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Pelican Technical Article:

Radiator Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$300

Talent:

***

Tools:

Set of sockets, wrenches, screwdrivers

Applicable Models:

BMW 323Ci Coupe/Conv (1999-00)
BMW 323i Sedan/Wagon (1999-00)
BMW 325Ci Coupe/Conv (2001-06)
BMW 325i/xi Sedan/Wagon (2001-06)
BMW 328Ci Coupe (1999-00)
BMW 328i Sedan (1999-00)
BMW 330Ci Coupe/Conv (2001-06)
BMW 330i/xi Sedan (2001-06)

Parts Required:

Radiator, hoses, engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Car will cool down again

Complementary Modification:

Change expansion tank, radiator hoses, thermostat water pump

Maintaining the cooling system so that the engine does not overheat is a significant step toward getting engine longevity. There are many components in the BMW E46 cooling system:

  • 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

When a radiator begins to fail, you'll notice that the car tends to overheat at high engine speed, such as driving on the highway. When you accelerate, the engine temperature will rise. When you idle the engine, it will return to normal range. Now, this is not always indicative of a failing radiator, but a good starting point. Of course, there are also leaks that occur at the side tanks of the radiator. In addition, the plastic side tanks can crack, causing major loss of engine coolant. 

In this article, I'll go over the steps involved with replacing the radiator on the BMW E46 models.

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're 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.

If you are looking for more Technical Articles to diagnose or repair cooling issues please visit our E46 page.

Start with a cool engine. Squeeze the radiator hose and check that it is soft, as this is a quick way to determine if the cooling system has pressure. Next, cover the coolant expansion tank cap with a rag and slowly remove it to relieve the cooling system pressure. 

Drain the cooling system. See our Pelican Parts Technical Article on Flushing Your Coolant.

Remove the cooling fan shroud. See our Pelican Parts Technical Article on Replacing Your Cooling Fan Shroud.

Remove the coolant expansion tank. See our Pelican Parts Technical Article on Replacing Your Coolant Expansion Tank.

Working at the lower right side of the radiator, disconnect the radiator outlet temperature sensor electrical connector (green arrow).
Figure 1

Working at the lower right side of the radiator, disconnect the radiator outlet temperature sensor electrical connector (green arrow).

Next, using a flathead screwdriver, release the lower radiator hose retaining clip by prying it up (green arrow).
Figure 2

Next, using a flathead screwdriver, release the lower radiator hose retaining clip by prying it up (green arrow). Then disconnect the hose by pulling it off the coolant radiator fitting. You may have to wiggle the hose a bit to get it to move free. Be careful not to damage the hose or the radiator fitting, both are made of plastic.

Models with automatic transmissions: Working at lower left side of the radiator, pull up on the ATF (automatic transmission fluid) heat exchanger release tab (green arrow).
Figure 3

Models with automatic transmissions: Working at lower left side of the radiator, pull up on the ATF (automatic transmission fluid) heat exchanger release tab (green arrow).

Remove the ATF heat exchanger from the radiator bracket by it pulling away.
Figure 4

Remove the ATF heat exchanger from the radiator bracket by it pulling away.

Working at the top of the radiator support, remove the plastic radiator fasteners (green arrows).
Figure 5

Working at the top of the radiator support, remove the plastic radiator fasteners (green arrows). The fasteners are quite long, as shown in the photo.

To remove the radiator, pull it from the radiator support toward the engine, then pull the up and out in the direction of the green arrow.
Figure 6

To remove the radiator, pull it from the radiator support toward the engine, then pull the up and out in the direction of the green arrow.

With the radiator removed from the vehicle, remove the expansion tank mounting bracket fasteners (green arrows).
Figure 7

With the radiator removed from the vehicle, remove the expansion tank mounting bracket fasteners (green arrows).

To remove the mounting bracket from the radiator, unclip from the top of the radiator and pull it out of the bottom of the radiator.
Figure 8

To remove the mounting bracket from the radiator, unclip from the top of the radiator and pull it out of the bottom of the radiator. This photo shows the connection at the bottom of the radiator.

Inspect the bracket and check that all the fittings (yellow arrows) are in good shape and that the thermostat is intact (green arrow).
Figure 9

Inspect the bracket and check that all the fittings (yellow arrows) are in good shape and that the thermostat is intact (green arrow). Install the expansion tank bracket onto the new radiator. Use coolant to lubricate the o-rings to ease installation.

Lower your new radiator into the engine compartment and install on the support.
Figure 10

Lower your new radiator into the engine compartment and install on the support. Check that the rubber insulator is properly installed before installing the radiator (yellow arrow).

Move the radiator toward the front of vehicle and install the plastic fasteners.
Figure 11

Move the radiator toward the front of vehicle and install the plastic fasteners. You can check the position of the radiator using the fan shroud fastener hole. It should be flush as shown in photo (yellow arrow).

Install the lower radiator hose - the retaining clip is properly seated when an audible click is heard. Connect the radiator outlet temperature sensor electrical connector. Install the expansion tank. See our Pelican Parts Technical Article on Replacing Your Coolant Expansion Tank. Install the air filter housing, cooling fan shroud. Now, fill and bleed the cooling system. Once complete, check the cooling system for leaks and top up if necessary.

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Comments and Suggestions:
Grapedog Comments: Oops, I meant to say that my expansion tank had a hose in the middle and at the bottom. :-
August 14, 2016
  Followup from the Pelican Staff: No problem, got it. - Nick at Pelican Parts  
Grapedog Comments: 2001 BMW 325ci. Good DIY write up! My car was a little different during radiator removal. A Torx screw on the top driver side of the radiator needed to come out before the radiator was free. The expansion tank had a hose at the bottom as well as the one at the bottom. I couldn't see how to drain the expansion tank other than removing the hoses which showered me with coolant, something I sort of expected. Removing the air box 2 10mm bolts is quick and easy, giving much more room to work with the expansion tank. I couldn't get the lower radiator hose off the old radiator. I should have just purchased new hoses when I ordered the radiator. Good time to do belts during this project.
August 14, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
SAMMY Comments: HELLO,ON MY 2001 BMW 325I AUTOMATIC I HAVE A LEAK COMING FROM WHERE THE BOTTOM OF THE RESEVOIR CONNECTS TO THE RADIATOR. I FEEL LIKE SOMETHING IS MISSING THERE BUT CANNOT PIN POINT IT. CAN YOU HELP PLS?
July 28, 2016
  Followup from the Pelican Staff: The tank or fitting may be leaking. Pressure test the cooling system to pinpoint the leak. - Nick at Pelican Parts  
Not Sicilian Comments: I have a 2001 325xi wagon. American specs. I live in Sicily. My mechanic says my radiator is leaking I saw some chalky gray stuff by it, and he says I need to replace the radiator, water pump for good measure and the thermostat. Ching-Ching. I called my former mechanic in Germany. He said only replace the radiator and thermostat. Any thoughts?
March 24, 2016
  Followup from the Pelican Staff: It's up to you. However, you only have to repair what is leaking. Unless you are looking to perform preventive maintenance. Just repair the leak. - Nick at Pelican Parts  
Steve Comments: so once the expansion tank is out the thermostat just pulls up and out?
March 22, 2016
  Followup from the Pelican Staff: The thermostat can be pulled straight up to remove E46 models. - Nick at Pelican Parts  
Steelthrottle Comments: Okay so a couple of days ago my 325xi 03 broke down, it was a result of serpintine belt breakingredients off and my idle pulley, I just replaced both and my car has started overheating, and coolant starting leaking out the cap I tighten it down further and it no longer leaked but I still have no heat and overheat. Everything worked good before and I don't know what needs fixing
December 12, 2015
  Followup from the Pelican Staff: 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  
Andreas D. Comments: This maybe a stupid question but I need help. I replaced the radiator on my 2000 323i with Manual transmission. After removing the expansion tank, I did NOT see a thermostat in there. I looks like the previous owner had already replaced the expansion tank since the Part is from Behr but there was no thermostat in the mounting bracket. Was this as mistake from the last mechanic working on the car or is it because the car has manual transmission that it doesn't have a thermostat is there. I've been searching all the threads but there's nothing about this anywhere.
September 23, 2015
  Followup from the Pelican Staff: Manual trans won;t have it. - Nick at Pelican Parts  
55 going on 85 Comments: Okay, sorry super dumb question.
I have a 2002 325i. I installed new radiator and expansion tank this weekend. I took it apart 4 weeks ago and cant for the life of me remember where the 4th torx screw goes.
1 Long one top or radiator passenger side.
2Short one top drivers side, I think. im at work right now
3 Bottom drivers side of radiator holding on expansion mounting bracket.
4 Sitting on garage floor. I'm sure that's not where it belongs.
Thanks :
September 14, 2015
  Followup from the Pelican Staff: Review the article you commented on and check for the fasteners you mentioned.

There are screws at the side tank and top. - Nick at Pelican Parts
 
Billy Comments: Nick, It is not losing coolant and no white smoke. The coolant system will hold pressure. We pulled vacuum on the system and all air is out now but still gets hot. The thermostat opens and everything seems to be working. Could the radiator be bad? We have also checked the head gasket and there is no emissions in the coolant.
August 27, 2015
  Followup from the Pelican Staff: If the thermostat is opening, check for coolant flow. Look inside the reservoir, there should be a steady stream of coolant out of the small hole. If not, the water pump may be faulty or there is a restriction in the system. - Nick at Pelican Parts  
Billy Comments: I have a 2004 BMW 325i, I have replaced the water pump, expansion tank, upper hose, thermostat/housing, fan clutch, serpentine belt, temperature sensor. We have bled the system over and over but there seems to be air in the system because it gets hot. My dad pulled a vacuum on the system so there is no leaks and tested the head gasket. What are we missing and why is the car still getting hot? Radiator was replaced in 2013 prior to buying the car.
August 22, 2015
  Followup from the Pelican Staff: If you have confirmed the thermostat is opening, the head gasket may be faulty. White smoke is likely coolant. 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  
buckannear Comments: If trans cooler thermostat is broken , which I suspect it is as it separated into pieces when I was replacing expansion tank.would that cause overheating? I recently replaced expansion tank and thermostat ,at head, have repeatedly bled for air bubbles and still thermostat wont open, as top hose is hot and bottom hose is cool, what else would cause thermostat not opening even when ehgine is hot.
May 15, 2015
  Followup from the Pelican Staff: If it is causing a restriction, it could. - Nick at Pelican Parts  
megasquirter Comments: I have a leak coming from the m/t mounting bracket lower left right underneath the mounting screw were it plugs into radiator showen in figure 8.Is this sealed by an oring and what is this hole for? Thanks
March 16, 2015
  Followup from the Pelican Staff: Yes, there is an O-ring there. This is for coolant to flow into the thermostat assembly. - Nick at Pelican Parts  
cb Comments: Why is the hose on my 2006 325i is coming off evening with the silver clam holding it on? And I did hear it lock on...
September 24, 2014
  Followup from the Pelican Staff: What hose? - Nick at Pelican Parts  
sal Comments: Best write ups i have seen so far. Very good instruction and makes DIY a walk in the part for someone who doesnt work on cars that much. Thanks a lot
September 4, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Fozi Comments: What is the REAL INDICATOR VISUAL ASSURANCE that my system is completely Bled! Can I say that my system is completely bled when a water stream starts coming from the small hole located on top of the expansion tank? Is there a possibility that e46 may or may not have the stream flowing in expansion tank hole located on top? Thanks
August 6, 2014
  Followup from the Pelican Staff: Yes, a steady stream fromt he small hole in the reservoir is a good indicator. - Nick at Pelican Parts  
Mayerbrand Comments: you guys are always posting late E46 stuff and it confuses anyone with a 2000 automatic. throw this DIY away or tag it better for proper search
July 4, 2014
  Followup from the Pelican Staff: Thanks for the feedback. The article is labeled to apply to:
BMW 325i (2001-2005)
BMW 325Xi (2001-2005)
BMW 325Ci (2001-2006)
BMW 325ti (2001-2004) - Nick at Pelican Parts
 
Jon Comments: Just finished replacing my radiator 02 325i and everything seems fine, car warms up and the temperature gauge stays at about 12:00. However, I now have no heat coming from my vents when I turn the heater on. I believe I've bled all the air from the system, but not entirely sure. Any ideas?
April 3, 2014
  Followup from the Pelican Staff: If the heater hoses are not hot, there may still be air in the system. Put the heat on high when bleeding. - Nick at Pelican Parts  
Gfmjr1957 Comments: Do you have to pull out the radiator to put in a new trans cooler thermastat mine broke when I took out expansion tank .
October 6, 2013
  Followup from the Pelican Staff: It would make it easier, but you should be able to do it in vehicle. - Nick at Pelican Parts  

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