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Old 06-28-2003, 11:46 PM
GregS GregS is offline
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Join Date: Apr 2000
Posts: 459
w104 waterpump replacement - reporting from the front lines

Some of you may remember that I was asking about waterpump replacement advice a few days ago. Well, I just finished the job on my 300CE today (w104 engine), and I thought I would share my opinions of the job in case others are interested.

1) First of all, if you are not a really, really competent and incredibly patient DIYer, you really should consider paying someone to do this job. I got quotes of between $700 and $800 here in Rochester, NY, and now that I finished the job, I realize why they would charge so much. It really took all day, it was incredibly difficult to access some of the fasteners, and you need a pretty good toolbox to get the job done.

2) Speaking of tools, lots of people mention the Snap-on tool for this job. I just want to mention that a very good alternative is a 13mm universal joint socket from Sears. I'm not talking about a socket with a universal attached, I'm talking about a socket with an integrated joint on it. Combine this with a 6 inch extention, and you have the same tool Snap-on sells for a lot less money.

3) You must have the following: 6mm, 10mm and 5mm 3/8 drive allen sockets. A huge array of 1/4 and 3/8 drive extentions, including a 3/8 5 inch wobble extention (I found one at Pep Boys). A long 3/8 ratchet was really helpful - I have one that is about 14 inches long with a movable joint at the head. 1/4 and 3/8 universal joints, with some electrical tape to tape them up so they don't flop around too much. A strap wrench from Sears to hold the pulleys while you unbolt them.

4) You need to be sure you order a new head-to-water pump hose, and two o-rings for the two heater pipes that bolt to the waterpump. Only one o-ring came with my pump.

5) You will see some people say they can do this job without unbolting the power steering pump and moving it aside. I would say that is an impossibility, and would love to see someone do it. Its easy to move the pump, so just do it and get on with the job.

6) I was able to access all the bolts holding the pump to the block from up top. The only thing I really needed to crawl underneath for was to undo a bolt that holds the heater pipe to the underside of the manifold. Don't bother getting under there thinking you can get a better view of the bolts holding the pump to the block, you can't see anything.

7) People also say that the fan can be removed with a 1/4 rod and an allen socket. On my car, a 1990 300CE with the w104 engine, this is not true. There is no hole to stick such a rod into. Fortunately, I was able to remove just the fan blades by removing three 5mm allen bolts that hold the blades the center bearing housing. But, if you can remove the whole thing, do so, because I had a really tough time accessing one bolt that holds the tensioner bracket to the block.

'84 300D, 174k
'90 300CE, 165k
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