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Subject: Writeup for the water pump, thermostat and some hoses enclosed. LONG.... Author: Magnum : member since January, 2004 : 3968 posts Posted on: 2006-06-11 00:16:41

First thanks to JerryK, scottmm, ArbysNight, DavidC, 747 and yes Claudio for your past post on this and associated repairs! I have to say the model year 1999 and up is ever so slightly different than 1998 and below, but it went great!

If you ever hit this post and the pics are "red X'ed", please click here for a full .pdf on this repair.

Also for reference and torque specs, is a .pdf of all the TIS documentation for this.

I hope it all loads properly, x'ed.

Magnum’s Water Pump replacement, Thermostat replacement
and a few Hoses to boot......

Let’s start out with some part numbers and prices as of June 2006, all these parts allowed me to apply my 10% BMW CCA membership discount my local dealer offers:

11 51 0 393 336 - Water Pump - $133.65
11 51 1 731 372 – Water Pump Gasket - $3.11
11 53 1 710 048 – O-Ring - $2.07
11 53 1 710 055 – O-Ring - $.86
11 53 1 436 386 – Thermostat - $63.12
17 11 1 427 156 – Vent Hose - $17.70
11 53 7 505 229 – Hose - $28.47
11 53 1 711 381 – Water Hose - $25.61
11 53 1 711 385 – Water Hose - $25.61
11 53 7 505 228 – Water Hose - $39.85
82 14 1 467 704 – Coolant [Gallon] - $17.33 x 2

When you click on the hyperlink above, it will open a new browser and take you to realoem.com. You’ll be able to see a mini diagram of the part.

Let’s get on with the info, hope you enjoy reading and looking at the pics.

I started noticing a mysterious coolant leak, and upon some discussions and looking I went with the water pump. Shit, that’s about the only thing cooling system related that hasn’t been replaced with the last 3 years. So by doing all the parts in the article, I should hope I’ll be good until the radiator or expansion tank goes again, LOL…!

This wasn’t as bad as I originally thought, I’m no professional mechanic and you should be able to tell by what I call stuff. Everybody has different tools in the shed , but I used a variation of tools including:
- Sockets, ranging from 5mm to 17mm
- 3/8 and 1/2 inch socket drive
- 10mm wrench
- Torque wrench
- Hex Key [I forget the exact size]
- 32mm thin fan clutch wrench
- A home made pulley holder tool to get the fan off.
- Rubber Mallet
- Some silicone lubricant for the o-rings
- Floor Jack
- Jack Stands

Torque values? See enclosed copy of TIS, but nothing was real tight, but I did torque what I called important. Read the TIS for these values.

Enjoy, and remember ALWAYS work safe and I assume NO RESPONSIBILTY for your actions, mechanical abilities or anything that may occur during the nature of the repairs.

While reviewing this, make mental notes of the work you are actually doing. I basically followed the TIS for the parts I was replacing. It went smooth!


First, I have to show you the tool I made to hold the fan pulley....lol.....she’s a keeper ......it turned out and worked great! You can buy one, be it universal or BMW specific, but what the hell this cost $4 and gave me a little time to screw around with the drill and dremmel one evening. Thanks for the idea “ArbysNight”:



Here’s some of the stuff I’m replacing. I gotta’ love the shine of new parts, here is the water pump, gasket and o-rings:



Here’s the thermostat:



Lets get started removing the MAF and air box. Remove the sensor by pinching the side clips as depicted below:



Then pop out the clips:



Remove the bolt that attaches the MAF Hose from shifting around:



Now loosen this hose clamp and lightly pull it off and set it on top of the engine:



Now onto the air box, loosen this hose clamp and remove slide off hose:



Remove the 1 bolt that holds the air box down:



Loosen this hose clamp, and finally slide out air box:



Air box removed:



Now I did a little prep work on the expansion tank, fan cowl and fan prior to putting the car on jack stands. First I loosened the fan, I did not totally remove the fan yet, I just loosened it so it was easier to remove once the car was in the air. This is where your need the home made pulley holder and 32mm thin wrench. The fan are reverse threads, righty loosy - lefty tighty:



Then I removed the attachment thing for the expansion tank. Remove the cap and then pinch where indicated by arrows with your fingers and pop it off:



Now there are 2 push connectors holding the fan cowl in place. Remove both of them, 1 on each side of fan cowl:



Let’s get the car up, here is where I place the jack to get the whole front end up at once:



Now put the stands under, *make sure they are totally secure*, lower the jack and give the front end a nice side to side push just to double check stability:



Now remove the lower engine cover, there are 8 [I’m remembering] phillips head clips that hold it on. 1 or 2 turns each and they are loose, they do not come totally out:



Here it is removed, some nasty dirty shit here, but I’m glad it’s here rather than my garage:



Before you get back under the car remove the expansion tank cap, bleeder screw and o-ring. MAKE SURE you get the o-ring out:



Let’s drain the radiator. Here is what BMW called the drain plug, HAVE your bucket ready and simple turn it towards the X and then pull like a mother f’er. I actually put a fat screwdriver in there to get some leverage and it popped loose:



It’ll take a while to drain, btw I drained out just a little over a gallon and a half:



Now let’s take out the expansion tank and other parts, like so.
- Unplug the sensor at the bottom on the expansion tank.
- Then remove the AUC sensor [the black box attached to the fan cowl] below the expansion tank.
- Then loosen the lower expansion tank hose clamp and pull off the hose, HAVE your bucket near by.
- Then lift the tank up slightly, pull it out slightly and loosen the vent hose clamp and then pull the hose off. You can see the hose in the pic, it runs along the top of the radiator.
- Now climb under the car and make sure the clips on the bottom of the fan cowl are unclipped and lift the fan cowl straight up out of the car. Be careful around the fan blades.
- Finally, because we have already loosened the fan you just need to fully remove the fan with a 32mm thin wrench, see arrow, and pull it straight up and out:



I’ve read that you should be careful with the fan and clutch, and don’t lay it flat down. I took extreme caution with the fan and actually hung it upright from the wall:



BMW recommends you mark the direction of travel for the belt if you are reinstalling the belts, well I am as mine only have about 30K miles on them. I just took a piece of chalk to mark it:



Now I moved onto removing the belts. The main serpentine belt is easily accessed through the hood. Loosen the bolt [#1 in the pic] on top of the welded bolt, then loosen the bolt [#2 in the pic] located on the slider arm. Once this is loosened, you will immediately be able to see the tension decrease, you may even hear a crack when you remove the tension:



Slide off the belt:



Let’s go to the AC belt, crawl under car and do the same steps as above. Mark direction of travel. This pic is of me tightening the belt, but loosening it works the same as the main belt. Loosen #1 in the pic and then loosen the slider arm bolt #2 in this pic and slide off belt:



Now remove the vibration damper. This is easy, remove the 8 bolts [you can’t see them all in this pic but they are there, and it will slide off with easy. Have a firm hold on it as it does weigh a little, not much, but a little. If you have a 1999, 2000 or 2001 this MUST be removed to get the water pump out:



Here it is removed:



Now let’s take off the pulley mounted to the water pump. Simple, remove the 4 bolts and then I had to put a small metal stick behind it and rock side to side, and it finally popped right off:



I’m replacing most of my hoses, so now let’s do those. The hoses are fairly cut and dry, most of them have metal clips you slide out and then pull the hose. The most difficult part is pulling the hose, because the o-rings inside provide a nice tight seal:

Pictured here is the hose located at the top of the radiator leading to the water pump, with a split to the alternator. ’99 and up have a water cooled alternator. BMW recommends you cover the alternator from any liquid, so I did this. I didn’t get any coolant out of the hose when I pulled it, but I also don’t want to mess up my alternator, better safe than sorry. Pop the clip up and pull the hose, it’s that simple:



Now remove the radiator side and water pump side. You can see here how you pry the clip up. Have your bucket ready:



There first hose out, the rest are the same but some are harder to get at than others:



Next, the clip at the radiator side was a little tight for space so I used a piece of wire I have for removing my built in wall speaker grates in my house, worked like a champ. Have your bucket ready, then remove the other end of the hose hooked to the thermostat:



This hose is a little tight to get at [#1], and if you’re not changing the hose you can just disconnect it at the water pump [#2]. This hose come off the water pump and “T’s” off with one hose going to the expansion tank and the other routes down near the hose we disconnected to drain the radiator:



Now that that hose is off we need to disconnect the hose holder. I twisted the hose straight up and down, and then took needle nose pliers to pinch it and pull it out:



Now remove the plug on the thermostat. Simply push in on the clip and pull up:



Then remove this, a crescent wrench works good. I pulled the sensor first, set it aside and then removed this:



Now with all that shit out of the way, we can finally remove the Thermostat and Water pump. A little hint here, I had to remove the thermostat first because there is a metal tube that runs right in front of the water pump and restricts bulky things from passing through. The thermostat is held in place by 4 bolts, I removed those and had to pry a little to break the tight seal. Disregard my arrow and screw driver, instead look right and you’ll see 3 of the 4 thermostat bolts:



Here is the metal pipe that runs in front of the water pump:



With the thermostat removed we’re ready to remove the water pump. First look around and locate all the bolts. Once I removed the bolts, I put them in the corresponding holes on the new water pump that was located on my work bench. Why? Because there are 2 bolts that are long and you want to make sure you put everything back together right. BE CAREFUL with the 2 tubes you see here, you DO NOT want them to come out of their spot in the back of the engine….. It took a little force to break the seal, but once that was done it came right off:



I guess in all my happiness of finally getting there, I forgot to get a good pic of the old water pump…LOL…but at least you’ll have the surprise if you have to replace your water pump …..! Now getting the water pump out with that metal tube there is a maze, but can be done. After I got the water pump out, I started cleaning off the old gasket residue. Don’t use a sharp object, I used a plastic putty knife, my finger nails and some shop towels to get the old gasket off. Take your time here, you want a nice clean surface when installing the new gasket and pump:



All cleaned up with the new gasket installed. DO NOT put the thermostat on the new water pump until the water pump is already installed. The gasket didn’t stay like that for me as I put the water pump in. So just get the water pump there and then fit the gasket in, make sure you take your time and position the gasket good because if it doesn’t seal tight you’ll be going back in, then put the Thermostat on:



I guess in all my happiness of finally getting the new water pump in, I forgot to get a good pic of the new water pump installed…LOL…but at least you’ll have the time to reflect once you get your water pump in …..!

Now it’s basically reassemble time. I put the vibration damper on first:



Then the pulley:



Then the hoses, they go on the same way they came off. Make sure you seat them correctly on the install, they have o-rings in them for seals:



Next:



Next:



And one more hose that goes behind the water pump and to the expansion tank, sorry no pic.


Now put the belts back on. Here’s the belt routing for main belt per TIS, remember the arrow if you are reusing the belts. Thanks Arbysnight :



Now tighten them down, put the 17mm socket on the bolt labeled 1 and turn to get tension, once the slider [labeled 2] is maxed out on tension tighten 2, then go back and fully tighten the bolt on top of 1:



Now the AC belt, reinstall in the same direction as earlier marked, then turn 1 to take up tension and then once 2 has maxed out the tension tighten it, then go back to the bolt on top of 1 and fully tighten it:



Then the fan, remember reverse threads so that means righty loosy, lefty tighty:



- Now slide the fan cowl in, make sure the bottom is seated respective slots and then put the push pin clips in.
- Then plug the AUC Sensor in on the fan cowl.
- Then put the expansion tank in, secure the top bleeder hose and then the bottom expansion tank hose.


Now let’s put the MAF and air box in, I’m getting closer to completion. Make sure you still have your o-ring for the MAF sealing:



Now put the air box in and get it situated, make sure you seal get these hose connection lined up right:



Now tighten down the 1 bolt that holds the air box in:



Now position this hose and tighten the clamp:



Next, one of the secondary air pump hoses gets attached to the air box:



Now secure the MAF hose down:



Now connect it to the intake:



Then plug in the MAF sensor:



OK, put the lower engine cover on, take the car off the stands and get ready to fill and bleed the system? I am……Hope it all works . I use BMW coolant, many will say this and many will say that about what coolant to use…..I took out just about a gallon and a half so I’ll take one of my half full jugs and mix it. Don’t mind my chicken scratch, it’s so I know what I have in the cabinets:



Filling and Bleeding the system, hmmmm, I can’t really take pics of it but I’ll try to explain in good detail how I did it and ended up with great results:

First remove the expansion tank cap, bleeder valve and o-ring:



Now the filling and bleeding process, it helps to a 2 people but not necessary:

- Mix the proper mixture of coolant and water, I used 50/50.
- Fill the expansion tank SLOWLY until the dipstick tells you it’s full.
- Put the key in the car, turn it to position 2 and turn the heater temp up to 90 degrees and put the fan speed to nothing.
- Now start the car.
- Go back to the front and SLOWLY refill coolant as needed until the dipstick says full, refill as necessary
- Once the cars temp has hit the first white notch on the gauge, have your helper rev the RPM’s to 1000.
- You’ll start to see bubbles coming out of the expansion tanks bleeder valve.
- Wipe as necessary or let your pan catch it, your choice.
- Once the bubbles stop, and it appears to be all coolant let it keep going……….for about one minute.
- Then close off the bleeder screw, put the expansion tank cap on and you’re DONE……..!!!!!
- The following morning check the coolant level and fill to appropriate level.


Miscellaneous pics of new parts below.......

Water Pump:









This is where the o-rings go:









Thermostat:






Hoses:














"The Tool", lol....






Need one......



I hope you enjoyed my repair.........and maybe learned something along the way!!!!


1999 740iL – Valentine One / Stealth One, Escort ZR3 Laser Jammer, Bluetooth w/ Blackberry 7100g,
Victor Steering Wheel, Leather / Wood Inlay BMW Shift Knob, Instrument Cluster Gauge Rings,
16:9 Nav. Display, TVonNav, Soundgate AUX 3, 6 Disc DVD/CD/MP3 Changer “In Stereo”,
iPod [40 gig] Hardwired, XM, Backup Camera, 2 12” Rockford Fosgate Subs, Rockford Fosgate Amp,
1 Farad Monster Cap, Custom Enclosure, Style 95’s w/ 245/40/19 F & 285/35/19 R Falken FK-451’s,
Clear Indicators, Tint, Chrome Grills, AC Schnitzer Pedals, M-Style Electronic Folding Mirrors, Xenons,
DDE's w/ Euro Fog Light Switch Activation

• Writeup for the water pump, thermostat and some hoses enclosed. LONG.... (pic) (url) - Magnum 2006-06-11 00:16:41 (16925 views)
  • I have a question - kevhouston 2006-06-12 11:41:06 (557 views)
  • Awesome writeup! Well done! The only thing I might add is - Stu 2006-06-12 10:59:10 (532 views)
  • That is a great write up..............Thanks! (nt) - Blue740i 2006-06-12 07:50:31 (311 views)
  • Is there an award for best DIY?? surely this wins in the cooling category. =) - NoahGo 2006-06-11 22:01:01 (306 views)
  • Wow This has to be your best work yet Thanks (nt) - BJames38 2006-06-11 21:50:01 (254 views)
  • Thanks, Magnum! Can somebody put this on e38.org, please? (nt) - dborja 2006-06-11 14:12:27 (276 views)
  • standing up/clapping hands...great write up...your pics/instr & (Peter's) bmw635 - 1 min belt swap tip....Q 2006-06-11 11:54:30 (286 views)
  • D@mn Magnum, that is one helluva job and thorough writeup. - Ultymte 2006-06-11 09:39:11 (229 views)
  • 'Bowing, with hands above my head', while repeating 'We're - sealbeach740 2006-06-11 02:09:53 (287 views)
  • Outstanding work! Definite e38.org material. (nt) - DavidC 2006-06-11 01:46:43 (248 views)
  • The kind of Post and Talent that make this Board GREAT! (nt) - giff 2006-06-11 01:15:04 (227 views)
  • Magnum, a superb write up. Interesting differences between '99 and '98 and - JerrytheK 2006-06-11 01:11:14 (298 views)
  • WOW....You are brave Magnum..Nice write up...... (nt) - johngoga 2006-06-11 00:33:48 (264 views)
  • Fantastic post! It's going to make the job a lot easier for the rest of us. (nt) - Peter 2006-06-11 00:33:15 (263 views)