Top 10 Parts to Fail on your E46

Top 10 E46 Failures

These 10 parts will certainly fail on you

The BMW E46 3-Series produced from 2000 to 2006 is one of the more reliable BMWs you can buy.  You may have read my widely distributed and viewed post on the BMW E46 Cooling System detailing the common failures and the catastrophic results a single failure can result in, or you may have read my other posts on E46Fanatics.com which recommend full system replacements rather than picking, choosing, and replacing each individual part as they fail. I highly recommend you check out those threads including the links in my signature.

Check out Mango's E-Store =) http://astore.amazon.com/e46acc-20

However I realize not everyone can afford to replace $3,000 worth of parts to restore their BMW E46 3-Series back to reliable and well handling condition.  So I've created a top 10 list of must-replace items for your BMW E46 3-Series.  These parts are the 10 failures of the E46 platform and are certain to leave you stranded, frustrated, or leave your car with dangerous sloppy handling.

Number One - Expansion Tank

While I still recommend full replacement of the E46 cooling system, the expansion tank is an absolute must.  It is not optional and it should 100% absolutely be replaced upon your purchase of an E46.  Do NOT skimp on this.  The common failure is for the tank to develop a hairline crack down the side of the tank resulting in a low coolant light and shortly (seconds) after that, an engine overheat which will destroy your soft aluminum engine in mere seconds.  Many have been in big trouble because they've neglected to replace this $60 part.  You can also buy the E46 Expansion Tank here on Amazon.  The links are to OEM expansion tanks.  Do not buy this part aftermarket.

Number Two - A/C Blower Final Stage Resistor

This part fails on ALL BMW E46s.  And E36s for that matter.  The BMW E46 Final Stage Resistor is responsible for your A/C Blower Fan speed.  The failure is erratic fan speed behavior or the fan completely failing to turn on.  This is torture on a hot summer day.  This failed part has also been known to cause car fires.  Very dangerous.  

Number Three - Fuel Pump

Experiencing long cranks? Hard starts?  Does your engine just crank and crank but doesn't turn over? If you haven't experienced any of these symptoms, you will.  This failure will happen. Replace the fuel pump on your BMW E46 every 60k miles or 5 years for maximum protection from being stranded.  Some go longer, others aren't so fortunate. Luckily it's extremely easy and cheap to replace. Pull up rear seat and voila.  Right there.  Don't forget the seal.  Buy the pump here on Amazon.

Number Four - Throttle Body Intake Boots

Very common failure.  The boots that connect your air filter box to your throttle body dry out and crack over the years.  Will cause vacuum leaks.  The symptom is poor fuel mileage and/or stumbling, idling problems and stalling.  Replace your upper and lower intake boots.  Cheap stuff. Don't skimp.  Make sure you align the tab on the lower boot with the space on the throttle body.  Very easy install.
325i/323i/328i lower boot: http://amzn.to/2d4fv8s  and the upper boot: http://amzn.to/2dukMEr
and 330i lower boot: http://amzn.to/2dlUTKj and upper boot: http://amzn.to/2dmSP0y

Don't forget the throttle body sealing ring:

323/325/328 models: http://amzn.to/2dlVBas
330 models: http://amzn.to/2d1aK1S

Double check your model's part #s before ordering.

I read that the M56 powered BMW 3-Series uses the 330 boots. Check to make sure. 

Number Five - Crankcase Vent System

The BMW E46 Crankcase Ventiliation Kit will certainly fall causing a vacuum leak.  Poor idling, stumbling, poor fuel mileage.  Rubber and plastic cracks and fails over time.  Replace it once and never touch it again.  I recommend Genuine BMW but the above linked kit is available at a fraction of the price.

Bonus: Don't forget to replace the vacuum tubing that connects to the F connector to semi-hard line that goes to the fuel filter.  

Info credit to HodgkinsC330i: Hose diameter: 5/32", available from O'Reilly part# P3340: $3.49 - Product Description: Thermoid Windshield Washer & Vacuum Tubing 5/32" x 6'

Post here showing diagrams of the system (see post #6): http://www.bimmerfest.com/forums/sho...d.php?t=574814

Number Six - Control Arm Bushings

The rubber in your front control arm bushings rot over time and will cause sloppy and loose steering/handling.  If totally failed, your suspension will clunk as you brake and your entire front wheel will move forward 1 to 2 inches -- very dangerous at highway speeds.  If you can't brake, you may crash.  Easy install, two bolts hold it on.  Get a 3-jaw puller and pull the old one off.  Spray windex or soapy water on the new bushing and tap it on with a rubber mallet.  Torque it down and enjoy your new handling. Buy them here on Amazon.

Number Seven - Rear Trailing Arm Bushings (RTABs)

Same as above.  These rot out and cause sloppy rear handling.  Replace every 50,000 miles or 35,000 miles if you are really picky.  These are responsible for rear wheel toe control.  Give your car gas and if the rear end wags under acceleration, your bushings are toast.  Very dangerous if they fail. Buy here at Amazon.  

Bonus: I recommend M3 rear trailing arm bushings as an upgrade for more solid handling.  Direct fit. Plug and play. This kit comes with the famous shims for even greater control.

If you want to do these yourself, I recommend an RTAB tool.  You can also search Google for an "MIS RTAB tool."

Number Eight - Alternator or Voltage Regulator

Battery light flickering? Constant dead batteries?  Even if you don't experience those symptoms, you will.  It's usually the voltage regulator that fails, but many just replace the alternator which will include a new voltage regulator (it's bolted to it.)  Many figure "why not?"  You can also just replace the voltage regulator here for $40 -- this is surely to leave you stranded one day as the brushes on the regulator wear down! It bolts on the back of the alternator using a screw driver.  Make sure you look at yours closely and see what plug it uses. The one I linked is the square plug. Usually the one installed on most E46s.  

MAKE SURE YOU GO LOOK AT YOUR CAR TO SEE WHAT CONNECTOR YOU HAVE. SQUARE OR ROUND?  Also install the same or higher amperage as what your car came with.  

More common square plug alternator for 325 and 330: https://www.fcpeuro.com/products/bmw-alternator-90-amp-e46-x5-z3-al9405x

Less common round plug alternator for 325 and 330: https://www.fcpeuro.com/products/bmw-alternator-z4-al0816x

323/328 square 3-pin alternator: https://www.fcpeuro.com/products/bmw-alternator-323i-328ci-328i-528i-z3-al0738x

Number Nine - Pulleys and Belts

These pulleys carry your belt system and will dry out and rot over time.  Do your pulleys sound like skateboard wheels when spun?  Does your engine make a squeaky noise as it runs?  Your pulleys are ready to fail. When they do, it will throw the belts off and take your engine down with it. Instant overheat. Instant engine rebuild.  Don't risk it.  Don't forget to get new belts. You may as well.

See my thread here for what parts you need and where to buy them: http://www.e46fanatics.com/forum/showthread.php?t=974746

Number Ten - Battery - Autozone H8 DLG

Very simple.  Replace with a battery from your local parts store. Personally I went with Autozone brand -- paid $200 for my battery.  You may be able to find it for $150.

BONUS - STARTER

Prevent yourself from being stranded when you need to go to work -- or worse yet when in gang territory. This part is known to suddenly and unexpectedly stop working.  Get it here

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Inquiries: e46mango@gmail.com

The Definitive Mango BMW E46 Cooling System Blog with Complete Parts list and tips!

PROTECT YOUR E46

This blog post is for you if you just purchased your E46 3-Series and/or have more than 75,000 miles on your current cooling system on your E46 3-Series BMW.

The BMW E46 3-Series 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 a BMW  3-Series 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 BMW E36/E46 3-Series cooling system.

If your temperature gauge does go into the red zone, shut off the car immediately and have it towed.

BMW E46 Complete Cooling System List 9-26-16

Mangos Engine including Rebuilt Cooling System

Appreciate your support over the years and using my links--I earn a small amount when you use them and it doesn't affect you at all.  Much love! 

The List.  11-16-17

1) Radiator

(Manual transmission) link to buy

(Automatic transmission) link to buy

2) Expansion Tank

link to buy

3) Expansion Tank Cap

link to buy

4) Water Pump

 link to buy

5) Radiator Hose Lower

link to buy

6) Radiator Hose Upper

link to buy

7) Expansion Tank to Pipe Lower Hose (VERY important)
link to buy

8) Thermostat

link to buy

9) Radiator Fan Switch

link to buy

10) Water Pump Pulley

URO Aluminum link to buy

11) Coolant drain crush washer at engine-block

link to buy

12) Water pump pulley bolts (You can reuse these if you are careful)

link to buy

13) Belt Tensioner Pulley (Main central pulley)

link to buy

14) Alternator Deflector Pulley

link to buy

15) Coolant
link to buy

A/C PULLEYS

See this thread before ordering to make sure which A/C pulley you need. http://www.e46fanatics.com/forum/showthread.php?t=974746 

16) A/C Tensioner Pulley - Mechanical

Dayco 89133 link to buy

Alternative:**Thanks To Terra, you can also buy BMW X5 part for your hydraulic tensioner.  #11287549557  it comes with a backing plate you won't be using. Discard it. Just reuse your bolt**

16) A/C Tensioner Pulley - Hydraulic
link to buy

17) Alternator/accessory belt (Main large drive belt--The same across all model year cars)

link to buy

18) A/C belt (Differs dependent on your build date--see below)

link to buy (5-rib production date up to 9/2002) 

or;

link to buy (4-rib production date from 9/02)

Expansion Tank Mounting Plate Manual Transmission (Optional--You may reuse--For manuals only) link to buy

ATTENTION!!

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)

Genuine BMW link to buy

Automatic Transmission Thermostat (often crumbles apart upon removal of original--DO NOT GET CAUGHT WITH YOUR PANTS DOWN ON THIS--REQUIRED FOR AUTOMATICS)

Genuine BMW link to buy

Automatic Transmission Fan blade (Optional yet recommended)

Genuine BMW link to buy

Automatic Transmission Fan Clutch (Optional yet recommended)

HELLA link to buy

Automatic Transmission Cooler O-Rings. (Highly recommended as the old ones tend to not seal the same) Order two of these for the transmission cooler.
OEM link to buy

Prices, information, and brands/prices/links subject to change. These are current as of 9-25-16

The total cost for manual cars is around $500. For automatic cars, around $750 which includes the fan blade/clutch.

The failures:

How, why, and when do the failures typically occur?

Expansion Tank

The number one cause of cooling failure for the E46 3-Series is the expansion tank.  This tank has a 100% failure rate and fails on every single E46, usually around or before 90,000 miles.  This can be installed in your driveway in 45 minutes or less using simple hand tools.  If you can change a light bulb, you can change your expansion tank.

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 either while driving or when the car is parked.  Come back to your E46 and there's a puddle under it? Yep that's your expansion take 9/10 times.   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 and a $5,000 engine replacement and lost down time, towing fees, rental car fees, headaches, etc. Again, buy here.  DO NOT BUY THIS AFTERMARKET IF OU CAN AVOID IT.  GENUINE BMW ONLY.  Genuine BMW is maybe $20 more but it's worth it.  If you do not buy Genuine BMW, you may buy OEM which as of time of writing, is the brand CoolXpert.

If you just need the expansion tank cap, buy here. It's good to keep a spare cap or replace at 25,000 mile intervals because the seals on the cap are known to harden and lose their ability to seal, even between tank replacements.  They're around $12 -- good investment.

Pulleys and belt(s) systems 

Our M5X and S54 engines have three belt-driven tensioner pulleys. The role of the tensioner is either to provide belt-spacing/traction and to quell crankshaft vibrations due to irregular accelerations from the crankshaft. This is done to prolong the life of belt-driven accessories and likely to quiet engine operation.

When should you replace your pulleys?

If your pulleys are original: replace them.

If you don't know how old they are: replace them.

If they are noisy or have excess play: replace them.

If they have 60,000 or more miles: replace them.

This is a crude diagram of the front of an M5X engine: 

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.Your dashboard will light up like a christmas tree and your temp needle will fly into the red zone.

Belts.  Obviously the belts themselves can fail causing an otherwise brand new cooling system to not operate. Replace every 35k miles. You can find it here.

This belt system is no joke.  E46s are prone to pulley failure.  I've seen it time and time again.  Is your E46 squealing and whistling?  Replace your pulleys. They're cheap and very easy to replace.

See my thread here for more info and discussion: http://www.e46fanatics.com/forum/showthread.php?t=974746

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 which will in turn throw the belts off effectively rendering your cooling system useless.

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.  If you insist on the Stewart water pump, it can be found here.

You'll need to remove the fan on your automatic E46 to access the water pump. I recommend this fan clutch tool here: http://amzn.to/2dWyHTU

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.  Thermostat can be found here.

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.   Manual Trans unit here and Auto Trans unit here.

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.

BONUS - WHY IS YOUR E46 OVERHEATING?

Written specifically by Mango

In order for your car to not overheat, these basic requirements have to be met:

1) Cooling system must be filled to capacity. That is to say the system must have no leaks and no air bubbles or pockets 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 added blockages or weakened drive force due to a damaged water pump or slipping/missing belt. 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 properly working sensors.

If your car is overheating, at least one of the above is not being met or you have bigger problems with the headgasket (unlikely if you've never overheated before)

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 pocket/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) Or you have debris between your radiator and condenser. Time to break out the a toothbrush and garden hose.  Remember you must have proper coolant/water flow and proper air flow!! You need both.

COOLING SYSTEM INSTALL TIPS:

Bleeding the system: (VERY IMPORTANT-DANGER DO NOT SKIP!!)

This step is extremely important. No amount of brand new cooling parts in the world will work if you do not bleed the system properly.  The point of bleeding is to remove air bubbles/pockets.  The cooling system is most efficient when it is circulating only fluid. Heat cannot radiate away from the surface of the radiator if there's air pockets.  You are essentially reducing the size of your radiator significantly if you have air pockets running through it.

Here is the official procedure per BMW TIS:

Here is a quick cheat sheet on how to bleed the BMW E46 Cooling System:

Raise front of car on ramps (Not necessary, but recommended)

CAUTION: ONLY DO THIS WHEN CAR IS COOL AND ENGINE IS OFF. At no point should the engine be turned on.

1) Remove expansion tank cap and bleed screw and set aside

2) Turn ignition to ON (dash lights on but do NOT start the car)

3) Set heat to MAXIMUM (90) and fan speed to low (this opens heater valve)

4) 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.

5) 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) :thumbsup:  The mileage is just a guide. Your results may vary.

Happy motoring
-Mango

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For inquiries: e46mango@gmail.com