Over-Heating issue
 

Hello all. I just changed the thermostat in my 95 Blazer with a 4.3 L Vortec. I was having an Over-Heating issue. That's what prompted the thermostat change. Now with a new thermostat and new coolant in the radiator it is still running abnormally hot. And for some reason it's not running the same. After starting the blazer it will idle for a few seconds then the idle will pick up. Idle at a higher rpm for a few seconds and then idle back down. I did some reading on a few other threads and I have determined I may have an air bubble in my coolant system. I did more reading on how to get air bubbles out of coolant system. And I am still a bit lost. I read a few different ways to get the air bubbles out. And I think I should've read about how to air bubbles out first. I have a full radiator and a full over-flow tank. But as I said. My Blazer is still running abnormally hot. If anyone can give me some advice/information on how to be sure all air bubbles are out... Please!! I am getting a incredibly frustrated with chasing my tail on this.

Your water pump might be shot

please tell us how a water pump can cause this

If it's not pushing the fluid through the engine, would that not mean the water pump is not working? I had mine go after a new rad,cap,thermostat.... unless I'm mistaken on how the water pump works....

You sound skeptical, but it's either that or a head gasket/head/block problem. And it is probably not those, so.. If a water pump is spinning but the impeller inside is not circulating the coolant then it is kind of the same as not having one.

Does your cooling system pressurize? If not.. probably bad water pump.

If it OVERpressurizes, then that would tell you something, too. And will pop whatever hose is the weakest one. Replace hose, repeat..

please explain how this could happen to a GM water pump

please explain the concept of the physics behind this statement

please explain what can cause this

Well I've never taken apart my shot water pump to see what caused it to fail. But I'm sure it has something to do with age and not everything last forever.... GM is great and all, but parts do fail...

Good luck OP, hope the solution get resolved. Not sure what Billy thinks the issue is but I'm interested in hearing his points...

I feel like a kid is asking me "but why?" after getting any kind of answer...

Let me straighten stuff out. Once I filled the rad with coolant and then started my Blazer. I watched the coolant bubble and burp a bit. And watched the level drop. So I kept putting more in until it stopped bubbling and dropping. But as I said in my original message... My Blazer is still running abnormally hot. And I'm trying to be sure that all air bubbles are out of my coolant system before I go further into this issue.

If you are loosing fluid, double check for any wet spots around the engine. Also check oil for discoloration and smell.

the needle shouldn't go past 100(canadian dash) when all is good.

Google it.

Now..if we are being nice:
1. You seem to be suggesting a GM water pump does not have an impeller. It is possible for water pumps to no longer pump water/coolant.

2. Overpressurization can occur if pressure gets too high, .. you want physics, I would say "things expand as they get hot" now let's move along with it.. and then the weakest point would be .. see below:

3. Head gasket failure can cause exhaust gasses to pop coolant hoses like balloons. Pinhole leaks in the weakest hose, etc.