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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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#2,257 ·
Freq you'll see the date of manuf stamped on the side of the ET. Check your's.

Every once in a while you'll see a coolant system go high mileage. Just most here don't want to gamble on stranded or fail.

Use www.realoem.com to get the part #'s you need and then plug into vendors listed at
www.furiousmethod.com to shop for prices for only first rate brands. If you don't know the answers to these questions already, you need to get the education gained by doing the research.

Come back when you have questions you can't answer with searches. In the more than a decade of this forum most info has been written before many times.
 
#2,260 ·
A quick update: they put in a Sachs as they were unable to get the Behr on short notice. HUGE difference, car sounds close to like it did from the factory again now, and the clutch properly disengages when I start driving cold (which is when the no name Chinese "OEM copy" part was noisiest). Thanks for all the input.
 
#2,261 ·
The hard plastic Water pipes on mine went at 116k in October of this year. I replaced everything minus the radiator and ET which had been already done with a BMW OEM piece.

I did this all in my free time after work or at night when the family went to bed.

Following the advice and instructions here made the job super easy
 
#2,264 · (Edited)
Quick vid showing what you should expect to see when bleeding the system.

2002 BMW e46 330ci coolant bleeding: http://youtu.be/v5lzKx5yFz4


In the vid I had the expansion tank filled to the top, air escaped about every 10-20 seconds and the level in the expansion tank dropped about an inch every 5-10 mins.

Originally my car's low coolant light would seemingly only come on in the winter with the heat blowing on high for the past 2 winters. Then recently over the past 6 months it has been intermittently coming on regardless of heat or a/c on or off but the level always looked good on the expansion tank gauge.

2002 E46 BMW 330ci coolant light: http://youtu.be/awIOP74fodA

So that's when I decided to try again for the third time in the past year to bleed it again and that's when I found more bubbles escaping like in the first video above.

Another issue I've had is that now this winter when I have the heat on highest I only feel heat while driving when I come to a stop the air blows cold like in traffic or red lights so besides bleeding it again I also ordered a new heat valve which will be here Monday... Hopefully I will finally have a good coolant system. The water pump was done in March and was bled when it was swapped and now again today. At first try I ran the engine for 15 mins and the low coolant light did not return yet. In the past 3 years the expansion tank, fan, fan switch, temp gauge, upper hose, and thermostat have all been replaced. What else can any of my issues be and what else could need to be replaced??? Only thing I can think of is the radiator but would that cause these problems?





Sent from my HTC



Sent from my phone using the wi-fi's
 
#2,268 ·
I would just like to update n say my heat seems to be staying steady n not fluctuating since reattempting the coolant system bleeding. Th low coolant light has gone out n stayed off, hasn't returned not even once this time. Even though I will still be replacing the heat valve for pm since the existing one is 12 years old.

Sent from my phone using the wi-fi's
 
#2,265 ·
My 318i N46

Helo car Docs and fanatics?
My 318i N46 has engine oil in the radiator, the engine oil is running out quickly and there is a whitish smoke when its raved. What could be wrong? there is no trace of water mixing on the stick whether after engine running or cold. what could be wrong buddies?
 
#2,266 ·
Helo car Docs and fanatics?
My 318i N46 has engine oil in the radiator, the engine oil is running out quickly and there is a whitish smoke when its raved. What could be wrong? there is no trace of water mixing on the stick whether after engine running or cold. what could be wrong buddies?
Neglected to tell us anything about the car. Year and mileage?
Sounds like a possible blown head gasket. Overheat recently?
Compression test and leak down test suggested.
You might need a new engine.
 
#2,270 ·
Try filling the expansion tank til it is totally topped off then while it is still open remove the bleeder screw then turn the key to ON, Do Not Start the Engine. Put the heat fan blowing on lowest, temp set to 90 or 91° with the knob between the two middle vents at three red dots. Leave it like this for 10-30 mins you should see the level in the expansion tank slowly drop as the engine takes in more coolant and as bubbles of air trapped in the coolant system escape from the bleeder hole. Once you see that it appears there are no more bubbles escaping then syphon out any extra fluid that may be in the expansion tank, mine was so low that eventually the expansion tank level was fine and I had no need to remove any extra fluid.

If you still have no results the coolant level sensor may need to be replaced.

Sent from my phone using the wi-fi's
 
#2,272 ·
If ur batts almost dead it is possible, if ur batts good then most likely not. But I used to think the same thing and every time I was bleeding it I couldn't figure out why the low coolant light kept returning. But I used to bleed it only 5-10 mins. This time I let it go til I no longer saw any bubbles. If u think ur batt may die make sure the car is in optimal position to make a jump start easy, i.e. don't park nose facing a wall at the end of a narrow driveway.

Good luck

Sent from my phone using the wi-fi's
 
#2,290 · (Edited)
The car doesn't overheat. I don't see coolant on the driveway either but maybe it has dripped onto that plastic panel under the engine. I will examine the engine bay again but now my coolant light constantly goes on and off whereas before it didn't.


Put the car on ramps and nothing happened. Took a picture of where I found a leak



I replaced the radiator in the spring and correct me if I am wrong but in the above picture it looks like it is coming from the radiator
 
#2,297 ·
Went to the dealer to have something inside the car changed. Every time I pop open the hood to add coolant I notice that when I open the bleed screw, the coolant level in the tank via the cap opening seems to rise back up and the dipstick comes up too. Still doesn't bleed and after letting the car warm up a few days ago I saw a coolant puddle in the driveway. I also have heat now.....I'm going to have to do an overhaul the sooner I get the chance.

As for the cooling system being serviced; I bought the car with 71,000 miles and now it is at 97,500. Anyone know where I can get a vehicle history report without having to pay for it?
 
#2,298 ·
If you bought it at 71k the system has never been serviced. Don't worry about the history. On most cars I would say first issues appear at around your mileage - thermostat soft fail and coolant leak out of the lower hose sensor are the first issues you will see.

When you just top-off coolant or check level do not open the bleed screw. You only open the bleed screw for bleeding.

I also wondered about the level rising when I opened the bleed screw, but that's just the way it works. Do not open it if you are checking or adding coolant.

If you are bleeding, yes you open the bleed screw, once the air bubbles come out you close it and adjust the ET level

From your posts it sounds like your thermostat failed. Mine failed around the same mileage as well. I don't know by what you mean "still doesn't bleed". If you followed Mango's procedure in the first post of this thread, it's bled, you're done. This is also the procedure in the Bentley manual, and I think the BMW service manual. So it's the proper bleeding procedure, and not something someone just made up.
 
#2,299 ·
I broke down and had to get a tow. Whatever the problem was it finally let go and dumped coolant all over the road. Hopefully when I get the car back it will be fixed and hold up for me to save some money and do the overhaul. The thermostat seemed to work fine but since the car couldn't hold coolant it has been acting up.

As far as topping off, every time I would open the main cap the tank appeared empty and when I would open the bleed valve I would watch the coolant level rise back up
 
#2,300 · (Edited)
Great post! I will be doing this replacement soon. I have never had my car overheat since I purchased it a few months back, but did check my coolant just the other day and the red stick did not pop up past the cap. Once I warmed the car up a bit then checked it again and it now pops out of the cap showing that its at the appropriate level. Is this normal or am I losing coolant somewhere? I figured maybe when I warmed the car up it may have started boiling ? and that is why it is level at operating temperature? After a few days I got some BMW coolant and added it while it was cool and it only took like 5oz to bring it up to full (via red level stick). Any help would be appreciated, I am NO mechanic by any means but have done quite a few fixes on my BMW thanks to forums like this, youtube and manuals.

ALSO.. I got the UV Dye and light to check for leaks, but haven't decided to do it yet. I also noticed after a few days it would show low again when the car was cold, and It would only take 4-5oz to get it level again? not sure if that helps anyone understand what may be wrong, I would think a leak in certain areas would leak out all the fluid just not 5 oz. Makes me think maybe it's the Expansion tank reservoir. I did not get much information on the car (2000 323ci) when I bought it, but it was for sale by owner for $2k and I got it for only $1,500 which seems like a pretty good deal compared to other cars I test drove at that price range (beat up civics etc...), Also the radiator looks like it was replaced shortly before I bought it (still looks brand new) compared to how dirty some radiators that I have seen on these cars.

Thanks Again!

Cody
 
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