Author Topic: Newbie with heater problem 94 318i (Read 2376 times)

vandal171 · « **on:** May 23, 2011, 08:47:57 PM »

Hello all new to the board. I have searched but not found an answer so here goes. The other day the heat stopped working in my 318. The odd thing is it still blows heat if you keep the revs up over 2000 but when you back out of the throttle it gets cold almost instantly. I replaced the water pump thinking maybe a bad impeller and bled the system thoroughly, there is no air in it. The car warms up to operating temp normaly and does not overheat. This started all of a sudden like flipping a switch. I thought maybe the flap door was vacuum controlled and possibly losing vacuum to a leak but it appears to be cable operated. I'm at a loss on this one. Any thoughts?

DesktopDave · « **Reply #1 on:** May 23, 2011, 09:56:02 PM »

Check the heater valve. Some cars also had a bypass/crossover installed (to heat the core up a little quicker as well?). That might be bad. It's in the heater core line on my e30, might be on yours too.

monko141 · « **Reply #2 on:** May 24, 2011, 09:26:09 PM »

I am having the exact same problem on my 325 e36. Over 2k nice and toasty, under 2k it goes cold. Since it effects both sides of the climate control I am thinking there is some kind of blockage in the inlet of the duel control valve next to the brake booster.

DesktopDave · « **Reply #3 on:** May 24, 2011, 09:41:43 PM »

Did they put that restrictor bypass in e36's? I'm pretty sure it was an e30 thing to protect from overpressure bursting the heater core.

I'd be strongly tempted to clean out that heater control valve.

vandal171 · « **Reply #4 on:** May 25, 2011, 03:06:01 AM »

I can't find an overpressure safety valve on it so may be an E30 only deal. Perhaps I will hook up a temporary bypass line around the heater valve and see what happens.