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Old 10-12-2008, 07:12 PM   #1
showdown
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Knocking sound when heaters on!

Hey i did a bunch of searching but cant narrow this problem down.

I just recently changed my radiator hoses, Thermostat, water pump, belts, and changed the coolant ( bmw 50/50 mix) and also a new Axillary fan switch.

The original problem was the thermostat ( car wasnt heating up properly to operating temp ) so while i was at it i changed the other stuff. ( no expansion tank i know, hopefully don't pay for that one )

Everything went fine, i was spewing coolant from my old axillary fan switch, but i replaced it and alls good, no leaks.

Soon after doing all this work, my car was finally heating up fine, no over heating, running good. Then with the heater on i noticed a knocking sound from the engine bay. i can feel the vibration from it in the pedals and steering wheel mostly, but is also audible. when i turn the heater off, it goes away. I cant figure out what might make this sound? heater control valve maybe? I cant say for sure if just happened recently or has happened during the summer. i dont use the heat or A/C in the summer, but now that its getting cold in canada, i'm using the heater.

It doesnt sound good and i would really like to get a diagnosis on this right away so i can fix it and move on without harming more things.

Car is a 00 323i. any and all help is greatly appreciated!

EDIT** i guess you can also say its when the auto climate control is on, not just heat. the only way i can stop the knocking is when the ACC is off, no fan, nothing.
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Old 10-13-2008, 10:38 AM   #2
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Bump! any help is greatly appreciated!
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Old 10-14-2008, 05:43 PM   #3
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bump! nothing?
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Old 10-14-2008, 06:33 PM   #4
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Sounds like it could be your Heater Control Valve (Aux. Water Pump).
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Old 10-15-2008, 06:31 PM   #5
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Quote:
Originally Posted by DesertMotorWorks View Post
Sounds like it could be your Heater Control Valve (Aux. Water Pump).
Would this failing make any kind of knocking/thumping sounds?

I timed it out, it thumps/ knocks ruffly about every 4 seconds.

I get heat and also get A/c, both are working fine in terms of temperature.
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Old 10-18-2008, 12:04 PM   #6
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bump
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Old 10-18-2008, 12:24 PM   #7
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it only does it with the heat on? not with the a/c? will it do it with the car off?
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Old 10-18-2008, 12:39 PM   #8
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it only does it with the heat on? not with the a/c? will it do it with the car off?
It does when the climate control is on. Unless i turn it all off.

I havent tried with the car off, but i will.
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Old 10-18-2008, 12:40 PM   #9
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so basically whenever the blowerfan is on? have u gotten under the hood when it does it and see if u can pinpoint the area of the noise?
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Old 10-18-2008, 02:04 PM   #10
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I hear it too, knock.... knock..... for me i put my finger on the top of the Heater Control Valve and can also feel the vibration from the knocking sound.

Anyone know it this needs to be replaced ?

everything appears to be working, as i have just reached 150k, searching this site a few weeks ago and did not find anything.
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Old 10-18-2008, 04:30 PM   #11
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I'm going to go test some more and try to narrow it down to the exact area its coming from.
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Old 10-18-2008, 04:51 PM   #12
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Ok, so its definitely coming from the area of the heater control valve. I also put my hand on it and i can feel the knocking sounds quite a bit, also the hoses connected to it.

It almost feels like a pressurization and then a release causing the knocking sound.

I turned the car off and left the key in position 2 with the heat on, and the knocking was present for a less than a minute and then stopped.
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Old 10-18-2008, 05:55 PM   #13
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possibly bad heater valve. i couldn't see what else it could be...
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Old 10-18-2008, 06:32 PM   #14
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so why would the heater valve go bad after doing a coolant flush? Cause now that i think about it, it didn't do it at all before, but immediately after i did the flush it happened.
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Old 12-30-2008, 01:59 PM   #15
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I'm reviving this thread since I've got the same issue with the heater valve, after my radiator has been replaced.
My guess for now is that they didn't open the valve by setting the heater temp to max prior to refilling the cooling system, thereby trapping an air bubble inside the valve.
I also noticed that the valve knocking does not happen all the time, but it definitely goes away after turning the blower off or setting the temp to high (not necessarily the maximum of 32C/91F). What's puzzling is that the knocking can occur even when the engine is off and the water pump is not running (but the blower is on by keeping the key in "accessory" position).
The first thing I did was to take the car for a spirited ride with the blower and the heater temp set to max in hopes the air bubble will move away from the valve. I'm going see if there is any improvement today. If not, the next thing to do will be to change the coolant myself, making sure the valve is opened during the entire procedure. If that will not solve the problem, I guess I'll have to replace the valve.

Any other suggestions?

Last edited by Megalocnus; 01-18-2009 at 01:28 AM.
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Old 12-30-2008, 05:10 PM   #16
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Update

Looks like the knocking has gone after yesterday's ride with heater and blower set to max.
I drove the car for about an hour today while the heater was set to low temperatures (16-18C/60-65F), parked several times with the engine running and went out to check the heater valve.
I found the easiest way to do this is just to put a hand on the front left fender, the knocking can be felt there almost as well as when placing a finger directly over the valve.
If I keep my hand on the fender long enough, I still feel an occasional "knock", but that's nothing like the rhythmic sequence my valve was playing before. I guess this is a normal process of adjusting the heat since the car is parked and no longer moving.

So, the problem seems to be solved for now. I will pay close attention to the heater valve for a week and then will change the coolant anyway, since I suspect it was an air bubble issue, hence the coolant has not been properly fed into the system.

Last edited by Megalocnus; 12-30-2008 at 07:19 PM.
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Old 10-13-2009, 04:32 AM   #17
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bumping this... seems like im experiencing the same problem
what there ever an actual fix?
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Old 10-31-2009, 03:38 AM   #18
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^ Yes I've solved the heater valve knocking issue I had. It was most certainly due to the coolant being drained while the valve was closed.
Have you had your cooling system worked on recently? If yes, try the remedy described in my previous post. If it doesn't work for you, drain and refill the cooling system proprely.
If the knocking started without anything being done to the cooling system, it may be time to replace the heater valve.

Last edited by Megalocnus; 10-31-2009 at 07:20 PM.
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Old 10-31-2009, 04:07 AM   #19
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any DIY for replacing the heater valve?
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Old 10-31-2009, 07:20 PM   #20
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^See the DIYs by forum member Paraklas.

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