Well, I fixed my "new" BMW up to non-drivable, and now need help.

I live in Germany, and bought a beater, 150K mile 1994 316i. It runs strong, and I picked it up cheap. Anyway, I changed the oil, oil filter and air filter--all was going good.

But we had freezing weather hitting, and I checked the antifreeze with one of the little prestone antifreeze gauges. It showed hardly any protection at all, so I went and grabbed a jug of Prestone to put in so I wouldn't crack the block.

I know that BMWs are supposed to have phosphate free "genuine BMW" antifreeze to prevent aluminum corrosion, but I figured in a pinch, anything was better than nothing.

I did not flush out the whole system. Instead, I just drained the radiator from the bottom when it was warm. I filled it back up with a mix of Prestone and water.

Now the problem: The car now overheats, but the heater stays cold. The main hoses to and from the radtiator to the block heat up though, and the water in the radiator gets hot too, indicating to me that the themostat is still working.

What did I do? Did I air-bind the water pump? Did I knock loose a chunk of corrosion and clog up a passage somewhere? Or maybe something else?

Thanks in advance for any help or advice!

Sounds like you're water pump is shot which happens on those. They are plastic and break after time. You may have a clogged radiator as well. Change the thermostate no matter what you do. It could in fact just be the thermostate not opening.

Run your car and check the hose leading to the thermostate. When your car is at temp check the hose going back to the radiator to see if the two hoses become the same temp. If not the thermostate is bad and is your problem.

If all you did was drain the radiator and refill it with 50/50 you likely need tt blead the air from the system. It's unlikely the impellor sheared from this simple task. Start the engine with the cap off the surge tank. Run the engine until it starts to warm up. Shut it down and leave the cap off for an hour. Go back out and pump the upper hose. (squeeze it a couple times to see if you can hear coolant or air. Add more coolant and repete.

No heat would mean your still too low on coolant. There isn't enough to pump through the heater core. My 525I T was low once and did the same thing.

BMW used to have a bleeder valve located on the top "T" stat housing. It worked very nice for purging air.

What is a 316? I've had many BMW's but never had a 316...

Thanks--I'll give it a try.

The 316i is just a 3 series with the smallest engine available installed. They came in normal coupe style (with trunk), as well as the bob-tail hatchback version. Mine has the trunk. Below is stats on the little engine:

M40B16
The M40B16 is a 1.6 L (1596cc) version of the M40 producing 102 hp of mechanical power and 105 ft (32 m) lbf of torque using Bosch M1.3 fuel injection.

Applications:

1988–1995 E30 316i
1990–1994 E36 316i

It is geared low, so acceleration is fine, but it runs out of guts on the autobahn after about 90 MPH (it goes faster, just takes a while to get there).

I had a 520i too (6 cyl)--same idea: small engine that was never imported to the US, but used as a base model in Europe.

Oh ya, E30.

Check to see if you have the bleed valve on your thermostat housing. If it's there, loosen the bleeder and fill the system. It will bleed the air as you fill the system. Then run the engine and crack it open after you run it.

It worked! No bleeder valve however--I really wished it had one though--that was a pain. I've never had a coolant system get air-bound like that before.

Thanks for the advice!

Bleeder valces make everything so much easier. My 98 doesn't have one either but I knew what I had to do before messing with it. Glad you found out what was wrong. I have seen these water pumps and thermostats raise hell on occation and they are no fun to change out. Well, the water pumps anyway.

Gotta burp it, like a baby