DIY - Cooling System Overhaul E46 M3

[bimmer]

Credit to original author: BlazenXLT. Link to the cached version I was able to save from m3forums before it disappeared. It's on my OneDrive until the forum allows me to attach files. Unfortunately pics were already busted from photobucket.

https://1drv.ms/b/s!AurP56v3ZyPPnE2jxAPSVguoGnvV?e=TJurD0

[blazenXLT]

Thanks for saving what you could, even I don't have a copy of this... too bad photobucket really took a dump on so many old threads.

[Shonky]

Full credit to BlazenXLT as above. Hopefully this one massive post doesn't blow up submitting... Let me know if you see any mistakes.

Edit: yes the images did blow up but I do have them. Should be all fixed now.

======

This thread is meant to serve as a guide/suggestion to those with older E46 M3’s. BMW cooling systems are known to be a weak link, especially as a car gets older. E46 systems don’t seem as prone to failure as E36’s, but regardless, I find that it’s generally recommended that the system, or at least parts of it, be replaced as a preventative measure around 100k. With a model year 2002 (Nov. ‘01 build date) and 113,000 miles, I was due (maybe even overdue). I haven’t seen a write up that consists of the entire cooling system and that is M3 specific, so I thought I’d write this up and provide some pictures.

There are several other resources I used during this process that are definitely worth checking out:
1- Write-up on coolant flush by Function7
http://www.m3forum.net/m3forum/showthread.php?t=248557
2- In the above thread, there is also a link to this thread by TRACK-CZAR with tons of good pictures
http://www.m3forum.net/m3forum/showthread.php?t=327613
3- Water pump and thermostat replacement by Surk///M
http://www.m3forum.net/m3forum/showthread.php?t=233102
Thanks to the members above for great write-ups and valuable pictures. Also, if you don’t have a Bentley manual, get one.

I decided to overhaul the entire system (water pump, thermostat, hoses, radiator, gasket, o-rings, temp sensor, and fluid). Since this is a relatively common repair, a few vendors offer all the parts as a package. Off the top of my head, I know that Tischer and Turner offer the package and I imagine there are others. I have no preference or affiliation with either, but ended up ordering from TMS. When I did my initial research, their prices were virtually identical, so take your pick. Note: my kit did not come with two items I wish it did. 1) New hose clamps and 2) a new washer for the engine block drain plug. In both cases, I was able to reuse these parts, but it may be something to think about prior to starting this project.

If you search the forum, you’ll find a number of threads about upgrading to an all-aluminum radiator. I have yet to see evidence of a radiator that is a true upgrade and fits perfectly. Considering that, and the fact that I’ve never had a problem with coolant temps (this includes 10+ track days a year), I decided to go all OEM.

Disclaimer: Obviously, I’m not a mechanic. This thread is simply informational for the average owner. If you’re not comfortable with doing this work yourself, find someone to help you, or take your car to a pro. In total, this work probably took me 7-8 hours, including taking my time, several coffee breaks, making notes, and constantly taking my gloves on and off to take pictures. If I had to do it again with no distractions, I could probably do it in 3 hours.

Tools: I’m not going to list all the normal stuff (ratchet, pliers, sockets, various extensions, ect.). I’ll assume that if you’re thinking of doing this, you already have a decent supply of standard automotive tools. I do want to highlight a few things that are critical that you might not have.
• 32mm cooling fan wrench (I got mine on Amazon for about $20)
• Security torx wrenches (the tamper proof type). You’ll need this if you want to remove you MAF, which isn't necessary, but it's a good time to go ahead and clean it.
• Rags/blankets you don’t care about ruining
• Empty containers for used coolant (milk jugs work, and they’re free!)

Set-up: I work in a very small garage, so space was a little tight. I did this entire project with the front of the car up on ramps. The red blanket is my drip catcher. I use taped notes on the wall to remember steps, torque values and make notes.



I also use small bags to organize fasteners/clips



The intake needs to be removed. The top of the airbox can simply be rotated out of the way as shown, but the lower section needs to be removed. In the picture, you can see the cover of the xenon control unit lifted up. This gives you access to the two bolts holding the lower half of the airbox. It simply lifts out.



Head underneath the car and take off the plastic panel underneath the engine and remove the two screws that hold the oil cooler. The oil cooler can be pushed back a bit, but I like to support it with something so it doesn’t stress the lines too bad.



Unplug the connection on top of the radiator and the temperature sensor in the lower hose. There is also a wiring assembly that is mounted on the passenger side of the fan shroud, it simply lifts out. These three items can be tucked away for now so they don’t get wet.





Remove the fan with your fan nut tool (32mm). There is a secondary tool that holds the water pump pulley steady while you break the fan free, but it’s not really necessary. Some people are able to get the fan nut lose by hitting it with a mallet, but mine didn’t seem to want to move. I was able to get mine loose by using a long thin screwdriver to keep the pulley still. Note: if you haven’t heard it before, the fan clutch nut is reverse threaded. Think righty loosey, lefty tighty.





found it easiest to remove the fan by dropping it out of the bottom of the car. Once the fan is out, you can remove the fan clutch. It’s held on by three 5mm hex bolts. Make sure to take a good look at the fan when you remove it so you put the new clutch in the correct way. I didn’t…more on that later. Be careful when tightening the new clutch in, you don’t want to crack the plastic fan. Torque spec is 10Nm (89 in-lb or about 7 ft-lb). You can also remove your belts now. The Bentley manual recommends that you mark the rotation of the belts so that they can be re-installed the same way. I’m not sure why this matters, but I did it anyways.
Edit: It's easiest to remove the fan assembly and the shroud together at the same time. Removing the fan with the shroud still in place is difficult.





Now you can drain the old coolant. E46 M3’s don’t have a radiator drain plug, which is kind of a pain. The simplest way to get around this is to drain fluid out of the temperature sensor in the lower radiator hose.




Since the fluid is going to drain up out of the sensor hole, I covered it with an upside down funnel to reduce the mess. Pull the plug out and let the fluid drain. Since the rest of the system is still closed, not too much will drain out. To ensure you drain all the fluid, turn ignition switch on (don’t start the engine) and set your temp setting to full warm. With the funnel in place, open the bleeder valve and let the fluid run. I used this method and was able to keep spills to a minimum.






Old and new temperature sensor.



Hoses can now be removed. As other DIYs have mentioned, the lower hose is really stuck on there and it’s difficult to get any leverage on since it’s in a tight space. As I’ll show in later photos, I was able to get my radiator out with the lower hose still attached.






continued...

[Shonky]

From the draining so far, I was able to get nearly a gallon of fluid out. You can turn your ignition back off now.



I don’t have a good shot of it, but this is when I removed the fan shroud. Once it was out of the way, you can remove the last screw holding the radiator in place. Then it can be lowered out the bottom of the car with the lower hose still attached.




Old and new.




Tip the radiator on its side to get the last of the fluid out.



With the radiator out, you’ll have access to the back of the A/C condenser. This is a good time to clean it as there is likely a lot of debris in there. I recommend a tooth brush and a vacuum.




To get the remaining fluid out, you need to drain the engine block. Get your rags ready. The drain plug is a 13mm bolt on the passenger side of engine. From underneath, it’s basically impossible to see. You can move this canister out of the way for easier access, but I was able to reach the plug with a simple extension.



A lot of fluid is going to come out, and because it’s going to hit other things, it will spray everywhere. The bucket will catch most of it; the rest will just have to be mopped up. Consider it a chance to clean your garage floor.




Here is the total so far, not including the half gallon that ended up on the floor. The system capacity is 10 liters or about 2.6 gallons. I figure I was able to get pretty close to that, although it may have been better to have the car more level and not leaned back slightly. In any case, I was happy with the results. This is a good time to mention that if you are able to drain the system completely, and want to refill with a 50/50 ratio of coolant to water, you’ll need two gallons of BMW coolant. I had two on hand just in case.



Here is the drain plug. I reused the washer. Re-torque to 18 ft-lb.



Remove the four bolts from the water pump pulley.




Here is the pump with no pulley.



Next, remove the three bolts that hold the thermostat housing (on the top of the Y-pipe).




Next, remove the five bolts holding the water pump and remove it carefully. Again, I was a bit OCD on keeping bolts organized.




Here is the old system with the new water pump in the background.



Parts!



Replace the o-rings on these three pipes. Clean the area where the new pump will seal with the block.




With all the o-rings in place, put the new gasket on the back of the water pump and install. A new o-ring goes on top of the pump where it will seal with the thermostat housing. The thermostat housing then slides into place. Make sure everything is lined up properly before re-installing the torquing the bolts back down. Again, this is an area where you don’t want to use too much force. Both the coolant pump to the timing chain cover, and the thermostat housing to the pump are only 7 ft-lb. Too much torque could ruin a seal, or worse, break a bolt head. I wish I had gotten some pictures of this step, but my hands were full. If you’ve dis-assembled the system, putting it back in will be simple.

Shonky edit: Hi temp O-rings recommended https://nam3forum.com/forums/forum/m...6638#post86638 and https://nam3forum.com/forums/forum/c...cooling-system

You can then re-install the pulley to the new pump (10Nm). As a small side note, if you need to do any other work to the front of your engine, plan on getting it done now while you have plenty of room. If you have high mileage, it’s probably a good time to replace your alternator or pulleys. See the DIY reference sticky for more info: http://www.m3forum.net/m3forum/showthread.php?t=349996



Slide the new radiator in



continued...

[Shonky]

Attach the new lower hose and push in the new temperature sensor. Remember not to attach the top hose until you put the driver’s side shroud back in place since the hose goes through it. You can now put the fan shroud back in place loosely.





Re-install both belts (easier to do without the fan in).

Be sure to put your fan back in before you screw the shroud into place. Again, I found it easiest to put the fan in from underneath. Tighten fan clutch nut to coolant pump to 29 ft-lb. The next two pictures show that I put the fan clutch in on the wrong side of the fan, so as I tighten it, it hit the front of the engine. Luckily, this was a simple fix, I just took the fan out and put the clutch in the correct way.




With the shroud in place, you can plug connections back together.



Put the top hose through the driver’s side shroud and attach.



The screw that hold the driver’s side of the radiator and shroud can be difficult to get to. I recommend removing the headlight bulb for more room.



With the new system in, you’re ready to re-fill with fresh fluid and distilled water.



Again, switch your ignition on and set the temperature to full warm, and make sure your bleeder valve (on the upper radiator hose) is cracked open. I recommend have a paper towel underneath the valve. Slowly add fluid into the expansion tank (on the passenger side of the engine). I did not pre-mix the coolant and water, but alternated every ¼ gallon or so while filling. You can hear the fluid as it flows back into the engine block and down the new radiator. Fill until fluid runs out of your bleeder valve. My car took a gallon of coolant and a gallon of water.



You can now re-install your airbox. Give yourself a few minutes to look over everything before you turn the car on for the first time. Once it’s on, let it idle and make sure everything looks and sounds ok. If it does, you can go for a short ride to get everything warm. In all likelihood, your low coolant level warning light is going to come on. That’s ok. Running the car is helping to get any air bubble back to the top of the cooling system. Once home, let the car cool, then re-bleed the system with the temp controls set to full warm. My car took another ¼ gallon or so of water. I figure this put me at about 45/55 coolant to water, which should be fine for 99% of climates. Take your car for a real drive and keep an eye on your gauges. If it starts to read hot, get somewhere safe and turn the car off, you have an issue somewhere.




At this point, you can re-install the plastic panel underneath the engine. I would actually recommend keeping it off for a day or so to make it easier to check for leaks and make puddles obvious. Remember that when you drained the engine block, a decent amount of fluid will end up on the top side of the aluminum reinforcement plate under the car. This fluid will run out of various places once the car gets moving. Don’t mistake this for leaks. Be sure to properly dispose of the old fluid. It’s poisonous, especially to animals, so don't dump it outside or down the drain.



Go have a beer after a job well done and enjoy your next 100,000 miles.

[Cubieman]

Awsome, thanks for getting this posted.

[WOLFN8TR]

Don't forget the Hi-Temp Orings, link is in my SIG. 😎

[Tbonem3]

FYI, the little black screw on the upper rad hose is vestigial. Our system is self bleeding. Exp tank is at the highest point and the cap is valved. Check the exp tank the next morning after the first drive as you'll likely have to add some once it's cooled and bubbles have risen to the top.

[cbean]

My favorite step in the last step!

[Shonky]

Don't forget the Hi-Temp Orings, link is in my SIG. 😎

Added a reference to this post and your thread.

[blazenXLT]

Well done boys! I wasn't looking forward to recreating this with the pics. I still have them all, just would have to rehost here on NAM3F.

[Shonky]

Well done boys! I wasn't looking forward to recreating this with the pics. I still have them all, just would have to rehost here on NAM3F.

I pulled them from photobucket (without the watermark if you use photobucket as the referrer). It was a little bit manual but was able to rip the photobucket links from the archive.org post and batch download them. I uploaded them here which I understand is the preferred way to go.

I then had to manually paste the text in largely step by step referring to the image number in the archive.org HTML to make sure I had the right ones in the right places. Took me maybe 45 minutes beginning to end. Not fun and can't paste images directly in here which would have been nice. Also got caught by 30 image per post limit.

If there are any other archive.org DIYs with borked photobucket links, I can take a look.

[M3Bob]

Glory to your house for restoring this!