Heat only works when moving/engine temp rises at idle!

[Mikes93325i]

Hello, I need help from someone with more knowledge/experience than I:

A bit of background- 93 325i auto with 135k miles.
Last year I had the thermostat and (aluminum) thermostat housing replace the factory plastic housing as preventative maintenance. Had aluminum impeller installed about 5 years ago so that was okay. Ever since then the heater only works when car is moving or when engine is revving at a stop. Before I had this work done I could start car in the morning and let it run and warm up in the driveway, the heater or defrost would become warm to hot with the engine. Now, I can warm up the engine temp. to the middle of the gauge and as long as my car is parked at idle, I only get cool air from vents with hvac temp gauge all the way up. Soon as I start driving it gets warm. Come up to a stop (for instance at street light) and it goes cool again until I start driving. Right after I had this work done at the auto shop, they claim that is normal for a car without electric heat I am told. None-the-less this was not a problem before this work was done.
I carry on driving for the last year and it's not that big of a deal until lately---I am stuck in traffic on the freeway, dead stop and then a slow creep for about a half hour... I notice the engine temp guage is slowly creeping up on me, to be cautious i crank heat up all the way to 90deg and fan on high as it's impossible to pull to the side of the road...only getting cool air out of vents and as long as I'm at an idle (700rpm or so). I had to put car in neutral, apply e-brake, and rev up the engine to 2,000 rpm... in doing so, vents produce warm/hot air and engine temp quickly goes back to normal operating temperature. That sucked bad! Stuck on a bridge with a hot engine and now having to be paranoid about it every time I drive.
Please help on what is wrong with my car!!!

I tried bleeding the coolant system and apparantly failed miserably. Had the car running for about 15 minutes as the coolant tank & bleeder hole shot steam and coolant mist up like Old Faithful. Not once throughout this attempt did the heat from the vents feel warm, including when revving the engine. The overflow tank was nearing empty when I finally gave up and shut off the car...at this point the temp gauge in the dash was starting to creep up just past the mid level again. I added about a half gallon coolant to get it back up to normal level, lightly sprayed the engine compartment down and am calling it a night, once again pissed off.

Could the thermostat be malfunctioning again already? Pulled out the receipt and had the stat & housing changed in January of this year but the symptoms seem to be very similar to the ones happening one year ago now.
*** Please help, I can't be the only one with this problem, right? ***

[markcm]

Bump--

I have a 96 328i that acts similar to yours, but without the coolant over/excessive heat. I have 165k mile and it's been doing it since I bought it with 80k. I've bled the coolant system a few times over the past few years but it hasn't helped any; it seems some people are having luck with removing air (click here to see another thread on this topic)

In previous experiences on cars other than my BMW, weak heat at idle were symptoms of a slowly failing water pump but in this case my cooling on my BMW works flawless and hasn't missed a beat in the past 80k miles, it never budges from half way (needle straight up).

I live in the Pacific Northwest; my only guess at this point is that the maybe I should run a bit hotter of a thermostat. Now that it is winter, I could also try to block a portion of the radiator with cardboard and keep an eye on the temp gauge to make sure it doesn't overheat which I doubt it would in the winter anyways...

If anyone has had these symptoms and solved them, please speak up... no heat sucks and it's a bit embarrassing with passengers as well.

[RascalKing]

I have the exsact same car as you, Markcm, and I'm having the exact same issue.
so +1 on that bump...aynthing? My floor heats up pretty quick once i get rolling, but my vents dont want to blow warm air it doesn't seem.

[Bris328is]

Maybe there is air in the system

[Goon]

There is an air pocket in the system it seems. I had the same symptoms as yourself and tried many many times to bleed mine without yielding positive results. I took it to the shop up the road, they bled it and it's worked fine ever since.

[markcm]

Thanks for the replies, difficult to remove air in the system seems to be a popular cause.

It may be time to take it in for a flush and a power bleed then; I've heard some shops force coolant in and use vacuum to pull any remaining air out; never had it done myself.

[Mikes93325i]

Wow, old ass thread... I forgot I posted this almost 3 years ago now. I sold my E36 about a year ago, and never solved this problem completely which went on for two more years after this post. I believe it had to be air in the system that was just a bitch to get out of there. There were at least 3 times I sat in the driveway for 30+ minutes trying every bleeding procedure I read about, after each attempt it seemed like I was making progress... car would blow some warm air at idle for 2-3 weeks then it would slowly go back to its old ways. At random I'd get the 'Check Coolant Level' on the OBC, level in the expansion tank was always full & no evidence of coolant loss under the car led me to believe there was air in there. Weird thing on a side note, when at idle, felt like I could feel/hear something near the foot pedals inside the car from drivers seat, sounding like something was trying to pump water but was only pushing air, kinda a clicking popping sound. I always thought this was coolant trying to go through the heater core but air preventing it from travelling correctly, had to be related to the issues. Maybe something was partially clogged along the feed/return line from engine to heater core, dunno. Oh yeah, one other thing that always had me wondering... when you pop the expansion tank cap and have the engine running, shouldn't there be coolant pouring from that little piss-hole into the tank for circulation? Mine never did, hot or cold. I figured that was air in the system too, I may not have the car anymore but still would be nice to know. Oh wise ones, please do chime in!

[berkeleyEE]

Hmmm, old thread indeed.

when you pop the expansion tank cap and have the engine running, shouldn't there be coolant pouring from that little piss-hole into the tank for circulation?

For sure. I saw that described in this understeer DIY: www.understeer.com/fanclutchmod.shtml
and that's how I did my coolant flush and refill. In addition I had the nose of the car uphill on a bit of an incline. Once I got it bled correctly, no problems.

[markcm]

Well...

I guess it has been longer than I thought since I checked my coolant level and bled the air. This weekend after following the instructions for bleeding air in several other posts (and linked above in my other post) my heat is working well again.

My coolant was only a tiny bit low but when parked on a hill and holding the RPMs to 2500, the resevoir tank would draw down to the bottom. Once I cracked the bleeder valve open at 2500rpm, it belched a few small bubbles, I added about 1 or 2 pints of coolant and my heat is working like new again.

Hope this helps others.

[stevemor909]

Wow I never even heard of this before nor have I ever had the problem until now. My 2005 Corolla is doing the same thing, no heat when idle, than heats up fine when running. Sounds like a pain in the butt to fix which may strengthen my plans on trading it in in the near future for a much newer model. It has almost 100,000 miles and also I believe there are some shock issues. Now out of warranty, might cost too much money!

[UnderCoverGuy11]

Wow I never even heard of this before nor have I ever had the problem until now. My 2005 Corolla is doing the same thing, no heat when idle, than heats up fine when running. Sounds like a pain in the butt to fix which may strengthen my plans on trading it in in the near future for a much newer model. It has almost 100,000 miles and also I believe there are some shock issues. Now out of warranty, might cost too much money!

Well this isn't the corolla forum, but shocks can be had for 150, it's a corolla so I'm sure they're alot cheaper, and maybe an hour of work. Bleeding isn't hard, but I'd also try to check if the thermostat is faulty. I think corolla is self bleeding anyway

[FadetoCrimson1]

Air in the system. Bleed the sh!t out of it and good luck!

[whoshaunq]

low on antifreeze.