S40 1999-2004 VVT pulley problem
 

There is an audible clacking from the engine when idling (seems to disappear at speed) and the engine responds erratically when a sudden load is put on it – typically, when pulling away from a standing start it judders and you need to slip the clutch to avoid stalling. Once running in higher gears our car was OK, and in fact did over 1,000 miles at speed in fifth gear on motorways quite happily, though I took care to drive without suddenly putting my foot down. At slower speeds in town I favoured lower gears to allow the engine to spin freely.

A lot of garages mis-diagnose the VVT solenoid at the top of the engine as being the item that is at fault. Unplugging the connector going into the back of the solenoid makes the noise stop. Plugging it in again re-establishes the source of power and the noise returns – hence the solenoid must be at fault.

However, the solenoid rarely fails and the reason it is making a noise is that it is being fed an erratic signal by the VVT pulley – which it isn’t when you unplug the feed wire!

It is worth saying that the solenoid is very easy to replace, easy enough for you to do it yourself (make sure that the replacement is one with a gasket). I replaced it on my car, but in sourcing one on the Internet it was immediately apparent that there were two versions, what I can only describe as ‘left handed’ and ‘right handed’ according to the fixing bolts – you’ll see what I mean should you ever need to do the same yourself.
With my new solenoid in place, the noise from it was the same as from the supposedly dud one that I’d just taken off – thus confirming that the actual fault lay elsewhere. In fact, the fault was with the VVT pulley at the bottom of the engine.

The VVT pulley is driven by the toothed cam timing belt. It is recommended (by any manufacturer) that these toothed belts are changed every now and then, so now is the time to do that. Our car had done about 95,000 miles. This belt also runs around two tensioners and the water pump, and so your garage will want to replace those as well, so that all the components involved are new.

That said, an entry on the Volvo Form states that the water pump rarely fails, so unless it is clearly faulty and needs replacing you can leave it alone. But they are cheap, so you might want to include water pump renewal anyway.

An important point about the replacement procedure is that since the old cam timing belt has to come off, the turning parts of the engine need to be ‘locked’ in place so that the timing is not lost. A special tool to do this is available from Volvo, though I think I’ve seen reference on the Volvo Forum about how one can construct one yourself.

When the work on my car was complete, the garage had some difficulty starting it, and said the sensors needed adjusting. That might have been the case, though one asks ‘why?’ I suspect that they did the job without the locking tool (which they would have had to buy/hire for my elderly Volvo), trusting that their expertise with other cam belt changes would suffice in this case. The car runs fine now, although the engine warning light comes on.

The various components used and their costs are listed below. Note that these also fit other Volvos and other manufacturers’ cars and so the prices vary considerably.

S40 (2003) cam belt kit
Unipart Timing Belt Kit: QBK615
Contains: timing belt and tensioner kit (box contains 3 parts).
Fits various Volvos and various Renaults late 1990s-early 2000s
Does not contain water pump.
£42.99 (6 March 2024).

Water pumps
Very cheap individually (£16-£38 – 11 April 2024), and can also be bought as part of the cam belt renewal kit (therefore a different kit number to the one given above).

VVT pulley
(camshaft timing gear, sometimes referred to as ‘camshaft adjuster’ or ‘cylinder head camshaft gear exhaust pulley’)
Volvo part: 6900015
Prices from £65 to over £160! (11 April 2024)

VVT solenoid
Stamped: INTAKE, 9454789, 4996-01 (or -02) Made by Aisin Japan.
Prices from £50 to over £180! (11 April 2024)