I'm thinking my belt tensioner is shot on my 400E. The adjustment rod on my tensioner runs out of travel or adjustment.

I took the tensioner off and on the back side where the adjustment rod connects to the flat plate which has the flat areas, and this in turns moves in adjust on the tensioner. The flat areas on the tensioner can be moved if I hold the wheel bracket still, which internally sounds like the rubber is turning inside.

When I set the initial tension, i.e. Belt semi tight against the basic tensioner and the adjustment rod in the lower to middle part of the threaded shaft.
The adjustment mark on the tensioner is set to the first mark to the left facing the car.
I then adjust the tension with the tension adjust screww till the marker is then in the middle of the 4 marks. I then tighten down the center bolt to hold the tension at this point and solid tighten the center bolt on the tensioner.

At this point when I pull up on the belt everything loosens back to very slack.

Sign of shot tensioner?

What's the corrent conversion of 100 Nm to Ft Lbs.s That's what the service book says is torgue spec for the center bolt.

Thanks for the help,




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Mike Mullins
71 250 Coupe
92 400E Sedan
90 944/S2 Cabriolet

The OE part has been modified several times due to failure, sounds like yours!
Convert from NM to FTlbs by mulitpling by .7
100nm = 70 ftlbs.

I would agree. He is an instance where something was overengineered. In talking to the parts man, I doesn't seem to matter whether it was a first run engine or even the later serial numbers they all seem to fail. someone wrote that this ought to be a maintenance item for all model using the the 119 motor. kinda of like the power steering hose leaking at the pump to supply canister.

Thanks for the response.

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Mike Mullins
71 250 Coupe
92 400E Sedan
90 944/S2 Cabriolet

Well, The tensioner was shot. Got a new one, 20 minutes later got the new belt to tension to correct setting and went for a test drive.

It seems this chassis (124.034) has it's down sides and I've had the most common ones so far.

1. Brake rotors warping
2. Power steering resevior to pump leak
3. Poly Ribbed Belt Tensioner malfunction
4. What next ?

Anybody else got any commonalities we 400E owners should be looking for?




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Mike Mullins
92 400E Sedan
90 944/S2 Cabriolet
94Toyota Pickem up

I think I've got a new one, and it's cheap to fix (BTW, I've done all of the above fixes on my 500E) but a real pain if/when it fails. There's a coolant return hose going from the expansion tank to the top of the radiator. It attaches to an L-shaped neck that goes into the top of the radiator. These little $2.50 parts can and do fail; the same one's on my 500E and 300TE, and it's already broken on the wagon (with LOTS of coolant being lost, but no harm otherwise 'cuz I caught it) and I'm gonna change out the one on my 500 as a preventative measure.

One other thing: I developed a driveline vibration at around 25 MPH; very annoying, and happened in 1st or 2nd gear. Turns out that the driveshaft center support's been upgraded several times since my car's production (6/92), and replacing it solved the shake issue...car's as smooth as can be.

Good luck all!

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All the best, Michael
500E
300TE