DIY – Water Pump & Thermostat Replacement (2007 335i w/Automatic Transmission) NOTE: This DIY may be used on other 335i model years and on xi models as well (part numbers may differ). I’ve started a list of procedural differences for those models based on Water Pump DIY experiences from other members. See end of procedure.
-Clear any and all water pump related ECU codes first.
-Caution: Only perform procedure when engine is cold.
-This procedure can be completed without having to remove the radiator, cooling fan and intercooler.
-Leave the new pump sealed in bag until ready to install.
-The 3 aluminum bolts for the water pump will have to be replaced as they are designed as a one time installation only.
-Remember to have a gallon of BMW brand coolant on hand to mix 50/50 with deionized water for a total of 2 gallons.
- Important information about the water pump: The latest part # is 11 51 7 632 426 which supercedes part # 11 51 7 563 659 and the original part # 11 51 7 588 885. The current design no longer uses the rubber isolator/spacers at the three bolting locations and thus the aluminum bolts are now made shorter (Part # 11 51 7 602 123) The bolts are now 26mm as opposed to 32mm. Make sure that you have the correct size bolts. (Edit) If you do receive the longer bolts by mistake and can't wait for re-ship, nc1mike recommends cutting 1/8" off the top bolt to prevent it from bottoming out. The other two bolts seem to be fine.
-(Edit: added) The draining procedure in this DIY is a partial flush only. A full flush cannot be performed using an incapacitated pump. A full flush requires removal of the intercooler to gain access to the radiator and activation of the pump. Contact your dealership for full flush coolant capacities. A full flush procedure (for a 330i) can be found in section 1 of the following link:
• Ratchet w/ 3/8 drive
• Ratchet w/ 1/4drive
• Ratchet w/ 1/2 drive
• Universal w/ 3/8 drive
• 6” extension bar w/ 3/8 drive
• 6” extension bar w/ ½ drive
• 10mm socket w/ 3/8 drive
• 6mm socket w/ 1/4 drive
• 8mm socket w/ 1/4 drive
• 13mm socket w/ 1/2drive
• E12 Torx socket w/ 3/8 drive
• 10mm box end wrench
• 6” awl
• Flat head screw drivers
• Torque wrench
• Coolant catch basin
• Trouble light
• Coat hanger or wire
• Rags/paper towel
• Disposable nitrile gloves
• Protective eyewear
• Cat litter for spills
• Empty gallon containers
• Pair of low profile ramps
Let’s Get Started
1. Raise front end of vehicle by driving up onto low profile ramps and apply e-brake.
2. Remove the 16 - 8mm hex head screws securing the engine splash guard from the underside of the vehicle.
3. Open the hood, loosen the coolant reservoir cap and the reservoir bleed screw.
4. Place coolant catch pan under the AT heat exchanger located on the driver’s side under the intercooler at the front of the vehicle.
Note: The majority of the coolant will be drained as a result of the next step after which you may then want to empty the contents into the empty gallon containers to lighten the basin for further usage. Caution: The coolant pours out quickly.
5. Separate the rigid black plastic elbow from the heat exchanger by lifting up the wire spring clip using a small screw driver then pulling the elbow away. Do not twist. Allow coolant to drain then re-attach the plastic hose connection.
6. Remove both aluminum splash guard support brackets located below the sway bar.
7. Remove the four nuts from the two sway bar bushing mounts using the 13mm socket and ½” drive ratchet with extension and carefully let the bar swing down out of the way.
8. Remove the 10mm bolt securing the power steering hose loop to the steering rack (nearer to the u-shaped pipe component). Look for the rubber isolation bracket. Tie back the hose using a length of coat hanger wire.
Note: The next section is thermostat removal which must be accomplished before removing the water pump.
Note: Four hoses need to be removed from the thermostat. The first one is a large u-shaped hose which connects to the water pump’s suction side.
9. Remove the 2 wire thermostat electrical connection by lifting the little metal spring tab using the awl then pull it straight out. Space is limited and if the connector bottoms out on the sub frame before complete separation, gently force it out between the plastic guides.
10. Again position the coolant catch basin, this time under the thermostat and water pump.
Note: Be prepared for more coolant drainage in the next steps. You will get about a pint from the hose in step 11 and trickles from others. Never face directly up at your work and have shop towels at the ready. Also be prepared in the next steps as some hoses are not so easily separated from the thermostat and water pump. The wire spring clip type (like that of the rigid plastic elbow at the AT heat exchanger) can be difficult. These can only be pulled off straight; not twisted off as they are keyed and don’t expect immediate results as the seal inside needs to be broken first. Break the seal by rocking the connection up and down using a fair amount of strength but be patient. Soon, the seal will loosen and break. Don’t fight it by trying to slide it off as well. Conserve your energy and slide the hose off only when you think the seal has been broken.
11. Using the 6mm socket with ¼” drive ratchet, loosen both clamps on hose number one (the large U-shaped hose that goes between the thermostat and the water pump). Note that there are only two water pump hoses. Its tight quarters but the little ¼ drive and socket will do the job. Carefully pry the hose off with a screw driver.
12. Now remove hose number 2 at the front of the thermostat going to the radiator. It’s one of those wire spring clip types with the rigid plastic connection. If you can’t reach the top of the spring to lift up on, try pushing the spring ends up from the underside of the connector.
13. Now remove hose number 3, the smaller diameter hose on top rear with the regular hose clamp.
14. Remove hose number 4, a plastic type. It’s the small one, top front. Rock it first then pull when loose.
15. Grab the 10mm socket with 3/8 drive ratchet and extension bar. Remove the two hex bolts securing the thermostat to the water pump.
16. Pull the thermostat out by working it forward and rotating it between the fan housing and the vehicle frame. Congrats, you removed the thermostat.
Water Pump Removal
17. Remove the 4 wire electrical connector for the water pump by pressing in on the plastic release and pulling back.
18. Using the 6mm socket and ¼ drive ratchet, loosen the clamp on hose #5 (water pump discharge). Do not try to remove the hose just yet.
19. Using the E12 Torx socket with the 3/8 drive ratchet and extension bar, remove the 2 aluminum bolts in view that secure the pump to the engine crank case.
20. Detach the pump electrical harness located at the topside of the pump near the third aluminum bolt by pulling it away from the spring clip.
21. Remove the third bolt by connecting the 3/8 universal to the tool setup in step 19 and reach up over the curvature of pump body. You can angle your head from the front looking aft so that you can actually see the bolt head just beyond the pump harness clip at the top. Feel the socket grip the bolt, hold the extension bar steady in place and begin turning slowly.
22. Lower the pump slowly allowing hose number 5 to naturally separate from the pump. Aha! It’s out!
New Water Pump and Thermostat Install
Note: The install procedure is basically the reverse of removal. Of course the same tool setup applies. Be careful not to overtighten the aluminum bolts as they may break off. BMW specified torque is 10Nm (88.5 in-lbs, 7.37 ft-lbs) or just turn the bolts until they begin to grab and then tighten another quarter turn.
23. Remove pump from bag. Remove the discharge orifice seal cap but leave the suction orifice seal cap in tact.
24. Pry the wire harness clip off the old pump using a screwdriver and fit it on to the new pump.
25. Raise the pump into position and attach hose number 5. Ensure that the hose clamp is in position but do not tighten.
26. Loosely fasten the pump bottom using 2 of the 3 new aluminum bolts.
27. Attach the top bolt and tighten.
28. Now attach the pump wire harness to the clip on the pump.
29. Tighten down the bottom bolts.
30. Tighten the hose clamp from step 25.
31. Using the reverse of step 16 to move the thermostat into place, orient the thermostat so that the barbed type hose flanges go in first. Visualizing the orientation of the installed unit helps.
32. Install and tighten the two steel mounting bolts for the thermostat.
33. Install the remaining thermostat hoses. Ensure that the two rigid plastic types are pushed in all the way. Return their spring clips to the locked position and verify lock by pulling back and forth on the connection.
34. Install the u-shaped water pump/thermostat hose and tighten the clamps.
35. Connect the water pump and thermostat electrical connectors. All connected!
Note: The next few steps are needed to safely lower the front end in preparation for system venting and still have fairly easy access to the hoses in the event of a leak.
36. Loosely attach the sway bar back into place using the 4 nuts.
37. Move the power steering hose loop into position, temporarily tying it up into place using wire. Ensure that it is raised so as not to droop. Keep the wire clear of any moving parts.
38. Leave off the aluminum splash guard support brackets for now.
39. Have your BMW brand coolant/de-ionized water blend mixed and ready.
40. Open the coolant reservoir cap make sure the bleed screw is loosened. Begin slowly pouring the new coolant. Air will escape through the bleeder. Continue filling until the floating level indicator rises up out of the reservoir. See the diagram on the cap for min and max fill levels. The indicator can stick at times so just tap it with a clean screw driver to make it float. The system should take close to one and a half gallons.
41. Replace the coolant cap and tighten down. Tighten the bleed screw.
42. Making sure that the area under and around the car is clear, start the vehicle, back it down the ramps and immediately turn off the ignition. Residual air in the system will need to be purged and running the engine for long periods of time in this condition could cause overheating, ultimately damaging your engine.
Venting Air from the System
Note: Make sure you have a watch or timer handy for this next part. Step 45 activates the water pump at which time you will need to set the timer for 12 minutes to allow the coolant to cycle around the system. The water pump will cycle on and off during this time and stop around the 12 minute mark. Allow the pump to cycle for the full 12 minutes. Hooking up a second battery beforehand will help save the car battery from running down. (See Connecting Jumper Cables under the Giving and Receiving Assistance section of the Owner's Manual.
43. Insert the key FOB into the ignition and without stepping on the brake, press Start.
44. With the climate control now activated, adjust the heat to the highest setting (both driver and passenger) and set the fan to low.
45. Now hold down the gas pedal for ten seconds and release. Start your timer now.
46. After the 12 minutes, take the key FOB out, open the reservoir cap, check the level indicator and top up the coolant if necessary.
47. Replace the coolant cap and tighten.
48. Start the engine and check the underside of the vehicle for leaks.
49. It’s time to button everything up underneath if no leaks are visible.
50. Drive the car up onto the ramps again, re-fasten the power steering hose loop to the steering rack (It’s tricky getting the bolt started and then use the 10mm box end wrench to finish), tighten down the sway bar bushing mount nuts to 16 ft-lbs, re-attach the two aluminum splashguard support brackets and replace the splash guard. 50 steps is enough! You’re done.
Procedural differences for other model years:
2008 335xi A/T
(posted by binaryagent)
-Both power steering line brackets must be removed so that the sway bar can drop out of the way. The 10mm bolt on the right side (looking from the front) is on top of a cross-member bar with minimal clearance and very difficult to get to.
-The stainless clamp screw on one of the water pump hoses was pointed directly at a solid cross-member with no way to get on top of it. The open end wrench must be used; slowly but surely. On reassembly, I turned the clamp around and lined it up with the available work area.
I cruised through this up to the point where I was putting the right power steering bracket bolt back. My wrench went over the top of the cross-member and into a crevasse. While struggling to get my hand over the cross-member to locate the wrench I pulled my power steering lines back. During that effort the lines suddenly eased up and moved out of the way and soon after I noticed oil dripping (I'm scheduled for an 8 hour drive for business today so that was the low point of this adventure). I then removed the 6 large bolts and pulled the thick aluminum pan below the engine. Found my wrench. Then I pulled my left front wheel and found the leak at the junction between the PS line and the PS pump. After 45 minutes of struggle I finally figured out that I could get a 3/8" driver with a 6" or 8" extension and a 19 or 20mm socket to the bolt on the PS line from the underside. I could see the bolt from the wheel well and that helped line up the socket/extension from the bottom. I used an extension bar on the 3/8" driver to get sufficient torque and had to lean on the intercooler rubber conduit somewhat to deliver that torque. If I turned that bolt it wasn't much. So watch out for dropping stuff over the top of the crossmember at the right PS line bracket. If you do just remove the thick pan. And careful when pulling on the PS lines because you will loosen the bolt securing them.