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Old 06-25-2003, 11:19 AM
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Join Date: Apr 2000
Posts: 459
w104 fan & waterpump removal

It looks like its time to do the waterpump on my '90 300CE, and I need a little advice (yes, I've already used the search function).

1) is it necessary to remove the fan? I've read some threads where people say they've done the job without removing it. If it is necessary, exactly how do I remove it?

2) what special tools are needed? Some people say the snap-on tool is nice, and others say a wobble or flex extention from Sears works fine. I already have extentions, u-joints, deep well sockets, hex sockets and wrenches - do I need anything else in particular? Will I need those little universal joint sockets that sears sells?

3) Any other advice on this job is appriated.

Thanks a lot.

'84 300D, 174k
'90 300CE, 165k
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Old 06-25-2003, 12:02 PM
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Join Date: Apr 2000
Posts: 459
Also, these are the parts I've already ordered, please tell me if there is anything else I need for the job:

-water pump
-t-stat housing-to-head hose
-upper radiator hose
-upper radiator elbow (for overflow tank connection)
-upper radiator hose hose-clamps
-Mercedes Coolant

Is there anything else I need? Does the waterpump come with all the gaskets and o-rings that I will need? Is the serpantine belt and tensioner reusable (it was replaced just 15,000 miles ago)? If I have the wobble/flex extentions, do I still need to remove the power steering pump?

This job must be started and completed this weekend (when all the parts suppliers will be closed!) and I need to drive the car back to VA, which is a 7 hour trip. Please help me out so that I have all the tools and parts that I need before I start the job.

Thanks again,

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Old 06-25-2003, 12:45 PM
sixto's Avatar
smoke gets in your eyes
Join Date: Jun 2000
Location: SF Bay Area
Posts: 18,746
Not sure about the M104 but the M103 has an o-ring at the union of one of the cabin heater pipes and the water pump block.

No need to replace the belt tensioner. I assume the tensioner shock absorber is pretty new as well. But you can replace that anytime.

95 S420
91 300SE
87 300SDL
83 300SD
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Old 06-25-2003, 01:28 PM
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Join Date: Apr 2000
Posts: 459
I've heard about that o-ring, and assume it comes with the pump kit. I'll check in the box when it arrives.

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Old 06-26-2003, 08:22 AM
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Join Date: Apr 2000
Posts: 459
Noone with any comments on this job? I know about the flex tool, but it looks like it has a regular socket on the end of it. My car is fitted with allen bolts, so that tool won't be much help. I'll have to figure out an alternative.

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Old 06-26-2003, 08:33 AM
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sounds like you've got all the tools to do the job Greg, it's been almost 2 years since I replaced mine and I don't remember anything too earth shattering while doing it. I didn't remove the fan but I did remove the water pump pulley, this allowed a little more room to remove the allen head bolt on the top left hand corner of the pump (of which is the only part that took some time). And yes, it is sealed to the block with an O-Ring.

Good Luck
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Old 06-26-2003, 08:55 AM
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Join Date: Jan 2000
Location: Chesapeake, VA
Posts: 396
The fan is held on with a single 8mm hex head (allen) bolt. You can cut off the short end of a conventional allen wrench (a hack saw works fine) and use a short piece of pipe as an extender to loosen/tighten it. To lock the hub you need a piece of 1/4" rod with a bend of about 30 degrees at the end. The bent end should be about 3/4" long. The whole rod should be at least 8" long to be able to work it comfortably. It fits between a pair of cast in ribs on the fan bearing housing. The short (bent) end of the rod slips into a hole in the back of the hub. You might need to move/shift some wiring at the front of the head to see down to the area I'm talking about. Your pump is held onto the block with hex head (allen) bolts. The earlier engines used conventional bolts. You cannot use the Snap-On tool. The bolts require a 6mm allen tool. It would be a good idea to have several different 6mm allen tools on hand. A ball-end allen tool is handy. If I remember correctly, two are a fairly straight shot. The other two are not. I think the bottom front is where I needed the ball-end allen wrench. A ball-end allen socket might be handy, but clearance is an issue. I used to remove the P/S Pump, but after reading this forum I tried it without removing the pump and it went fine. You will need to remove the belt tensioner and the three legged sheetmetal support in front of it. The outer bolts also fasten the P/S Pump, if I remember correctly. There are nuts at the back. I can usually access and hold them with a breaker bar and a 13mm socket. The tensioner turnbuckle assembly will fall off when you pull the tensioner. Look it over first so you know how it goes back together. I don't think the heater pipe "O" ring comes with the pump. Get a thermostat "O" ring also. You can remove the thermostat while you fill the coolant to easily aand quickly vent the air out of the block and head.
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Old 06-26-2003, 10:45 AM
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Join Date: Apr 2000
Posts: 459
Thank you, thank you, thank you! I've been craving information on the fan because this oddball Bently manual I have (published in South Africa???), says that the early fans can be removed with this bent rod people are talking about, but that the fan on the w104 is different. As long as I know I can get the fan off with the rod then I'm fine. The car broke down at my parent's house 400miles from here, so that's why I want as much info as possible from you all. I need to get all the parts, tools and info before this weekend, and be able to knock the job off and drive the car back to Virginia Sunday afternoon. I can't have any surprises!

Thanks for all the help. The ball-end allen is a great idea I hadn't thought about. I'll be sure to pick one up.

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