M104/95E320 Water Pump Dry Run
 

NOTE: I deleted the thread this was in because of a no longer relevant title and comments. Here is what was saved:

I did a dry run of sorts last night under low light and with all hoses, electrical & vacuum connections intact. Access to the four pump bolts was generally direct ,with just some minor angling of the tools required.

My goal was to see if I could 1) insert a 6mm allen key into each bolt and then 2) insert a 6mm allen head socket and the end of a wrench or extension into each bolt. Once inserted I would see if the fit was dry and snug when the tool was rotated. I succeeded with only minor difficulties:

Upper Left Bolt
Readily accessible from above with a ¼ drive ratchet and allen head socket. A 3/8 wrench is too big. With the upper radiator and bypass hoses attached I was able to get the 3/8 wrench head and socket in there but had no room to maneuver it onto the bolt. With a ¼ drive that would have been easy, even with hoses on. With hoses off (upper radiator, rubber bypass, metal bypass) there will be wide-open access for a ¼ tool.
* * There is no need to remove the fan or even the fan shroud. They are not in the way if you come in from above with a slim-head tool. * *

Upper Right Bolt
Option 1: Use 6” or longer wobble extension, or straight extension w/wobble connector, to go in from in front of intake (black plastic piping cover).
Option 2: Use 10” version of above to go in from beneath the intake.

Lower Left Bolt
Sight this bolt above the square reservoir that the pump leaks into when seal fails, then use a 10”- 14” extension for direct access.
* * Straight access with no apparent need for wobble but it might be useful nonetheless. * *

Lower Right Bolt
Sight this bolt by looking down the oil dipstick tube, then feed a long extension (12” or more) from below the intake. Do not confuse it with the other bolt, slightly farther down and to the right, that secures the (tensioner?) mounting bracket.
* * A wobble is essential on this one. Be mindful of the thin vacuum line that will be below your right arm; it snaps easily but can be rejoined with a short length of headlight washer hose. * *

Conclusions:

• Essentially, the pump gets in its own way. Fan, fan shroud, and PS pump did not in any way impede access to the pump bolts and do not appear to be in the way of removal.
  
  
• I was able to make direct contact with each bolt using just the allen key. Thin, maneuverable tools are essential.
  
  
• I will use 1/4" drive tools not only because 3/8" is too big to access the upper left bolt but also because 3/8” extensions are needlessly heavy, which impairs my ability to finesse them into place with just my thumb and two fingers.
  
  
• The bolts are dry and very tight so I will spray them with PBlaster the night before, then clean and dry them with brake cleaner before removal to help prevent any slippage.
  
  
• Since it is proving tough to find a long handled 1/4" ratchet I will get the strongest conventional one I can find and implement my "easy lug bolt removal protocol:”
  Got to Home Depot plumbing dept, get a section of iron pipe (in this case approx 24” to 30”) with an inner diameter that fits snugly over the handle of the wrench. Beginning gently, gradually increase pressure on the pipe/handle to loosen the bolt without breaking the bolt – or breaking a sweat. The long pipe handle allows the use of two hands: One, high up to maximize leverage, to turn the tool and the other, low down, to apply moderate pressure to keep the socket from slipping off the bolt.
  

Finally, in my experience, there is always at least one “gotcha!” with Mercedes repairs. Mine were:

A) The socket of the most accessible bolt – the upper left – either is larger than 6mm or, more likely, rounded and I will need a Bolt-Out standing by for that one.

B) The fact that my 95 E320 thermostat housing is the same as that of a ’96 did not mean the pump is also the same. I will therefore be putting off this repair until next weekend so I can exchange the wrong pump for the correct one.

I haven't done too many repair jobs where I literally used/tried every extension bar, step adapter, and wobble joint in my tool box. It's a fun one. That's for sure.

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.

Eric, I would be reluctant to buy any bolts or fasteners for our MB automobiles from Home Depot. Glad to hear they worked fine for your water pump installation.

Why not? They are all made in the same facory in China. :)

And almost any alternative is is better than the original allen head bolts I removed (and which they also carry at Home Depot).

Just for fun, try shopping around for 8x30mm bolts. I was shocked that Napa, and none of the three MB dealers near me carried them. (Napa had 8x60mm and suggested I cut them.)

Eric, I prefer to buy bolts intended for automotive service which should be stronger than a generic bolt from Home Depot, and meet higher quality design specifications/standards. Never considered Home Depot an auto store or parts supplier.

For example, the threads on lug bolts for a set of aftermarket wheels I bought for our 1991 300CE weren't cut properly and were difficult to turn by hand. After that experience I only buy quality parts for our MB automobiles.

I wouldn't hesitate to use a bolt from HD or Ace on a waterpump. Hardware used in a critical application is another matter, but I have yet to see Mercedes lug bolts on sale at either store.

I am envisioning my shiny new bolts popping out one by one.

I agree with having auto-spec bolts but also agree that water pump attachment is a non-critical application. I would not, however, not use Home Depot bolts to replace the pulley bolts.

I was in Napa a while ago buying some Zerex and asked about bolts.

The guy pointed out that there are grades printed on the package or notches cut on the head of the bolts to indicate whether they are case hardened or not (or something to that effect).

Grade 5 (3 notches) is about average where as Grade 8 is case hardened (or some such thing) for high-stress applications.

Those are SAE (USA) grades. Metric hardware will have a number, usually ranging from 6 to 12, with some lower and higher. The lower the number the weaker the bolt. Most German hardware is 8.8 which corresponds to grade 5 SAE. You'll find a lot of grade 6 on Japanese cars and that corresponds to grade 3 SAE. The absence of a grade on a common bolt means it is inferior.

My mechanic replaced the pump in my M103 (190E), he had an M104 in stock and they look nearly identical. From what I remember it's a TIGHT squeeze, and yes you'll need special thin tools with extensions and universal joints to reach in at an angle, and then fasten them in good order. With me helping of course it made installing the pump easier, but if you're to do it by yourself it would take more patience.

Interesting about the M104 using Allens, I don't recall ours having them but then again we were also replacing the belt, tensioner and fan bracket. Yes make sure they're seated well inside the Allens.

The factory fasteners on our cars are KAMAX.

http://www.kamax.com/en/products/materials/

With the right tools, I have yet to see KAMAX fasteners fail in all my DIYs. If I used the wrong tool, and manage to still remove the fastener, I'd replace it with the same brand from my spare box of fasteners (starting my collection). Only times I would trust generic fasteners are on non-critical items.

Here are the photos I promised. No rocket science or special needs other than the right sockets, bits and extensions.

1.) Old pump (MB-104 200 4701) with hoses and sensors attached:
http://www.cyber-valley.com/UG/A.jpg


2.) Fan shroud, sensors and hoses removed:
http://www.cyber-valley.com/UG/B.jpg


3.) 1/4" ratchet and 7/32"hex bit socket inserted directly into the upper-left bolt. This is the only bolt that bit worked on because it was the cleanest, and I was able to apply the most force. In this configuration, the extending bolt backed the ratchet into the thermostat housing and the tool got stuck. Tightening the bolt back in was the only way to release it:
http://www.cyber-valley.com/UG/C.jpg

4.) Alternative to above: Hex bit on a universal joint and extension. Wont turn much at near 90 degrees but then, it does not have to because once these bolts are cracked loose you can unscrew them with your fingers:
http://www.cyber-valley.com/UG/D.jpg


5.) 3/8" drive and extension with hex bit in upper right bolt. Straight shot, no wobble needed. If you have the allen head bolts, this is where the rounding will likely begin and you must use a bolt-out. If you have 13mm hex heads, you should be fine:
http://www.cyber-valley.com/UG/E.jpg


6.) 3/8" drive and extension with hex bit in lower right bolt. A wobble could help but was not needed. Repeat for lower left bolt.
http://www.cyber-valley.com/UG/F.jpg

7.) Pump lifted out and set atop valve cover. Note the brown gunk regurgitated from the block -- some of which is oil from a previous head gasket breach. That, combined with blown-back oil grime from my timing cover leak makes my engine bay look rather awful:
http://www.cyber-valley.com/UG/G.jpg

8.) New pump -- Aftermarket with OEM reference 104 200 4901 which cross references to 104 200 4701. Came with mod kit to close unneeded oil cooler outlet in the rear. Has one sensor port on top and one on the side:
http://www.cyber-valley.com/UG/H.jpg

9.) New pump installed -- after pre-assembling with pulley, sensors, thermostat and t-stat housing. Coolant temperature sensor to dashboard now sticks out horizontally. The other one remains as was:
http://www.cyber-valley.com/UG/I.jpg

I should clarify one thing:

If you have 13mm hex head bolts then the Snap-On FLX13 tool, or at least a 13mm universal socket would be a good idea.

A lot of force is needed to loosen the bolts and if you are using a wobble extension you will just pop the bit or socket off of the extension because you will never be able to apply as much angular force as you would with the Snap-On -- which is why I went in straight.