Problem with S-10 coolant system.
 

This is going to be a long post, so please bare with me. I've got a 2000 Chevy S-10 with the 4.3L Vortec V6. I originally started having problem with my truck overheating around September of last year, but ended up having to park it in November for several months and didn't get a chance to mess with it. Last week I finally drove the truck again for the first time and I wanted to try and knock out the heating problem. I had to drive the truck from where I live in Virginia Beach, VA to Rockingham, NC (I'm in the military and was going home on leave, plus that's the only way I had access to a garage) a 300 mile trip. When I first started driving I noticed that the truck was running a little hot (around 210oF) and that the heat wasn't working, so I stopped, checked the over-flow reservoir and was a little low. After filling it back up, my heat kicked in and the truck ran at normal temp for the entire 300 mile trip. I got the truck to the garage and started working on it the next day. I changed the oil, rotated the tires, flushed the radiator, replaced the radiator cap, and threw in a new thermostat. Truck runs fine for the next 4 days, including another 300 mile trip back to my home, and some running back and forth between apartment buildings (I'm in the middle of moving). The day before yesterday, my wife drove the truck to the bank and upon returning says that the heat wasn't working. So I do a little Googling and find a thing on eHow saying that you should "burp" your radiator anytime you do a flush (which I hadn't done). So I go out, pop the radiator cap off, fill it back up, crank the truck up letting it get to running temp, and fill it up again (ended up putting in around a half gallon of water, mind you the over-flow was full), and then everything went back to running fine. Then yesterday the same thing happened and after repeating the same process, goes back to running fine. And then it happened again today. I conducted the same process, but this time things were a little different. I drove the truck about 3 miles total to go to my new apartment (where the truck cooled for about 20 minutes) and then to the store. I noticed that anytime the truck sat idle and then I would hit the gas I could hear water filling into the heater core (heater core was replaced November '08) and by the time I pulled into my parking lot my truck was at about 210oF, but the heat was working fine the whole time. I'm not sure whats causing the problem outside of maybe the thermostat sticking closed, but that doesn't really account for the missing coolant over the pass few days. I'm also thinking it could be a cracked head gasket, but don't won't to jump the gun just yet (I'm not about to pay someone to fix that, I'll do it myself, but I know its a very time consuming task). Any ideas that you guys might have would be greatly appreciated.

The coolant is going somewhere, if theres no leak, it must be going into the bolck somewhere. hows your oiL??? discolored at all?

Oil color is fine. Not seeing any water or coolant in it. That's the thing that get's me, I'm not seeing anything in the oil, so my engine would have to be burning off all the fluid. I also figured I would get some sludging from the engine, but performance has been fine.

A little update: I drove it a good bit today moving, riding to a friends house, and my wife ran to a little department store to get some new throw pillows for the couch, all and all around 30 miles or so, and I haven't experienced the over-heating or loss of heat in the cab. I also noticed that after driving for about 10 minutes after doing the "burping" again this morning that I quit hearing the coolant filling the heater core. Maybe I hadn't gotten all the air out, that's what I'm hoping at least.

Keep the ideas coming though so I can check anything I may have left out. Thanks again.

could be a bad thermostat. new isnt always good. lol but that doesnt explain the loss of coolent..

it is possible too that heater core is getting clogged a bit. you might check the floor on passenger side to see if it's damp at all. if it is, could be a sign heater core is cracked.

are you using dexcool? 96 and newer gm vehicles use the dexcool. if you mix the green coolant with dexcool it will sludge up the cooling system and clog radiators and heater cores. it will cause a lot of cooling issues.

As stated in my original post I flushed my radiator out last week (ran clean water through the system 4 times with the thermostat out for 10 minute a piece) so I'm positive there isn't any coolant getting mixed with the old dexcool, plus I had already flushed the radiator before when I change the heater core out it '08. There no coolant leaking in the cab and the last time it the heater core went out I could smell the coolant in the cab, which I'm not this time. I had thought about the new thermostat being bad, but haven't gotten around to changing it. Thanks for all the new suggestions. I'll keep you guys updated with any changes or if it continues to run good tomorrow.

At any point do you smell coolant? I had a 97 that had a small leak at the rearr corner of the passenger side head. I could never see any coolant on the ground but I could smell it at times. The leak was in such a place the the leaking coolant evaporated before could leave the block. There is a dye you can put in the coolant and it can be detected under a black light. I finally found my leak with the truck on a lift running for an extended period of time. Bars stop leak cured it.
It isn't uncommon for those plastic intake manifolds to leak on the Blazers. Not a fun jub to fix my friend. Leavae a whole day free to do it. AND there is a trick. I'll post the trick tomorrow that will save you a ton of work.
Bob

Well it's gotten better. I did a final "burp" about two days ago and everything seems to be in working order, for now. I'm still going to continue doing daily checks of the coolant levels to make sure I don't have a leak somewhere but hopefully I've got it all straightened out. I'll post back here if I've have anymore problems there.

I'm having the same problem but need to find a fix. The truck overheats at a stop but not when she's running normally. It'll pop the check gauge light then back off to 210 or less. No coolant seen but it has a leak somewhere and the oil is clean. Heater core is fine. Replaced the radiator and thermostat. Water pump was fine. Used gasket fix and still not workin. Eats 1/3-1/2 gallon of water/coolant a day and now is throwing the PO206 code for cylinder 6 misfire. And ideas?