Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
I've already tried jacking up the front end till the rear bumper was almost hitting the ground and I also have the Matco Vacuum tool and have tried that also. I haven't tried pulling a vacuum on it since the hoses was replaced though. Do you normally just pull a little vacuum say about 15"hg and then open the valve for the coolant until the gauge reads zero and then repeat?
I'll try this either today or Monday first thing and let you know how it goes. Wish me luck and I'll come back and accept your answer.
You were right with your assumption I am a technician. With this engine I have always just opened the bleed screw that you mentioned and filled the system with coolant until it ran out of the bleed screw then replaced the screw, tightened, and started the engine and brought it up to operating temp. Then I would open the bleed screw until I got a steady stream of coolant coming out and re-tighten. In the past by doing this I never had a problem.
Sunday I went to the shop and pressure tested the coolant system again with the engine cold. The shop was quite and as soon as I put pressure to it I could here a leak. I found that the intake gasket was leaking.
Monday we replaced the intake gasket. Went through the fill procedure and had the very same results (No heat at idle). I placed a large funnel in the surge tank and filled it up. I then ran it through several temp. expansion cycles watching the air bubble out. After doing this I had heat with the engine at idle. I drove the car and after about a mile I lost heat again. The air temp. would fall off until it was cool and then all of a sudden come back and be extremely hot and then get normal heat again. It did this several times before me getting back to the shop.
I plan on running it through more cycles of the same today (Tuesday) and seeing if that will help? This thing has been a demon and defied all logical troubleshooting! If you have anymore suggestions please don't hesitate to let me know. The customer has been very patient so far but I'm not sure how much longer that can last. I'll let you know how today goes.
Thanks again for your input so far.
I went in this morning and when we started the engine up the first thing we saw was coolant gushing out of the surge tank indicating a blown head gasket. we pulled the heads and now have them sent out to the machine shop for re-surfacing. For what ever reason this thing never really indicated a blown head gasket until now. The leak was obviously very small and got larger all of a sudden.
I just recently purchased a 2004 Tahoe with 155000 miles