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NG6 Engine Thermostat and Water Pump Replacement
 
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Pelican Technical Article:

NG6 Engine Thermostat and Water Pump Replacement

Nick Czerula

Time:

4 hours4 hrs

Tab:

$400

Talent:

*****

Tools:

Set of sockets, wrenches, screwdrivers, two M6 bolts

Applicable Models:

BMW 525i/xi Sedan (2004-07)
BMW 528i/xi Sedan (2008-10)
BMW 530i/xi Sedan (2004-07)
BMW 530xi Wagon (2006-07)
BMW 535i/xi Sedan (2008-10)
BMW 535xi Wagon (2008)

Parts Required:

Water pump, thermostat, hoses, engine coolant

Hot Tip:

Work with a cool engine

Performance Gain:

Car will cool down again and repairing coolant leaks

Complementary Modification:

Change radiator hoses

In BMW E60 models with NG6 (N52 or N54) 6-cylinder engine, cooling system components consist of the following:

  • Radiator and coolant overflow tank.
  • Electric coolant pump bolted to the right front of the engine block.
  • Electric cooling fan attached to rear of radiator. The cooling fan is controlled by the engine control module (ECM) via an output final stage.
  • Electronically controlled thermostat.
  • Automatic transmission cooler (heat exchanger).
  • Heater valve and heater core (for climate control).
  • Coolant level sensor inside expansion tank.
  • Coolant temperature sensor at cylinder head.
  • Radiator outlet temperature sensor
  • Coolant hoses and lines.

Using an electric pump (as opposed to the engine-belt-driven variety) helps engine cooling efficiency and longevity as the pump can operate regardless of whether the engine is running or not and also regardless of engine rpm. For example, a low rate of coolant flow is maintained during cold start situations to help the engine warm up rapidly, while a high flow rate can be used for rapid cool-down, such as when the engine is shut off.

The electric coolant pump is controlled by the engine control module (ECM). Engine load, temperature, operating range and other factors are used by the engine management system (DME) to determine coolant pump operation and speed. The pump also has self-diagnostic capabilities. Fault codes for the following conditions are stored in the ECM and can be used for diagnosis:

  • Pump impeller speed deviation.
  • Pump shaft stiffness or obstruction by foreign object.
  • Incorrect water / coolant mixture.
  • Air the cooling system.

When a coolant pump begins to fail, you'll notice that the car tends to overheat at low engine speed, such as sitting at a stoplight. When you accelerate, the engine temperature will drop. Now, this is not always indicative of a coolant pump failure, but a good starting point. You may also want to try squeezing the top radiator hose with the engine warmed up and running. You should feel pressure build up on the back of the hose and surge once it is released. If you feel no pressure, it's a fair bet that the coolant pump is failing. The most common problem with the electric coolant pumps is a fault code for coolant pump volume.

If you remove the water pump from your E60 and plan on reinstalling it, store it with coolant inside it. Otherwise, it will corrode and fail shortly after reinstalling it. Always replace aluminum fasteners each time they are removed and never reinstall a questionable coolant hose.

The ECM also controls and monitors operation of the thermostat. Controlling the thermostat function according to a map allows the engine management system (DME) to raise engine operating temperature quickly and precisely to the optimal range and to maintain it there for maximum efficiency and minimum emissions.

If a fault occurs in the thermostat, a fault code is stored in the ECM, usually with a description of "Map cooling circuit". A fault code can be present, yet the vehicle will lack any cooling system issues, such as overheating. This is because the thermostat has a fail-safe mechanical function as well. If you have this fault code, replace your thermostat and bleed your cooling system. Other symptoms of a faulty thermostat are engine overheating, slow to warm up and lack of heat.

The thermostat is integrated with the thermostat housing; the two are replaced as a unit. This can be a tough part to change, as it is tucked away and behind many components. I like to remove the cooling fan when I have to replace a thermostat. It adds time to the job, but makes it a lot easier. If you have an all wheel drive E60 or one with active steering, you're going to have to remove the cooling fan anyway. So I say just go for it and make your life easier no matter which model you own.

In this article, I'll go over the steps involved with replacing the thermostat and water pump on BMW E60 models with the NG6 engine. Be sure to work with a cool engine and confirm that the cooling system lacks pressure before opening the cooling system.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Remove the engine splash shield. See our tech article on splash shield removing.

Drain the cooling system. See our tech article on cooling system draining and filling.

With the cooling fan removed, you have a pretty good view of the water pump (red arrow) and the thermostat (green arrow).
Figure 1

With the cooling fan removed, you have a pretty good view of the water pump (red arrow) and the thermostat (green arrow). A few of the hoses are tucked in behind them. I will do my best to show the location of the clamps. Due to restricted space, the ability to capture images is limited.

First you have to remove the front hose connected to the thermostat.
Figure 2

First you have to remove the front hose connected to the thermostat. Using a flathead screwdriver, release the thermostat hose retaining clip (red arrow) by prying it up. The hose clip will stop at the unlocked position (green arrow). I suggest leaving it installed on the hose so you don't lose it. Then disconnect the hose by pulling off the thermostat housing. You may have to wiggle the hose a bit to get it to move free. Be careful not to damage the hose. It is made of plastic.

Working at the bottom of the thermostat housing, use a small pick (green arrow) to release the electrical connector (red arrow) and remove it.
Figure 3

Working at the bottom of the thermostat housing, use a small pick (green arrow) to release the electrical connector (red arrow) and remove it.

Next, move the power steering cooling loop aside.
Figure 4

Next, move the power steering cooling loop aside. Remove the 10mm fastener at the rubber insulator (red arrow). If the rubber insulator spins while you try to remove the fastener, hold it steady with a pair of pliers. Pull the power steering cooling loop down and out of your way for the remainder of the procedure.

Next you will have to remove the smaller hose from the thermostat.
Figure 5

Next you will have to remove the smaller hose from the thermostat. Using a small pick, release the thermostat hose retaining clip (red arrow) by pulling it away from the hose. The hose clip will stop at the unlocked position. I suggest leaving it installed on the hose so you don't lose it.

Then disconnect the hose by pulling off the thermostat.
Figure 6

Then disconnect the hose by pulling off the thermostat. You may have to wiggle the hose a bit to get it to move free. Be careful not to damage the hose. It is made of plastic. Stay clear when the hose is pulled off. Coolant is retained in it even after draining. You don't want to take a coolant bath. Push the clip (red arrow) back onto the hose once it is removed.

With all the hoses disconnected, remove the two 10mm thermostat mounting fasteners (red arrows).
Figure 7

With all the hoses disconnected, remove the two 10mm thermostat mounting fasteners (red arrows).

Now it's time to remove the water pump fasteners.
Figure 8

Now it's time to remove the water pump fasteners. I remove these before the remaining hoses are detached. It allows for flexibility when accessing the clamps. Start at the top front of the water pump and remove the E12 fastener (red arrow). Throw this fastener away. It is aluminum and cannot be reused.

Then remove the two remaining E12 fasteners at the bottom of the water pump (red arrows).
Figure 9

Then remove the two remaining E12 fasteners at the bottom of the water pump (red arrows). Throw these fasteners away. They are aluminum and cannot be reused.

Now it's time to remove the remaining hoses.
Figure 10

Now it's time to remove the remaining hoses. This photo shows the pump and thermostat housing removed from the engine. This is the only way to get a good view of the remaining hose and clamp locations. Previously you removed the two hoses from the thermostat (blue arrows). Next you will have to remove at the minimum, the two remaining hoses on the thermostat and the main hose on the water pump (green arrows). I also find it helpful to loosen or remove the hose connection at the rear of the water pump (red arrow).

Working at the back of your water pump through the subframe, loosen the 6mm hose clamp (red arrow).
Figure 11

Working at the back of your water pump through the subframe, loosen the 6mm hose clamp (red arrow).

Then, lift the thermostat just enough to access the remaining hoses and loosen the hose clamps.
Figure 12

Then, lift the thermostat just enough to access the remaining hoses and loosen the hose clamps. I like to use a flexible 6mm nut driver (red arrow).

Once the hose clamps are loose, remove the hoses from the water pump.
Figure 13

Once the hose clamps are loose, remove the hoses from the water pump. Be ready to catch any dripping coolant when the hoses are removed. Lower the pump enough to access the final electrical connector. It is located at the rear of the water pump. Disconnect the water pump electrical connector by pressing the retaining tab (red arrow) and pulling it off. Then remove the water pump and the thermostat from the engine as a unit.

Transfer the hoses and the heat shield (red arrow) over to the new thermostat and water pump.
Figure 14

Transfer the hoses and the heat shield (red arrow) over to the new thermostat and water pump. Then install in the reverse order of removal. Install the new thermostat and water pump into the engine. Connect the water pump electrical connector. Pay close attention to the electrical connector. Once you think it is installed, try to pull it off. I found that the seal inside the connector can swell from oil contamination; this inhibits the connector's ability to fully seat and lock into place. If it will not lock into place, replace the seal on the electrical connector. It can be replaced separately from the connector. Install the coolant hoses and tighten the clamps. Install and tighten the water pump then thermostat fasteners. Install the cooling fan. Install the splash shields and fill and bleed the cooling system. Remember to check the cooling system for leaks and top up the coolant when complete.


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Comments and Suggestions:
07530xiNate Comments: I got a 07 530 xi which was giving overheating issues. I know its the water pump but i need alittle help installing it because its a different then this model. I will show a pic under my car
July 18, 2016
  Followup from the Pelican Staff: Your model is only harder due to the all wheel drive system. it limits working space.

We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
King Comments: 06 525xi. Threw the p0128 code. Cooling temp low. The fan cuts on sometimes. Sometimes it doesn't come on at all. The code is usually throw when it starts to rain hard or when it gets cold. Not chilly. Cold. Never has overheated nor came close to it. Is it the thermostat?
November 18, 2015
  Followup from the Pelican Staff: Most likely. - Nick at Pelican Parts  
Adam Comments: Hi guys I have BMW E60 525 2008 model with n52 engine on it my problem was I had to change the water coolent and after I put the water back in I can't bleed the system I can't activate the electrics water pump then I got new one and same problem water pump not working to bleed the system and other idea how to bleed the system without the water pump.Thank you
June 10, 2015
  Followup from the Pelican Staff: Is the water pump turning ON? Can you activate it using a BMW scan tool? Are there any fault codes for the water pump? - Nick at Pelican Parts  

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