E36 Water Pump
Water Pump Replacement
Up to10/95 (I think…maybe earlier than that) the water pumps in all the E36 3 series cars had the plastic impellers–but I figure if you’re here and trying to figure out how to change your pump, you already know. While these worked fine for awhile, they were prone to breaking where the shaft meets the impeller thus becoming nothing but blockage for the coolant. That’s about when the cooling system explodes. This has happened to a few people around 50k miles, but does not always happen. If you’re on this page thinking of doing it, you must be as paranoid as I. Hopefully you already have a good idea that you have a plastic pump. I know my pump is plastic since my M3 is #00076 w/ a build date of 3/94.
Keep in mind that I might have left something out since I’m typing this all out by memory. Don’t take this procedure as set in stone, and there might be easier ways to do this. Here’s my disclaimer so you don’t sue me.
Replacing the h2o pump can be broken down into three easy steps:
No, really, it’s easy. Also, since everything is apart, it might make sense to replace the main radiator hoses, the thermostat, and the drive belts. Keep reading for the links.
Depending on how much you replace, it can cost as much as $250 for parts from the stealer, or considerably less from mail order (BMW wanted $45 for the pump, stealer wants $100).
If the belts will be changed at the same time:
If the themostat and radiator hoses will be changed at the same time, check out:
First you want to flush the cooling system:
This is the radiator drain plug located at the bottom of the driver’s side (left side if you’re in the car) of the radiator. If you jack up the car, lay underneath it and look towards the front of the car, this is what you should see, although some of the drain plugs are black. Use a large flat bladed screwdriver to loosen the plug, or you can use an 8mm socket–it’s really easier to use a screwdriver, but do whatever the hell you want–it’s your car. Put a hose up to the drain plug and remove the plug so the fluid flows into the hose. Make sure something else is on the other end of the hose to catch the fluid besides your neighbor’s bushes…oops…
This view is looking down where the airbox should be (I have a Dinan cold air intake so the box is gone). See? The hose is on the drain. Use a shorter length of hose, mine was too long and the fluid backed up and spilled everywhere. Oh well, so much for being neat.
While the fluid is pouring out, open up the radiator fill cap and unscrew the vent plug (the blue arrow) with the same flat bladed screwdriver. This will help to turn the uncontrollable dribble coming out of the drain into a gushing mess.
Climb back underneath the car and locate the engine block drain plug. This is on the passenger side of the engine, hidden underneath the exhaust headers (as seen in the foreground in the picture). You can’t see this from the engine bay, so don’t waste your time looking. Trust me. Anyway, use whatever you can to open it (I used an open ended wrench, mine was 19mm, I’ve also heard 13mm). WORD OF CAUTION–lay as far back as you can and just ‘feel’ your way to that plug ‘cuz when you undo it, fluid will go EVERYWHERE since the headers are blocking the direct path to the ground.
See? I told you. Note the drain plug on the ground. Note the bucket under where the coolant should have been. Note the half gallon of coolant all over the ground. It was at this point that I found out that coolant really does taste sweet! Mmmmm! ANOTHER WORD OF CAUTION: ethylene glycol is not a food product; please do not eat or chew!!! After the coolant is done spiling out everywhere, put the plug back in. You can get a replacement crush washer for the plug if ya want, it’s probably better that you do. Don’t tighten it up too tight, cuz in my procedure it’s going to be removed again!. In retrospect, maybe if you put a big ass funnel up to the drain plug it wouldn’t be as messy. Oh well.
Put a hose in the radiator and turn it on. This will kinda clean out the radiator. Next, turn on your car and turn the heater on to full blast. This will help to get the thermostat inside the engine to open up and start circulating the water from the radiator though the engine. Run this for about five minutes, or until the water comes out clear. Or go crazy and do both! Your cooling system is now flushed.
Next, you want to remove the fan, the belts, and the fan pulley:
This is what you see from the top of the car, standing in front of the fan. The belts are behind the fan, and the circle highlights the bolt that attaches the fan to the water pump. The fan has to be removed since it’s bolted to the h2o pump pulley.
Okay, here’s the tricky part. The fan moves independently of the shaft that connects it to the water pump, which means that you can hold the shaft steady, but the fan will still rotate. There’s a couple of special BMW tools that you can buy to do this, but I’m on a budget so I did it geto-style. I found that an 8mm hex wrench will fit between the pulley bolts, while still giving you enough room to get to the 32mm fan bolt. I put a lock wrench on the hex wrench close to the bolts for maximum leverage, and then used this to keep the pulley from spinning. Meanwhile, I cranked the fan bolt w/ the wrench. The fan bolt is LEFT HAND THREADED, which means that to UNSCREW it you turn it CLOCKWISE, or towards the drivers’ side when you’re standing in front of the car. Some people used a hammer to break the bolt. Some people used a long bladed screwdriver instead of the hex wrench. Do it however you want, this way worked for me. One other thing to do which will help later: Loosen the four bolt that hold the pulley to the h2o pump before you remove the belts–it’s easier to do when the belts are holding the pulley still!
This is how the drivebelts are wound. There are two drivebelts (well, I guess one if you don’t have AC but we’re talking MY car here…) one for the AC and one for the h2o pump/alternator/power steering pump. They are threaded as such, and the drivebelt tensioners for each belt are labeled as such. To get slack in the belt to pull it off, you need to untension the tensioner.
Here we see the tensioner for the big drivebelt. Notice the plastic cover on it, you kinda hafta take it off to get to the hex bolt.
This is the tensioner for the small drivebelt. See? The 8mm hex wrench fits in there nicely. You probably should use the 8mm hex socket w/ a long socket wrench if you have one, but I didn’t so I just cranked it pretty hard.
Crank the tensioner CLOCKWISE and you can slip the belts off over the pulley. See? Pretty easy so far. Take off both of the belts.
Now you want to remove the pulley and the water pump:
Remove the four bolts that secure the fan pulley to the water pump (did ya remember to loosen ‘em up with the belts on? If not, you can back out a couple of the bolts and use the 8mm hex wrench to keep the pulley still). Now marvel at the job done so far–it’s almost done…sorta. And what’s with my hand? That thing’s lookin’ a little pale…gotta get more sun…get outta my cave…
This shows the nut locations that hold the h2o pump in the block (blue arrows). Use a 10mm socket to undo ‘em. The red arrows point to the M6 threaded holes that you will use to back out the h2o pump.
Insert your M6 bolts on both sides of the pump and screw ‘em both in a little bit at a time until the pump backs out of the block. You shouldn’t have to put them in that far.
Here’s a comparison of the plastic vs. metal impeller. I looked at the stock plastic impeller that I had for about 48k miles, and there weren’t any cracks or visible fatigue. Oh well. At least I’m good for pretty much the rest of the car life!
Okay, I got some new info about h2o pumps that leads me to believe that there is yet ANOTHER pump out there. Chad, with a 1/95 build date M3, just pulled out a pump that looks like the welded metal pump on the left, and replaced it with a pump that had a cast metal black impeller. That one sounds cooler, you might want to ask your parts guy or Steve D. when buying a replacement.
At this point, since everything is off, it might make sense to REPLACE BOTH RADIATOR HOSES as well as REPLACE THE THERMOSTAT!!!
Oh, and to put it all back together, wipe some antifreeze on the giant O-ring on the new pump. This is so the ring won’t dry out and start leaking. Push it back into the block, it might require some force. Put the pulley back on and torque the four bolts down, get ready for some fun ‘cuz the pulley’s turning as you’re turning the bolts.
Now it’s time to put the belts back on. REMEMBER: THE BIG BELT GOES ON FIRST SINCE IT GOES BEHIND THE SMALL BELT!!!!!!!! And then REMEMBER TO PUT THE TENSIONER CAPS BACK ON!!
So now that the belts are back on, put the fan back on–REMEMBER: the fan bolt TIGHTENS by spinning it COUNTER-CLOCKWISE or TOWARDS THE PASSENGER SIDE (when you’re standing in front of the car).
So now the fan is back on, the belts are on, and the pump is in. Now it’s time to finish up the cooling system.
Undo the engine drain plug again, spilling water everywhere. This is to get the water out of the cooling system so you can get an accurate mix of coolant. PUT BOTH OF THE PLUGS BACK IN! Tighten up the engine block plug and the radiator plug so fluid doesn’t leak out. With no water in the cooling system, you can pour in one gallon of BMW coolant first, and then one gallon of distilled water for a good mix (if you have zero math skills, that’s 50-50–that’s what one of the BMW mechanics was using) or you can adjust to taste. Turn the car on with the heater at full blast to circulate the coolant and to get all of the air out. Put the fill cap back on but not the vent plug. Coolant will bubble out of here when the air escapes so wait a few minutes until the fluid comes out bubble free and then put the plug back in. Turn your car off and then clean up. In the next couple of days, look for coolant leaks (check the drain plugs) or if the temperature is too high (past middle–might be air in the hoses, open up the vent plug again, but I doubt it).
Thanks to Martin Miller for his in-depth email on how to make this less painful…