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DIY: Do It Yourself
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Old 11-06-2010, 03:30 PM   #1
Rigmaster
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No heat after coolant tank replacement

A couple of weeks ago I replaced a cracked coolant tank on my wife's 2002 325iT. Everything was peachy, except I wasn't able to get the heat to blow hot at all. Not a big issue a couple of weeks ago, because the temps around here were still in the 70-80's during the day and ~60's at night.

I figured the system would bleed itself while she drove for a while- but it has not.

Now it's getting cold and the wife is not happy.


I've tried everything I can think of, I parked the car on an incline (nose up) and bled the system, I have tried running it for a long time, then bleeding it, but nothing. Today I even took the heater valve out to make sure it somehow wasn't stuck closed (it was fine).


Car runs fine, temp gauge sits perfectly in the middle after about 3-4 minutes of warming up from dead cold. No coolant leaks, no other problems that I'm aware of.

Today I was able to get a little bit of heat out of the vents, but it didn't last, like a little bit of warm coolant got to the heater core, but then it stopped.

I've got the center dash vents on the red dot setting.


Heater worked GREAT last winter, so no reason to suspect a bad heater core, and since the coolant temp sits right where it should, I don't think it's a T-stat issue either.

Despite my low post count on this forum, I'm a pretty decent mechanic, I've owned and worked on BMW's for ~25 years and only rarely do I let anyone else work on my cars.


So, any ideas??



ps- I hate to throw this in there since it might possibly confuse the issue, but I've noticed that the system does not seem to build up much pressure. After running it for about 30 minutes today I took the coolant cap off and it barely released any pressure. I was able to take it completely off and let the car run without losing any coolant. Seems strange to me, but I don't know if it's got anything to do with my no-heat problem. There are NO coolant leaks anywhere that I can see, the new coolant tank is seated nice and tight. Wife drove the car for about 3 weeks or so and the coolant level did not drop one bit.

Last edited by Rigmaster; 11-06-2010 at 04:49 PM.
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Old 11-06-2010, 04:02 PM   #2
Sansho
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When you bled the system, you turned the ignition key to position 2, set the heater thermostat as high as it would go, turned the vents to heat (3 red dots), turned the fan on low, etc? What you're describing sounds like a system that didn't get completely bled and has air in the system. Bit of a head scratcher when you throw in that it's not building up pressure ... is the expansion tank rod half way between full and the lower dot when you take the cap off?
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Old 11-06-2010, 04:47 PM   #3
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Originally Posted by Sansho View Post
When you bled the system, you turned the ignition key to position 2, set the heater thermostat as high as it would go, turned the vents to heat (3 red dots), turned the fan on low, etc? What you're describing sounds like a system that didn't get completely bled and has air in the system. Bit of a head scratcher when you throw in that it's not building up pressure ... is the expansion tank rod half way between full and the lower dot when you take the cap off?
Thanks for the reply.

I'll agree it's a head scratcher, I'd pull out my hair if I had any....

I have tried bleeding as you described, then with the car running and fan on every speed from low to high, but I still can't get heat.

The expansion tank rod is bobbing where it should be, the coolant level has gone down a little as I ran coolant out through the bleeder screw, but I've always topped it off as it got low.
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Old 11-06-2010, 10:16 PM   #4
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Tried for about 1.5 hrs tonight to bleed it some more, but no progress.

Best I can do is get light heat for a short time- as I mentioned before I think this is because some hot coolant is getting to the heater core, but then it cools off with the fan blowing on it and no fresh hot coolant coming in.


I didn't see any leaks, I tried "milking" the small hose that goes from the coolant tank back to the heater core, but could not make anything happen. It did not seem like much, if any, warm coolant was flowing through that hose. I pulled the hose off the tank to check and coolant spilled out from both the hose and the tank. I even tried pouring coolant into the end of the hose with the hose held up as high as I could get it, then quickly plugged it back onto the coolant tank- but no luck.


UGH~!!!!!!!!
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Old 11-06-2010, 10:24 PM   #5
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maybe there is a really big air bubble in there?

Have you tried draining the whole coolant system then refilling it? Maybe that way you could get rid of the possible air bubble that could be there?
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Old 11-08-2010, 06:25 PM   #6
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There is a solenoid valve that controls hot water to the heater. its separate from the thermostat - maybe you unplugged it?
I can't remember where it was but I do remember unplugging it when I did my coolant refurb. I think it was buried under hoses and attached to the wheel well.
http://www.realoem.com/bmw/showparts...=64&fg=18&hl=4
http://www.ecstuning.com/Search/64118369805/ES177235/

02 WATER VALVE 1 64118369805 $82.22

Also squish the heater hoses (small ones) see if you can feel the fluid in there.
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Old 11-08-2010, 06:34 PM   #7
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When you filled the system did you make sure to do what Sansho said? You want to do that as you are filling it NOT just after you fill it. I replaced my coolant over the summer and I had the heater on max while draining and filling it. You also want to make sure you fill it very slowly to prevent any big bubbles from building up.
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Old 11-08-2010, 10:25 PM   #8
Rigmaster
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Quote:
Originally Posted by wildcat293 View Post
There is a solenoid valve that controls hot water to the heater. its separate from the thermostat - maybe you unplugged it?
I can't remember where it was but I do remember unplugging it when I did my coolant refurb. I think it was buried under hoses and attached to the wheel well.
http://www.realoem.com/bmw/showparts...=64&fg=18&hl=4
http://www.ecstuning.com/Search/64118369805/ES177235/

02 WATER VALVE 1 64118369805 $82.22

Also squish the heater hoses (small ones) see if you can feel the fluid in there.
Quote:
Originally Posted by 04yfz View Post
When you filled the system did you make sure to do what Sansho said? You want to do that as you are filling it NOT just after you fill it. I replaced my coolant over the summer and I had the heater on max while draining and filling it. You also want to make sure you fill it very slowly to prevent any big bubbles from building up.
Guys,

thanks for the replies.

I checked the heater valve- I am pretty sure that it's open when there's no power to it, and applying power closes the valve- so if it fails you still have heat. Anyway, I removed the valve and blew through it and it's open. I even purposely left it unplugged just in case it was getting a bad signal and somehow closing when it shouldn't, but that made no difference.


And yes, I followed Shansho's procedure- though I still don't understand how that's supposed to circulate coolant any better than with the car running and the water pump pumping it..... But hey, I'll try anything at this point if it might fix the problem.


AND, keep in mind that the car has been driven several hundred miles since the coolant tank change, so one would think that any air bubbles in the system would have worked their way out by now......

Still no heat, and now it's getting dark out so early I don't have much time to even look at the car once I get home from work.


I'm seriously considering taking it to a local indy shop and asking the tech there to look at it- do a system pressure check to see if there are any leaks that I'm not seeing. I'm still concerned about the fact that the system barely builds up any pressure, even after I've run it for a long time, revving the engine up to get some heat in there, etc. I can crack the rad cap and it releases little to no pressure, but it's not losing any substantial amount of coolant.


Last edited by Rigmaster; 11-08-2010 at 10:27 PM.
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Old 11-26-2010, 09:25 AM   #9
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I'm having the same issue. Help!
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Old 11-26-2010, 12:32 PM   #10
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I had a similar problem once; couldn't get the thing fully bled (like you, I have bled E36 and E46 engines for 10 years now), though it was running hot. In this case, I was able to dislodge the air bubble by squeezing the upper and lower hoses repeatedly while the car was running. Allowed additional fluid to be added. Not saying it will help you, but this action helped me.
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Old 11-26-2010, 12:53 PM   #11
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Okay I fixed it. Started driving and temp started going up. Upper radiator hose was hard, so slowly opened bleeder screw. Tons of air came out, then heat started working. then drove more and coolant light came on. Checked level after it cooled off was way low. Added more, good to go.
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Old 11-28-2010, 10:35 AM   #12
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Odd question, but did you make sure the fluid levels were full? My dad did a coolant change on his corolla a week ago, and was wondering why he would have low to no heat. I came over and his coolant level was very low. Topped it up, and instant heat.
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Old 11-30-2010, 09:57 PM   #13
Rigmaster
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***UPDATE***

Well, I finally got the problem solved, after taking the damn thing apart about 5 times, and trying all sorts of stuff to get it to work. Tonight I took the car to a friend of mine who runs an indy shop and we went over it. He determined that coolant was not flowing through the heater core. We took the heater core hoses loose and held a garden hose to one of the open ends, and nothing would flow through. So, we figured out the coolant flow and ran the hose the opposite direction to back flush the heater core, and after a bit of pressure built up, some small black bits came out of the other hose and water started flowing again!! The theory is that the black bits came from the old coolant tank due to plastic deterioration (??)...


Anyway, once the heater core blockage was taken care of, the heat works like a CHAMP!!! Ran the car and cracked the bleeder screw a couple of times to get all the air out, and all is well now.


Thought this might be useful info in case someone runs into this problem in the future...
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Old 11-30-2010, 10:17 PM   #14
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You learn something new every day...... Thanks.
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