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BMWDoc, Independent BMW shop owner
Category: BMW
Satisfied Customers: 6457
Experience:  20 years of experience working with BMW's. Independent European shop owner and technician.
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yellow and red thermostat warning

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yesterday a yellow and a few seconds later a red thermostat warning light came on while i was on the interstate, i start losing some power while getting off the exit but a few seconds later it picked back up power. I let my car cool down for 45 mins and checked the coolant, i added about 25% to 30% of the coolant so my coolant was not completely low. I started my engine back up again and the lights did not come back on and i was able to travel on the interstate another 200 miles. What are some of the possible issues? i am nervous about getting back on the road because i have about 300 miles to travel back home.

BMWDoc :

Hello, I'm Jason. I will do my best to answer your question quickly and accurately using the information you have provided.

BMWDoc :

by far, the most common cause of this problem is a failed water pump

BMWDoc :

if this is the case and you keep driving, you will likely cause major damage to your engine

BMWDoc :

I'm sure this isn't the answer you were hoping for, but I'm trying to do my best to keep you from causing further issues

BMWDoc :

I can offer you a quick test that you can do yourself to see if the water pump functions

BMWDoc :

here's how you can check water pump function

BMWDoc :

  1. Switch on ignition.

  2. Set heater to maximum temperature and turn fan down to lowest speed.

  3. Press accelerator pedal for 10 seconds to floor. Engine must not be started.

  4. The venting procedure is started when the accelerator pedal is pressed and takes approx. 12 minutes.(Electric coolant pump was activated and shuts down automatically after approx. 12 minutes).

BMWDoc :

open coolant cap and check to see if coolant is circulating

BMWDoc :

if it's not, the pump needs to be replaced

Customer: replied 4 years ago.

how much it cost to replace a water pump for my vehicle

The pump itself, and replacement bolts are about $600 from a dealer. Labor to replace is 3-3.5 hours. Total job usually runs right at $1000
Customer: replied 4 years ago.

since my car is a BMW is it okay to get something like the water pump replaced at a place like Pep Boys etc or this is something that needs to be done by the dealer?


I recommend against a chain shop doing this job. You don't need a dealer, but a shop familiar with BMW is pretty important.
Customer: replied 4 years ago.

okay i just followed the steps above and nothing happen...meaning the heater did not come on at all unless i start the engine....please help...maybe im doing somehting wrong.


i inserted the key into the ignition and only the radio came on?

The ignition needs to be on, meaning all dash lights on. Not running though.
Customer: replied 4 years ago.

also will the themorstat light come back on if my car is overheating again? im about to try the steps above again

Yes, the light will come back on if it overheats
Customer: replied 4 years ago.

i have followed your procedures and nothing is happening, do i need to start the engine in order to follow the process above and then cut the engine off otherwise...i have a 2006 BMW Xi with a push key and start button

If the dash lights are coming on, and you have the hood up after doing the accelerator pedal procedure, and you don't hear the pump running or see coolant flow through the tank, you need a water pump. Again, this is an extremely common problem, and driving the car without a functioning water pump will result in about a $10k repair bill.
Customer: replied 4 years ago.

the dash lights are not coming on when i follow the procedures above, only the radio comes on. the dash lights and heater/AC only come on after i start the car?


Push the key into place. Without your foot on the brake, press the start button briefly. This will turn all systems on without actually starting the car.
Customer: replied 4 years ago.

okay will try that

Customer: replied 4 years ago.

okay i am now waiting the 12 minutes but i noticed that the fan has not come on yet or does it suppose to come on with this process?

Please follow what I have been saying. You're not listening for a fan. You don't need to wait 12 minutes. After doing the accelerator thing, the water pump, if it's functioning, should start. You need to have the hood open, and cap off of the coolant tank. Listen for the PUMP, not a fan, and look into the tank to see if coolant is flowing. If the water pump is not humming (it's quite apparent), and coolant is not flowing, you need a water pump.
Customer: replied 4 years ago.

okay here is what i saw after clarification from the steps above:


-i took the cap off

-i performed the procedures as indicated above

-i saw where small stream of antifreeze was flowing into the tank and occasionally a stream of antifreeze etc., would also stream out from the dip stick....this went on for about 12 minutes and afters it stoped

-i noticed a very low humming noise when the above was taking place but it was very low


when you say coolant flowing i am assuming you are talking about your last comment above and my observations in step 3 above.


i am not sure how loud the humming is suppose to be (like a fan etc.,) but i did here humming but again it was extremly hard to hear but i did hear it and i am not in a quiete location

Ok, thanks. Now, the stream should be pretty steady and strong. The water pump can "partially" fail, meaning not move nearly enough water that the engine needs to stay cool. I still recommend not driving it for any distance due to the potential for catastrophic damage. I don't believe that I can offer any further information beyond this, and the car should be repaired before repairs are made.
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