Air...
I had the exact same symptoms when I had air. I had flushed the heater core and radiator with a hose and got goood flow, so I figured there was nothing plugged up. Problems I saw:
1) Fan wouldn't come on--my diagnosis was that the fan switch was not seeing any heat because of air. (Not sure what the inside of the radiator tank looks like, but there must be some kind of baffle in the middle to keep the coolant from short circuiting from the upper hose to the lower). I got that air out by opening the radiator petcock with the system under pressure. The first water that came out was cold, then there was a blast of air, then hot water. After that the fans came on.
2) Boiling in tank--I almost thought I had a blown head gasket because there was so much "boiling" going on. After I had done the air purging, that stopped. It was probably a combination of air purging and coolant boiling going on.
3) No heat--the theory was that the heater core was air bound. I had a helper run the throttle at 3000 rpm while I alternately squeezed the heater supply and return hoses. The heat came back, first only at high RPM. After some more burping, it's now on all the time.
I did the burping with the right side of the car jacked up so that the coolant reservoir was at about the same height as the heater hoses. Not sure why that should make a difference, but it seemed to.
The other mistake I made in flushing the system was not draining the block. I was only getting about 1/2 the coolant out of the radiator petcock, which led me to believe the radiator was plugged. After reading Bentley, it was obvious that I'd left a bunch coolant in the block and reflushed by pulling off the oil cooler hose to drain the block.
I've worked on a ton of cars (Saab & Volvo, mostly) in the last 40 years, and this one was by far the hardest to get the air out of.
|