Question about 1984 Mercedes-Benz Mercedes Benz 300 Class

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I need to replace to replace fanbelt on 300D 1984 mercedes.

Can not get past Other belt

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  • laughing_w Jan 21, 2009

    But the question was how to change the second belt. Wound up cutting off the power steering belt to change fan belt.



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Transit Guru360 is right, It's not so hard and you might remove a few extra nuts...but once you've done it, it's a piece of cake the next time.

I just did this on my 300CD and this is what you do...

I dont have a AC belt since my AC doesn't work I removed it a while ago

1 You'll need:
a. a nice long pry bar (for tightening belts later)
b. a pair of 13m and 17mm wrenchs as well as sockets to do other side of each bolt.
c. a pan for the antifreeze to drip into since you'll remove the top hose to give you more room to
work and it will be full of antifreeze.
d. straight screwdriver
e. Some Gojo...yes working on diesels is a dirty dirty job

First take off top radiator hose, then smaller overflow hose, then upper and lower air intake hoses and unplug that little wire...not sure what it does, but it's in the way.

The power steering and alternator both have 3 bolts that hold them in'll have to remove the power steering belt first. These are all 13mm. If standing at drivers side, there's a bold at bottom of powr steering pump, its an adjustment kind, remove the nut or just loosen it but leave bolt in.

Then remove the other two bolts, they are recessed in the back of pump on lower side. You can see which ones they are by looking for the nuts on front of pump. Loosen them and remove them.

Pump will be totally loose now, take off that belt and carefully finagle it around fan and off if need replaced, if not, just drop and let hang for now.

Then onto Alternator which will be bottom left of engine as you look at front of engine. Theres a through bolt on bottom of alternator, just roll up your sleevesand climb under car and use 17mm wrench...the alternator is threaded so there's not nut down there to loosen. Dont remove this bolt, just loosen it well.

Now loosen the top 2 bolts, dont worry about the adjustment, mine was stripped...and my adjustment was the prybar:) Loosen those but dont remove them...wiggle the alternator until it gives you the slack you need to remove the belt, if you cant get the slack, you can wrap your fingers around the belt upper and lower and squeeze, this will give lots of leverage and force alternator to move in, then pop that belt off and discard.

Now just put the alternator belt back on, use prybar to get proper tension...and tighten. A half inch of play is about the right tension...but tighter is good with a new belt since it will stratch a bit over time.

Make sure all 3 bolts are tight on alternator then move to replace power steering pump belt, but you will have to put at least onee of the top bolts back on to pivot against when using prybar to tighten that belt, then once you have the tension you want, tighten adjustment bolt, then keep the tension and put 3rd bolt in and tighten, make sure all are tight and you have 1/2 inch play on that belt as well. Then put all the other things back together ...check to make sure all tools are out from engine compartment and fire it up, if it squeels, it's too loose, if not, you're good and you can wipe down your tools, put them away and use the GoJo:)

Good Luck!

Posted on Jun 12, 2009

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There are three belts there if I remember correctly. A power steering belt, an A/C belt, and an alternator belt. That's assuming your car has A/C.

The power steering pump has a few nuts on the backside that you MUST loosen first. Then you can use the adjusting bolt that's facing up vertically. I believe the adj nut is 10mm? Or 13mm? If you use the adjust bolts without loosening the others, well it just won't move.

The alternator has a different setup too. Loosen the nut on the backside underneath the alternator. Yes, it's a pain to get to without a lift.

Then you loosen the top nut on the back side of the long bolt with the teeth on it, which is on top of the alternator. Once those are loosened, you make your adjustments with a 10 wrench, or socket.

Of course, lefty loosey, righty tighty.

If you do the A/C compressor, it also needs nuts loosened on the backside before adjustment. I believe they're 19mm. I also think the A/C belt is last to go back on. But confirm that with your pulleys and alignments. I think the A/C compressor has a 10mm adjustment that you'll see from underneath the car.

Basically you put your farthest back belts on first, make your adjustments to get them tight, then tightens you nuts/bolts to make sure the adjustments are locked in.

These belts if new, will stretch, so try to get good at how to tighten loose belts.

The main thing you need to keep in mind is that the adjusting bolts won't adjust anything if the locking bolts aren't loosened first.

I've seen many an alternator bracket that has been bent b/c someone didn't loosen both the up and lower locking bolts first.

Take your time. It never hurts to loosen one too many bolts. You'll figure out which ones once everything starts coming together.

Posted on Feb 10, 2009

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You must remove the outside belt to get to the inside belt, no way around this problem.

Posted on Jan 18, 2009

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