eglaze88

2 weeks ago my wife was driving our '05 Suburban when it overheated. She pulled over immediately and turned it off. I went to come get her and check the car out. I checked the fluids and put a half gallon of coolant in. Other than that none were low. I assumed the coolant was low due to boil over through the overflow as my wife said she saw steam and the area around the overflow tube was indicative of a fluid loss. However, starting it back up after I filled it back up caused it to overheat. I had it towed back home so I could work on it. I bought a new thermostat and replaced the existing one. I tested both in boiling water and they both opened at 190 degrees. I went ahead and used the new one and also replaced the housing. Filled it back up with new coolant, burped the system and it still overheated. I drained it again and used the Prestone "Flush n' Fill" kit to flush the system. Again I added new coolant and it continued to overheat after @10 min idling. It has about 160,000 miles on it and has never had the water pump replaced, so I replaced the water pump as well as the lower belt (not serpentine). Put it all back together and it still overheated. I checked the fans and noticed they weren't turning on until the temp gauge reached 210-220 degrees. If I turned the AC on though, they turned on right away. I removed and replaced the coolant temperature sensor. Still overheated. I removed the fans, pulled the radiator and took it to a shop to check for clogs/debris. It was clean. Replaced radiator and fans, burped it according to GM's instructions and tried again, it still overheated. I checked the heat coming from the vents and noticed it wasn't as hot as it should be. So I bought a half gallon of CLR, disconnected the old heater core hoses, connected other longer hoses and poured the CLR in one end, holding it high until it came out the other hose, then poured it in the opposite hose, holding it higher this time. I did this several times over the course of 10-15 minutes, running the CLR through at full strength back and forth. Afterwards I ran fresh clean water through to remove all traces of the CLR (highly corrosive). Put everything back together and tried starting it again. It still overheated. I concluded that I had a failure in the head gasket even though my oil didn't indicate it nor did my coolant. I went to Auto Zone and rented a block test kit for $25 and bought the fluid for $8 and took it home to test for combustion gases in the cooling system. conducted 3 separate tests as well as a control test (sucking up exhaust fumes just to check and make sure the liquid actually would work). It did not indicate that there were any combustion gases in the system (blue fluid turned a blue-green color but definitely not yellow). Mechanic friends of mine recommended checking the fan clutch, electronic components and even suggested that my transmission was getting hot and overheating my coolant or that my catalytic converter was melted. I didn't check the cat since I wasn't experiencing any loss of power but I did check my tranny fluid and it was clean and full. By this point, I was out of ideas and decided to just take it to the dealer. I got a call back the next day and they had found the problem. After hooking up a vacuum to the cooling system they pulled the bubble and voila, no more overheating. I wanted to post this because someone else is bound to have this same issue, as the tech at the dealership said this happens pretty regularly. I thought I had put enough coolant back in the system as I (somewhat carefully) measured out the amount of coolant I was putting back in the system. I also took precautions to avoid getting an air bubble (filling in through the top rad hose, parking the car on ramps to keep the front end up) but apparently it didn't work. So, bottom line, if this is happening to you, be sure to double check the coolant capacity and carefully burp the system. Know that even going to these efforts may not help. As to what caused it to overheat in the first place, I think it was probably the water pump, or a clog but in repairing that problem I created another (the air bubble). Good luck if you're dealing with this yourself. My advice: if you're needing to do anything that involves draining the coolant in one of these, consider taking it to someone who can vacuum the line to avoid the air bubble issue. I'd be interested in anyone's burping techniques for this particular engine. There's no bleeder valve so it's kind of a hassle. I did try loosening the heater core inlet just a little until no bubbles came out but that clearly didn't work. Take Carr and happy tooling!

SWHouston

Thank you very much for your Post. It's rather rare that we see such informative reports such as yours.

aldo619

I'm having the exact same problem. I'm not as far along in my troubleshooting, but I'll definitely try to burp the system before proceeding further.

Big L Trucking

Thanks for your post! I was not having any problem with my Suburban other than my 7th Cylinder ticking. I had the mechanic to replace all 16 lifters, and Head Gaskets, along with new spark plugs. He left the job open outside for four months and exposed my engine compartment to many elements as the hood was only cracked so I don't know if water got into that compartment or not. Right before I fired him, he put the bottom end of the engine back in and informed me that he torqued the heads according to the specifications. I hired another mechanic who put the top of the engine back together for me, and he informed me before that when he did the test run for me that he ran out of coolant so I needed to put some more in there to properly top it off. I did that the next day and ended up pouring in about 2.5 gallons of Dextron into the reservoir while the engine was running. The vehicle drove excellent for about 40 miles even up to speeds of 75 mph with no problem, but I did notice that I smelled some fluid but the mechanic told me that some of the oil had spilled on the manifold so that was that smell. Later that same afternoon, I was driving about 60 mph and the vehicle started to bulk back and forth like it was trying to cut off. The thermostat went all the way back to 0, then to 210, then towards 260, then back to 210 and kept going up and down intermittently. It was crazy and produced a code for me which later at the Auto Parts store yielded a failed Electronic Coolant Sensor. I replaced the sensor myself along with the V-Shaped Heater hose which apparently had some kind of slit hole in it which I had found. I did not have a quick connect on the hose which goes back towards the top of the engine frame, so I used a C-Clamp with a Phillip's Head. The engine continues to over heat now over and over. I replaced the Thermostat and had a coolant flush and a leak down pressure test which revealed only a slight coolant leak, but all of the mechanics are telling me a have a blown head even though the engine has full power, no oil-water mixture, no hesitation, no white nor blue smoke. I am still not prepared to just chunk this engine and put in another engine because down in my heart I feel that it is only something minor in comparison to a blown head even though I am not a mechanic. Do you have any additional wisdom, because I have already spent over $1,600 on these repairs.