OK... When I bought this Envoy, it had a destroyed water pump and a bad fan clutch. (bearing was obviously fubar) The person had tried to take it apart, and failed, so they sold it cheap. I bought a water pump from Oreilly and a fan clutch online. Also had to do a couple other things like front wheel bearing and clean the VCT solonoid, but other than that runs good. I noticed that it was running cold, about 150. Then it'd run around 210, then once in a while, it'd overheat. Whenever it did, it'd be low on water. I spent about a month thinking I had a leak I couldn't find, because it'd only do it once in a while. I replaced the thermostat, and now it runs 210 or overheats. I have noticed a pattern of highway driving, then slowdown = overheat. However, yesterday, it started overheating on me when still on the freeway, so it's getting progressively worse. It is also getting progressively warmer here in south Texas too, so...ya. Here's what I know:
1. It runs 210 or overheats. No in between.
2. It IS overheating cuz it's boiling off water into the overflow like crazy.
3. It will go all the way to 260 (Had it go far enough to chime at me once)
4. When it does decide to overheat, the temp shoots up very quickly. 5 minutes tops.
5. Fan appears to be working as designed. I even bypassed the solid state relay once to effectively put it at 100% duty cycle, and it starts the fan roaring as it should.
6. I am fairly positive I have a coolant flow issue, as I pulled in to the drive yesterday with it starting to overheat again, and let it idle and let the temp rise. I put the water hose on the radiator (very cool water too) and it basically didn't even slow it down. Straight cold water flow on the radiator should have arrested an overheat instantly if it was an air-flow issue.
7. Even though the water has always been ridiculously clean, I just removed and disassembled the radiator, and to my dismay, found what I expected... nothing. Clean like new.
The only other thing I can mention is, when it has gotten it hottest, I hear a buzzing sound coming from the left side of the engine for a short time as it cools down. Almost like the thermostat is squeezing water thru. However, the thermostat is brand new, and it did it before on the old thermostat too, the old one just stayed open and ran it at 145-150 most the time. I'm baffled....
1. It runs 210 or overheats. No in between.
2. It IS overheating cuz it's boiling off water into the overflow like crazy.
3. It will go all the way to 260 (Had it go far enough to chime at me once)
4. When it does decide to overheat, the temp shoots up very quickly. 5 minutes tops.
5. Fan appears to be working as designed. I even bypassed the solid state relay once to effectively put it at 100% duty cycle, and it starts the fan roaring as it should.
6. I am fairly positive I have a coolant flow issue, as I pulled in to the drive yesterday with it starting to overheat again, and let it idle and let the temp rise. I put the water hose on the radiator (very cool water too) and it basically didn't even slow it down. Straight cold water flow on the radiator should have arrested an overheat instantly if it was an air-flow issue.
7. Even though the water has always been ridiculously clean, I just removed and disassembled the radiator, and to my dismay, found what I expected... nothing. Clean like new.
The only other thing I can mention is, when it has gotten it hottest, I hear a buzzing sound coming from the left side of the engine for a short time as it cools down. Almost like the thermostat is squeezing water thru. However, the thermostat is brand new, and it did it before on the old thermostat too, the old one just stayed open and ran it at 145-150 most the time. I'm baffled....