Originally posted at http://mywebpages.comcast.net/gsussman/cooling_system.htm

Cooling System

Of all the subsystems in the E38, the cooling system seems to be one of the ones with the highest failure rate. Somewhere in the range of 70 to 100K miles, you too will have to perform some major maintenance on it. This usually revolves around the two main components, the water pump and radiator.

Of the two components, water pumps give you by far the most warning. Normally it starts with the smell of coolant in the engine compartment and degrades to a small puddle of coolant on the garage floor after sitting all night. On others, the bearings begin to whine or shriek under acceleration or during normal running. In either case, you will know it is time to do the pump.

The radiator is the silent killer of the two. The E38 cars, as well as the 5 series cars are prone to a catastrophic radiator failure when the  upper hose neck breaks off. It is usually not a matter of if it will happen, but when. When it goes, there is no warning, and no getting home. You will sit on the side of the road, billowing steam until the flat bed arrives to pick you and your broken machine up. There are a number of theories as to why the upper neck breaks. Some say that the Behr radiators have a design flaw, while others put the blame on BMW directly. The why is not what I am going to discuss on this page, it is the "How to" when it comes to replacement.

The repairs for either or, or both of these components is within the capacity of a capable DIY mechanic, but it takes time. Don't set out with the mindset that "I will get the whole thing done this weekend", It's not going to happen! Murphy's law dictates that you will break a part, or need a bolt long after the auto parts stores have closed. For me, the end to end procedure took 2 weeks, but 1 of those wwas spent waiting for parts. Which brings me to my next topic.

If your car is drivable before the start of the procedure, do not start taking stuff apart until you have ALL of your parts in. Inevitably the parts that are missing will be the ones you need first, thus you will loose a number of days waiting for them to come in. It will also allow you to ensure that all of the parts are correct before you take them out of the box at 11:30pm Saturday night only to find that you either have a broken part, or the wrong part.

I did not intend on this page to be a replacement for the TIS procedures for the water pump / radiator replacement, only a source for lessons learned, and  information that is not part of the actual procedure. The TIS is an integral part of getting this job done right. Make sure you have it.


If you don't already have one, buy the BMW TIS CD (Technical Information Service). It is basically the entire factory service manual for all BMW vehicles, complete with drawings, pictures, and procedures for fixing, replacing, or servicing each and every part on your car. I would have never been able to complete this project without it. It will also give you the proper torque specs for all the bolts. Let me put it this way, if you are even considering doing this job yourself, then you undoubtedly do a fair amount of maintenance on your car. The CD will pay for itself in no time!

You can order your copy from: Central Letter Shop
Fairlawn, NJ

Required Tools

  1. Metric socket set 3/8" drive should do. (I actually used a 1/4" drive set for over 50% of the work. There are quite a lot of 6 to 10mm bolts to take out, and the 1/4" drive socket set is perfect for these)
  2. Socket extensions (1/4" 5 to 6" long, 1/2"drive 3" long) 
  3. 1/2" drive to 3/8" drive converter (if you do not have 1/2" drive metirc sockets)
  4. 1/2" drive breaker bar (you will need this to get off the vibration damper pulley if you decide to do the water pump)
  5. 1/2" drive Torque wrench, calibrated to at least 34 N/m
  6. 32mm open end wrench (you can not use a crecent wrench in place of this, it is too thick. The thinner it is the better) 
  7. Fan clutch removal tool (Click for a drawing of how to build it)
  8. Permatex gasket sealer (for the water pump gasket)
  9. Thread locker (medium duty, BLUE) (Water pump bolts)
  10. Jackstands (These are a must have. you will not be able to do the job without them...Ramps would also work, but I don't own a set that the 7's front end can get over)
  11. Floor Jack (in a pinch, you can use the jack in the trunk of the car) 
  12. Various screw drivers (philips and flat blade)
  13. 2 gallons of antifreeze 
  14. Brake parts cleaner (helps get off the antifreeze that is going to get everywhere) 
  15. Electrical contact cleaner (gets the antifreeze out of any of the plugs that get soaked) 
  16. Vibration damper pulley bolts (TIS specifies that these should not be reused. You can get them directly from the dealer or from Pep Boys. Make sure you get grade 10.9 bolts)

Required Parts

  1. Radiator
  2. Water Pump + gasket
  3. Upper Hose 
  4. Lower Hose
  5. Belts (Alternator and A/C)
  6. Thermostat + gasket (O-ring)
  7. Thermostat housing

The total parts bill was around $700 so prepare yourself. You can get most if not all of the parts through an aftermarket company that offers OEM BMW parts. I ordered all of mine through The Parts Bin (www.alloembmwparts.com). The service was great, and the prices were even better. The radiator for example is about $600 from the dealer, the same part (original BMW, not aftermarket) through these guys was $297.

Hints, Tips and Things to Watch Out For

While not directly applicable to the procedure, these tips, techniques and things to watch out for will potentially save you a number of days and dollars, while you wait for parts the were needlessly broken due to an accident.

  1. From the start, remove the air box top cover, air filter, air intake hose, and the mass air flow sensor. This will give you more room to work.
  2. You may find it easier to work if you remove the front bumper. It comes off with 4 small bolts in the wheel wells and 2 T-50 Torx bolts on the underside of the bumper, outboard the license plate frame. While there is no technical reason for the bumper removal, it keeps the paint from getting scratched while you are working, and gives you more room to work. The bumper can be taken off or put on in 5 minutes, so there is no reason not to do it.
  3. The entire engine block coolant drain does not have to be performed (TIS states you should). You are only really concerned with the radiator, and there is no need to drain the whole block. This will save you about 3 gallons of antifreeze.
  4. THE FAN CLUTCH IS LEFT HAND THREADED! If you are not thinking, it is easy to over-tighten it instead of loosening it.
  5. THE FAN AND POWER STEERING PUMP PULLEYS ARE PLASTIC AND EXTREMELY BRITTLE! If you even bump them with a wrench, there is a very good possibility that they will chip out, and require replacement ($20 dealer only part). I chipped mine, and the dealer ended up ordering the part 3 times because each one they got from the warehouse was chipped (4 days lost). It would be a smart idea to tape some bubble wrap around them as soon as you have access.
  6. To get the vibration damper bolts out, use the breaker bar. Use sharp quick pulls on the handle to break the bolts free. A long slow pull will actually cause the engine to turn. An impact wrench would be better for this application, but there is no room to get in there. I tried to use a 1/2" drive socket handle, but couldn't get enough torque to get the bolts free. The breaker bar made it easy.
  7. When removing the water pump, make sure that the 2 pipes running from the back of the engine to the water pump are not pulled from their mounts in the back of the engine. I have heard they are a real pain in the butt to get back on if unseated.
  8. The lower radiator rests, which support the tabs on the left and right side of the radiator, come off without unbolting them. There is a plastic latch that when pushed either toward the outside or inside of the car (don't remember which way) will release the rest and allow it to slide off.
  9. The BMW TIS specifies that the radiator comes out from the top of the car. I was unable to do that without removing the A/C condenser lines and bleeding out the refrigerant, so I removed it from the bottom. This required some coaxing, pushing and cussing, but is possible.
  10. Once you have the fan clutch removed, keep it vertical. Do not let it lay on it's face or backside. I have heard that laying it flat can cause it to leak and become no good. You also want to check it out and make sure that it has not already leaked. (This may be an additional replacement part)
  11. Check out your fan blade. Make sure it is not chipped or cracked in any way. If it is either, or if you suspect it in any way, REPLACE IT! The cost of a new fan is nothing compared to the cost of replacing the hood, if it comes apart while the engine is running.
  12. After things are back together, and you have refilled and bled your cooling system, be aware that over the next 2 days or so, your car will consume an additional 1/2 to 3/4 gallons of coolant. Be diligent, and keep a watch on the level. As a precaution, keep a gallon of antifreeze in the trunk until the system reaches the steady state level, this normally occurs within 2 days, or 4 heat up and cooldown cycles.

Just a quick insight of what you are in for:

Click on the thumbnails for a larger images