603 vacuum pump question

[MarkWells]

Hello guys,

I am getting ready to replace the belt tensioner on my 603 and started reading about vacuum pumps. (the archives are a great resource!). I thought "what the heck ..." and pulled mine off out of curiousity while everything was easy to get to (radiator is out).

I was glad to see the cam that drives the piston was in good shape. You can see a witness mark where the piston bearing rides, but it is smoothe. The bearings seem in good shape...no excess play or visible wear. I started to put it back on for now (I've spent a $1000 recently on 4 Dunlop Sport A2's, 4 Bilsteins, wheel bearings, converted solid rotors/calipers to vented since my brake pads/rotors needed replaced anyway). Then I came across this ...(thanks Dave)...

http://www.meimann.com/docs/mercedes/OM603_vac_pump_mod.pdf

"Engine cannot be switched off when cold..."

I have had this problem during cold weather and it says it is due to a damaged piston vacuum pump. What is damaged that causes this? Something worn...faulty design? As you can see, it still has the centering sleeve that is to be pulled and replaced with the metal gasket/dam. Should I bite the bullet and replace the pump now anyway? It looks good, but if there is a problem I will replace it. Thanks guys....

[sixto]

Mark,

You didn't give the mileage of your car or say if you have the pump with a riveted cover or screwed on cover (would indicate original vs replacement). Prudence calls for replacement of the pump every 100-150K miles.

You replaced the rear rotors with vented rotors? Why? Rear brakes don't do much work.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

[MarkWells]

Last part first....

I didn't convert the rear rotors.....I converted the front. The car is a 1985 W124 300d non-turbo euro car....a very early W124. It had solid front rotors. I made the mistake of trying to turn them but they were too thin. (I'm glad my buddy only charged me 10 bucks to turn both...lesson learned....check for the minimum thickness number on the edge of the rotor). I found solid rotors at coximports.com but after I snapped off a bleeder, then broke a ez-out off in it, I needed a caliper and could not find one for the solid rotor anywhere. The guys at cox imports allowed me to exchange them for the updated vented setup like W124 turbo 300D's and 300E cars came with. I appreciated the help.

Second part....

The car has 248k on it. As for the cover, you may be talking about a different pump. This cover appears pressed on...no rivets or screws. I am not sure what a 617 pump looks like.

thanks for the help...

[speedy300Dturbo]

If the front of your pump is flat without these screws, it's the old style one and is overdue for replacement!

The new style pump looks like this:

http://www.meimann.com/images/mercedes/head_gasket/vac_pump1.jpg

[BJ300SDL]

Welcome on board Mark!! We are almost neighbors!

[sixto]

Mark,

Sorry about that. I didn't realize that anything a 603 came in had solid front rotors. I also meant pressed, not riveted on the pump. It might look good and perform well, but I think the majority will recommend replacing it.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Sounds like a very interesting and rare car you have there! Any pics? Is it a manual or automatic?

[MarkWells]

Thanks for the help and the pic, guys......I figured you would encourage me to change it. I was just having a hard time getting my wallet back out.

I've lurked on this board for a quite a while and appreciate it very much....it is very valuable to the newbie as well as the veteran mercedes owner. I've always been a DIY'er if I can find the info.

I've always wanted one of these cars ever since I climbed into a cab when I got off the train in Franfurt West Germany in 1980. In my 21 months there (US Army), I developed a love for german cars, beer and a girl or two . I picked this car up last summer but didn't go about it right....the uneducated impulse buy .
It seems to be a good car but I paid too much....one of many newbie lessons that I have learned. It looks good thanks to a more recent paint job. I don't think it had any rust....just oxidized bad from sitting in the sun too much. The motor doesn't use any oil or leak at all. I changed the valve cover gasket and replaced a cracked breather elbow. I was surprised how clean the valve cover was...no gunk build-up at all. It started giving me a squeek recently from the front of the motor that I thought was the water pump. When I looked, the tensioner was sitting crooked and the belt was nearly 1/4 off. I found out lots of info about it in the archives . As soon as I get the tensioner and pump replaced, it's time to troubleshoot my vacuum system and hard shifting tranny.

The car doesn't have the speed of the turbo but there sure is lots of room under the hood and it is much simpler....no trap oxidizer, turbo or egr. I may use some of that space for a bypass oil filter. It will run at 70mph all day and the type of driving I do in central Indiana...that's all I need.

I enjoy working on the car. My son is 17 and has car/truck fever. He's changing the oil on his mom's Park Avenue ultra (he loves that supercharged 3800!) as I write this.

Have a good one!