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.

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

By the way, don't forget to put the pointer back on the belt tensioner in the right position before you install it. I didn't and had to guess how tight to make the belt.

Could anyone out there give me an idea how tight their serpentine belt is on the long run between the water pump pulley and pasenger side idler?

Thanks,

GregS

That's interesting. I did the same job on Sunday morning, after 5 hours sleep and jet lagged having just got in from Europe. Perhaps it was the fatigue, but I didn't find the job particularly difficult. About 2 hours to take the old pump out, and 2 hours to put the new pump in. No problems encountered along the way. Now, my '93 model is a bit simpler, it has one less connection at the pump, as it lacks the oil-to-water cooler present on earlier m104 engines.

I found every allen head could be easily accessed using just a regular swivel (u-joint) and extension, or with a standard allen key. Shoot, the hardest part was getting the hoses off the old water pump in one piece - they really take a set after ten years!

- JimY

Hum, you said you did the job in 4 hours, lets see:

-there's always at least one or two parts or tools you need to run to the store to get. That takes at least one hour.

-tool clean up and garage clean up take at least 1/2 hour (probably more)

-putting your old coolant in containers and driving it to the shop for recycling takes at least 45 minutes

-cleaning the engine and parts of dirt and grease while everything is apart takes at least 1/2 hour

-test driving the car to let the air work out of the coolant system, refilling, and checking for leaks takes at least 1/2 hour

Thats 3 hours and 15 minutes already and you haven't even picked up a wrench yet. Did I get the old pump out in 2 hours and the new one installed in 2 hours? Yes. Did the job only take me 4 hours? Obviously not.

GregS
'84 300D, 175k
'90 300CE, 165k

Fair enough. I guess we're using different definitions of the start and finish of the job. Four hours is about how much wrench slinging is required for this job. I agree about the remaining time the job will consume, but don't really look at it as work. Any task which permits you to consume a coffee/coke/beer I don't include in my "work" time.

If it makes you feel better, I stated at 8AM and finished at 3PM. In between I watched some TV, ate lunch, ran to Lowe's for pool chlorine, hosed out the garage, talked on the phone, idled the car and topped up the coolant, etc. Didn't drink any beer - my loss.

- JimY

I'm a bit surprised by the difficulty you ran into. I've done several of these, the longest was the first on an M103 where I followed the book exactly, and it didn't take more than a couple hours. However, I must admit I had all the tools. The last one I did was on an M104 in a C280. Much tighter than a 124 E Class. That one went fine without removing the P/S Pump. Two real oddball things:

1) I have never seen one of these engines without the hole for the fan hub locking tool. Are you sure you didn't miss it somehow? Sometimes it is difficult to see, especially on an M104.

2) I can't figure out what the extra "O" Ring was for on the pump. Normally it is one for the pump to block and one smaller one for the heater pipe. But, I can't figure out how the pipe is bolted to the "manifold". The pipe usually runs across the front of the timing cover and connects to a hose. Are there two heater pipes?

It does sound like your pump was fastened to the block with conventional capscrews rather than socket head screws, which would be somewhat unusual for an M104.

At any rate, this whole thread may help someone else in the future

I believe my car does have two heater pipes. One is the pipe you are thinking of, which runs across the motor and behind the fan, and I have another which runs under the manifold to the back of the engine. It appeared to be a return pipe from the heater core. Anyway, on my car that pipe was bolted to the bottom of the intake runners, and could only be accessed from under the car with about 2.5 feet of socket extensions. It bolted to the driver's side of the water pump with its own separate o-ring. This is on a coupe, and was the first year for the w104, so it may be different than other cars (which may also explain the fan situation).

GregS

I think the repair time depends heavily on whether you have done it before. The first time I removed a pump, it took about 3 hours just to get it out. The second time I did it (just recently), I timed it at just under 40 minutes.

Boy, that is truly odd. The pipe that runs across the front of the engine is the heater return. The supply pipe is off the left rear side of the head. The returns go through the mono valve, which should be in the compartment with the battery. What could the second pipe be coming from? As for the fan holding system, that was used from the start on the M103 and carried over on the M104. Also odd. This has me scratching my head. Maybe someone else has seen this or can comment.

I agree with you Vince on this one, I've changed the waterpump on my M104 twice now and I didn't run into half of what Greg did. As a matter of fact the first time it took about 4 hours to do and the second time was only about 2.5. Greg, are you sure you weren't changing a waterpump on a Honda???

GregS has an early m104 - it's in a 1990 300CE. Early m104 engines included an oil-to-water oil cooler. The third pipe is the return from the oil cooler. This was eliminated on later versions of the engine. If you look up the water pump for these cars, you'll see two versions, one for cars with the oil cooler, one for cars without. You have to know the engine number in your car to purchase the correct water pump.

- JimY

great to see someone from Rochester, NY :-)

I got mine done in the spring @ Morris Auto for about $600 (with tax)

I also go to this other place GMW out in Webster and he's been great...265-4040 (Curtis)

Thanks, $600 is actually a good price. I was quoted between $700 and $800 at both the dealer and Craig Automotive. I never heard of Morris, so I didn't call them. I'll keep them in mind though. I actually (unfortunately) don't live in Rochester anymore. I'm in Arlington, VA, but Rochester is where my family and freinds are.

As for the time it took me to do the job (which I'm taking a lot of heat for ) - it definitley took me longer because it was my first time. Plus, I was working very methodically so I knew the job would get done right the first time AND not give me problems on my 400 mile trip back to VA. The job had to be done with absolute confidence, so I definitely did take my time.

What I really started this thread for was for those in the future doing the same job. I didn't think there was a lot of info on this page in relation to this job, so I just wanted to have this thread in the archives. I hope it helps someone in the future.

GregS