My 2000 S-10 Blazer runs very hot (about 230 degrees) in stop and go city traffic when the outside temperature is above 90 degrees. The radiator is new, there is no air in the system. It seems to me the problem is the fan clutch is not engaging when it should. When it gets this hot, I hear it engage once in a while, but only very briefly. It doesn't seem to be a thermostat problem because it never happens when the outside temperature is below 90. Has anyone had a similar problem and is replacing the fan clutch a difficult job? Any special tools required? Thanks in advance.

Do you have a new cap cause low pressure=low boiling point so thats a $5 first thing. Dex cool 50/50 mix also. New rad should put a new thermostat in too to be sure for another $5.

You will need a 36mm open end or large cresent wrench (16" up so it opens wide enough) for the fan nut where it attaches to the waterpump. Loosen that nut before taking the belt off and a sharp rap with a hammer will help on the wrench - that nut is often tight and the belt wants to slip around - they make a special tool to hold the 4 bolts on the pulley but about $25 and often use only once.

Does it ever boil? If not the gage may be suspect and may not be overheating at all (or not to the point of worry)

Thanks for the replies. It was definitely the fan clutch -- probably was bad for a long time but I only noticed it because of the particularly hot weather around here lately. Apparently the radiator alone without much help from the fan is enough to keep the engine cool when the outside temperature is in the 80s or lower. I had to drive home from the autozone with the heater on full blast and the windows down in 95 degree weather today to keep the coolant temp below 200 degrees. Even in that heat I did not hear the woosh of the fan running at all, and when I got home with the hot engine there was still virtually no resistance on the old fan clutch. Once I put the new clutch in, I could hear the fan "woosh" right from the start and a good test drive flogging couldn't raise the temp gauge beyond 190. That 36mm nut was a real challenge to get off as I don't have the special tool and hammering the wrench didn't work for me. I finally managed to get one of those funky shaped vise-grips to hold two of the pully bolts while I loosened the big nut. Once that loosened, the rest of the job was a snap. Start to finish was about an hour. As always, thanks for the help!

Glad Your Back On The Road Again,
And Thanks For Posting Youre Fix...

Thanks for the replies. It was definitely the fan clutch -- probably was bad for a long time but I only noticed it because of the particularly hot weather around here lately. Apparently the radiator alone without much help from the fan is enough to keep the engine cool when the outside temperature is in the 80s or lower. I had to drive home from the autozone with the heater on full blast and the windows down in 95 degree weather today to keep the coolant temp below 200 degrees. Even in that heat I did not hear the woosh of the fan running at all, and when I got home with the hot engine there was still virtually no resistance on the old fan clutch. Once I put the new clutch in, I could hear the fan "woosh" right from the start and a good test drive flogging couldn't raise the temp gauge beyond 190. That 36mm nut was a real challenge to get off as I don't have the special tool and hammering the wrench didn't work for me. I finally managed to get one of those funky shaped vise-grips to hold two of the pully bolts while I loosened the big nut. Once that loosened, the rest of the job was a snap. Start to finish was about an hour. As always, thanks for the help!

Still, reaplce the rad cap.

Do NOT stay with the stock one, it is defective from the factory.