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Discussion Starter · #1 ·
I just replaced some parts in my cooling system. Now I want to get it properly filled with coolant and get the car back on the road. I'm a little nervous, though, so I want to get some opinions before I proceed.

This job started with two problems. First, the expansion tank apparently had a small crack, so I was loosing coolant, which I replaced regularly. Second, the main serpentine belt broke while driving, which of course lead me to this point where I'm working on the car.

I replaced the upper and lower coolant hoses, the expansion tank and cap, the two belts, the fan clutch, and the fan. (I thought I would wait on the pump and the thermostat until I did this job and knew how much work it would take.)

My worry is that when I removed the blue drain plug from the bottom of the radiator, very little coolant came out. I have the car on jack stands, so the bottom of the front bumper is about 18 inches off of the floor. I don't know if most of the coolant is back in the block and the heater system, or what is going on.

While I was replacing the hoses, the upper hose had no coolant in it, which didn't surprise me. However, the lower hose was also nearly empty, and it was dry at the end near the thermostat. A little coolant came out of the radiator when I took the lower hose off, but not much.

Anyway, I added 1:1 BMW coolant and distilled water to the expansion tank. I would say about two quarts before the bulb came up out of the tank. I turned the heater temp up to high (91 deg F) and turned the fan on.

I started the car and it seems to run fine.

I ran it for about 30 seconds, rev'd the engine a couple of times and went back to check the fluid level. It's not changing. The temp gauge on the dash is below normal, so I don't think it's overheating.

I squeezed the upper and lower hoses. They are not firm like I would expect if they had coolant in them.

I don't see any bubbling in the expansion tank.

My problem is that after adding only two quarts of coolant, I'm afraid that I might damage something. The engine sounds great, no sputtering. As far as I know, the only indicator I have that it's not too hot is the gauge on the dash, but I was wondering if there might be some conditions where that's giving me a false reading while the engine is overheating.

Can someone walk me through this, please?
 

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Discussion Starter · #2 ·
Filling the system

I guess I can answer part of my question. I found this link on filling the system. Basically it says keep filling the expansion tank until it overflows. While doing this with the engine off, I noticed the coolant going into the system through the upper hose. When It looked full I started the engine. Then I just kept filling until no more would go in. Loosening the bleeder near the expansion tank, the volume in the tank dropped, so I put more in. Eventually, coolant starts spitting out the bleeder. I closed it, closed the tank cap and watched for leaks.

It looks like I have a leak at the thermal sensor on the lower hose. I had replaced the hose but not the sensor. I guess I'll get a new sensor and see if that fixes the problem.

The engine appears to be running smoothly after taking nearly 2 gallons of coolant. I still don't know why it was completely dry. That worries me a little, but since the engine is running smoothly, I'm not sure what to make of that.

After I replace the sensor, I'll do some more air purging, and then take it for a drive.
 
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