I have an 88 735i. I got off the highway to see the needle getting higher and a blast of coolant shooting up at the window on the inside. Found out the belt had broken. Replaced the belt and on the way home, coolant still was coming up in the car. Did a head gasket blow, did the heater core go out, water pump go out, or what happened? I won't really be able to look at it further til later on in the week.

For it to be coming up onto the windshield, I'd say it's just a hose somewhere. But with a leak that bad, you're just gonna keep over heating, and should be easy to spot the problem.

Check the hoses going to the heater valve (right near the brake booster), and check the coolant reservoir tank overflow hose. I had a bad overflow hose (and a blown head gasket) which sprayed coolant on my leg once while driving.... not pretty.

Check the hoses going to the heater valve (right near the brake booster), and check the coolant reservoir tank overflow hose. I had a bad overflow hose (and a blown head gasket) which sprayed coolant on my leg once while driving.... not pretty.

It all happened so fast and my feet were already cold because I had some socks and sandals on, but I thought I felt coolant spray on my foot. I thought I was just panicking because the windshield filled up with smoke and the smell was that sweet smell that got caught up in my throat and I couldn't see anything.
I'll have to get out and check things tomorrow...

Man, if my leak was that bad, I dont think I could wait more than 5 minutes to find out what it was!? Anyways, good luck with it, I am also voting on it being the return line from the radiator to the fill tank (I cannot remember if the 735s had the same line as the 740...)

I have the same issue with coolant on the windshield. Looks like the previous owner jury rigged the radiator hose and the bypass hose. Grrrr.... should be illegal to screw up a fine piece of German engineering with back woods fixes.

I'm in Indiana and the weather was horrible the day all this happened. It's still cold outside and we're expecting MORE snow.
Anyway, it looks as if it's the heater core after doing some searches on the forum. To top it off, the brake booster has gone out too. For now, I'll bypass the heater core and wait till the summer to fix it if I don't get rid of the car at all.
Thanx for everyone's help!

Edit: I'm an idiot, I completely missed the whole "inside the windshield" part...