You may or may not have given a thought to servicing your BMW alternator belt or your Mercedes-Benz air conditioning belt but the chances are pretty high that if your car is less than ten years old it is fitted with a stretch belt. What in God’s name is a stretch belt you may ask, have we not got enough to worry about?
A traditional Serpentine belt drive with tensioners
Many years ago our cars were fitted with a traditional “V-Belt” which would take drive from our crankshaft and power the engine’s water pump, and alternator perhaps. Things move on somewhat and our cars have an option of power steering, an other V-Belt is added to a second position on the crankshaft pulley. Air conditioners come along and of course the refrigerant pump needs a drive… cue a third drive from the crankshaft pulley. How about an air pump to help with emissions. No way, not a fourth belt? This is all getting a bit busy so the clever automotive engineers take the construction of a timing belt, flat and in-elastic and then instead of synchronous teeth across the belt, they mould multiple “Vee” profiles on the inner drive side of the belt to increase area and friction and “Voila!” the poly-v belt, multi-v belt or serpentine belt, call it as you will. This new belt is super flexible and has superb drive characteristics allowing pulleys to be made with smaller diameters and lower inertia, everybody is a winnner!
The Poly-V belt
These new designs are also super simple with just a single belt weaving around the front of your engine, one single tensioner and that’s it! Time stands still for nobody however and pressure for lower emissions and ever more efficient engines with lower manufacturing costs and evolution sees a new belt in town. The “stretch belt”.
This is almost identical in appearance to a traditional poly-v or serpentine belt to look at but search all you like at your Ford alternator or Subaru power steering belt and you won’t see a tensioner anywhere! These belts are elastic, well to be precise, they are sufficiently elastic to be installed over fixed pulleys with a special tool and then they will maintain enough tension to deliver quiet power transmission for years.
In OTTO we sell a lot of stretch belts, Mercedes power steering belts and BMW air conditioner belts are very fast movers but most European and Asian marques now use these from Ford to Mazda and Subaru to Opel. If you need to service your belts or any of the accessories driven by these you will need tools to remove and fit the belt. We stock several solutions from our range of tool supplers, Klann, Hazet and AST Tools all manufacturing tools for this job. We also supply tools from Continental for elastic belts but our fastest mover is without doubt the Vigor 2646 followed closely by the AST Tool.
How do these work? Put simply the tool uses a ramp profile to guide the belt off the side of the crankshaft pulley for removal or a ramped flange that will drive the side of the belt onto the pulley for installation. We have a sequence of images showing how to use the Vigor removal and installation tools below and a nice little video short-cut for belt removal at the bottom of the page which might just get you out of a jam!
Belt removal
Manufacturer instructions suggest that we cut the used belt for simple removal but in some cases the belt may be quite new or may just require removal for inspection of either the belt or one of the accessories it drives. In this case you may wish to use the Vigor removal tool to slip the belt off the pulleys un-damaged. Here we show how this is done:
The ramp on the removal tool eases the belt off the side of the pulley
Without the belt we can see how the removal tool engages the pulley flange
Belt installation
To replace the belt wrap the belt around all pulleys in the correct position and guide the belt towards the crankshaft pulley. Place the Vigor installation tool onto the crankshaft pulley so that the slot on the underside of the tool engages the flange at the side of the pulley. Slide the tool clockwise around the flange of the pulley until the ramped flange on the tool is pressed against the side of the belt. The tool will wedge into position between the belt and pulley at this stage. Using a suitable tool rotate the crankshaft pulley clockwise while holding the tab which extends out the side of the installation tool. This will drive the belt across the pulley until it clears the side flange and will drop the belt into the grooves of the pulley. Have a look at the image below which shows the belt, tool and pulley all in place just before the pulley is rotated to install the belt:
Use the ramp flange of the installation tool to ease the belt onto the pulley
And here as the belt is pulley is rotated the belt drops onto the pulley grooves
Check the installation
Be sure to carefully check that the belt is fitted properly onto the crankshaft pulley and that it has engaged all of the vee grooves. Also check that the belt did not move out of position in any of the other accessory pulleys while you were installing:
Check your installation carefully before operating the engine
You will definitely need to buy a tool if you are going to replace a stretch belt on your engine so don’t be tempted to try any short-cuts. The belts have just sufficient elasticity to allow installation and any attempt to bodge without the proper tool will damage the structure of the belt and will probably leave you stranded on the side of a motorway, towing charge and all the bells and whistles too! Use your registration or vehicle make and model to look up replacement drive belts and grab a fitting tool at or Web Shop – www.ottocarparts.com. See how simple we made that!
Now I did promise a short-cut for belt removal so if you are badly stuck or need to bring the belt into one of our Dublin branches at Tallaght or Swords or regional branches at Galway or Cork, then root out about 300mm of heavy ratchet strap web material. Click on the video below to see how the web can be used to remove the belt but do make sure the engine is stopped, keys removed from ignition and all other safety precautions are taken before you attempt this:
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