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EricSilver · #3 03-14-2011, 01:49 PM

Completed this yesterday. This should have been a 3 hour job at most but turned into a 10-hour job (including a dinner break) because of the 4 items under ”Issues.” Getting the pump out took about 6 hrs. Washing out the hoses, preassembling new pump, putting it back in, cleanup, and 30 minute test drive all took about 3hrs in total. I will post a few pics in the next couple of days, after I offload the camera.

Issues
Removing Allen Head Bolts
If your pump has these, prepare to be frustrated. In all likelihood, particularly if the bolts are not perfectly clean and dry, your tool will slip and round out the interior. A Bolt-Out (from Sears) (size 7) will solve the problem so make sure you have it standing by. Otherwise, access to the bolts is a non-issue. Although I used wobble extensions I did need to not utilize their unique feature.

Bits, Extensions and Adapters
Bolt removal would have been a lot easier, and faster, if I had a 1/4 to 3/8 upsizing socket adapter. This would have allowed me to snap the Bolt-Out onto my ¼ drive extensions and shave perhaps four hours off the job. Unfortunately, I had to rely on my 3/8 ratchet set – which was short by just 1.5 to 2 inches in extension length -- making that a long, miserable task.
* * * IMPORTANT : Don’t even consider using a 7/32” allen head socket in these 6mm bolts unless you want to see how fast, and how effortlessly, you can round them out. Trust me.

Also, if you use a ¼ ratchet on the upper-left bolt, just crack it loose and then remove it by hand. If you try to use the ratchet beyond that, the emerging bolt will push it against the thermostat housing and you will not be able to remove the tool – until after you reverse it and screw the bolt back in.

These allen head bolts, in my opinion, are a passive-aggressive thing that German engineers do to piss people off.

Heater Bypass Pipe
Why this is not mentioned much is a mystery to me. It took a long while to remove because, apart from being generally sticky, it has a small foot on the bottom that latches onto a timing cover bolt. It must be wiggled and forced to the left to remove.

Getting it back on was a challenge since it does not simply slide back into place, no matter how much you force it. And the aforesaid foot seems to get in the way. Eventually I broke off the foot, which still did not help. Then I realized the trick is to align the hole on the hose flange with the bolt hole in the pump and turn the 10mm fastening bolt by hand until it catches. Then ratchet it in, letting the bolt pull the pipe into place.

Bolt Washer Recovery & Recycling
With the old bolts out I noticed their washers were on pretty tight and could not be removed by hand. This washer is obviously there for some reason so I set about removing them by gripping the washers with pliers and turning the bolts with a ratchet or allen key. If you have a vise use that to hold the washer. The pliers method takes a LONG time. I recovered all of them but was able to recycle just two, so those are on the bottom and the tops are “bare” -- but in plain view and readily accessible if I ever discover the washers are essential.

Shortcuts
The only things that need to be removed are the fan shroud, hoses and black plastic front cover.

Leave the pulley on the pump.
Conventional wisdom says remove it while on the car but that is entirely unnecessary. Also, the serpentine belt does not secure it tightly enough to allow you to crack loose the pulley bolts. Much easier to do when it is off the car. (And the radiator is like a cheese grater; one slip and there goes the skin on your knuckles, so just remove the pulley after it is off the car.)

Preassemble the new pump with pulley, thermostat and sensors.
I also had not issues with the o-ring. You just need to keep pressing it in until it sets, and no longer pops out.

Use new 8x30 13mm bolts
Have mercy on yourself, or the next guy, for when the next time the pump has to be replaced. There are chrome colored galvanized steel ones from Home Depot for about 50 cents each.

In summary, if I had 13mm bolts, foreknowledge of the heater bypass pipe installation, and some new tight-fitting washers, I could have done this job in no more than 3 hours. On the M104 it is not as hard as on the M103 but can still be a nightmare if you are not prepared for what awaits you. I hope my experience helps. And, as I said, some pictures will follow.