Author Topic: Lost interior heat (Read 7574 times)

BlueBMW · « **on:** February 07, 2010, 02:24:36 PM »

I replaced all the hoses under the intake about a week ago. I did everything back to stock (meaning I didn't delete the heated throttle) I replaced all the heater hoses also. I filled the car with coolant, drove it home and parked it for about a week. I drove the car yesterday and today and I have a new problem... No coolant leaks at all, car runs great. But, while driving I dont have any heat in the cabin. When I come to a stop the heat slowly comes back, but when I get back going again it cools down. I tried to re-bleed the cooling system to make sure there wasn't a massive air bubble causing all this. Its very consistent... good heat stopped at idle... no heat while cruising. Also, when the heat does start working the temp gauge drops a bit, while driving it sits a bit below the middle mark. I'm thinking maybe the thermostat failed while it sat for a week and is now stuck partially open? Any thoughts?

KenC · « **Reply #1 on:** February 07, 2010, 02:38:47 PM »

Are you sure your heater hoses at the fire wall aren't reversed?

BlueBMW · « **Reply #2 on:** February 07, 2010, 02:49:46 PM »

I suppose its possible, but I thought I was pretty careful to hook them up correctly. I'll try swapping them and see what happens. Although I did get my fuel lines backwards when I did all the work. I was scratching my head for a while on that one.

dvmotorsports · « **Reply #3 on:** February 07, 2010, 05:15:34 PM »

Clogged heater core?

BlueBMW · « **Reply #4 on:** February 07, 2010, 05:42:19 PM »

The heater core was recently replaced by the PO not long before I bought it. I'll try flipping the lines and see what happens.

iamcreepingdeath · « **Reply #5 on:** February 08, 2010, 10:48:50 PM »

Bump, I have an identical problem. When I come to a stop, BAM! hot air. start moving and within seconds the hot air is cooling back down to outside temp. Very annoying. What can it be?

BlueBMW · « **Reply #6 on:** February 09, 2010, 06:31:21 AM »

Someone suggested to me that it might be the heater control valve? I guess its on the side of the heater core? I'll check it out and let you know.

BlueBMW · « **Reply #7 on:** February 10, 2010, 08:39:45 PM »

I fixed it. Turns out I was the moron. When I did the mess under the intake and replaced all the coolant / vacuum hoses, I also replaced the heater hoses. They were confusing because of a little extra valve and hose on the heater core supply hoses. Turns out the valve was an add on for a bulletin back in 93 (SIB 17 03 93) to bypass the heater core in the event of overpressure so that it wouldn't explode and burn the driver's legs. I had that valve installed backwards... AND I had my two heater core lines reversed lol. I fixed all that and now the heat works perfectly.

iamcreepingdeath · « **Reply #8 on:** February 10, 2010, 10:14:34 PM »

so these bypass valves were added in 1993 to these cars? i guess I should check if mine has one, because i know the PO did alot of stupid stuff to this car, and this is probably the issue. (this is not my Alpine E30 in my sig, i just picked up another 1991 318is recently)

BlueBMW · « **Reply #9 on:** February 10, 2010, 10:24:02 PM »

Apparently it was a big class action suit or something because people got injured by coolant exploding from heater cores. So they added bypass valves. If you get new heater hoses from a dealer they come un-cut so you'll have to cut that like those pictures show above.

We actually had an 91 E30 come into our dealership to replace a heater core (UNDER WARRANTY!) because it blew up because of this problem. (this was within the last six months) Craziest part... the E30 had an M50 swapped into it! And we STILL did the heater core under warranty.... Someone higher up said do it so we did lol.

iamcreepingdeath · « **Reply #10 on:** February 10, 2010, 10:31:45 PM »

Quote from: BlueBMW;87183

Apparently it was a big class action suit or something because people got injured by coolant exploding from heater cores. So they added bypass valves. If you get new heater hoses from a dealer they come un-cut so you'll have to cut that like those pictures show above.

We actually had an 91 E30 come into our dealership to replace a heater core (UNDER WARRANTY!) because it blew up because of this problem. (this was within the last six months) Craziest part... the E30 had an M50 swapped into it! And we STILL did the heater core under warranty.... Someone higher up said do it so we did lol.

that's because 24v swaps are bad-ass!

at this point i don't care if i run the risk of my heater core exploding, I want the heat to work!! it was freaking 0 degrees Fahrenheit yesterday morning!!

BlueBMW · « **Reply #11 on:** February 10, 2010, 10:32:41 PM »

Some people say you dont have to have the valve at all and remove it completely. Guess its up to personal preference. I don't like the idea of if the car ever has a coolant system problem that my heater core might explode and burn me lol. (I don't want to put another heater core in it!)

BlueBMW · « **Reply #12 on:** February 10, 2010, 10:33:54 PM »

Quote from: iamcreepingdeath;87187

that's because 24v swaps are bad-ass!

at this point i don't care if i run the risk of my heater core exploding, I want the heat to work!! it was freaking 0 degrees Fahrenheit yesterday morning!!

The car was awesome! It was just odd doing a warranty repair on an 18 year old car! Its strange enough doing catalytic converters at 7 years.

ecalder · « **Reply #13 on:** February 10, 2010, 10:40:32 PM »

Damn that explains the extra hoses in my engine. I couldn't understand where all of that extra stuff came from since it doesn't show it on realoem or the manuals... I was thinking of getting rid of all of that when I replaced the coolant hoses, now I'm glad I didn't. And I was pissed when the dealer hose had to be chopped to fit right...

I feel for you in 0 degree weather. We're at 40 here and we think it's cold. My heater only works when I'm moving fast and blows ambient air when I'm stopped at a light and that's annoying. I'm told I have an air bubble in the system but my needle doesn't jump around and I haven't overheated. Considering howmuch trouble people have bleeding their coolant system I figured I'd leave it unless it casue more problems. Instead I just drive even faster to get warm air flowing!

///M3Mike · « **Reply #14 on:** February 11, 2010, 08:24:42 AM »

Quote from: BlueBMW;87160

I fixed it. Turns out I was the moron. When I did the mess under the intake and replaced all the coolant / vacuum hoses, I also replaced the heater hoses. They were confusing because of a little extra valve and hose on the heater core supply hoses. Turns out the valve was an add on for a bulletin back in 93 (SIB 17 03 93) to bypass the heater core in the event of overpressure so that it wouldn't explode and burn the driver's legs. I had that valve installed backwards... AND I had my two heater core lines reversed lol. I fixed all that and now the heat works perfectly.

Hmm....this might be my problem, too. Do you have part numbers for that bypass kit?

Author Topic: Lost interior heat (Read 7574 times)

///M3Mike