I am about to replace a water pump on my 1990 300E. I would appreciate procedure for pump replacement. If nothing else, information on serpentine belt tensioner adjustment. How is the belt properly removed and then adjusted on replacement? Does the tensioner mechanism have to be removed to replace the water pump? It looks like it would be easier if I remove the radiator...agree? Any special tools required before I start? I have a 1988E, 1990SE, and 1992E. I could probably benefit from a repair manual. Any idea where to find one. Many thanks, in advance, for any help you might be able to give me.

Dennis, I don't have a scanner, and you really should have at least the appropriate pages from the manual to do this. The serp belt tensioner has to come off, if you have over 150k miles, now is a great time to replace it. The y-bracket that holds the tensioner has an engine opening on the left side that needs to be resealed or you'll have an oil leak when you get done. Permatex red works has worked fine on mine. My '91 was done without pulling the a/c comp off as the manual suggests and without the fabled Snap-on 13 mm flex drive allen head socket. The p/s pump does need to be unbolted and pivoted towards the driver's side fender.

Make sure you put all new o-rings everywhere, the heater hose coming across the bottom of the distributor and inside the pump. I didn't use any sealant on the o-ring sites and I have no leaks. I hate putting sealant over o-rings, but a lot of pros do it to prevent comebacks. They definitely don't want to redo water pumps on their dime. I think the shop labor is about 4 hours. The radiator doesn't need to come out, just pull the fan and the p/s, w/p, crankshaft, and idler pulleys off. That gives you enough room to get to everything.

That's the little stuff that I remember from doing it over Christmas break but the manual is really what you need. Good luck.

Dennis if you get in touch with me privately I will send you the instructions on water pump replacement from my W124 CD. I should be able to e-mail them to you. BTW there is no need to remove the crank pulley.

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Scott Diener
89 300E
93 300E
92 Volvo 740 Wagon aka "Mutt mover"

Check out the SEARCH facility here. Benzmac and others have posted all sorts of good info relevant to M103 H2O pump replacement.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Had the pleasure of seeing my friend's repair bill for a water pump and t-stat replacement from the local metro dealer. She has a 95E320. It went some thing like this:
Water pump $202.00
Labor- install pump,t-stat $499.00
coolant, tstat $ 37.50

I have an extra CD repair manual that I will send you to help you avoid the above. It is an early issue of the CD that was updated by MB, so it might not work perfectly, but it is just sitting here doing nothing.
E-mail me if you want it.
Steve

The only special tool you will need is a fan clutch holding tool, I have used a saw-off allen key to keep the cluch fan from rotating. You may also want to replace the small hose between the thermostat housing and the cylinder header.

jack

I just remembered a very good tip. Do yourselves a favor and get the small hose between the water pump and the head from MB or from someone who can order it by p/n. The two ends are different sizes! Not by much, but enough where I suspect this is where a lot of leaks come from when people replace this hose with a piece of generic hose.

I happened to be talking to a dealer parts rep about some small parts and he told me about this. If you get the mb part you'll see what I mean about it being an easy source of trouble if you are unaware. The difference is not much.

trust me. Let someone who has done it before do it. You'll live longer

Been there, done that, hated it. Bought all parts from these guys. Just tell them what you are doing and they'll get you the right stuff. It's a bloody-knuckle job, but it is doable for a good DIY mechanic.

On My 2.6, there is one BOLT that has to be sealed. Seemed bizzarre to me, but many before me warned me about it.

Replace the tensioner. Mine has been replaced twice now in <120K miles.

You have to take it out anyway, so go for it. Tensioning was easy. getting the blasted fan clutch out was a challenge.

You do not have to remove the fan clutch, unless you are replacing that as well. It can be done w/o removing fan clutch or fan blades. It will be easier if you remove the fan blades and fan shroud.

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.

Dennis,
i know it has been some time now but do you still have the repair manual, email info or anything pertitnent to doing this job? i hope you can help me, have a great day.

thank you in advance,

leo

Hi, if you have the info on 300E water pump replacement please email to me to henryk@henryk.com
thx
henryk

I expect that if you were to search: 300E water pump or m103 water pump, you could come up with at least as much material as you would find in a service manual.

The search tool here is a great thing, try it.

Good luck,

Online MB Doc -> http://mb.braingears.com/

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Another on-line manual:

MB Service Library

Or you can have your own copy of the CD service manual for $10 that covers all three cars. The CDs are essentially the same thing found in the on-line manuals... same .pdf files.

http://www.peachparts.com/shopforum/showthread.php?t=128001

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95 E320 Cabriolet, 159K