If this is the original water pump, it is *possible* that the impeller has worn down and does not pump fast enough. Only way to see the pump impeller is to remove it or use a goose-neck digital inspection camera.





Most likely though, is that your radiator is clogged still.

 

Ok, this is the exact same issue that I have been having with my 99 Blazer Vin W.

Dex Cool is horrible. I kept getting the brown slude issue, stooped up heater core, the whole 9 yards. I am sick of flushing and refilling.

Here are the things that I finally did to rectify the issue. I got a new radiator, when I took out the old one it felt significantly heavier, so I knocked off the side caps of the rad, lower 1/3 of the rad was completely stopped up with the brown sludge. So much so, in fact, that it cannot even be blown out with the air hose.

As well, I also replaced the fan clutch, and heater core. In doing so I found several other issues that the previous owner/abuser had attempted to fix under that tree in his yard from which he should have hung himself. Those issues are to come under other threads and headings.

Needless to say, the 4.3 Blazer has a history of being a rock solid driver, and i used mine for the last 2 years to lead several roofing crews out of, so you can imagine the abuse I have laden upon it.

 

I ran into the same problem with my 2004 Blazer. Replaced the thermostat, water pump, and finally the radiator to correct the overheating problem.

 

Well it looks like I found the problem!

So as I was driving her blazer down to the part store to run the check engine code I noticed the transmission seemed to be slipping. At first I figured it was just me being used to driving mine, and the part store is very close. Hooked it up to the scanner and sure enough it was a slipping tranny code....So obviously first thing was to check the fluid. There wasn't a drop on the dip stick.....checked coolant that I had green the day before was reddish/brown in color. Looks like I'll be replacing the radiator in the near future. Pulled it off today and it's definitely leaking internally on the tranny cooler lines side.

I know there are some who just do a external tranny cooler and block the old outlets off but I'm not going to mess with that. The thing needs replaced. Now I just hope this leak didn't cause damage else where...

Thanks again for all of your guys help!

 

my 2000 blazer is running hot but only when it is sitting idle and then when moving the temp drops back to a normal range. do you think its the termostat?