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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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#86 · (Edited)
If you dont want to waste $26 like me on a lower radiator hose fan switch; you can re-use your old one but you must replace the O-ring; otherwise it will leak.
I did some research/ spoke to dmax and found out you are able to get one on pelicanparts.com for $1.00. Its the O-ring from the air intake temp senser part # 13621743299
Its the same size and material and has been used before by other fanatics will no ill effects. Again:
PelicanParts.com
Part # 136 217 43 299
$1.00
 
This post has been deleted
#88 ·
The switch is already on the list. It comes with a brand new O-ring. no need for the separate part unless you're buying separately. Since buying separately doesn't exist in my book, i won't bother adding it =) I'd only be encouraging people for their cars to break down
 
#92 ·
I have 85K on my car, do you suggest buying a new one?
I know they last for hundreds of thousands of miles!
I bet it can easily go another 60-70K until the next cooling system overhaul;
then I would change it. You can make the part # available just to give people a choice to decide for themselves. You got to admit it is extremely easy to access and replace!
 
#91 ·
Good! G35 has its own problems. Like cross-contaminantion of the cooling/transmission fluid due to poorly designed couplings at the cooler. This happens frequently to Nissans and Inifnitis including my mom's brand new G37 which had its transmission replaced (among a sh!tload of other things)

Relative to the total price of the car, $500 is not a lot to ensure a reliable vehicle. And given the age and mileage, you'd have to be replacing the cooling system of any car. Two of my friends with other brands of cars just experienced cooling system failures last week. A Jeep and a Toyota. Both around 100k miles.
 
#98 · (Edited)
I'm assuming its the expansion tank since is comming from the driver side... ? radiator looks great.

water pump was replaced at 65k miles along with thermostat and some hoses. I don't think i need to replace them again so i just ordered the expansion tank, parts and hoses that goes a long wtih that side of the rad. It seems to only leak when I add coolant to the full mark which only takes like 1/6 of a quart roughly so i assuming there is still plenty of coolant in the radiator and block. I need my car so for a temp fix i am going to pull the expansion tank and solder the crack with extra plastic until the parts come in. That i hope should hold for atleast a week.... :banghead:
 
#99 ·
Don't get me wrong; I wish you good luck with your repair.

I'd suspect you would not be able to get the ET to hold for a day much less a week. You are flirting with a fairly serious downside here.
The ET is molded out of some sort of thermoplastic composite clearly designed to withstand high temps. I'd guess it would not lend itself to being melted together.
Do let us know how you make out please?
 
#100 ·
Maybe taking it easy on the car for a whole week will help keep it from cracking again before the parts comes in. Of course, it depends where the fracture is too. If its on a flat side, it shouldn't be a problem for just a week but if its at a bend then yeah, i don't see it holding for long.

We'll see. I'll definitely keep you posted on the repair.
 
#103 ·
Stinger9, ET cap is rated 29psi , not 15. Our system runs on 2bar pressure. 2bar=29psi . The cap is stamped 200Kpa in the inside. 200 kPa = 29.0 psi

Ilovecars800490, please stop crying about how plastic is bad ,this and that. I can send you a box of tissues if you want . Plastics have revolutionized the automotive industry and made things possible that havent been possible before , they made mass production affordable and generally only carry benefits, so please stop talking bad about plastics.
 
#104 ·
Ilovecars800490, please stop crying about how plastic is bad ,this and that. I can send you a box of tissues if you want . Plastics have revolutionized the automotive industry and made things possible that havent been possible before , they made mass production affordable and generally only carry benefits, so please stop talking bad about plastics.
Not once did I say plastic is bad.
 
This post has been deleted
#110 ·
2006 330CI - No front auxiliary fan?

Hi, I have been out of the BMW scene for a while (since 2007) when I hit a deer with my 2001 330CI M/T but just yesterday bought a 2006 330CI ZHP with 6-speed manual trans. My wife has a 2005 330CIC auto trans and this morning I noticed that my car does not have the "pusher fan" on the front of the radiator like my wife's automatic car has.
I googled and couldnt find out if my car was ever equipped with both a pusher and a pull fan. Does anyone know the answer?

Thanks for any help
 
#112 ·
Wanted to share some information for those of you looking to grab some parts to do the work yourself.

I placed a $300+ order with BMA last week on a bunch of parts i needed to do a cooling update on my 325xi. The are great people to deal with. Very communicative and friendly people.

I had a few issues with my order though and wanted to point this out for reference...

A/C tensioner pulley
(hydraulic, SKF $15.93) Part# 11281748131
(mechanical, Dayco 89133 $21.94) Dayco 89133 - Amazon.com
I ordered two of the SKF pulleys for my 2003 325xi (AUTO). THESE DO NOT FIT. The center hole that the is used to bolt the pulley on is too small and does not accommodate the recessed bolt. Had to run to the local auto parts store for a Dayco. Need to return these.

I also went with the OEM Saleri Waterpump, which arrived damaged. The plastic impeller was cracked and there was no way i was putting that into the car. Since my OEM Waterpump had some play i needed to replace it. Went and grabbed a GMP (metal impeller) and put that in, although i wanted to go with composite. Little disappointed as i ended up paying more for this water pump than i wanted. Have to return this also. FYI make sure you check for this is you are getting the plastic impeller as it might be easy to overlook.

Overall i changed the following:

  • Coolant Expansion Tank
  • Coolant Expansion Tank Cap
  • Waterpump
  • Waterpump Pulley
  • Belts
  • Tensioner Pulley's
  • Idler Pulley

All went smooth and didn't take very long, aside from the running to the parts store. I will be doing my brothers in the near future and will for sure do a DIY article. I didn't have as much time as i would have liked so i was not able to document it.
 
#126 ·
Wanted to share some information for those of you looking to grab some parts to do the work yourself.

I placed a $300+ order with BMA last week on a bunch of parts i needed to do a cooling update on my 325xi. The are great people to deal with. Very communicative and friendly people.

I had a few issues with my order though and wanted to point this out for reference...



I ordered two of the SKF pulleys for my 2003 325xi (AUTO). THESE DO NOT FIT. The center hole that the is used to bolt the pulley on is too small and does not accommodate the recessed bolt. Had to run to the local auto parts store for a Dayco. Need to return these.

I also went with the OEM Saleri Waterpump, which arrived damaged. The plastic impeller was cracked and there was no way i was putting that into the car. Since my OEM Waterpump had some play i needed to replace it. Went and grabbed a GMP (metal impeller) and put that in, although i wanted to go with composite. Little disappointed as i ended up paying more for this water pump than i wanted. Have to return this also. FYI make sure you check for this is you are getting the plastic impeller as it might be easy to overlook.

Overall i changed the following:

  • Coolant Expansion Tank
  • Coolant Expansion Tank Cap
  • Waterpump
  • Waterpump Pulley
  • Belts
  • Tensioner Pulley's
  • Idler Pulley

All went smooth and didn't take very long, aside from the running to the parts store. I will be doing my brothers in the near future and will for sure do a DIY article. I didn't have as much time as i would have liked so i was not able to document it.
Should have just returned the defective part. Let it be known that the metal pumps everyone gawks over have been known to have cheap spot welds which come apart and balancing issues causing premature failures. This is why BMW stopped producing the metal impellar pumps. You just got a defective/damaged item and your results should not at all in any way be attributed to the pump not being "metal."
 
#114 ·
Car only has 50K miles on it. Gave the hoses a good inspection and did not find any reason to change them. They are easy to replace in the future if needed.

Yes, got the metal waterpump pulley.

I have a couple good friends who work as BMW techs and they recommended the plastic impeller over the metal. I trust their judgment as they deal with these things on a daily basis. If it ever breaks i don't want metal bits floating around in the system.
 
#118 · (Edited)
Hydraulic vs. mechanical is the mounting structure that the pulley is attached to and which supplies the pressure to tension the serpentine belt.

Got to get in there on your engine front to tell the difference unless you know what you are looking for.

Does this give you a clear idea of the difference?
 

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#119 ·
Hey guys, im back with a bad news...

Recently I purchases an after market radiator, aluminum alloy at that and I was hoping it would fit my car. Turn out it did fit, but require to purchase an addition slim performance fan! stock e46 assembly fan would not fit with the new 56MM radiator size, it would touch the engine, pulleys and etc... Unfortunately our stock radiator sizes 42MM I suppose?? :banghead:

Im such a dumb azz!! But luckly for me, atleast they accept return with full refund.:D

Sent from my HTC Glacier using Bimmer App
 
#120 ·
Hey guys, im back with a bad news...

Recently I purchases an after market radiator, aluminum alloy at that and I was hoping it would fit my car. Turn out it did fit,

Sent from my HTC Glacier using Bimmer App
Condolences for the bad fit, but I would have stayed away from anything other than oem for the rad.
Oem is good enough for 100k miles and cheap enough not to sweat. And cools totally fine.
 
#125 ·
I'll make this simple. OE/OEM (Saleri) water pump should be first priority. Aftermarket is FINE (Graf, Hepu, Geba). Personally I'm using a Graf pump (was in a rush at the time and my supplier (BMA) couldn't get the OE pump so I just settled for A/M. It's holding up fine as well as the countless others I've installed in other BMWs.

DO NOT AT ALL PAY ATTENTION OR BE OVERLY CONCERNED WITH THE MATERIAL OF THE WATER PUMP IMPELLAR. WHETHER IT'S PLASTIC, COMPOSITE, OR STAINLESS STEEL AKA "METAL" IS ABSOLUTELY IRRELEVANT. DESIGN IS EVERYTHING AND FOR ALL INTENTS AND PURPOSES, OE IS BEST AND THE BIGGER AFTERMARKET BRANDS ARE PERFECTLY FINE. E36/E46 WATER PUMPS HAVE GOTTEN TO A POINT NOW WHERE THEY AREN'T FAILING DUE TO IMPELLAR MATERIALS, BUT SIMPLY DUE TO MILEAGE AND WEAR. THIS WAS THE CASE 10-15 YEARS AGO. THE OE PUMP IS NOT FAILURE PRONE. IN FACT, IT'S QUITE THE OPPOSITE. THX
 
#128 ·
I need to do this ASAP my radiator is leaking, I do have 110k on the car...

My questions are if I were to get that kit from Ebay that was just posted, a Behr radiator, and new belts that should be enough right?

Also how hard is it to do myself and do I need any special tools?
Im not that great at mechanical work though, so I was also wondering what a shop might charge for the labor?

Thanks
 
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