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1M views 4K replies 593 participants last post by  ///Mark_D 
#1 ·
This post is for you if you just purchased your E46 and/or have more than 75,000 miles on your current cooling system. The E46 is among certain BMW models that are known to to suffer from cooling-related failures, often times catastrophic due to warping the engine block. The 6-cylinder in your E46 is a straight six design featuring an aluminum head and block. This design has inherent benefits for which BMW engines are known for. However this design also has inherent drawbacks. When overheated even for seconds, the long aluminum head on a BMW straight six is particularly vulnerable to warping. The fix is a risky and costly top end engine rebuild or a complete engine replacement. The cost is $3,500 and up.

When an E46 overheats, the result is usually a blown headgasket causing coolant consumption, coolant/oil mixing, or an overpressure situation in the cooling system. Either way, the car will not run long during any of these three conditions. This happens to so many people on a daily basis but can easily be prevented with $500-750 worth of parts every 75,000 miles. As such, it is absolutely imperative that you maintain your E46 cooling system. If your temperature gauge does go into the red zone, shut off the car immediately and have it towed.

How, why, and when do the failures typically occur? The number one cause of cooling failure for the E46 is the expansion tank. This tank has a 100% failure rate and fails on every single E46, usually around or before 90,000 miles. Some fail sooner than that while some last longer. These tanks fail because of heat cycling of the plastic material they are made of. Typically the failure will make itself known when you see a yellow low coolant light on your gauge cluster. You will open the hood and the tank will look fine but what you don't see is the hairline crack that formed down the side of it, usually invisible to the naked eye. This crack expands under pressure and water spews out. If the water/coolant level becomes low enough, there will not be enough coolant for the water pump to circulate. No circulation means no flow through the engine/radiator. No flow through the radiator/engine means overheating.

Belts and Pulleys
Other common failures are the pulleys and belt systems. The main belt drives the water pump, alternator, and power steering pump. This belt is guided by pulleys. These pulleys contain ball bearings and grease. After around 60k miles, this grease dries up and the pulleys are vulnerable to failure. The belts are then thrown off once this pulley fails and you now have no cooling system, no power steering, and no charging system. Obviously the belts themselves can fail causing an otherwise brand new cooling system to not operate. Replace every 35k miles. Your dashboard will light up like a christmas tree and your temp needle will fly into the redzone. See my pulley thread here: Mango's definitive pulley thread

Water Pump
The water pump is another potential failure point but admittedly not as common. It can fail in at least three ways. 1) The impellar itself will break and cannot continue to push water. 2) The seal may leak and, 3) The bearings will fail causing the shaft to wobble and break. You might hear nightmares of water pumps with plastic impellars, but don't pay attention to this. Replace your water pump due to age and/or mileage, not because what its made out of. The latest BMW water pump design (at least 10-15 years old) features a plastic composite impellar. BMW did once try metal impellars but quickly phased those out due to premature balancing and bearing failures. Design is more important than physical materials. Some people insist on installing the Stewart water pump. Some recent reports suggest that these are low-volume production items and may fail prematurely. Others report success. It's up to you.

Thermostat
Generally fails in the open position leading to a "cold" temperature needle on your gauge not allowing the car to warm up, this item can leak as well or worse yet, fail closed or partially closed. It's a good idea to replace it.

Radiator
The E46 radiator is typically robust, but the end tank seals are rubber and harden over time. You'll notice staining or slight weeping. The radiator has thin passages which can become clogged with sediments as well and may cause water to flow slowly to where it needs to go. This may cause problems in traffic or while stopped. The plastic end tanks may also fail but this isn't that common of a failure mode for this part. They are cheap enough to replace anyway and is one of the most vital cooling parts--arguably the most important one. Don't skimp on this.

Fan and Clutch
Fan blade and clutch (for automatic transmission equipped vehicles). Another failure point. If the blade chips or deteriorates, there goes its balance and will explode in your engine bay. There goes your belts, hoses, hood and whatever else it feels like taking out. The fan clutch is typically robust, but is good practice to replace it anyway. It controls the speed of the fan. You don't want it spinning too slowly or too quickly. A fan that cannot blow sufficient air over the radiator will fail to cool the water/coolant and thus the car will overheat. This typically happens when the car is stopped in traffic, say at a red light.

In order for your car to run at an optimal temperature and NOT overheat, these requirements MUST be met.
  1. Cooling system must be filled to capacity. That is to say the system must have no leaks and no air in it. Car must have correct amount of coolant/water.
  2. Water must be able to be driven without any unnatural hindrance. That is to say the water pump must be able to push water throughout the system without blockages. The thermostat should also be opening and closing as designed.
  3. Air must pass over the radiator in sufficient quantity at the correct moment. That is to say your mechanical and/or electrical-driven fans must be operating correctly when triggered by working sensors.
If your car is overheating, at least one of the above is not being met. If your car is overheating at idle (say in traffic) and you are sure that 1) you have adequate water in the system and 2) said water is air/bubble free, then air is failing to blow over the radiator. You need to investigate why. Either the fan(s) aren't operating properly (not blowing air or enough air) or your fan switch isn't telling the fan to turn on. (or both)

The Parts
OK, Mr. Mango, you have convinced me to replace the entire cooling system. Where do I get the parts? We have many great part sponsors to choose from here. Please visit the E46Fanatics Vendor section to see which vendors suit your needs best. The List of the parts that make up the E46 Cooling System which I recommend replacing.
  • Radiator
  • Expansion Tank
  • Expansion Tank Cap
  • Water Pump
  • Radiator Hose Lower
  • Radiator Hose Upper
  • Expansion Tank to Pipe Lower Hose (VERY important)
  • Thermostat
  • Radiator Fan Switch
  • Coolant Temerature Sensor
  • Water Pump Pulley
  • Coolant drain crush washer at engine-block
  • Water pump pulley bolts (reuse if careful)
  • Belt Tensioner Pulley (main pulley)
  • Alternator Deflector Pulley
  • Coolant
  • A/C Tensioner Pulley - Mechanical
  • A/C Tensioner Pulley - Hydraulic
  • Alternator/accessory belt (main large drive belt)
  • A/C belt (9/02 and pre 9/02 models have different belts, check your model first)
  • Expansion Tank Mounting Plate Manual Transmission (Optional--You may reuse--For manuals only)
If your E46 has an automatic transmission, you'll need to add at least some of the following parts to the above list:
  • Automatic Transmission Expansion Tank Mounting Plate (Again, optional--you may reuse)
  • Automatic Transmission Thermostat (often crumbles apart upon removal of original)
  • Automatic Transmission Fan blade (recommended)
  • Automatic Transmission Fan Clutch (recommended)
  • Automatic Transmission Cooler O-Rings (two)
Additional hoses for additional security! (Less likely to fail but if you want to be thorough, some fanatics have replaced the 4 additional hoses.
  • RETURN HOSE - Runs from the coolant connection fitting (automatic) / radiator mounting plate (manual) below the expansion tank to the front hard composite pipe near the throttle body.
  • INLET HOSE - Runs from the rear hard composite pipe beneath the intake manifold inlet runner number six to the heater valve inlet.
  • SHORT HOSE - Runs from the heater valve outlet to the heater core inlet.
  • LONG HOSE - Runs from the heater core outlet to the connector on the rear of the expansion tank, about halfway up. This hose runs on the chassis rail, higher up than the return hose.
Bleeding
This step is extremely important. No amount of brand new cooling parts in the world will work if you do not bleed. The point of bleeding is to remove air bubbles. The cooling system is most efficient when it is circulating pure fluid.
CAUTION: ONLY DO THIS WHEN CAR IS COOL AND ENGINE IS OFF. At no point should the engine be turned on.
ATTENTION: DO NOT EVER UNDER ANY CIRCUMSTANCE BLEED OR PERFORM WORK OR INSPECTION ON A HOT COOLING SYSTEM. IMMENSE BODILY HARM CAN RESULT

Here is a quick cheat sheet.
  1. Raise front of car on ramps (Not necessary, but recommended)
  2. Remove expansion tank cap and bleed screw and set aside
  3. Turn ignition to ON (dash lights on but do NOT start the car)
  4. Set heat to MAXIMUM (90) and fan speed to low (this opens heater valve)
  5. Begin to fill your expansion tank with ideally a 50/50 mix of Genuine BMW coolant and distilled water (do not use anything else--no reason to. The proper stuff is cheap) The system might take a while to swallow the water. Massage the hoses if you think it will help. Keep pouring. Water will begin to pour out of the bleed screw hole with air bubbles. The point is to keep filling and filling until the bubbles are gone. This may take a while--be patient.
  6. Once you are satisfied that a continual stream of bubble-free water is emerging from the bleed hole and that your cooling system is adequately filled, go ahead and replace the bleed screw (do not overtighten). The expansion tank will be full to the top at this point so you'll need to siphon off any excess so that the appropriate tank level can be achieved.
Congratulations. Your E46 is now ready for another 75k miles of trouble-free driving. Never will you have to worry about being stranded with your wife, girlfriend, pets or kids in the car. Never will you have to worry about posting a thread asking why your car is overheating or why your engine is stained with coolant. Never again will you have to worry. (at least for another 75k miles) 👍 The mileage is just a guide. Your results may vary.

FAQ
Q) But Mango, isn't full cooling system replacement a waste of money?! Can I wait for the parts to fail and replace one at a time?
A) Preventative maintenance is a risk assessment. It boils down to your acceptable level of risk. For me, on critical parts, that's 0 or near 0. As the cooling system is the one aspect of the car that can bring your engine down with it requiring a full engine rebuild or replacement, that's one system you don't want to mess with. I understand some people that argue this can't afford to maintain their cars or may be on very strict budgets so this issue is personal for them and they get angry and lash out but really we should all try to help eachother try and maintain our cars and especially not give newbies a false sense of security. I've given advice on partial cooling replacements as well. If you're an adult, have a decent job, and need to get to work every day. Full cooling maintenance should be a priority if you own an E46. It's your way of life. It's how you put food on the table for you and your family. But MANGO?! You mean to tell me $500 is all I need in the context of adult car ownership is all I need to spend protect my engine from total destruction? Deal of the century. Sign me up! You are all driving once-$40,000 German luxury cars for $5,000. And you're going to complain if that car now costs $5,500 and is more reliable, to boot? What planet are we on? $500 over 5 years is $100 a year. Or $8 a month. Is that too big of a pill to swallow?

Q) Mango, what brands do you recommend?
A) I recommend OE (Genuine BMW), OEM (parts like Behr, INA, Wahler, Rein, CRP, CoolXpert, Saleri, Contitech, etc.), or OEM or equivalent/higher such as Meyle HD pulleys, Graf, and in some cases Gates.

Q) Mango, where do I get the parts?
A) Plenty of E46Fanatics sponsors such as ECSTuning, FCPEuro, or in some cases people like BMA out of Los Angeles. Up to you.

Q) My car has 50,000 miles, do I still need to replace xx part?
A) Rubber and plastics deteriorate with time. You'll probably be better off than a person with 90,000 miles but nobody can predict the future. If you want to be safe, I recommend full replacement. These cars are 12-14+ years old.

Happy motoring!
 
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#130 ·
Forget ECSTuning. This is why I posted a parts list. If you want to throw away money, go ahead. Also just DIY. It's easy. I can't imagine anybody stopping midway through saying "this is too difficult!" and throwing their hands up. You'll be fine. Don't worry.

And, by the way folks... I told you guys. The failing radiators are just about starting to happen. Radiator armageddon! lol
 
#134 ·
Step 1) Use eyes to look at ECS price

Step 2) Go to another vendor such as bmaparts.com, enter all the parts in ECS kit

Step 3) Compare prices

Save???

:thumbsup:

If its easier to just purchase a kit, sure. Have at it. But kits are incomplete. That's why I put together a list of parts.
 
#137 · (Edited)
My water pump and or thermostat housing failed while my wife and I were on a trip up to Virginia Beach to prep the Mitchum Motorsports BMW 128 series cars racing in Grand-Am CTSCC ST class. I noticed the low coolant light had come on an hour earlier so I kept an eye on the temp gauge. As soon as we got off the freeway in VA Beach, she really started to pump coolant everywhere. So the next morning I finished my race shop work, filled the tank and headed home. It wasn't 5 minutes and the low coolant light was back on. :( But my baby made it the 400 miles back to Charlotte with a couple of stops to try to get some water back in her. As long as we were moving air across the radiator, temps stayed good but if we got off the freeway for any reason, temps sky-rocketed quick. She hit the red 3 times for about 15 seconds before getting back to speed and air pushing across the radiator. God Bless BMW, we made it home safely.

So, I came across this post and followed the OP's advice and replaced everything since my 2002 325i had just hit 150K. I did not order online and got everything from Hendrick BMW here in town and I thought I would post the retail numbers. Retail cost for everything on the OP's list was $1740.06 and my BMWCCA discount was $1441.70. It took me about 5 hours to disassemble everything and about 4 hours to put it all back together with simple hand tools. No leaks and running like a top. Thank you very much for the write-up on this, it made a $3500 repair bill $1441.70. :thumbup:



 
#140 · (Edited)
Super awesome. :thumbsup: Excellent picture. Now you can have a trouble-free cooling system for a long-time and you won't be one of those multitudes of people who post threads asking for help because their car overheated. I even see you bought the water pump pulley and bolts! THAT'S DEDICATION!
 
#143 · (Edited)
Just ordered my cooling kit.


Item Name Item Price Quantity Item Total
--------- ---------- -------- ----------
07-11-9-963-200-M131 $0.25 1 $0.25
Seal Ring for Block Drain Plug 14x18mm - Brand: Fischer & Plath

----------------------------------------------------------------------
11-51-1-436-590-M253 $26.00 1 $26.00
Water Pump Pulley (Black Anodized Aluminum Version) - Brand: APA

----------------------------------------------------------------------
11-53-7-509-227-M322 $64.25 1 $64.25
Thermostat with Integrated Thermostat Housing (includes gasket), BMW
E46 3 Series, All Except M3, Each Brand: Behr Thermotronic

----------------------------------------------------------------------
17-13-7-553-919-M253 $9.00 1 $9.00
Coolant Level Sender, BMW E46 3 Series, All (1999-05), Each Brand: Uro
Parts

----------------------------------------------------------------------
11-51-7-527-910-M52 $46.00 1 $46.00
Water Pump (uses a composite impeller), BMW E46 3 Series, All Except
M3 (1999-05), Each

----------------------------------------------------------------------
17-11-9-071-518-M6 $148.00 1 $148.00
Radiator, For Manual Transmissions, E46 323i/Ci, 325i/Ci/Xi (through
4/05), 328i (from 10/98), 328Ci, 330i/Ci (through 4/05), 330Xi
(through 4/05) Brand: Behr

----------------------------------------------------------------------
11-53-1-436-408-M21 $27.25 1 $27.25
Lower Radiator Hose (NOTE: Also use water temperature sensor 13-62-1-
433-077-M9), BMW E46 3 Series, All Except M3 (1999-05), Each Brand:
Contitech

----------------------------------------------------------------------
17-12-7-510-952-M21 $30.50 1 $30.50
Radiator Hose, Radiator to Thermostat, BMW E46 3 Series, All Except M3
(1999-05), Each Brand: Contitech

----------------------------------------------------------------------
17-11-1-742-231-M148 $11.75 1 $11.75
Radiator Cap, 2.0 BAR, BMW E46 3 Series, All (1999-05), Each Brand:
Reutter

----------------------------------------------------------------------
17-11-7-573-781-M58 $80.50 1 $80.50
Coolant Expansion Tank (cap not included), BMW E46 3 Series, All
Except M3 (1999-05), Each Brand: OEM

----------------------------------------------------------------------
Shipping for Package 1: $FREE

Total Price: $443.50


All OEM, except for the coolant level sensor and the pulley, but the pulley is aluminum, and I haven't heard of one bad thing about it from any members.

For the level sensor, yeah yeah yeah I know, URO parts suck, but hey it's $9, it's just a sensor, and if it doesn't work it's no skin off my bones. I don't think mine works as it is, anyway. Much cheaper than OE. I can get 3 of them for OE price :p

I can't wait to get it all installed and have more piece-of-mind when driving. I'll finally stop having to constantly gander at my temperature gauge!

I plan on re-using my temp. sensor since it's working just fine, so I just ordered a new O-ring. P/N for that little guy is 13621743299

My cooling system has lasted me 104,000 miles. All I've got is a minor radiator leak somewhere in it. Takes about 3 months for the level to actually go down noticeably.
 
#144 ·
Wow very thorough guide, I definitely plan on doing this once school gets out.

I've replaced little bits and pieces along the way (water pump, belts, pulleys, tensioners, etc.) but I haven't had the need to replace any other components as of late, nothings leaking for me :dunno: (knock on wood)

But $250 isn't much to spend for peace of mind :thumbsup:
 
#145 · (Edited)
Just did my cooling system change I changed the water pump, compressor, alternator, radiator w both upper and lower hoses thermostat espantion tank and expantion tank hose pulleys from plastic to aluminum belts I think the only thing that don't get changed was the fan.. lol but car is running great now cold a/c back :) and I'm getting my new tires put on in 6 hours :) took me about 1100 parts and about 300 labor but I'm happy ..

Most of my parts came from autohauz and radiator and alternator came from eBay ..
BTW I used a 25$ water pump with metal impeller from uro let's c how that holds :)

Sent from my PC36100 using Bimmer App
 
#147 ·
BMA's catalogging system isn't updated as much as it should be. They sell parts for all other brands as well (Isuzu, Ford, Toyota, etc.) so their system doesn't get as much attention as BMW-specific sites. FWIW, they've done a great job. It's still a work in progress. I talked w/ Patrick. If you don't see what you want, call them or e-mail them and ask. They can get any OE/OEM part.
 
#176 · (Edited)
The water pump pulley is much more hollow and large than the other pulleys, and tiny stress fractures in the plastic/composite material can form. When it lets go, it really lets go. The aluminum pulley is cheaper than OE, too, which I find funny. Other pulleys you can replace when they start squeaking or just look worn, but this one you'll have no warning.


I'm using a Behr and it fit 100%. You sure you didn't order the auto transmission one? ;)
:eek: Hope not. I think I just got unlucky. Oh well, it fits, it works, it's got a warranty, I'm good :thumbsup:
 
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