How to replace the auxiliary belt and tensioner on Volvo 850, S70, V70 or C70

by: dooby


Hi folks,
another job today was replacing my aux belt tensioner. It had been squeaking for some time, and neither WD-40 nor 3-in-1 light oil was helping long-term.

I found a new one listed on eBay as a Renault Laguna/Safrane part. It’s identical to the one several Volvos (including my 850). I paid £15 for it, plus £9 P&P. When it turned up it was a genuine, Volvo badged part! I was quite pleased ‘cos although I often use PartsForVolvos their price for an after-market one is £55!

Here’s how it all looks to start with:

First, disconnect the fresh air feed to the ECU housing and undo the metal strap. If yours is original (i.e. a metal cone) you may struggle – mole grips I suggest! I replaced mine with a 10mm hex nut.

Next, remove the cover – two opposite clips, you’ll want a long flat head screwdriver I think.

Remove the ECUs (they only fit one way round, but take note). Remove the wash wipe fluid filler neck. Unbolt the top of the casing, on the wing and undo 3 clips (see picture). Last, pull out the cold air outlet.

As you can see, still not quite enough room to get a 3/4″ breaker bar into the tensioner 🙁

Pull the air outlet tube off where it connects to another pipe nearer the bulkhead. It just twists off. This exposes another bolt – undo it. I also unclipped a bit of the plastic wiring loom holder opposite the bolt to allow movement.

Now there’s enough access. Get a 3mm drill bit or similar ready.

Move the tensioner until you can insert the bit to lock it – be careful the breaker bar doesn’t slip, you don’t want to round out the hole!

Undo just enough of the belt to free up the steering pump wheel to see the tensioner bolts.

I was able to undo both bolts with a 1/4″ 12mm socket, universal joint and extension bar.

Here’s old vs new.

I put the new one on in its natural position, I can rotate it and put the locking pin in once bolted in place. I don’t know the real torque setting, Haynes didn’t say but 20Nm felt tight enough.

Use the breaker bar again to move the tensioner until the locking pin can go in.

Re-route the aux belt carefully, take the slack off the locking pin with the breaker bar and let it take up tension on the belt. I found I needed to move the coolant expansion tank to do this – no need to undo any hoses, just slide it up and disconnect the level sensor.

Refitting is the reverse of removal (I put the parts I take off in order, so I can put them back in the opposite order). Here it is all back together!

Have fun! Cheers, Pete


The instructions in this tutorial will work in the following models / years:

– 1991,1992, 1993, 1994, 1995, 1996 and 1997 Volvo 850 Petrol Engines
– 1997, 1998, 1999 and 2000 Volvo S70 Petrol Engines
– 1997, 1998, 1999 and 2000 Volvo V70 Petrol Engines
– 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004 and 2005 Volvo C70 Coupe and Convertible / Cabrio Petrol Engines