Where do I start!!! My 01 Blazer has 130000 miles and has now begun to overheat within 5 miles of driving. I have replaced the themostat twice in the last two weeks. I had a small radiator leak and put in bars leak and it solved that problem. The gauge would get to 200 and blow heat and then jump to 230 and blow cold. It would then jump back down to 200 and blow heat. That stopped and it then just blew cold air and ran at 230. On Saturday I blew out the heater core and refilled the system and purged out the air in the system. I also replaced the radiator cap. The temp was perfect and the thermostat kicked in and I was getting really good heat. Thought my problem was solved. I drove it around a few miles with no issues. Three hours later I started it up and got twenty feet from my house and I got a very bad leak from what looks like underneath the radiator/ water pump. It blows cold air and overheats to redline. I get steam and a hissing sound underneath the hood. I have parked it and will not drive it until I know what ther problem is. I am thinking waterpump, but, maybe their are other possibilities. Any input would be appreciated.

Thanks, Jeff

 

Sounds like the bars stop has found a home in your heater core.
Gonna have to start it up and look for leaks around waterpump.

I used bars stop once to help me limp thru till i could do intake gaskets...flushed core couple of times. Did the job i needed it to to..just had core issues for a while.

 

Radiators are about $125 new by the way. A heat core can cost $1000 depending where you get it installed.

The S10/Blazer radiators often need replacing around 100K/10 years of age.

A new radiator at the time of replacing intake manifold gasket set makes sense on several levels and it makes replacing the water pump at the same time easier too.

 

So I replaced the radiator and waterpump and burped the system two weeks ago and I had no leaks for a week and then all of sudden I got a rather large coolant leak which seemed to be coming from underneath the water pump. Pulled the waterpump off on Saturday and noticed that I had not clamped the hose which comes from the right side of the waterpump where it attaches to the engine block. Clamped it and reintalled the same waterpump, burped it again and ran the engine for a 1/2 hour without any leaks, but my thermostat never popped open even when the engine got to 200 degrees. Blew heat nicely. Is this normal? Drove to work this morning (6 miles) and looked underneath when I parked and had no leaks. All of this is strange to me. I am not a mechanic so I am wondering what could cause such events.

Thanks, Jeff

 

I dealt with an overheatting problem for over 3 mths cause no one could pin point the problem. I changed my thermostat, temp sending unit, fan clutch, flushed the system....and my heat also returned. By chance my mechanic decided to pressurize my radiator after learning my water pump was fine, and once pressure started to build in the radiator it revealed a hairline crack that we couldnt see by just looking at it. I learned thru this that the radiators with plastic tanks can have SEVERAL cracks at any given time but not be large enuf to leak coolant or to even evident period. So ur best bet I would say is to either replace ur radiator (the stop leak is not a great idea as it can junk ur heater core) or at least have ur radiator pressure tested. My blazer would run fine as well, but after about 3 mins of driving it would begin to overheat as well. So when I read ur post, it was like seeing a post I could hav written myself just a few wks bak. THE BEST OF LUCK

 

Yes, your thermostat opened or the heat would have kept climbing. You know it's open when the top hose gets good and warm and you feel heat behind the fan.

 

I have a 2000 Blazer 2 door with A/C. I have no leaks, the heater blows cold. I took the thermostat out and am running it without one. Straight water, no coolant right now. Just flushed the system and replaced the fan clutch. Run great, but heats up to around 230. Driving me nuts. I am not a mechanic. Waterpump was replaced with a new, not rebulit, about one year ago. Any Ideas??

 

Your radiator was plugged up with bars, trust me, its happened to me