heating

kp · Post by kp » Tue 12 Jan, 2010 18:38

Does anyone know if the following is common with the zed 3, my heater blows cold when im stationary, when im driving the heater blows warm and is fine, this hapPens even when the car is running at the normal temperature half way.

I have had a new thermostat on the zed just over a year.

Post by **Robert T** » Tue 12 Jan, 2010 19:24

Fairly normal. I have noticed with mine that if the heater is not on "hot", that it will blow at a nice temperature when moving at a decent speed, but when I slow down or stop, it blows somewhat cooler. AFAIK this is just the way the heater valve works - all you are doing is controlling how much water is allowed to flow through the heater matrix, not setting the temperature at which it blows. If you slow down there is less heat being generated, so the matrix is not as hot and it heats the incoming air less.

If what you are experiencing is more extreme than this, then you may have a problem.

Cheers R.

MarkR · Post by **MarkR** » Wed 13 Jan, 2010 08:24

I had this on my 1997 2.8. BMW put a second in line pump to make it blow hot when stationary. The temp should be the same at omph and at 100mph.
If it is in warrenty get BMW to fix it.

BonBon · Post by **BonBon** » Wed 13 Jan, 2010 16:02

If set on full heat it is not hot - you may have air trapped in your heater core.

kp · Post by kp » Wed 13 Jan, 2010 19:24

hi guys thanks for the feed back

gookah · Post by **gookah** » Wed 13 Jan, 2010 21:37

Robert T wrote:Fairly normal. I have noticed with mine that if the heater is not on "hot", that it will blow at a nice temperature when moving at a decent speed, but when I slow down or stop, it blows somewhat cooler. AFAIK this is just the way the heater valve works - all you are doing is controlling how much water is allowed to flow through the heater matrix, not setting the temperature at which it blows. If you slow down there is less heat being generated, so the matrix is not as hot and it heats the incoming air less.

If what you are experiencing is more extreme than this, then you may have a problem.

Cheers R.

is it not the fact that the water pump is not turning as fast when you are idling? try increasing the revs with your foot on the accelerator, I bet it blows warmer then. you pump more hot water through the heater matrix as the revs increase.

Post by **Robert T** » Wed 13 Jan, 2010 23:34

gookah wrote:is it not the fact that the water pump is not turning as fast when you are idling? try increasing the revs with your foot on the accelerator, I bet it blows warmer then. you pump more hot water through the heater matrix as the revs increase.

Probably a combination of both. Less revs generates less heat and less water flow will transfer less of it to the heater matrix.

Cheers R.

Windsurfing · Post by **Windsurfing** » Thu 14 Jan, 2010 22:59

You might want to check your coolant level. If the coolant is low there is not enough pressure for the heater matrix to work correctly.

If everything is working correctly you should be able to get warm air even when stationary. If you do a search on bmw forums for e36 heater problems you will find this problem reported quite a few times. My wifes bmw had this problem over Christmas. The coolant was not quite at min but was close to it. I topped it up and heating worked wonderfully again

Hope this is useful.

Mike Fishwick · Post by **Mike Fishwick** » Fri 15 Jan, 2010 10:41

Several people have foud that this problem is cured by fiting a new water pump. Older engines have a plastic impeller, which can expand and come loose on the shaft. The resultant slipping is proportionally greater at low engine speeds - hence the poor heater performance.

The Z3, like all modern cars, has an air-blending heater, in which the water flow is constant (NOT controlled by a heater valve as on an old Mini etc) and the temperature set by the amount of cold air blended ino the hot air.

Your problem is certaily not 'typical' - for example, my Z3 can produce heaps of really hot air at idle. As a car designed for the US market, a poor heater would not be tolerated.

Frank.A · Post by **Frank.A** » Sat 16 Jan, 2010 11:24

I agree with Mike that a slipping impeller is the most likely sause of poor heater ouput at idle.At least the pump is driven by an auxilliary belt.

Several other marks suffer with ths problem.If you own any vehicle such as one from the VAG range with a cam belt driven water pump it is advisable to change the water pump at each cam belt change.

The extra cost of doing this is relatively small compared with the cost of the cam belt change.

If the OEMs water pump has a plastic impeller which at best can slip on the shaft and at worst disintegrate,it could momentarily jam the pump and destroy the cam belt.If the engine is of the interference variety,as many are, this can prove catastrophic.

Mike Fishwick · Post by **Mike Fishwick** » Sat 16 Jan, 2010 11:55

Why anyone would try to cure this problem by fitting a second in-line pump really makes me wonder - it's just trying to sure the symptoms.

It seems from the comments on this thread that quite a few people have this symptom, and regard it as normal, when it is the sign of a problem.

Post by **Robert T** » Sat 16 Jan, 2010 13:59

Mine produces plenty of heat if you leave the heater on full, regardless of engine speed, however if you turn it down a bit for a comfortable temperature, when you slow down the temperature of the air noticeably reduces. I still believe this is a symptom of the design rather than a failing water pump, as AFAIAA mine has done this from new. If the car failed to produce heat at idle but the temp gauge started to rise, then I would suspect the water pump.

Cheers R.

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