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George
George, BMW Technician
Category: BMW
Satisfied Customers: 1861
Experience:  BMW Master Technician over 20 years BMW Dealership Experience. BMW Auto Repair Shop Business Owner
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1996 BMW 328i: flushed..the heater core..cooling system..water pump

Resolved Question:

Hello...Not sufficient heat from 1996 BMW 328i....I have flushed the heater core and complete cooling system and have assured air is bled out of system.I have also installed a new heater control valve which I have verified that it works...But..I am getting no ground signal to the control ground wires on the heater control valve..The heat does work better when the engine is revved up ...I am suspecting a possible bad engine water pump,bad auxiliary pump (which I have yet to locate) and a bad heater control head,or a combination of these...Any help on this matter would be appreciated..Thank you,Jeff
Submitted: 5 years ago.
Category: BMW
Expert:  George replied 5 years ago.

George :

Did you check the thermostat to make sure it is not stuck open?

Customer:

Yes...Temperature guage rises normally and reads normal

George :

Are you there?

Customer:

yes

George :

Yes but did you check to see if it is stuck open by checking the hoses to see if they are heating up at the same time, or if the outlet side hose of the thermostat is staying colder until the thermostat opens.

Customer:

yes thermostat has been verified as working properly

George :

Are you 100% sure? Because the hot water valves even if no power or ground are supplied, their failsafe mode is full open position.

Customer:

Yes I understand that

Customer:

Is there a possibiity that it could be the water pump or auxiliary coolant pump?

George :

Do you have proper flow in the radiator?

George :

If it was the water pump you should be overheating.

Customer:

Not sure how to check that

George :

Is the fan clutch working properly?

Customer:

Thats what I thought...No overheating problem

Customer:

Yes fan clutch is working normal

George :

Can you tell me how you tested the fan clutch and also the thermostat?

Customer:

Could it be a bad auxilary coolant pump?

George :

Yes.

Customer:

the return hose was staying cool intill I ran the car and then it became warm..The engine tempersature guage also reads normal after 6 to 8 minutes after starting engine

George :

How long before the hose became warm?

Customer:

Let the engine idle about 10 minutes on a cool morning then took it a good drive around the block and then the return hose was good and hot

George :

I want you to check it the proper way I will give you the instructions.

Customer:

Thanks

George :

Let the engine get fully cold, once it is you will monitor the temperature of both of the hoses to the thermostat from cold. Once you start the engine rev the engine to 3,000 rpm's and hold it there while monitoring the temperature of the hoses, if the temperature is the same throughout this process the thermostat is stuck open and will need to be replaced. If the thermostat is good the outlet hose will stay colder then the inlet hose from 5 - 10 minutes of running the engine at 3,000 rpm's. While performing this procedure keep the heater/ac in the off position.

Customer:

Thanks I will try this....I have 2 more questions if the thermostat is good...Where is the location of the auxilary coolant pump and is there a way to test it?...Also because I am getting no ground signal to the heater control valve does this mean the control head is bad?..Also I have checked all fuses in this car

George :

Do you have a ground signal when the temperture settings are set to the full cold position? Remember the failsafe position of these valves are normally sprung open and power closed. So in the full hot position you will not have these signals present.

George :

Can I have the last 7 digits of your VIN #

Customer:

No ground signal in either positions...AV44251

Customer:

I actually tested the ground signal to the heater control valve because I suspected it to be staying in the full open position because the AC was not putting out cold air with a full charge of freon

George :

Give me a moment to look it up for you.

Customer:

sure...

George :

The auxiliary water pump is located on the drivers side of the engine compartment, about 1/2 way down the shoch tower area. You can follow the supply hose to the hot water valves back to it to see the exact location, bit it is not hard to spot. Located behind the airfliter box location, it has a metal body and black plastic end.

Customer:

Thank you...Now do you think I need to try a new control head since I am not getting any signal to the heater control valve?

George :

Before we get into that area we need to verify the thermostat operation, since it is obvious you have more then one problem going on here.

Customer:

Bad thermostat according to your test instructions...that is if the heater control valve being in the full open position made no difference...Appreciate your patience

George :

Not a problem.

George :

I recommend replacing the thermostat and then filling and bleeding the coolant system, then re-check the heater operation before doing anything else.

George :

Do you have the proper procedure for bleeding the cooling system?

Customer:

sounds good...Yes I have that procedure....

George :

Ok great.

Customer:

Thanks again

George :

Your welcome.

George and 2 other BMW Specialists are ready to help you
Expert:  George replied 5 years ago.

Thank you very much,

George

I will always leave positive feedback all I ask is for the same.

Expert:  George replied 5 years ago.

Thank you very much for the Bonus,

George

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