in a new one you might as well do it

 

I would flush and use the Fleetgard ES compleat ES Compleat?
that is their spelling. It is also available in a concentrate so you can do the flush easier. and you might have some deposits In the radiator that could be boiled out in a shop tank. the coolant is a blue color. It has superior heat transfer and corrosion protection to Propylene glycol and excellent service life too. water pump is good till it leaks. but pretty cheap to replace and the fan hub clutch is pretty cheap to fix too. and can cause heat management problems cause it regulates the airflow across the radiator and around the motor.

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you should take care of all that when you do the KDP fix.

 

Is the fan clutch working? They are pretty common on going out also


Ready to be back in a truck