So i knew i had a leaky water pump and yesterday it finally went out... started overheating sitting at a stop light from 210 to 260 in seconds... so i went to the auto store bought a new water pump, new thermostat and new bolts.. installed everything, added new coolant.. started it and slow tested it.. temp stayed good.. so i let it sit for a bit temp got to 210 held then went above 210.. i had the heater on so i turned it off.. temp went back down below 210 then slowly started up again... wth.. anyone have any ideas on what else it might be?

 

Sounds as if you may still have some air in the cooling system.
Hopefully you didn't blow a head gasket but if the overheating still occurs then you may be pulling the heads.

 

I like to think there is some air too. Try jacking the front end way up in the air, or pulling up a ditch side so you are sitting at 45 degrees and open the rad cap up. Ive seen it in a lot of fords that they get bubbles in the cooling system and putting the front end up with the hoist to an extreme angle let us put another couple litres in the system.

how was the condition of the inside of the cooling system? lots of sludge etc?? I like to fill mine with a bottle of CLR cleaner and run it for a half hour before flushing out the old coolant, that stuff cleans out the rac and heater etc like hot damn, better than any cooling system flush they sell at the parts shops.

 

Honestly there wasn't too much crap if any at all.. gaskets r fine tested the fluid.. i did an air bleed method and got some good bubbles... my upper hos eis hot as hell while the lower is staying cool so i think i may have a blockage or something somewhere so im going to try and do another couple flushes tomorrow including a reverse flush since i didn't do that yet... hopefully this fixes it... very puzzling to me tho... the thermostat i got is a fail safe so once the temp gets to a point it will lock open but if its still over heating w/ it locked open then what?

 

Yep, I would check out that thermostat...

 

Ok so got it narrowed down after doing several flushes and talking to a shop... i need a new radiator.. anyone know of any good sites or threads on how to replace? the Chilton for this blazer is very non descript and fizzy as they didnt make one for the 4.3 s10 blazer ont he base model blazer or s10

 

It's pretty straight forward to remove and replace the radiator... probably will take an unqualified shade tree mechanic about an hour.
Be sure to replace the thermostat and hoses while you are at it... don't forget to flush the coolant outta the engine block as well.

 

If you radiator is not leaking, then I would not replace it. the stuff that builds up inside the rad is CALCIUM, LIME and RUST...

They sell this amazing stuff at walmart and canadian tire and zellers and a whole lot of places called "CLR", funny enough, it stands for CALCIUM LIME RUST remover and it is AMAZING.

Just take out your rad, dump out all the coolant so its empty, and lay it down flat with the hose holes facing upward. Now dump about 2 bottles or 2 litres of CLR into the hose holes so its full of this chemical. Wait an hour, or overnight, agitate is a few times and flush out with water. The rad will look like new on the inside as this stuff will remove all the scaling on the inside of it.

Ive dont this many times. 20 bucks worth of CLR beats buying a 200 radiator anyday. Save a little bit to put in water and run it through your coffee maker too (no filter and coffee in it of course) and your coffee will taste better and it will clean out the pot. Make sure you run just water through it a couple times after the CLR though to get all the chemical out.

 

well now im not sure its the radiator.. i took out the brand new thermostat i just put in.. and have been running my truck for 2 days now w/out it in and my temp is staying down around 120.. i used to run my Subaru STI like this int he summer to keep my turbo temp down.... and so far it seems to be working.. idle is a lil high which im ok w/ but more importantly not over heating which is making me wonder why it would overheat w/ a thermostat in....

 

Ive heard of using CLR before... can you run it through your system w/ water w/out taking out the radiator? i think the main clog is somewhere other than the rad.. from the symptoms ive been experiencing