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Draining and Filling Cooling System
 
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Pelican Technical Article:

Draining and Filling Cooling System

Nick Czerula

Time:

1 hours1 hrs

Tab:

$60

Talent:

**

Tools:

Flathead and Phillips screwdrivers, 13mm socket

Applicable Models:

BMW 525i/xi Sedan (2004-07)
BMW 528i xDrive Sedan (2009-10)
BMW 528i/xi Sedan (2008-10)
BMW 530i/xi Sedan (2004-07)
BMW 530xi Wagon (2006-07)
BMW 535i xDrive Sedan/Wagon (2009-10)
BMW 535i/xi Sedan (2008-10)
BMW 535xi Wagon (2008)
BMW 545i Sedan (2004-05)
BMW 550i Sedan (2006-10)
BMW M5 Sedan (2006-10)

Parts Required:

Engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Cooling system parts lifespan increased

Complementary Modification:

Replace hoses

Engine coolant is the working fluid for the cooling system, which controls the operational temperature of the engine. Each combustion event inside your engine creates a lot of heat that the engine needs to be at a certain temperature to operate efficiently. Engine coolant maintains about the same temperature year round, regardless of ambient temperature.

A properly maintained cooling system must have a few things in order: adequate supply of coolant, a radiator that acts as a heat exchanger with the outside air, a fan or air flow source, a water pump to keep the coolant circulating, and a thermostat to regulate the engine at its optimum operating temperature. The coolant must also have the correct mixture and chemical compounds to promote heat transfer, protect against freezing, and also inhibit corrosion. To keep your BMW operating correctly, it's important to check the level, strength, and overall condition of the coolant on a regular basis. You also need to change the coolant before it degrades to the point where it doesn't perform its job adequately.

One failure mode associated with dirty coolant is known as electrolysis. Electrolysis occurs when stray electrical current routes itself through the engine coolant. The electricity is attempting to find the shortest path. Impurities in the coolant often generate a path of least resistance that the electricity travels across. The source of this stray electricity is often from electrical engine accessories, which have not been properly grounded. A missing engine or transmission ground strap can also cause the coolant to become electrified. Sometimes the path of least resistance becomes a radiator, a heater hose, or even the heater core. These components are often well grounded, and offer a ground path from the engine to the chassis by means of the semi-conductive path of the coolant.

Electrolysis can destroy your engine quickly. Although it's semi-normal to have very small amounts of voltage potential in your coolant system, values greater than about a tenth of a volt can start reactions between the coolant and the metal in your engine. In particular, electrolysis affects primarily aluminum engine components, resulting in pitting and scaring of the aluminum surface. This eating away of the metal can cause coolant system leaks, and in particular, radiator leaks around aluminum welds. Cast-iron components are also vulnerable, but typically the aluminum metal parts fail first. On BMWs in particular, electrolysis can be easily seen attacking aluminum cylinder heads. Figure 1 shows a picture of the thermostat area of a cylinder head that has been partially damaged by electrolysis. Notice how the aluminum has been eaten away, and eroded by the chemical/electrical reactions.

The process works somewhat like electrical discharge machines (EDM). These machines work by passing a large electrical current through metal, literally zapping away bits of material until nothing remains. Unfortunately, the electrolysis process works in a similar way, zapping bits of metal in proportion to the amount of electrical current passing through the coolant. A poorly grounded starter can literally destroy a radiator or head within a matter of weeks, depending upon how often the car is started. A smaller current drain, like an electric cooling fan may slowly erode components over many months.

How can you test for electrolysis? Other than actually seeing visible signs of erosion, you can perform a current flow test. Connect the negative terminal of a voltmeter to the chassis ground. Test for adequate continuity by touching another point on the chassis - the resistance should be near to zero. With the engine cold and running, submerge the positive probe into the coolant tank; making sure that the probe does not touch any metal parts. The voltage should be less than .10 volts. If not, methodically turn off or unplug each electrical accessory until the reading reads below .10 volts. Have an assistant switch accessories (like the A/C compressor, heater blower, etc.) while you measure the voltage.

If an accessory doesn't have an on/off switch, test it by temporarily running a ground from the housing of the accessory to the chassis. Ground each component and check the voltmeter. If the wire restores a missing ground connection to the accessory, then you've found a component with a faulty ground.

During this test, be sure to check the starter. Not only will a poorly grounded starter struggle to turn over the engine, it will also zap away tremendous amounts of metal in your cooling system. Watch the meter carefully when starting the engine. Any voltage spike will indicate a faulty ground connection.

Your BMW will lose a little bit of coolant here and there over time due to evaporation from the reservoir. However, a significant loss of coolant over a very short period of time almost certainly signifies a leak in the system. Sometimes a leak can be seen when you park the car overnight. Often the coolant leaks out and then evaporates while you're driving, leaving no tell-tale mark of coolant on the pavement. If you suspect a coolant leak, visually inspect all of the hoses, the water pump, the reservoir, and the radiator for seepage or the 'weeping' of coolant out of seams and gaskets. Check the seal on the radiator cap. Check that the radiator cap is fastened securely - the way the BMW radiator cap is designed makes it easy to make the simple, yet deadly mistake of leaving the cap cocked - allowing coolant to leak out when the engine is running. If you suspect a leak that you cannot see, a pressure test can verify the integrity of your system. See our tech article on cooling system leak testing.

Draining and filling your cooling system is a maintenance requirement as well as being part of many repairs. Be careful when working with coolant. It is poisonous and especially dangerous for pets. Clean all spills immediately and rinse the area with water.

6-cylinder engines used in BMW E60 automatic transmission models hold about 10.6 liters of coolant. Manual transmission models hold 10 liters.

8-cylinder engines used in BMW E60 automatic transmission models hold about 14.2 liters of coolant. Manual transmission models hold 13.8 liters.

In this article, I'll go over the steps involved with replacing the engine coolant on the BMW E60 models. Be sure to work with a cool engine and confirm the cooling system lacks pressure before opening the cooling system.

Lift and support the front of the vehicle safely. See our tech article on lifting your BMW E60.

Remove the front engine splash shields. See our tech article on engine splash shields removing.

Draining cooling system:
Draining cooling system: Working in the engine compartment, remove the expansion tank cap.
Figure 1

Draining cooling system: Working in the engine compartment, remove the expansion tank cap. Be sure that the engine has cooled before removing the cap. Cover the cap with a rag when opening. If there is still system pressure, this will lessen the spillage.

Draining cooling system: Place a five-gallon bucket (yellow arrow) under the left side of the radiator.
Figure 2

Draining cooling system: Place a five-gallon bucket (yellow arrow) under the left side of the radiator. Remove the radiator drain plug and drain the coolant (green arrow). You can use a pair of pliers to grab the petcock (if you are gentle). Allow the coolant to drain into the bucket. Once the coolant has stopped dripping, reinstall the radiator drain plug.

Draining cooling system: Most engines will have a 13mm drain plug (green arrow) on the right side of the block.
Figure 3

Draining cooling system: Most engines will have a 13mm drain plug (green arrow) on the right side of the block. Remove the drain plug and drain the coolant into the pan.

Filling and bleeding cooling system:
Filling and bleeding cooling system: Using a 50% distilled water 50% engine coolant mix, slowly fill the expansion tank until the coolant level indicator reaches MAX.
Figure 4

Filling and bleeding cooling system: Using a 50% distilled water 50% engine coolant mix, slowly fill the expansion tank until the coolant level indicator reaches MAX. The level indicator diagram is located on the tank (green arrows). Reference this when filling to obtain the correct level. The red float (red arrows) may stick. Be sure it is free before filling. Check the level of the float with the top of the fill hole (inset-red arrow). Trapped air is common when filling a cooling system and can result in improper cooling. It is important to bleed your cooling system each time the cooling system is serviced. Install the expansion tank cap and be sure all bleeder screws are tight. Turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and blower fan speed to Low. Start and run the engine at idle until it reaches operating temperature and check the cooling level, top up as needed. When done, check the cooling system for leaks. On late 6-cylinder models with electric coolant pumps: Install the expansion tank cap. Turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and the blower fan speed to Low. Press the accelerator pedal to the floor and hold it down for ten seconds. Run the electric coolant pump for about 12 minutes to circulate coolant and bleed air from the cooling system. Once the pump has run the cycle, check the level of coolant in the expansion tank and adjust it as needed. Start and run the engine at idle until it reaches operating temperature and check the cooling system for leaks.

Filling and bleeding cooling system: When tightening the reservoir cap, tighten it all the way.
Figure 5

Filling and bleeding cooling system: When tightening the reservoir cap, tighten it all the way. Then check that the arrows (green arrows) are aligned. This ensures the cap is on correctly.

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Comments and Suggestions:
Sm76 Comments: I turn the ignition on with the a/c on the hottest ,i pressed the pedal for 12 or 15 seconds and i went to check if the water pump was running and it wasnt,i did it with the expansion tank cap on and off and still did the same,i started the motor and without the expansion tank cap you can see the water flowing from the upper hole that the expansion tank has and that has a hose that came from the radiator i guess,i didnt do coolant service i was changing the upper radiator hise that goes from the radiator to the water pump and i was trying to bleed the system but apparently or im doing something wrong or my car has something bad,i ran the car for 3 days in a row and i entered the hidden menu and make the twmperature of the coolant visible so i can check if the car was overheating and it was running always between 103c and 104c,honestly i need help
November 11, 2016
  Followup from the Pelican Staff: If coolant is coming out of the small hose in the reservoir, the pump is running. Possible your vehicle has an issue or sequence to activate the pump is not correct.

If there isn't a check engine light, the pump is likely OK. Most times it will set a fault code. Try running the engine until warm with the cap off. Do not allow coolant to overflow, shut engine down if level begins to rise. Once warm, shut off and allow to cool. The trapped air should escape this way. - Nick at Pelican Parts
 
Sm76 Comments: I have a 2008 550i and im doing the bleeding process exactly like it says for 2008 550i,i leave open the expansion tank ,turn the ignition on with the temperature of the ac in hot and the fan in low,i pressed the pedal for 12 seconds and when i go to check in the expansion tank if water is flowing from tje small top hose it doesnt ,i can hear the pump trying to start but i dont see any movement of water ,then i turn on the car and the water start flowing from the small upper hose of the expandion tank,please help me because i dont know if im doing it right or i need to replace something
November 8, 2016
  Followup from the Pelican Staff: The pump should run. Was there a problem, or were you just performing a coolant service?

Try to run the pump with the expansion tank cap on. - Nick at Pelican Parts
 
lucas Comments: I have a bubble in my reservoir tank i think thats why I am getting warm air not hot out of my vents how do I get this to go away 550i 2010 bmw
October 26, 2016
  Followup from the Pelican Staff: Filling and bleeding cooling system: Using a 50% distilled water 50% engine coolant mix, slowly fill the expansion tank until the coolant level indicator reaches MAX. The level indicator diagram is located on the tank (green arrows). Reference this when filling to obtain the correct level. The red float (red arrows) may stick. Be sure it is free before filling. Check the level of the float with the top of the fill hole (inset-red arrow). Trapped air is common when filling a cooling system and can result in improper cooling. It is important to bleed your cooling system each time the cooling system is serviced. Install the expansion tank cap and be sure all bleeder screws are tight. Turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and blower fan speed to Low. Start and run the engine at idle until it reaches operating temperature and check the cooling level, top up as needed. When done, check the cooling system for leaks. On late 6-cylinder models with electric coolant pumps: Install the expansion tank cap. Turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and the blower fan speed to Low. Press the accelerator pedal to the floor and hold it down for ten seconds. Run the electric coolant pump for about 12 minutes to circulate coolant and bleed air from the cooling system. Once the pump has run the cycle, check the level of coolant in the expansion tank and adjust it as needed. Start and run the engine at idle until it reaches operating temperature and check the cooling system for leaks. - Nick at Pelican Parts  
pat Comments: hello
I have a 2005 530, no temp problems and thermostat seems ok but I do not get max heat in winter anymore, coolant is full but I also never changed it. I know there is a switching device for water flow to heat core on left wall and a valve under the dash, any way to verify their operateing well? or some other cause you may suggest?

thanx
October 2, 2016
  Followup from the Pelican Staff: Check if the valve allows hot coolant to flow to the inlet hose to the heater core when heat is ON. Use an infrared temp gun to measure increased hose temp as you turn heat on. - Nick at Pelican Parts  
Gino Comments: I have a 2009 535i xDrive Wagon. Where is the block drain plug, is it difficult to access? The article mentions the right side. The right side is the passenger side crrect? Thank you for your help.
September 6, 2016
  Followup from the Pelican Staff: Yes, right side when seated in vehicle. - Nick at Pelican Parts  
Justin Comments: My model is the M54B33. I have 2 questions. It looks like this engine does not have the engine block drain plug, is that correct? Also does this engine has an electric pump? If there is no engine block drain plug can I just drain the coolant from the radiator drain plug? Thanks Justin
August 27, 2016
  Followup from the Pelican Staff: M54 should have a block drain. M54 doe snot have an electric pump. - Nick at Pelican Parts  
MadJake Comments: I have a 2004 E60 545i. The 10-second-fuel-pedal-electric-waterpump-procedure does not come on on my car, and I can not find any of the plastic star-shaped bleeding screws anywhere on the cooling system. How will I bleed this car ?
May 4, 2016
  Followup from the Pelican Staff: use a vacuum bleeder. - Nick at Pelican Parts  
Ccc Comments: Hello Pelican,
My coolant light goes on for 3 minutes whenever I start the car and then goes off. I checked the coolant expansion resovior and noticed that the red float level indicator, as in Figure 4., is no longer there. This is after I took the car in for service. Looking into the resovior I can see the sort of triangular floating base the red dipstick like indicator use to be attached to. 1 Can I just buy the level indicator part or do I have to replace the entire resovior? 2 Is the missing level indicator the cause for the coolant fluid light to go on for 3 minutes every time I start the car? Thank you! Ccc
March 20, 2016
  Followup from the Pelican Staff: The float is only a float, not the level switch.

See this article, http://www.pelicanparts.com/techarticles/BMW-E60/22-WATER-Coolant_Expansion_Tank_Replacement/22-WATER-Coolant_Expansion_Tank_Replacement.htm the level switch is shown in step: 7


You can replace just the switch.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Joe O Comments: Does 2006 550i have a standard water pump or electric water pump?
March 16, 2016
  Followup from the Pelican Staff: mechanical pump. See: http://www.pelicanparts.com/techarticles/BMW-E60/10-WATER-N62_8_Cylinder_Coolant_Pump_Replacement/10-WATER-N62_8_Cylinder_Coolant_Pump_Replacement.htm

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
td Comments: 2006 530xi n52, wagon, can't turn on electric water pump to bleed the coolant system. Tried...key on not started, both driver & pass heat controls full hot, automatic then low fan speed, also just low fan speed and no luck turning electric water pump on.
February 11, 2016
  Followup from the Pelican Staff: The water pump may be faulty. Check for fault codes and activate the pump using a BMW scan tool. - Nick at Pelican Parts  
Hammer Comments: Yes...where might the bleeder be on my 2007 550i e60...can't see it around the tank ?
February 3, 2016
  Followup from the Pelican Staff: Might be on the plastic neck of the radiator hose. - Nick at Pelican Parts  
B_i_g_M_a_n Comments: Help!!! Where are the bleed screws on a 2008 BMW 535i? I need to put coolant in the car and bleed the system. It's going through Coolant really fast which results in overheating. I never see any coolant under the car when parked though. I only seem to go through the coolant quickly when driving.
December 23, 2015
  Followup from the Pelican Staff: You could have a leak. I would pressure test the cooling system. If the system will not hold pressure and there are no external leaks the head gasket may be faulty. - Nick at Pelican Parts  
James Comments: I have a 2010 535. I was wondering where the radiator drain plug was on that model? Also I heard you need a battery charger to bleed the cooling system properly. Is that true? Thanks, James
December 9, 2015
  Followup from the Pelican Staff: Fig 2 shows the drain plug.

A vehicle power supply is not necessary to bleed the system, unless you have a weak battery. - Nick at Pelican Parts
 
siease Comments: hi guys can anyone tell me how often do i have to top up coolant on e60 545i and also advise how to bleed it.

your assistance will be appreciated

here is my email: sieasem@gmail.com
November 14, 2015
  Followup from the Pelican Staff: You should only have to top up if there is a leak or during a major wervice. - Nick at Pelican Parts  
Dan Comments: On a BMW 530I, the cooling fan pulses on and off when the engine is started and has not had a chance to warm up. And then the overheat light comes on after driving it approximately 5 minutes. I'm getting a 597 OBD code which suggest changing the thermostat which I did. Still having the same problem. Does this sound like bad sensors or water pump? Thanks, Dan
November 12, 2015
  Followup from the Pelican Staff: The code indicates a faulty thermostat. That may be the issue. - Nick at Pelican Parts  
BNG Comments: Just want to clarify concern @HP.

Nick I'm afraid you didn't catch the question of HP. Of course 550i have its own second/auxiliary electric pump which is used to bleed colling system. BMW part #64 11 6 988 960.
If HP correctly trying initiate aux pump and it doesn't work then maybe it is need to change to pump or at least check the connections..
November 7, 2015
  Followup from the Pelican Staff: The aux pump shouldn't prohibit from bleeding, but yes. Good point if faulty, it will not circulate coolant through the heater core as designed. - Nick at Pelican Parts  
HP Comments: Does 2007 e60 550i have the electric pump? I tried to active the electric pump to bleed the cooling system and pump wasn't on. Does it mean I need to bleed the system in the conventional manner; run the engine at idle
September 22, 2015
  Followup from the Pelican Staff: Your model have a standard water pump. You will want the heat on high when bleeding. Fill system, then run engine. - Nick at Pelican Parts  
Mandorake Comments: If you're replacing the expansion tank on a 2010 550i V8, do you have to bleed/replace all the coolant or can you just replace it and refill the expansion tank?
August 11, 2015
  Followup from the Pelican Staff: Just refill and bleed what was in the reservoir. Some coolant may leak out of the engine, so be prepared with a little extra coolant. - Nick at Pelican Parts  
AM Comments: Please let me know where to access engine drain plug for V8 550i2008 N62 engine? Is it on the left side? I removed splash shield and reinforcement plate but nowhere to be found. If you could add a picture for V8 model would be great. Thanks.
July 5, 2015
  Followup from the Pelican Staff: It's on the left side of the crankcase, near the steering coupler. - Nick at Pelican Parts  

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