DIY - E60/N52 Cooling system overhaul
Here is my experience on a 2007 530xi, 3.0 liter, 6-cylinder N52, 94k miles. The work was done in May 2012.
Use this for your reference only. I cannot guarantee the accuracy of what you see here. This project is fairly difficult due to working in tight spaces. This procedure
was assembled from my recollection and from photographs taken during the work. You will certainly find gaps and inconsistencies in my explanations. Use your own best judgment and work safely.
Replaced 8 of the 9 HOSES. Only the metal-rubber hybrid was not replaced due to the difficulty of access. Read more below.
Hose clamp L12-14.5_____32411712735____1____$1.02
this item was not replaced due to access difficulty
Inlet pipe______________11537516414____1____$95.32 Half-steel, half rubber pipe; o-ring & seal included
Exp. tank cap __________17137516004____1____$6.86 URO brand because it was $8 cheaper
Hose clamp(vent)12-14.5_32411712735____2____$2.04 I think only 1 is needed but I got 2
Return hose ____________17127521778____1____$36.05
Supply hose (1)_________17127546064____1____$63.18
Return hose (7)_________17127560160____1____$81.30
Hose clamp _____________17127533721____5____$6.35 These may not all be necessary, depending on condition
Water Pump______________11517586925____1____$382.65 (ebay kit comes with 3-bolt kit!)
Thermostat (Wahler)_____11537549476____1____$95 ($8 more than BMW OEM but photos show a more robust unit)
Hex bolts_______________07119903851____2____$3.06 Attaches thermostat to water pump (aluminum, single-use)
2 Alu bolts for t-stat__11537521049____1____$3.06 (aluminum bolts must *NOT* be re-used)
My total, including tax & shipping for all component
All new components Expansion tank, 9 hoses, pump, thermostat, clamps, hose routing clips, coolant
Electric water pump
Pump, thermostat, "U"-pipe, expansion tank
Motivation to overhaul
I wanted peace of mind.
After 94k miles I was feeling unsure of my E60's cooling system. After all, a coolant system blowout will leave you stranded and may possibly destroy your engine. I won't repeat what is often said about the BMW cooling system reliability. I think it's a pretty good system but needs attention at regular intervals. As I approach 100k miles, I feel like this cooling system was living on borrowed time. Therefore, I decided to shell out nearly $1,000 and my time to make the system reliable.
Electric water pump an innovation
The high-tech, aluminum-magnesium composite, VALVETRONIC N52 engine is 22 lbs less than its predecessor (Bentley E60, p. 010-11), the venerable and cost-effective M54 that I am used to working on. Also the N52 gains about 3 hp by using an electric water pump, a BMW innovation, as I understand. The water pump for the old M54 can be had for less than $100. If you shop around, you can get the N52 pump for just under $400. The N52 has 9 rubber hoses for just its cooling system, ignoring the heater hoses. The M54 has 3.
The good news is that the water pump is self-diagnosable (Bentley E60, p. 170-2) and can throw codes for:
Impeller speed deviationA Check Engine Light can prompt you read the codes for impending water pump failure, as I understand it. That sounds good and maybe it's really not necessary to replace the pump until then. From my perspective I like having the peace of mind of a factory-new component for such a critical function. I've gotten a good service life (94k miles) from the original unit, though.
Hose replacement is straightforward
The hoses are all generally well-accessible and were easy to replace. The expansion tank is a cinch. To prevent confusion, take photos. But if you don't it's really not a serious puzzle. Only 1 hose didn't get replaced--more on that, below. Plastic hose-routing clips will be brittle. Buy replacements. I don't have the part numbers. Look on realoem.com.
Pre-assembly of Pump-Thermostat-Assembly (PTA)
The pump and thermostat are physically connected in two ways:
1) A pair of bolts holds them fast to each other, andPTA PumpThermostatAssembly (reconstructed from removed parts) Viewed as if from the front, right of the engine block; the "radiator" is the white, cardboard box at left.
In order to avoid kinking or stressing the "U" hose that clamps onto the pump and thermostat, I felt it was necessary to orient the pump and thermostat in-place, loosely, in order to allow the "U" hose to be correctly oriented prior to clamping. This is how I did it.
The new pump and thermostat should be attached with the u-shaped hose (see photo) after bolting together the pump and thermostat. The 2 bolts holding them together should then be removed after the PTA has been correctly oriented and the hose clamps tightened. You will need the freedom of motion to get that assembly into the tight space. Once the PTA is put in place, prior to applying final torque to the mounting bolts, connect the pump outlet to the metal-rubber hybrid "INLET PIPE" that attaches to the engine block. Clamp the "INLET PIPE" to the pump outlet. Then the PTA can be bolted together with the two steel bolts.
Here's the step-by-step procedure (recalling from memory). I've ignored telling you to drain the coolant from the system and have left out other details.
1. Remove the old PTA (pump & thermostat) and discard or keep it for a reference as I did.Random thoughts
The Power Steering high-pressure line is in the way of pump installation. A single bolt holds a hanger for the right end of line. That bolt is attached to the chassis UNDER the PTA by a single bolt with a 10mm hex head. This provides an interesting dexterity challenge to re-mount the PS hanger. This is a key reason for not bolting together the PTA until the end.
The PTA installation will consume a large amount of time. I spent 9 hours with this project but this was my first time and I had only the Bentley manual to give lightweight and non-subjective directions.
The aluminum bolts require a 2-stage torque sequence. Good luck on getting a torque wrench in there-no way. I did it by feel, approximating the 10Nm and following with an "additional 90 degrees." The aluminum bolts are one-use only. Be sure to have 3 new replacements on-hand-I bought a "kit" on eBay that included the pump and the 3 aluminum mounting bolts.
In hindsight, the original hoses were all in fine condition, showing no signs of deterioration. I had gotten no codes from the water pump. Could the cooling system have been ignored until codes were thrown or leaks noticed? Maybe, but I'm glad to have a new cooling system.
The problem hose (called "INLET PIPE" on realoem.com)
PN 11 53 7 516 414
This "hose" is really a hybrid pipe-hose, being made primarily of heavy gauge steel(aluminum??) and having a rubber hose fused to one end. It won't come off without removing the entire exhaust system. I chose to not replace it.
These photos tell the story better than words.
Location of pipe/hose attachment to block
Engine block with pipe in place, without the exhaust manifolds
The other eight replacement hoses went back together without issue. Only the metal-rubber hybrid "INLET PIPE" was not installed. It's metal for a reason. It is connected to the block on cylinder 2, under runners 1 and 2 of the exhaust manifold. Its composition changes from metal (iron/steel) to rubber when it is clear of the heat hazard and must be attached to the pump's output port. I did get a socket on one of the two bolts (the bolt at the 2 o'clock position) holding the unit to the block-I did *not* loosen the bolt. The socket connection was a confidence-inspiring near-straight-on fit. I did this using a mirror and flashlight. It was impossible to connect to the second bolt (at the 7 o'clock position). Even if both bolts could be extracted, I don't think the pipe could be removed from the block because the pipe extends several millimeters from the mounting flange into the engine block. The exhaust manifold for cylinders 1-3 almost contacts the pipe and would prevent the wiggle-room needed to remove the pipe.
Here's a view from the expansion tank (removed), looking downward toward the motor mount. It shows where the "INLET PIPE" would be mounted to the block.
The next photo is a mirror view into the "INLET PIPE" mounting area
You can forget about replacing this pipe unless you're willing to remove the exhaust system. I'm going to wait until when and if this pipe ever starts leaking. I'm betting it will be OK.
The pipe is plugged into the engine deeply. There is not enough room to back it out in these tight confines.
I turned to Bentley to find out how to remove the front manifold (cylinders 1-3) -- the exhaust manifold consists of 2 parts.
Step 1: "Remove rear manifold." In order to do that, perform step 2, next.Therefore, you have to remove the entire exhaust system from stem-to-stern. I've removed the "exhaust system" before. It consists of a 90-lb 8-foot-long section, connected at the front to the exhaust manifold outlet. Not too hard. But the removal of both exhaust manifolds was making this a very involved project.
I left the pipe in place.
I justified my decision since the coolant in this pipe is the coolest coolant in the entire system since it has already been passed through the radiator and is being sent back into the engine block. The rubber on this pipe has had less exposure to hot coolant than any other pipe in the system.
Expansion tank plug ("blind plug") PN: 11 53 1 436 850
The existing expansion tank has 4 connections, one of which is plugged. You must reuse that plug so pull it off carefully. It's held in-place with the normal clip-type wire bail that is common to the other hoses.
Hose PN 11537522999
The coolest coolant in the system comes from the water pump, goes into the INLET PIPE and into the engine block. There is a take-off pipe on the INLET PIPE that connects to the top connection of the hose shown.
This pipe connects to hose in the previous photo. There is a notch in the hose end that keys onto this tube. The pin on the tube orients the hose properly so you don't have to think about it.
Very nice.. Thank You.. I'm also in the process of Replacing the electric water pump, thermostat (Wahler Brand), Serpentine Belt and 2 Gal BMW Coolant.
Those hoses were all in good condition when I replaced them. Pretty tough material.
Amazing writeup. Does the cap on expansion tank need to be on or off when doing the bleeding?
A couple of comments, after doing this job yesterday (bad pump, PM the thermostat since I was in there) on my 07, 65K mi E60.
First, the pump control electronics are what fails. Other sites note that intermittent codes are sometimes thrown prior to failure, but realistically you'd need to regularly check the codes in memory every so often, since no one has seen the check engine light go on solid in advance of a "achtung! Stop zee effing car right now!" dash warning.
That said, you can confirm pump failure by trying to start the bleeding routine. It won't start. If you want to confirm it, put a meter on the pump control line while the bleed routine is running and you'll see +6VDC on it, but the pump still won't run. If these are your symptoms, you can be confident that it's a failed pump.
Electrical diagram below. Navigate to engine cooling for your year E60/61 and you'll find wiring color coding, fuse location and control line location. Do yourself a favor and check the fuses before you climb under the car.
Second, the above writeup is really well done, so if you use it this is a straightforward but fiddly job for a confident shadetree mechanic. But, I don't recommend it as the first repair you decide to do on a car. You really don't want this job to fail again because of a loose clamp or improperly seated hoseclip...
Third, pump and thermostat are probably a $900-1000 dealer job. DIY with parts from Pelican and Bav Auto are $450-500 or so net of shipping.
Couple of cooling system diagrams attached, as well.
Again, absolutely a great writeup, and it will guide you through the process if you decide to attempt it. Good luck.
Post-Mortem on aftermarket stuff:
Don't do it.
In my list of components, I said I saved $8 on an aftermarket cap for the expansion tank. Well, after 10k miles that part snapped in two. Note to self: stick with OEM
any idea what this is?
2006 530I (N52 Engine) with active steering
Thanks for all the useful info on this thread!
I think I am ready to take the challenge. :-)
From the information I gathered, it seems like my car is set up differently (more hoses that are in the way) because it has active steering and Active-Roll Stabilization System.
Please see the picture and the indicated red arrows. If I loosen them (red arrows), will I have enough space to disconnect the water pump and thermostat assemblies? More importantly, am I going to risk any damage to the active steer/active-roll stabilization system?
Happy New Year!
Can someone please tell me if I need to remove the three hoses (see red arrows in the pic) to get access to the water/thermostat assembly?
Or will dropping the sway bar be enough to get those three hoses out of the way?
I wonder why my last two posts don't get bumped to the top for people to see?
My last two posts didn't get bumped to the top for people to see. I am replying to this post simply to see if it would fix the issue.
After almost two months (since my purchase of the parts), I finally gained the energy/desire and installed my new water pump and thermostat. It took me a little less than 4.5 hours; and I am so glad I got this project out of the way!
At 83,240, the hoses still look like they can probably last another 80,000 miles. The old pump and thermostat can probably go for another 20,000+ miles. In any case, I know this preventative maintenance will save me money and time in the long run.
More importantly, I want to say the three hoses that I previously asked about do not have to be removed. Lowering the active stabilizer bar was all that was needed for the necessary space to finish the job! I hope this confirmation will put someone at ease when attempting the task some day.
Thank you, OP, PCY, BimmerFan52, my mom (for giving birth to a multi-talented kid, j/k) and everyone (you know who you are) for your help! ;-)
Thanks for the update!
You're welcome, I am glad the update was useful!
I was hesitant to replace the water pump and thermostat because I didn't want to mess up the expensive to replace/fix hydraulic system for my ARS and steering. lol
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