I have a 1994 S10 Blazer 4.3L "Z" motor. started overheating, seen the water pump leaking from the weep hole and I replaced it along with the thermostat. started up and drove it overheated again. found lower radiator hose leaking replaced it and thermostat. test drove again all ok. drove for two days and seen more coolant leaking and it overheated, found radiator leaking at the center lower portion. replaced it and thermostat again, also replaced upper radiator hose. drove again for 1 day then overheated again. replaced water pump again. checked for flow through radiator flow is good, but continue's to overheat had tech at GM shop do a block check and it checks OK. They are as baffeled as I'am now. at this time I'am driving the vehicle with the thermostat out of it and it will not go above 120 degrees. Unfortunitely I don't have a choice. Please HELP!!!

 

Only thing I can think of is the water ports in the intake manifold and or heads are clogged up with crud stopping the flow of coolant throughout your engine.Also when you changed the thermostat are you sure you put it in the right way?

 

I would do a full flush on the cooling system. Pull the block drains hook a hose up to the heater line with something like and flush the crap out of it.

These trucks come with dex cool in them, if you switch it out for the standard green stuff without flushing it REALLY well than it will gum up and start clogging things really bad.

Once it is flushed really well, than I would put your block drains back in and refill with the green coolant and make sure your thermostat is good and clean. Also when filling it with coolant, get it as full as you can, than start the truck with the cap off and and let it warm up, turn the heater on full blast and let it bleed the air out of the system, you will probably have to add some more in. Another good way to bleed the system is to fill it up as much as possible than get it warm and make sure the overflow tank is full and run the truck up a couple of hills to get it generating a bit of heat, that should make it pull coolant out of the tank. At least that has worked well with mine.

 

I will flush the system tomorrow and let you know how it went. Yes, I did install the thermostat in correctly, I thought of that and triple checked, but is definitely in correctly. Thank You both for your help and will let you know how I make out.

 

good luck, just remember mixing dex cool with the green coolant is a really bad thing, if you switch to green make sure it is flushed really well.

 

First gens did not come with dex cool.

 

oh, I didn't realize the first gens didn't come with dex cool.

 

Sounds very familiar. I had a hose blow and that was the start of all my trouble.
Running hot and over heating. I ended up changing both hoses, the thermostat a couple times, the radiator, fan clutch, checking for a blow head gasket several times, all for nothing as none of it helped. This was an ongoing problem for probably 6-7 months, every time I thought I had it licked, it would do it again.


I think what finally "solved" the problem was hooking up the garden hose to the engine (I don't recall where now, heater hose maybe?) and running the hose for 30-45 minutes. I don't think I was flushing it, so much as getting all the air out. I may have even run it some while doing this. I say "solved" because that was the last thing I did when it stopped doing it.