If you're reading this, you probably have a car... most likely a Saab, even. Your Saab does many things, it moves, it stops, it turns, and inevitably it breaks.
Well, chances are if your Saab leaves you stranded on the side of the road the cause is one of three things
1. A Direct Ignition Cassette
2. A Fuel Pump
3. A broken Serpentine belt or pulley
I'm going to venture to say that about 60% of the "HEY! I'm on the side of the road and broken down" calls I receive are specifically related to serpentine belt or pulley failures.
What is a serpentine belt, you ask?
The Serpentine belt and its various pulleys can be seen on the left side of the engine in this photo.
A serpentine belt is a multi ribbed rubber belt which operates the engines various accessories such as air conditioning via the AC compressor, the charging system via the alternator, the power steering system via the power steering pump, and the cooling system via the water pump. It is driven by a single power pulley, known as a crank pulley, which is externally mounted on the engines crankshaft. Tension on the belt allows for the friction of the belt against the various other pulleys to operate these pumps and devices. Tension is applied and removed from the belt via a tensioner with a pulley that adjusts and absorbs shock as the belt turns. Saab 9000's use a hydraulic tensioning system with a shock absorber, whereas NG900's, 9-3's and 9-5's use a spring loaded mechanical tensioners.
This is a 9-3 and 9-5 style mechanical tensioner with tensioner pulley
Classic 900's (79-93) use a multi belt system which total 4 belts and has mechanical non automatic tensioners which must be adjusted by hand.
Anywho, the serpentine belt and its pulleys receive much wear and stress from its constant turning while the engine is operating. The belt is engine speed dependant, so the faster the engine is revving the faster the belt is turning. The pulleys on the accessories, such as the AC compressor, alternator, waterpump, and power steering pump are fairly resilient and do not typically wear (but I would suggest replacement if the parent component is replaced), however, there are two (in some cases 3) specific pulleys that cause problems for Saabs.
The pulleys in question are idler pulleys and the belt tensioner pulley itself. They do not drive any specific function on the car, and since they are hard mounted on the side of the engine itself, they contain bearings which allow them to turn. Their purpose is solely to direct or provide tension to the belt itself. The bearings they contain wear over time and the pulleys can separate from the bearings, which will throw the belt off track, stop the critical functions of the car from functioning, and will leave you stranded where you are.
Also, the serpentine belt can become weak over time and will snap, also leaving you with the same scenario. However, from personal experience, the pulleys will let go before the belt does, as untrained technicians will many times replace the belt but not the pulleys.
I follow Saab's suggested service listing for these bearings, and that is replacement every 60k miles. The pulleys and serpentine belt are included in the 60k mile service, but as stated before, that does not mean they are always changed.
The lesson here is check your belts condition. Belts and pulleys will sometimes make noise and give you some warning before they go, but many times they just go. When you come to me for an initial service, this is one of the first things I will check and suggest to you as a client to keep you motoring safe and happy!
Parts cost varies per model, but an idler pulley, tensioner pulley, and serpentine belt replacement usually runs in the $250 range with labor included.
Please leave comments to let me know how you guys are liking the blog. Also, if anyone needs anymore clarification or explanation, feel free to ask!