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Old 08-31-2012, 11:28 AM
latitude39 latitude39 is offline
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Location: US - Colorado
Join Date: Feb 2010
Posts: 100
Mein Auto: E46-325xi; F34-328GT
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.
• Replaced the COOLANT PUMP.
• Replaced the THERMOSTAT.
• Used new clamps-the quality, exact replacements from BMW.

Parts List

Water hose______________11537521049____1____$23.06
Water hose______________11537522999____1____$40.86
Hose clamp L12-14.5_____32411712735____1____$1.02
HoseClamp L42-48________07129952119____3____$2.10
HoseClamp L18-24________07129952109____2____$2.22

this item was not replaced due to access difficulty
Inlet pipe______________11537516414____1____$95.32 Half-steel, half rubber pipe; o-ring & seal included

ASA-Bolt ZNS3___________07129902813____2____$0.99
Water hose______________11537544638____1____$20.76
HoseClamp L23-35________11537547945____1____$2.51
Expansion tank__________17137542986____1____$79.99
Exp. tank cap __________17137516004____1____$6.86 URO brand because it was $8 cheaper
Vent pipe_______________17127521775____1____$29.44
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
Temperature sensor______13621433077____1____$20.97
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)
BMW Coolant_____________82142209769____2____$19.65

My total, including tax & shipping for all component
Approximately $950

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 deviation
• Stiff operation or blocked by foreign objects
• Incorrect mixture ration coolant / water
• Air in cooling system
A 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

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, and
2) the U-shaped rubber pipe that feeds coolant from the thermostat to the pump provides a flexible connection when the bolts are removed. Removing the bolts give the PTA freedom of motion for easier installation.
PTA – 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.

2. Bolt the new pump and thermostat together, with just enough torque to orient them in their final position. There are 2 steel bolts with 10mm hex heads.

3. Attach the U-shaped hose to connect the pump and thermostat. Think about accessibility of the screws in case you need to access them when the PTA is in place. Tighten the clamps fully.
PN 11537521049 PN 07129952119 (2 pieces)

4. Remove the 2 bolts holding the PTA together. Now, only the U-shaped hose holds the PTA together.

5. Remove the silver, metallic hanger that suspends the right end of the PS high-pressure line, a flexible line. It is held in place by a single 10mm hex-head bolt located inconveniently under the PTA. This allows the PS line to dangle a few inches to give you room to work.

6. Place the PTA in its space and push the pump outlet onto the "INLET PIPE," which should have a new 42-48mm clamp-same as the other 2 clamps on the PTA.

7. Using 2 of the old aluminum pump-mounting bolts attach the pump in place (this is temporary so do not tighten it beyond firm contact).

8. Now the PTA is held in correct orientation to the "INLET PIPE." Torque down the clamp on the rubber section of the "INLET PIPE."

9. Remove the aluminum pump-mounting bolts.

10. Re-hang the PS bracket using the 10mm hex-head bolt. This is the "interesting dexterity challenge" that may give you some consternation. It can be done. It's a PITA for sure. I used a short 12-point combination wrench and with many 1/12th wrench turns the bolt was seated.

11. Bolt together the pump and thermostat using the 2 steel bolts. Tighten to 10Nm, as per Bentley E60, p. 170-15. 10Nm is 7.4 (Seven point four) ft-lbs.

12. Bolt the pump to the engine block using the 3 *new* aluminum bolts. Torque till it feels good or…..........follow Bentley's recommendation of 10Nm + 90-degrees (Bentley E60, p. 170-17). Torque this down ONCE AND ONLY ONCE! The aluminum bolts are to be tightened only once. If you need to back them out then off to the dealership you'll go. My subjective experience with this final 90-degree twist is that I could feel the bolt deforming under the tension as if it were a threaded Tootsie-Roll. It's unnerving for us old-school, steel-bolt guys.

13. The hard part is over.

14. Connect the rest of the hoses using new plastic clips to route them. I don't recall any special challenges.

15. Double-check your connections; close the radiator drain plug.

16. Mix BMW coolant 50/50 with distilled water. I used an old 1-gallon water jug, filling 1 liter of coolant and then 1 liter of distilled water to make 2 liters, which I then poured into the expansion tank. Peek under the car to check for leaks. The system is 10 liters. I was able to put in 8.5+ liters. I'm not too concerned about getting a complete flush. 85% replacement makes me happy.

17. Once the red level indicator pokes up out of the expansion tank to the second bubble, run the "bleed process" according to Bentley. To my recollection it goes: 1) Plug key into ignition, 2) press the "Start" button but do NOT place your foot on the brake-to prevent engine from starting. Again, do NOT start the engine. 3) Turn heat controls to 91 degrees, the top of the scale, and turn the fan on the lowest setting, 4) Press the accelerator pedal to the floor and hold for at least 10 seconds. The ECM will begin the bleeding process. You'll hear water rushing through the pipes and the low hum of the electric motor. This takes 12 minutes. Be patient. When it's done check the level again, topping-off as necessary. I ran the bleed process a second time but Bentley did not recommend this. I don't think it hurts. I was able to top-off after that.

18. Look for leaks. When you are satisfied that everything is sealed, continue.

19. Finish reassembling.

20. Start the engine with the hood open. Look for obvious leaks.

21. Road test around the neighborhood, radio off. Listen and watch the dashboard for lights.

22. Upon success of the previous step, take it for a short road trip to tax the system a bit.

23. Let the car cool, overnight hopefully. Check the coolant level and use a flashlight to inspect for drips.

24. Done.

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
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.

Alternate access

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.
• Step 2: "Remove exhaust system."
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.

Last edited by latitude39; 08-31-2012 at 01:34 PM. Reason: Not done yet
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