E46 Fanatics Forum banner
Status
Not open for further replies.
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!
 
See less See more
#915 ·
Well I got everything in the mail now, including a new radiator. I know my thermostat is bad as I got the CEL and the car is running cold. I have to admit, I am hesitant now to start replacing everything else as I have ZERO leaks or any other problems with the coolant system or belts or pulleys.

I like to stock up on the parts I may need and replace them when they begin to go. Convince me please why I should do this proactively? I need a nudge in that direction. I mean I want to do it, but I'm a little hesitant as I'm scared that I'll create problems by going in and replacing stuff that ain't broke. I bought this particular car with 107,000 miles (it has 120k now) and came with NO maintenance history - although I know the belts at least were replaced at some point as they are CARQUEST stamped.

Help.
 
#916 ·
Well I got everything in the mail now, including a new radiator. I know my thermostat is bad as I got the CEL and the car is running cold. I have to admit, I am hesitant now to start replacing everything else as I have ZERO leaks or any other problems with the coolant system or belts or pulleys.

I like to stock up on the parts I may need and replace them when they begin to go. Convince me please why I should do this proactively? I need a nudge in that direction. I mean I want to do it, but I'm a little hesitant as I'm scared that I'll create problems by going in and replacing stuff that ain't broke. I bought this particular car with 107,000 miles (it has 120k now) and came with NO maintenance history - although I know the belts at least were replaced at some point as they are CARQUEST stamped.

Help.
Failures don't always come with warnings. If you have no prior history for the car, truth is you don't know how many miles or how much time is on the parts. Given that your engine can be destroyed with an overheat, you'll have to decide whether or not it is worth it to spend $500 now or possibly spend $3,000 + 1 to 2 weeks of down time later.
 
#917 · (Edited)
After doing the project last week, I would not recommend that you replace the thermostat without doing the hoses also. How old is the expansion tank, water pump and radiator? The connections on the radiator are plastic, so you need to be gentle when you replace the hoses. You have 120K on a 2005 compared to 118K on my 2001, I see that as more wear in a shorter period of time and think that a overhaul is in order. The cooling system is nothing to tempt to fail, it will make you crazy. Hell, I checked the coolant level every time I went out to drive it for the eight days since doing my refresh. But when you're finished, you shouldn't need to mess with it for 3-4 years. Just move on to other projects.
 
#918 ·
Yeah I hear ya. and the fact that BMW had ZERO history on the car (not even the free maint was done at a BMW shop) and that the PO put on CARQUEST belts - what other shoddy stuff was done - or NOT done in this case. I'm getting ready to crack a Sam Adams and get this thing going...tonight! Thanks for the voice of reason guys!
 
#921 · (Edited)
man. those bottom water hoses on both the radiator and the ET are a biatch! I can't seem to get them off. I was just going to pull the whole shebang out with them attached, but the radiator won't come out with them both attached.

Just went to realoem.com to look up the part number for the A/C tensioner because I thought I forgot to order it, even with all the discussion on here about it, and remembered that I in fact did order it - its that DAYCO one that I ordered from Amazon - it just didn't come in yet. Hopefully it will tomorrow.



Anyway, the things all apart now - hope I can get her back together.
 
#923 · (Edited)
my two cents for this DIY:

First another question: What do you guys clean off the aluminum where the thermostat and water pump seal up against the engine? Mine are looking pretty corroded and I'm not sure what to clean them with or how?

1. Order new bolts for your thermostat P/N 11 53 1 740 317. They are cheap to replace and probably rusted bad like mine were anyway.
2. When removing your ET, you don't have to remove the bottom most water hose - it stays attached to the ET carrier. I had to take a hammer to the bottom of my ET (hammering UP) to remove mine...this was after trying to get that bottom hose off for over an hour, thinking it was what was holding it on. It wasn't. I went as far as to remove the alternator cooling vent duct to try getting that bottom hose off - to no avail.
3. Make sure that you give yourself time for the unexpected. I.E. when removing the water pump, one of the bolts from the thermostat that I was using to loosen it got stuck then snapped. Luckily I was able to jiggle the water pump free anyway.
4. Make sure you have ALL the parts before you start. I did not, and my car is now sitting in the garage opened up. I need new thremostat bolts (hopefully the stealership has them in stock) and I forgot about my A/C belt tensioner which hasn't come in yet from Amazon.
5. The Bentley manual is neat - but don't rely on it for all the details - they are missing for this DIY.

Most of my components were date stamped on the tags. All that were had a date of 2004. My car was built in Sep of 2004, so they were all original. Most were in pretty bad shape and would have failed soon I'm sure. So if you are double thinking this like I was, I say do it. It will save you from an emergency repair and high dollars if anything is blows out on the highway and you overheat or are stranded.

Thanks again for this site! I'm not done with my coolant overhaul yet, but feel pretty confident that with a little patience and time, I'll get it all completed and put back together by the weekend.

Stay safe and warm - looks like most of us on the east are in for a cold snap.
 
#925 · (Edited)
my two cents for this DIY:

First another question: What do you guys clean off the aluminum where the thermostat and water pump seal up against the engine? Mine are looking pretty corroded and I'm not sure what to clean them with or how?
If the Al surface is corroded some, clean it first with a gasket scraper and then perhaps an easy touch with some medium/fine wetsand paper.
If you think the gasket will not make up to the surface properly, consider some gasket sealer to fill in the recesses. And let it set for a few hours before filling the system. Overnight is best.
 
#928 ·
Meh so expansion tank busted, bought everything except expansion tank mounting plate (even though I wanted this too, snapped retaining spot where tank sort of "clips" in.

Took roughly 2 and a half hours, started bleeding system and then saw coolant pour out and I was baffled... Had to push the expansion tank down even further so it latched on, originally I was scared I'd break something pushing it so hard while holding the retainer but finally went in. Bled it, all good now running at 95C :)
 
#931 · (Edited)
So I got everything back together. Car wouldn't start though as when bleeding I left the lights on and the door open and killed the battery. Jumped it and it started right up. Is running right in the middle on the temp gauge.

However, I couldn't get the two screws that hold the ET to the ET carrier all the way in - they are about half sticking out. They stripped - they are both in such hard to reach places. Otherwise running great and the "putting back together" part is pretty easy. Can't help but think something isn't put together quite right though, and it'll "blow" at any minute. Like the ET into the carrier like just mentioned, or one of the hoses isn't on tight enough, or those 10nM torqued bolts on the W/P and W/P pulley just aren't tight enough.

Not too worried though, I remember thinking the same thing after I finished my vanos rebuild - and it's held up.

thanks again for this thread Mango. Good stuff.

Now I have to figure out a few things:

1. vibration under load accelerating,
2. rear passenger window seal isnt' tight - wind noise is annoying,
3. A pillars are sagging - guess I'll have to order some of them, probably not till next fall though,
4. I'm starting to get the blower motor squeal - annoying more than anything.
5. I have a new fuel filter and complete suspension, and new passenger side window switch and complete center console sitting in my garage...oye!

there's no end is there? Maybe its about time to bite the bullet and get another 1-2 year old 5 series and ride out the remaining free maintenance and warranty under CPO for another 4 or 5 years.
 
#935 ·
there's no end is there? Maybe its about time to bite the bullet and get another 1-2 year old 5 series and ride out the remaining free maintenance and warranty under CPO for another 4 or 5 years.
You have a seven year aged car. Within relatively recent memory cars would be in the junk yard with those years and less mileage.
It is expected that lots of parts will be replaced to keep our cars driving like new, and reliable.
 
#940 · (Edited)
so my bottom left (with the coolant temp sensor) hose on the radiator doesn't seem to be connected on all the way straight. I can get the clip closed with no resistance at all, but it looks ever so slightly canted and appears to have a very small amount of coolant coming out from somewhere around that connection.

I took the fan back out and tried like hell to "snap" it into place - would wiggle and move, but just won't go on any further. System is fully filled with brand new coolant, so that should be providing the lubrication needed for the o ring.

After I played around with it I replaced the fan and then went for a very spirited 15 minute drive. on return there was one little drop of coolant clinging to the bottom of the connector. I put a piece of cardboard under it and am going to let it sit and see if it is still leaking.

Otherwise system looks and performs like new.
 
#941 ·
Bottom RIGHT hose has the coolant temp sensor on it. Learn this stuff well so we know what you are talking about.

Did you lube well?
Remove, clean, reposition O-ring, lube and retry.
Full system does not do what you need. Sorry, you need to drain.
I'd not leave my car where yours is now.
 
#944 ·
so i drained and pulled the RIGHT side hose off the radiator. I put it back on, it snapped into place and I locked it down. Still looks ever so canted - not much better then before. I'm going to run it like this for a few days, keeping a close eye on it, and see how it goes.

I mean it's locked into place - could have just been loose the first time, then residue coolant leaking out around the next few times I checked. We'll see.
 
#945 ·
I will have to add this(since it is my problem now)the LOWER RADIATOR HOSE TEMPERATURE SENSOR COOLANT!,I have a 2003 330ci A/T,the dash was constantly showing the lower coolant level warning light..it was hard to find,but today showed it was the culprit,the o ring in this sensor degraded and allowed a small amount of coolant to drip....my two cent here!
 
#950 ·
Its a good kit, I just used the kit from pelicanparts.com which came with all the necessary and is around $400. I added a new oem expansion tank, Ac belt, and idler pulley. Total was around 520.
*no radiator included.
Radiator is approx an additional 200



Sent from my SAMSUNG-SGH-I747 using Bimmer App
 
#952 · (Edited)
Its a good kit, I just used the kit from pelicanparts.com which came with all the necessary and is around $400. I added a new oem expansion tank, Ac belt, and idler pulley. Total was around 520.
*no radiator included.
Radiator is approx an additional 200
$400 with no radiator or ET doesn't sound too competitive.

And new oe rad is under $150

Can edit posts.
 
#955 ·
Can I ask you a question about the bleeding TIS. Should we put the car on ramps before we remove everything? How do I move it to ramps once I have no coolant? Trying to figure out the best way.

Thanks,Joe
 
#956 ·
Can I ask you a question about the bleeding TIS. Should we put the car on ramps before we remove everything? How do I move it to ramps once I have no coolant? Trying to figure out the best way.

Thanks,Joe
 
Status
Not open for further replies.
You have insufficient privileges to reply here.
Top