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heater core?

Discussion in 'E28 (1982-1988)' started by 1983533i, Mar 6, 2011.

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    It seems I have too much heat. I replaced thermostat and still not fixed. Does anyone know if there is a valve which controls the flow of cooling fluid through the heater core or does it flow freely all the time? I thought there might be an issue with the direction of the air through the duct work also. Thanks

    cwbiii guest

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    follow the cable...

    There is a cable that goes from the dash to somewhere near the firewall. This cable operates a valve that controls coolant flow (heat) to the heater core. With age and lack of regular use they tend to freeze (rust) up and need to be replaced... often this is also the case with the cable as well. The cable is usually the most difficult to replace but if the valve is in a difficult place to get at it also can be a challenge. The first thing is to find the valve and remove the cable and see if it can be made to open and close then deal with whatever parts of the system are preventing its proper operation.
    I am not familiar with your particular model but if you look around you should spot it.
    It should be somewhere in the coolant line that comes off the engine usually near the water pump... it could be on either side (inside vs outside) of the firewall and is usually on the passengers side near the heater core. Plan on replacing the coolant hoses if you need to remove or replace it. Its a stock diameter hose you buy by the foot. It's also possible that someone eliminated it as a quick fix... in this case you should be looking for the end of the cable I was talking about. It will originate at the control mechanism on the dash for heat control. In this case you will need to purchase one and install it... find a maintainence guide of some sort for pictures of where it should be.

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    Search realoem.com and see if your model has a water valve -

    this link is for a production month 10/87 535i, start at the beginning of realoem to select your exact model, or input the serial number...


    I don't know all ins & outs of E28's either, there may be a cable that controls a water valve, if your model has one; I think the 3 bowden cables shown in realoem.com manually actuate flaps directing airflow to windshield, dash vents, and footwell.
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    There is on a 2002. Not on an E28. It's an electric valve on the firewall just about dead center behind the engine that's controlled by the heat sensor (down low on the right side of the steering wheel) and the heat control knob to regulate heat at a set temperature. The valve has a rubber diaphragm that fails. BMW sells the insert for some obscene amount, but you can buy it as a Mercedes (it's Bosch) part for about $35. Head over to www.MyE28.com and do a search for it because I don't remember the part number. I already have one in my trunk ready to go.
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    Right on. Another cause of too much heat is a failure of the little temp sensor that CR mentions is down low (just above your left foot.) If that fails or if someone didn't hook up the vacuum line to it (that is designed to pull air over it so it can measure in cabin temps) then you will either have full heat or no heat (when you turn it to cold.) And mye28.com is where to go to get accurate info.
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    heater issue 533i E28

    OK guys (and maybe gals), thanks for all your answers, I will tackle all these suggestions. Am new to this forum and it is a great asset and it probably has already paid for itself. Cheers.
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    If it is the sensor, you should get NO heat if you set the knob to the fully cold position (all the way to the left), and you should get FULL ROASTING HEAT in any other position. If this is the case, make sure your interior temp sensor (drivers foot well) is plugged in, and that the vacuum line is attached to it (the vac line ensures air is constantly drawn across it for improved accuracy, is my understanding).

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