Serpentine belt on my 87 300d makes me feel stupid - PeachParts Mercedes-Benz Forum

#1 11-06-2003, 05:14 PM

Hello everyone,

I did a search on serpentine belt replacement and I still am having some trouble.

Last night I could not get my belt on. I had replaced the waterpump, thermostat and now want to change the belt.

I tried but just dont know how to manage the tentioner device. I have read that we need to reset the tention or something and I can not find any info on the cd about it.

This car is a PITA to work on so far.

W123 are alot easier for those considering a w124 be prepared for some challanging moments.

do I need to dismantle the tentioner device and/or adjust it due to the new belt. It is not even close to going on.

thanks

bob c

gsxr · #2 11-06-2003, 06:43 PM

Bob, when you figure it out, you're going to kick yourself. It's really simple and soooooo much nicer than the positively sadistic milti-V-belt setup on the OM61x engines. You need to find the long bolt with a 13mm nut that goes *through* the cylinder head, at the top right front corner (facing the engine). Remove the nut. Now stick a long 3/8 extension bar into the round hole in the black plastic thingy near the top hook of the spring. Press to the left, release tension on the long bolt, press/tap the bolt back, and when it's free the spring will release (reduce pressure on the bar and let it move to the right). Now push down on the idler pulley, against the shock, and you'll have plenty of slack to work with. It's a slick setup.

If you've done all this and it still won't go on, either you have the routing wrong (verify with the manual), OR you may have the wrong belt length (compare to the old one).

gsxr · #3 11-06-2003, 06:45 PM

Here's a photo. The nut is a half-inch in front of the top spring hook, which has a small dab of lavender paint in this photo:

psfred · #4 11-06-2003, 07:42 PM

I wish MB had used the nice spring setup on the M103, too, much easier.

If you have the fan clutch on, remove it. Takes less time to R&R the fan clutch than to wrestle the belt around. I've done it both ways, and the fan comes off now.

Getting the belt up around the crank pulley is the worst part with the fan on, you will have to reach up from underneath to pull it down -- the "loop" for the tensioner goes between the crank pulley and the fan pulley. If you don't want to remove the fan, I would recommend getting the belt over the other pulleys (AC, PS, alternator), then pulling it up and over the tensioner on the alternator side, leaving it off the crank. Crawl under and reach up through the cooling slot in the sound encapsulation panel and pull the belt down and around the crank pulley. It's too stiff to work it in from the top, to say nothing of the fan being in the way.

With the tensioner loose, the belt should drop right on. Do check the length -- if it's too short it ain't gonna fit!

Peter

#5 11-07-2003, 11:15 AM

Thanks guys,

This was so easy I feel even worse now.

I had the belt on wrong. If I looked at the picture it would have been a five minute process.

I thought that I looked at it well enought before I put it on.

I was very easy.

THanks for the detailed advice.

But I did manage to brake the thermostat housing GREAT

It is only 15 bucks so I wont cry to long.

I tried to seat the thermostat into place with a long screwdriver.

I would not recommend that.

I crack the housing at the bolt.

I though that I had it all done until I started filling it up with antifreeze and having it pour right out.

Is there any way to remove the air intake tube that goes to the turbo. It would make the thermostat job alot easier.

Thanks again.

I still feel that this car is cursed.

Also the water pump was a PITA to get in. The cd says to remove the whole housing. I did not do that as I thought it would waste to much time. three hours later I got it in.

Thanks guys for your support and hope for a great car when I am done braking things

bob c

gsxr · #6 11-07-2003, 11:30 AM

Bob,

For most jobs, the trick is figuring out what to remove to make it easier, which isn't always mentioned in the service manual. For example:

1- For the thermostat, first pull the rubber intake elbow off between the airbox and the turbo. There's a clamp on each end, you need a long Phillips screwdriver to get to the screw, and the turbo side may need to be accessed from the bottom. Second, remove the round electrical sensor directly forward of the t-stat housing. Pull the wire off, unscrew the sender. This makes access to the t-stat a zillion times easier and faster. BT, DT. On a side note, make sure you use an OE or OEM t-stat - not one from AutoZone, NAPA, etc... must be Wahler or Behr. And the t-stat only fits ONE way and has a locating notch too.

2- For the water pump, you don't need to remove the housing. Just pull the fan clutch, pulley, maybe the belt tensioner (can't recall if you need to do that), and then the w/p mounting bolts (one or two are hard to access on the bottom). Should be pretty easy, just time consuming.

3- Final note. Only use MB anti-freeze, or Zerex G-05, which are the same thing (amber/yellow in color). DO NOT use any "green" anti-freeze, GM Death-Cool, or other "long life" neon orange junk. MB or G-05 only. The G-05 is available at most AutoZone, NAPA, and other McParts places for about $9/gallon. G-05 comes in a gold container and says "For Chrysler Vehicles" on it, which now also means Mercedes.

mplafleur · #7 11-07-2003, 05:30 PM

I got a bunch of Zerex G-05 at Autozone for about $5-6 gallon.

gsxr · #8 11-07-2003, 07:01 PM

Wow- $6/gal or less is a killer deal. It's $8-$9/gal everywhere I've seen it. A friend saw it at NAPA for $7/gal when they first started carrying it, but within a couple weeks it shot up to $9. I'd stock up before they fix the price!

#9 11-07-2003, 07:15 PM

Thanks

I will put in the zerex stuff . I had bought the cheap peak stuff but now know better.

I will pull off the turbo hose when i change out the thermostat.

thanks again everyone

bob