Sunday 21 July 2013

E39 530d: Air-Con Drive Belt Snapped - Fixed, now heatwave over...

With the recent heatwave I noticed my air-conditioning appeared to be struggling. It must have been over a year since I last stuck it on full snowflake mode and I know these things fade-off, but it had been working fine, so before I shelled out the £40 or so to get the system re-charged with gas, I figured I'd check the pipes and filters to make sure nothing was clogged up, as everything else had been round MOT time. Apart from a few errant sycamore seeds the system beneath the filters was like new, so a quick peer down the front of the engine showed the real culprit - the drive-belt had snapped and was wrapped like a snake, almost out of view, around a radiator hose.

I was surprised there is no warning-light on the dashboard or the climate-control unit for this, as there is with the alternator-belt, the air-con simply stops and the system functions like a normal blower/heater. With British summers being the way they've been, the belt may have been snapped a year or two ago and I've been totally unaware. It took our recent heatwave, and this is the first time it's been anywhere near 30 degrees for 5 or 6 years, to decide something was actually wrong. I think the most likely cause is all the time I spent running the car with the compressor turned fully off while the battery was in poor health, the constant resistance snapping the belt.

Naturally I would have gone straight to BMW for an OEM belt, but it was 2.30 on Saturday afternoon and they'd closed for the weekend, so I hit up Euro Car Parts, who had the right belt in stock at their new branch which is less than 2 miles from my house. It's an OEM quality part, made by Continental and came to £9.84, so I can't really complain!


I fitted the belt in about 30 minutes, without raising the car, removing the fan or even moving it onto the drive, using a quick and dirty method, which is fine for the air-con belt, but wouldn't work for the main drive-belt covered in this post.

1. Remove the front-piece of the engine cover [the slim one covering the PAS-fluid filler] by undoing the two bolts on top and one down the left-hand side using an M4 allen-key.

2. Undo the six fastening lugs for the front engine-undertray using a crosshead screwdriver, bend the tray back, free the leading edge from the front-bumper and lower it out of the way.

3. Place the new drive-belt over the two main pulleys from above and wedge the belt over the tensioning-pulley so it doesn't slip off and can be accessed from beneath the car.

4. From below the engine, hold the belt in place at the tensioning pulley and use a 16mm ring-spanner to rotate the tensioning-pulley downwards on its spring-bracket. [An open-end spanner will slip off easily and there isn't quite room for a ratchet-handle without removing the fan.]

5. Push the belt over the tensioning-pulley so it forms a 'pair-of-glasses' shape, as shown on this page of Ensure the belt is still in place over the two main pulleys, it may take quite a bit of rotating the tensioner to achieve this, and release the tensioning-pulley.

6. Refit the engine-cover and undertray - you're done, cold air!

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