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M117 AC drive belt tensioner

Started by TitanBenz, 13 April 2023, 05:57 PM

TitanBenz

Hi everyone,

When I purchased my car, the AC drive belt was disconnected, I have since bought a new set of drive belts for the vehicle from MB (ex Germany). Found that the tensioner/tensioner pulley (#5 on diagram below) on the AC circuit is faulty. MB advised that they don't manufacture or stock the original item nor the superseded part anymore.

Anyone have any insight into where I can purchase this from? Thank you in advance.
With the amount of cars I own, some call me crazy. To them I say: I'm just in love.

goldacre

QuoteIna A/C Drive Belt Idler Pulley; 15mm Bolt Hole
P/N: 1161300460

AutohausAZ website for a base 450SEL 1979.
USD$41.99

Replaced mine about 12 years ago using this part and all good  8)

G

PS I understand that the Bolt size can be different? Not sure what time period the variance is, measure yours first to make sure.
12/1979 450 SEL 148K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)

TitanBenz

Quote from: goldacre on 13 April 2023, 09:36 PM
QuoteIna A/C Drive Belt Idler Pulley; 15mm Bolt Hole
P/N: 1161300460

AutohausAZ website for a base 450SEL 1979.
USD$41.99

Replaced mine about 12 years ago using this part and all good  8)

G

PS I understand that the Bolt size can be different? Not sure what time period the variance is, measure yours first to make sure.

Thank you for that, so it seems this is the pulley which I can still source locally. I am after the tensioner/ Arm that it attaches to. The arm on mine seems to move pretty freely, I assume that there should be some tension? I'm unsure though as I am new to the W116. I'm used to my W126 and W140 :P
With the amount of cars I own, some call me crazy. To them I say: I'm just in love.

goldacre

#3
QuoteThe arm on mine seems to move pretty freely, I assume that there should be some tension?

Ummmmm... OK, part number is 116 132 03 04, Google that and a few come up, ECS Tuning have one for USD$75. BUT...

It moves? The arm bit is solid and if it moved it would have to be in at least two pieces  :o Looking at mine the arm assembly is held to a plate that supports the AC compressor at the front of the engine. The idler arm is held there by a very big bolt, a spacer washer and a bolt head washer.

Yes, definitely needs alot of tension to hold Pulley in place when adjusting, behind the Pulley the neck is like a square, this is the attachment point to tension the Pulley, must be a special tool as is a pig to do with spanners, you lever the tension to a point then tighten up that big bolt to hold in place (after loosening it of course...  ::) )

I fear the thread in the support plate could be chewed out, or the extra bit of metal attached to the back of the plate to hold the thread depth has come adrift? That would cause the movement me thinks, unless the AC front bracket is not bolted to engine fully?? Or... the bolt is not tightened up? It's a two way job, spanner on arm neck to tension then at same time tighten the bolt up, fiddly to do and volunteers normally run off screaming

Both can be fixed but getting access will require a heap of bits removed to get down there to play with it, or worse to remove it to repair, but do-a-ble.

G
12/1979 450 SEL 148K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)