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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 12-13-2013, 09:27 AM   #1
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Cool DIY: Upgrade To A Stewart EMP Water Pump in 10 Easy Minutes!


This DIY will begin with the engine air box components out, the engine bay fan out, the belts off. I have a specific DIY for those elements elsewhere in the forums. See the two links directly below:



Tools Needed for this DIY:

1 - One Soft Rubber Mallet ($5 at AutoZone for the 16 ounce one)
for tapping off the Water Pump Pulley. Have a metal Hammer nearby and Liquid Wrench if you have a metal pulley that is rusted and seized onto the old pump.

2 - One Small Handle Sturdy Ratchet with a 10mm socket for the Pulley's 4 bolts and Water Pumps nuts.

3 - The two 10mm Bolts that hold your air box into place. Don't ask just take them out and put them in your pocket. More on that later.

3- Aluminum Cooking Pan to catch coolant and plastic sheet.

4- 1 Gallon Bottle of BMW Coolant/Distilled Water (50/50 mixture) nearby to replenish lost coolant unless you are planning to be ratchet and reuse the old coolant that pissed out into the catch pan.

5- Two Small Tire Jacks (Like the OEM one in the trunk) or one big Hydraulic Jack to raise the front end of the car . You don't need jack stands but you only need to raise the front end of the car for a 1 to 2 minutes when you are bleeding the system.

Replacement Parts you may want to buy beforehand just in case:

1. Water Pump Pulley - If you have the original plastic one still on the car EXPECT it to be brittle with age and break apart when removing it. If you have an old metal pulley that was previously put on without anti-seize lube then it will warp and/or chip when you remove it. I went to the Dealership and bought a new OEM plastic pulley ($40) instead of putting in another metal pulley in my car.

2. Water Pump Pulley 10mm Bolts and Water Pump 10mm Nuts - These things can easily be damaged or lost during the DIY. Having a few extras around will be good insurance.

3. Bleeder Screw w/ Washer For Expansion Tank - Another thing that costs less than $15 that can be easily lost or damaged and prevent your car from being road worthy.

Minute 1. Get yourself ready. Take a deep breath:

Minute 2. Remove the four 10mm water pump pulley bolts (turn left to loosen):

Minute 3 (Allow 2+ Minutes). After the bolts are out you may find that the pulley is seized on and does not want to come out.

If you have an aluminum pulley then a metal hammer and liquid wrench is the best way to whack at it. Even thought it is metal it is still not invincible and may warp and chip as you remove it. Be sure to check for this if you plan on reusing the pulley!

If you have an original OEM BMW plastic pulley then the rubber mallet alone is enough to get it loose. Expect it to crack in multiple pieces and crumble off.

Minute 5. Once the pulley is off remove the old water pump's four 10mm nuts with the same socket you used on the pulley bolts. They are not threaded deeply and will come off really quickly with a few turns so be careful not to drop them.

Within the same step you are going to retrieve the two 10mm air box bolts that you put in your pocket earlier. BMW designed these specific two bolts to be used for the Water Pump extraction.

Insert them into the two slots as shown in the picture below and screw inwards. Use the socket to screw in the left bolt first then the right bolt then left bolt again back and forth until the pump pops out. Remember alternate sides until the pump is out. Doing one side first all the way in may warp or damage the neck of the water pump which can break off sending bits of impossible-to-retrieve plastic shards into your cooling system.

Minute 6. Get your plastic sheet over the pulleys beneath the water pump and the catch pan below that. As the pump comes out so will coolant. I lost about 1/2 a gallon into the catch pan.

Another view of the extracted pump. My pump was still working and good condition but most of you doing this DIY may already have failed pumps that will come out in pieces or come out disfigured so expect that:

Minute 7. (Optional)
Compare the old pump to the new Stewart Pump and marvel at what the heck BMW was thinking using their choice of OEM pump:

Minute 7. Time to put in the new pump. REMEMBER to first clean out any debris from the water pump cavity. Use some of the spilled out coolant to moistened/lube up the new rubber seal on the Stewart pump and insert pump into cavity.

Minute 8. The Stewart Pump will easily pop into place. Get the four 10mm nuts and tighten in a crisscross pattern. I don't have torque specs. I just hand tightened moderately.

Minute 9. Put on the new pulley and also crisscross tighten the bolts. The holes of the pulley are somewhat TRICKY to line up with the holes on the water pump base. You may want to finger thread ALL FOUR of them first before bringing in the socket to tighten. Keep that in mind.

Lightly thread the bolts on with your fingers to get ALL the bolts on first:

Then apply the socket to cross tighten all the bolts in a that crisscross pattern:

Minute 10.
Bleeding the Coolant. THIS IS 10000% REQUIRED!!!!!

Open expansion tank. Take OFF Bleeder Screw w/ Washer. Put Key in ignition to turn on car (NOT ENGINE). Turn on heat to 91 or High/Max. Turn Fan on Low. Jack up the front of the car slightly so the front end nose is higher than the bumper.

Pour in BMW coolant/Distilled Water 50/50 Mixture UNTIL the Bleeder hole farts out a big bubble of air and coolant. When it does this that means you got all the air out of the system.

You may find that you just put back in way more coolant that what you saw come out. If you are worried about this then get a Turkey Baster into that Expansion Tank and suction some coolant out until the Expansion Tank's indicator is slightly lower than normal. Replace coolant until the indicator is at normal.

That is it. You are done. Most shops and dealership will labor in the costs of draining and refilling the ENTIRE cooling system when replacing the water pump. Shop Labor with parts (that normally will not include a stewart pump) can run anywhere from $350 to $600+. Dealerships will charge more.

So in about 10 to 20 minutes of light manual work and a bit of smarts you just saved a lot of money.

By the way Stewart's Lifetime Warranty on their EMP Water Pump refers to your lifetime not the life of the car.

I also did the Fan Delete/Electric Fan Modification at the same time as well. The car drives so much better as a result. Plus having a lifetime component at the heart of the cooling system has instilled in me a new and wondrous driving confidence.




Last edited by delmarco; 12-13-2013 at 12:03 PM.
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Old 12-13-2013, 05:37 PM   #2
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Location: CT
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I installed the Stewart water pump when I did my cooling system maintenance a couple of years ago. Agree, it does bring a sense of confidence, as you don't hear of them failing. When I do my next cooling system maintenance in 2015, that's one component that shouldn't need replacing.
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Old 12-13-2013, 06:28 PM   #3
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My Ride: 2002 BMW 325i
Nice tutorial, and great pics!

2002 BMW 325i sedan
Manual gearbox, but of course!
Tasteful mods
128K miles and counting
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Old 09-25-2014, 10:23 PM   #4
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Join Date: May 2011
Location: Seattle, WA
Posts: 31
My Ride: 2000 328i
DelMarco Rocks!
I always find your DIYs helpful and some the things you post about I didn't even know you could do! Tha last DIY of yours that I did was to install the push-button cup holder in my rear armrest. Before that I installed a new rear view mirror with homelink and compass that came from an X5. Who knew? I love it. Thanks for your contributions.

I'm overhauling my cooling system shortly and this will help. And, yes, I DID get the Stewart water pump. It may be overkill, but it's worth it to me to have a more robust cooling system especially since, years from now, we may be living with average temperatures in the triple digits ;-).
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