Good Morning,
About 6 months ago I bought a 87 s10 blazer for a winter rat as I have a 1970 Chevelle ss that I store for the winters. Well since the price of gas looks like it's not coming down (why more people are not complaining I can't understand) anyway I was going to take this off the road come may but now it looks like the Chevelle will stay in storage as I'm on disability & can't aford the gas.
Anyway my Question is she is running hot around 260 I put a new thermostat in her and flushed her out but she still runs in that range. The guy I bought it off of bored her out 30 over went with a holley tbi & intake headers changed the cam. Why he did this to a 2.5 I have no clue!. Now I'm thinking of changing the radiator as I noticed the fins are not the best looking. But what I can't understand is when she runs past 210 the engine light comes on. I checked the code and I get an o2 sensor which I replaced but she still comes on at around 210 and stays on could this have to do with her running hot?. I wouldn't care but I'm going to be driving this in the summer so any info you could give me would be very helpfull!. Give me the cars without all the sensors Thank You Will,

 

Is the radiator partially plugged? I had a vehicle that the bottom half of the radiator was plugged off on the inlet header. Chased the cooling problem until I finally put my hand on the front of the radiator and felt the bottom half was cold when the engine was hot!

Older engines can have scale buildup on the inner cast iron block surfaces. Scale will inhibit heat from ever reaching the engine, causing overheating. The less aggressive radiator cleaners nowadays won't eat this scale away, what was used 'back then' was an oxalic acid based product, DuPont made one. An acid neutralizer was used after flushing to get rid of any leftover acid before refilling.

Other than clean surfaces and a good radiator, you need a good water pump (good thermostatic clutch??), w/good pump vanes, a good thermostat and airflow.