* E46 Cooling Guide (Information w/parts list/bleeding) *
Parts sources: Amazon, AutoHausAZ, BMAparts, ECSTuning, RMEuropean
This thread 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.
Before we move onto the cooling system, click here if you've just acquired your non-M E46.
The E46 3-Series (as well as the E36 3-Series) are known to have somewhat of a delicate cooling system which are sometimes known to fail prematurely. In the event of a failure, the results are often times catastrophic.
The inherent design of the inline-six BMW engine having a long block/head coupled with the fact that the head is made of aluminum means that the head is particularly vulnerable to heat damage (or warp). This damage to the head and headgasket can occur in seconds once your car is overheated and usually means a top-end rebuild which may cost around $2,500 to repair.
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, immediately shut off the car and have it towed.
How, why, and when do the failures typically occur?
Plastics. Your E46 contains lots of it. The typical first failure of the E46 cooling system is the expansion tank. It will typically develop a hairline crack anywhere from 60-95k miles (give or take a few). That crack will expand under heat and water will leak out. This will trip the low coolant warning on your dash. If this 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.
Other typical 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. Your dashboard will light up like a christmas tree and your temp needle will fly into the redzone.
The water pump is another potential failure point. 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.
Failure isn't that common but can still happen. 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. You might hear stories and internet legends about the Stewart water pump (and they may be true) but really it is unnecessary and a waste of money (unless you plan to drive your car enough to justify the cost--at least 180,000-220,000 actual driving miles)
The thermostat sometimes fails around the time the expansion tank does. Maybe a little longer. They are generally designed to fail stuck open but don't risk it. Just change it.
Belts. Self-explanatory. No belts, no cooling system. Replace them every 35k miles.
Radiator is typically robust, but the endtanks are made of--you guessed it--plastic. The rubber seal between the endtanks and the main body may deteriorate as well. 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.
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 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 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 list with prices as of 4-6-12:
(Free plug for sponsor ECSTuning :))
OK, Mr. Mango, you have convinced me to replace the entire cooling system. Where do I get the parts?
There's many places. Personally, I like BMAparts.com, RMEuropean.com, and OEMbimmerparts.com. All are cheap and lightning fast. I put together the following parts from BMAparts.com and partly, Amazon.com (for one part)
I included part numbers so you can cross-shop and get your own prices.
Behr $137.30 (Manual transmission) Part# 17119071518
Behr $139.29 (Automatic transmission) Part# 17119071519
Expansion tank Part# 17117573781
Genuine BMW $63.29
Expansion tank cap Part# 17111742231
Water pump Part# 11517527910
Saleri (OEM) $54, BMAparts.com part# BMW006731 (you won't find it on their site as of 4-9-12 but you must add it to your cart using the store part#)
Radiator hose lower Part# 11531436408
Radiator hose upper Part # 17127510952
Thermostat Part# 11537509227
Radiator fan switch Part# 13621433077
Genuine BMW $26.01
Water pump pulley Part# 11511436590
URO Aluminum $22.68
Genuine plastic $30.55
Coolant drain crush washer at engine-block Part# 07119963200
Fischer & Plath $0.05
Water pump pulley bolts x4 $0.25 ea. Part# 07119904524
Belt tensioner pulley Part# 11281748131
Alternator deflector pulley Part# 11287841228
A/C tensioner pulley
(hydraulic, SKF $15.93) Part# 11281748131
(mechanical, Dayco 89133 $21.94) Dayco 89133 - Amazon.com
Alternator/accessory belt Part# 11281706545
Part# 11281437450 (5-rib up to 9/2002) $8.72 or;
Part# 11287512762 (4-rib from 9/02) $7.91
Expansion tank mounting plate (optional) Part# 17111436250
RMEuropean Genuine BMW $54.53
Automatic cars: (If you drive an auto trans., add the following parts to the above list)
Expansion tank mounting plate (optional) Part# 17111436251
RMEuropean Genuine BMW $54.53
Thermostat Part# 17111437362
Fan blade Part# 11521712058
Fan clutch Part# 11527505302
Grand total manual transmission cars: $500.23
Grand total automatic transmission cars: $738.20
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 point of bleeding is to remove air bubbles. The cooling system is most efficient when it is circulating pure fluid.
Here is the official procedure per BMW TIS: http://tis.spaghetticoder.org/s/view.pl?1/06/06/86
Here is a quick cheat sheet:
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.
(if there's anything which I should address, edit, or add. Let me know)
Great resource! I'll be sure to reference this when tackling my upcoming cooling system replacement.
Glad to help. There's also other misc. hard pipes and even one soft hose which connects to back of expansion tank and goes to the hard cooling pipe towards the firewall. But nobody replaces that but maybe I should add that too. I totally forgot about it when I did my cooling update. But, FWIW, I don't think I've ever heard of a hose failure on these cars.
Couldn't hurt to include it anyway.
Excellent write-up, as always, and perfect timing. I will be doing the complete refresh this summer.
Sounds good! Thanks!
I bought a kit for my 330ci from Mike at the thebmwpartsstore.com. Really nice guy. You included some extra parts that I'll keep in mind. I just bought a 323ci and sell the 330ci so I'll keep my parts for the 323ci.
I wonder if the mods would think its a good idea to sticky this since the cooling thing is asked about by newbies on almost a daily basis.
Should be stickied since everyone suffers from the cooling system issues at least one time in their ownership of a e46
My car's PO purchased the car at ~100k miles and drove it from Florida back to MO. Somewhere along the way the coolant tank had cracked and leaked out all the coolant and it overheated. The PO turned the car off as soon as he saw the temp spike but by that time, it was too late and it lost the head gasket and warped the head.
He replaced the entire cooling system and had to deck the head and rebuild it. There's unfortunately nothing he could have done to prevent this as it happened on his way home after buying it. He was left with a 2k plus bill even after having super cheap BMW club people helping with the rebuild. It ruined his experience with the car which is why I have it now.
Plastics deteriorate with age just as it does mileage so even if you haven't put on 75k miles, if your car is ~10 years old, consider Mango's advice...change it out...
Great story. How many miles on the rebuilt head? Glad to see its doing well to this day. And yes, age will also kill plastics. A lot of people come on here saying their E46 has 50k miles and thus needs no cooling maintenance. Nothing could be further from the truth.
This needs a sticky.
Request sent to SolidMod. Haha. Not to be off topic, but I noticed you have an M5, Halo. (Gorgeous car, btw. it looks perfect how it is in your pic) you mentioned you have other cars. Whats the other car? E46??
Thanks for this, I always see you going on and on about the cooling system and now there is one place to find all the information we need!
I was really paranoid so I had a compression and leakdown test and compression was solid across the board around 180-190 cold and leakdown zero on all cylinders except two that were at 1%. Solid as a rock now. The PO is an enthusiast and he had BMW certified techs doing the repair, so it was done right thankfully. They even went so far as to time-sert the block in case the aluminum threads had weakened from the heat and addressed vanos as well while in there.
Cooling system also looks to have been done right. I was given the order sheet from Pelican with every part replaced and it seems to be doing its job well.
It's not a death sentence, but it's definitely an expensive repair. I just went through and looked at his cooling system overhaul parts bill and it was 900, so you've clearly put together a very cost effective means of addressing it. :thumbsup:
Awesome. Yeah I don't even want to know what the dealer price would be for all these parts and labor. I'm guessing way north of $2,000
This was the labor bill for the head rebuild:
Valve job BMW: 192
Pressure Test: 60
Needless to say, he got a good price on all that. Dealership labor would be....significantly higher.
What about the mounting plate that goes between the radiator and the expansion tank? When I was doing my refresh, the nipple that plugged into the radiator broke off when I removed it. Seems like this should be part of the refresh, especially since the o-ring that is on it seems to be non-serviceable. There is a difference between the manual and automatic mounting plates, so that has to be kept in mind. Nice thread. There is plenty of useful info in here. I just hope that I won't need it for quite awhile! :eek:
Sure, I can add the mounting plate. In my experience, it's a robust part and is essentially just a plastic frame. should be fine if you're careful. I'll add it!
Since this part isn't a typical failure item, I didn't include it in the grand totals. It's $54 and somewhat substantially drives up the cost of the rebuild.
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