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Pelican Technical Article:

Flushing Your Coolant

Nick Czerula

Time:

1 hour1 hr

Tab:

$50

Talent:

*

Tools:

Set of sockets (13mm could vary), 6mm Allen bit, Flathead and Phillips screwdrivers, Eye protection

Applicable Models:

BMW E46 3-Series (1999-06)

Parts Required:

Engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Cooling system parts lifespan increased

Complementary Modification:

Replace your water pump

BMW E46 cooling system components include:

  • Radiator and coolant overflow tank
  • Belt driven coolant pump bolted to the front of the engine block
  • Electric cooling fan attached to rear of radiator -- the cooling fan is controlled by the engine control module (ECM) via an output final stage
  • Automatic transmission models: Belt driven fan attached to front of coolant pump -- viscous clutch controls fan speed based on engine compartment temperature and rpms
  • Electrically heated ECM-controlled thermostat
  • Automatic transmission cooler (heat exchanger)
  • Heater valve and heater core (for climate control)
  • Coolant level sensor inside expansion tank
  • Coolant temperature sensor at cylinder head
  • Radiator outlet temperature sensor
  • Coolant hoses and lines

Engine coolant typically consists of a 50%-50% mix of ethylene glycol and water with various additives (example: water pump lubricant). Hot coolant eventually dissolves various internal engine parts, particularly as it ages and mixes with impurities. The manufacturer therefore recommends strongly that you drain and flush the cooling system approximately every two years. Be careful when working with ethylene glycol coolant. It is poisonous and especially dangerous for pets. Clean all spills immediately and rinse the area with water.

Draining and filling your cooling system is not only a maintenance requirement but also a prerequisite of many repairs. Engines used in the BMW E46 models hold about 8.5 liters of ethylene glycol- water mix, while M3 E46 models hold 10 liters.

In this article, I will go over the steps involved with replacing the engine coolant on the BMW M52 and M54 engine. Be sure to work with a cool engine and confirm that the cooling system lacks pressure before opening the cooling system.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you are working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

In this article, I will go over the steps involved with replacing the engine coolant on the BMW M52 and M54 engine. Be sure to work with a cool engine and confirm the cooling system lacks pressure before opening the cooling system. If you are looking for more Technical Articles to diagnose or repair cooling issues please visit our E46 page.

Lift and support the front of your vehicle safely, refer to our Pelican Parts Technical Article on Jacking Up Your BMW. Remove the engine splash shield. See Pelican Parts Technical Article on Removing the Engine Splash Shield and Reinforcement Plate.

Draining the cooling system:
Working at top of radiator, loosen the coolant expansion tank bleeder screw (green arrow).
Figure 1

Working at top of radiator, loosen the coolant expansion tank bleeder screw (green arrow). Place a three gallon bucket under the left side of the radiator.

Working at the lower left side of your radiator, remove the radiator and coolant expansion tank drain plugs (green arrows).
Figure 2

Working at the lower left side of your radiator, remove the radiator and coolant expansion tank drain plugs (green arrows). Allow the coolant to drain into the bucket. Once coolant has stopped dripping, reinstall the radiator drain plugs. Place an empty three gallon bucket under the right side of your engine, near the suspension sway bar. Working at right side of engine block near engine mount bracket, remove the engine block drain plug.

Some engines will have a 13mm hex block drain plug.
Figure 3

Some engines will have a 13mm hex block drain plug.

Some engines will have a 6mm Allen block drain plug.
Figure 4

Some engines will have a 6mm Allen block drain plug. Allow coolant to drain into the bucket. Once coolant has stopped dripping, reinstall block drain plug.

Filling cooling system: 
Using a 50% distilled water 50% engine coolant mix, slowly fill the expansion tank (green arrow) until the coolant comes out of the expansion tank bleeder screw (blue arrow).
Figure 5

Using a 50% distilled water 50% engine coolant mix, slowly fill the expansion tank (green arrow) until the coolant comes out of the expansion tank bleeder screw (blue arrow).

Bleeding cooling system:

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. 
Working at top of the radiator, loosen the coolant expansion tank bleeder screw (green arrow).
Figure 6

Working at top of the radiator, loosen the coolant expansion tank bleeder screw (green arrow). Turn the ignition ON (do not start engine), set the temperature controls in vehicle interior to full warm and blower fan speed on low. Slowly fill the expansion tank until coolant is coming out of the E46 expansion tank bleeder screw and is free from bubbles. Once coolant is free of bubbles, tighten the expansion tank bleeder screw. Start and run your engine at idle until it reaches operating temperature.

Shut the engine OFF and allow it to cool.
Figure 7

Shut the engine OFF and allow it to cool. Check the coolant level in expansion tank. Top up coolant until level indicator is at MAX. Once at MAX, your cooling system is full. Min and Max levels are embossed on the coolant expansion tank for reference (yellow arrow).

Reinstall the engine splash shield and check the cooling system for leaks.

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Comments and Suggestions:
Mort Dog Comments: 03 330I E46 ZHP anyone else having trouble reaching and getting leverage on the 13mm hex drain? I can get the wrench on, but can't turn even with different extenders...
November 25, 2016
  Followup from the Pelican Staff: Try a six point socket on a 1/2 drive ratchet. - Nick at Pelican Parts  
Jonny Comments: 2003 525i Coolant light comes on going up and down hills.Also does not generate much heat .Plan on changing thermostat with BMW part ,flushing system with prestone and changing anti freeze with zerex GO5 .Does that sound like a good idea? Thanks
November 17, 2016
  Followup from the Pelican Staff: Yes. You may have a slightly low coolant level contributing to the light. I would also check for coolant leaks. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
grapedog Comments: 2001 325ci, AT. I've never been able to get all the air out of my system after a coolant replacement task, leading to the temp gauge running higher than normal. One technique that worked well on my Porsche 944 was to get the car up to operating temp after following all the directions for refilling the cooling system found on this page, then open the bleed screw on top of the expansion tank so that hot coolant and any remaining air can escape. Yes, you may burn yourself if not careful, but this has been the only way I can get the new coolant to keep the engine in normal operating temps. Just FYI.
August 23, 2016
  Followup from the Pelican Staff: Thanks for sharing your process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
charloe Comments: My belt and pulley went bad and fell off..this led to the pulling out of my radiator upper hose thereby spilling water...I did a refill and followed the bleeding process;but my coolant level keeps going down after every 6 miles. What could be wrong?
August 2, 2016
  Followup from the Pelican Staff: COolant loss somewhere. 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  
Eddie Comments: Can I clean the coolant system with a product like Preston Radiator Flush and cleaner on my 325i 2006?. I suspect someone once put oil in the coolant tank. Sludge inside the side wals of tank.
July 14, 2016
  Followup from the Pelican Staff: I would advise against it. Just run water through the system. If the radiator or tank look dirty, take it to a radiator shop to have it cleaned. - Nick at Pelican Parts  
James Comments: Thanks for the quick reply. When it overheats, the upper radiator hose is hard as a rock. I've read that this means bad thermostat. You're thoughts? Will draining the radiator/tank and refilling possibly help get rid of the air pocket? Car has 88K miles, in pretty good shape. Thanks again Nick
July 8, 2016
  Followup from the Pelican Staff: hard hose or hoses just means high temp. It could be. You'll have to check for fault codes and check if the thermostat in opening, temp changes at hoses.

You can try bleed procedure again or drain system and use a vacuum bleeder. - Nick at Pelican Parts
 
James Comments: Recently replaced AC condenser so cooling system was empty for several days. Coolant is coming out at the bleed screw. Runs fine at idle, but if I drive it for 5 miles or so and then stop and it quickly overheats. Let it cool down, check coolant level, bleed screw both are good. Also, when cool It will idle forever with no problem, but as soon as it's driven, quick spike of temp gauge. Any ideas or suggestions? Thanks John
July 8, 2016
  Followup from the Pelican Staff: Air could still be trapped, if not you have a fault thermostat or water pump. Something could be seized from sitting dry. - Nick at Pelican Parts  
Mathi Comments: Can't find the engine drain plug. Could you send a more zoomed out picture of were it is? BMW E46 M53 engine
June 16, 2016
  Followup from the Pelican Staff: We don't have M53 engines in the US, you may have the info for your vehicle mixed up. - Nick at Pelican Parts  
jay Comments: hi followed your steps and I had to add 1 litre next day on top up. is that normal? Car never never over heats.
June 2, 2016
  Followup from the Pelican Staff: It's possible you didn't get all the air out first time around. That would be considered normal. - Nick at Pelican Parts  
Skomo Comments: I want to replace oil cooler from e46 318i 2004 model and flush the cooling system can you please assist me
May 18, 2016
  Followup from the Pelican Staff: Follow the instruction sin this article for replacing the coolant.

For the oil cooler, see our tech article on radiator replacing:

http://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E46/34-WATER-Radiator_Replacement/34-WATER-Radiator_Replacement.htm - Nick at Pelican Parts
 
Skomo Comments: I have e46 318i 2004 model I want to change the oil cooler and flush the cooling system can you please advise me what to do I never flush the cooling system.
May 18, 2016
  Followup from the Pelican Staff: Follow the instruction sin this article for replacing the coolant.

For the oil cooler, see our tech article on radiator replacing:

http://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E46/34-WATER-Radiator_Replacement/34-WATER-Radiator_Replacement.htm - Nick at Pelican Parts
 
Sam Comments: @nick it says fill up until come out bleeder arrow blue then it says turn heater on and fill until it comes out uf you fill it until ut comes out before then wont ut just spill everywere since its fill to were it comes out b4 you bleed it
April 29, 2016
  Followup from the Pelican Staff: That is the BMW procedure. The air escapes first, then coolant. You close the bleeder when air is done escaping. - Nick at Pelican Parts  
Sam Comments: It doesnt make sense it says fill it up until its coming out the bleeder arrow and once the heaters on fill the radiator more wouldnt it be full already since you have not started the car
April 29, 2016
  Followup from the Pelican Staff: No, there will be air in the system. - Nick at Pelican Parts  
dmv Comments: Hi, I've just completed a coolant flush along with replacing the water pump and thermostat but now the car has developed a leak around the expansion tank drain plug. To remove the old plug, is the idea to just pull it out and destroy the old plug in the process or is there a "less violent" option?
April 4, 2016
  Followup from the Pelican Staff: You will have to get the old plug out, replace it and the sealing washer. If stuck, there is no easy way to get it out. You will likely have to destroy the plug. Be prepared to replace the tank.

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
 
thurston88 Comments: I did the flush as directed. So i could replace the thermostat. Finished and it only took about a gallon and a half. Was i supposed to turn the heater on during the drain the instuctions didnt say so. Havent refilled it as the engine is still hot.
March 27, 2016
  Followup from the Pelican Staff: The bleeding procedure at step 6 instructs you to turn heat on. See the final two steps for bleeding. - Nick at Pelican Parts  
Northy7 Comments: So should I turn ignition on and heater on full when draining the engine to insure the heater core drains properly?

Thanks

Adam
March 27, 2016
  Followup from the Pelican Staff: No, that is not necessary. - Nick at Pelican Parts  
srl Comments: working on a 04 325xi. do the drain plugs for the radiator and expansion tank have to be replaced every time they are taken out? also does the engine block drain plug have to be replaced as well or just the sealing washer? thanks and always great info.
March 22, 2016
  Followup from the Pelican Staff: No, but most times the sealing O-rings /washers should be replaced. - Nick at Pelican Parts  
Mal Comments: How often should i replace my coolant?
January 17, 2016
  Followup from the Pelican Staff: depends on the vehicle. Either 30k, 60, 70k, or 100k miles. - Nick at Pelican Parts  
gp Comments: Notes for some of the above:

@ozEboy: green coolant means your old coolant is still in there, if they don't remove the engine drain only half of the fluid will come out, so the coolant will be green-blue instead of green or blue. If still green, they didn't do it, or they used their own coolant instead of yours. Probably the wrong stuff if so...

@scottyboy: Coolant left in the bottom of the overflow tank is normal if you do not remove the engine drain plug s well as the radiator drain plug.

@Leo, Your BMW's coolant should be blue BMW type, sometimes referred to as 'Cool Blue', common with some Merc and Volvo spec fluids. Some aftermarket fluids that are Orange generic Glysantin G48, yellow Prestone and Zerex G05- these are the same spec HOAT coolants. Do not use anything else, it will eat away at plastic or metal parts and cause costly failures.

@Seelot: Prestone yellow is known to be good where BMW specifies its G48/Cool Blue.

@Tyz325ci: Heater core will drain naturally through the engine drain if the ignition is on and the cabin temp control is set to maximum.

All: BMW e46 323, 325, 328 & 330i all have a capacity of 8.4L. Never fill your BMW with concentrated 100% coolant straight from the bottle as it will not mix with teh engine coolant for a very long time and may blow the expansion tank in some situations. Best to aim for 33% mix with water- I usually fill with about a 40% mix and top off with pure water ONLY in warm climate cars. In a freezing climate, using a stronger concentration max 50% will protect the system from freezing to lower temperatures. Note: Coolant will not transfer heat as effectively at high concentrations, so only go above 33% if you need extreme protection from freezing cold temperatures.
January 16, 2016
  Followup from the Pelican Staff:

Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
 
o2eZy Comments: just need info on this
BMW coolant is blue and is 1.1 mix
booked in E46 for coolant change and supplied 4.5ltr BMW coolant
after coolant change the coolant is still green ..so question ..would the BMW coolant change color after 30 miles
running or the coolant was not changed
December 18, 2015
  Followup from the Pelican Staff: Coolant should not change color, it remains blue. - Nick at Pelican Parts  
Tyz325ci Comments: How do you drain the coolant from the heater core? Seems like there would still be some coolant left in the core and the lines?
November 2, 2015
  Followup from the Pelican Staff: There likely will be. The only way to be sure it all gets out, remove the heater cores hoses and flush the heater core with clean coolant. - Nick at Pelican Parts  
Graham Comments: Hi started my coolant replacement but noticed the head of my drain screw on the radiator has been broken off at some point. Any tips or recommendations on how to remove screw.
Thanks Graham
October 16, 2015
  Followup from the Pelican Staff: First get a new drain plug. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.


Then, screw in a screw (into the old plug), then use the screw to remove it. - Nick at Pelican Parts
 
Zambian Comments: Hi nick. I own a bmw 318i e46. Assuming all cooling system leakages are sealed. How long is a fully filled cooling system supposed to last in terms of MILES covered, before the radiator light comes on the dash, to indicate LOW COOLANT?

Regards
October 8, 2015
  Followup from the Pelican Staff: OOF - impossible to know. I would suggest replacing coolant at 60k and hoses at 100k. The low coolant light may be due to a fault sensor in the reservoir. - Nick at Pelican Parts  
Joe Comments: Hi when at the end I have to tight the bleeder screw do I have to do it all the down or just hand tight? Thanks
September 12, 2015
  Followup from the Pelican Staff: Which bleeder screw?

Most times, you will be tightening bleeders by hand. - Nick at Pelican Parts
 
Leo Comments: Hi, I have a 1998 BMW E46 318i, I am not sure what colour of antifreeze to use, there is a dilema on using in between red and green coolant? Which one is the correct ?
July 29, 2015
  Followup from the Pelican Staff: What do you mean the difference?
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
 
Edgar Comments: Previous owner said he put in non BMW coolant. I want to flush the whole system and replace it with BMW coolant. Will this procedure work?
July 27, 2015
  Followup from the Pelican Staff: Yes, just be sure the cooling system is completely drained before filling. - Nick at Pelican Parts  
Ceelot Comments: Which coolant for a 2002 bmw 325 i
Is prestone ok?
July 24, 2015
  Followup from the Pelican Staff: BMW coolant is best, likely what is in there now. - Nick at Pelican Parts  
Richie Comments: I recently had a leak I could not pin point on my cooling system for my 2004 325i. Kept getting a low coolant light and then a engine service light for a coolant problem. Decided to replace the water pump, thermostat, resovoir tank, and upper n lower radiator hose myself. Cleared the error codes and still over heating. My AC starts blowing hot air as soon as the engine starts over heating. I'm stumped in the problem. Richie
May 29, 2015
  Followup from the Pelican Staff: Is there an external leak you can see? Coolant on the ground 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  
LORI Comments: CAN YOU PLEASE TELL ME WHICH ANTI-FREEZE I SHOULD USE IN MY 2005 BMW 3251.
THANK YOU SO MUCH FOR YOUR HELP!
May 8, 2015
  Followup from the Pelican Staff: BMW factory coolant.

Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
geoffy Comments: replaced radiator filled with water had no coolant all fight for about a week water light came on topped up water the top hose blow were it connects to the filla bottle
April 15, 2015
  Followup from the Pelican Staff: I would replace the faulty hose, be sure the coupler it attaches to isn't broken. - Nick at Pelican Parts  
So Cal Man Comments: I am going to order the coolant from here to do this, but I noticed my indicator is broke just below where the rounded tip used to be, question is, does that come with the coolant level sensor? that way I have everything I need. thanks
December 14, 2014
  Followup from the Pelican Staff: What vehicle are you working on? It may or may be part of the reservoir. Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 
arthury Comments: How much replacement coolant to buy for a 325i?
September 3, 2014
  Followup from the Pelican Staff: Not sure what year you have, but for the vheicles covered in the article you commented on, it is mentioned in the first paragraph: http://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E46/32-WATER-Flushing_Your_Coolant/32-WATER-Flushing_Your_Coolant.htm
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. Engines used in the BMW E46 models hold about 8.5 liters of coolant while M3 E46 models hold 10 liters. - Nick at Pelican Parts
 
Nick Comments: When you open the coolant cap with the engine off does the expansion tank suppose to look full or empty when you look in the coolant tank?
July 13, 2014
  Followup from the Pelican Staff: It should be within the correct level. - Nick at Pelican Parts  
Jazzy Comments: Coolant flush shows the 325 BMW series.
What should I look for in my 2004 330 Ci BMW when doing a Coolant Flush ?
Any info will sure be appreciated.
Regards,
Jazzy
June 5, 2014
  Followup from the Pelican Staff: It is the same procedure. - Nick at Pelican Parts  
miko Comments: Did you remove both drain plugs? The expansion tank drain and radiator drain?
April 22, 2014
  Followup from the Pelican Staff: Yes. - Nick at Pelican Parts  
scottyboy Comments: I attempted to flush my coolant this past weekend out of my e46 because the coolant light has been coming on, and the fluid hasn't been flushed in awhile. I followed your directions up to the point of removing the bottom drain plug. Some fluid came out, but when I looked down into the radiator, there was still enough fluid to keep the indicator floating with the end of it sticking out of the radiator. I didn't go any further to drain the engine block because I was concerned there may be another issue. Your thoughts?
December 3, 2013
  Followup from the Pelican Staff: It sounds like there is some crud floating around inside the radiator and maybe now it's blocking the drain hole. Use a very thin piece of wire to carefully poke up into the drain hole and see if you can clear the blockage. - Nick at Pelican Parts  

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