Hey Scotty, I have a an automatic series 115 Mercedes 240D diesel that I need to replace the two belts that connect to the alternator, fan and engine. The car makes a squealing sound when I start it. I can’t seem to find a tensioner pulley. Would tension be released by loosening up the alternator bolt. The reason I ask is because the bolt is unique because it has spikes the align with a metal spoke and the alternator bolt is worn out. I’d rather leave it in there if won’t loosen the belts.
Thanks for the help!!
If it's anything like American cars in that era, there is no tensioner pulley. Each accessory has its own drive belt, which is wonderful. There's one for the A/C if equipped, one for the water pump and fan, and the other for the alternator. Tension on the belt is released by slightly unscrewing the bolt holding each accessory in place and sliding it toward the crank pulley. The accessories have pivot points that are large lag bolts and they move rather easily.
To return the belt to tension, you will need a pry bar and a solid anchor on the block to wedge the prybar against. Put the accessory against the pry bar and give it a tug. You don't want it too tight. It should flex around a half inch to an inch on the longest unsupported section of belt. Mark the bolts' positions on the brackets with white paint so you have a reference point.
You might be able to find a replacement bolt on RockAuto or elsewhere online that specializes in old diesel Mercedes vehicles.
Thanks Justin that’s all the directions I needed!!
No problem! Some can be annoying. On my 1979 Pontiac Catalina, the belt for the power steering is in front of the belt for the alternator. The alternator belt broke last summer so I just replaced the pair. I forgot another belt, there should also be one for the power steering pump as well. Haha.
stretch belts are back in fashion now too. And there's no adjustment bolts. You have to mount the belts with a special tool.
I vaguely remember Scotty talking about those, maybe a year or two ago. Manufacturers using them to cheapen up the serpentine belt lines even more. I'm pretty sure they delete the tensioner pulley with those. Spring-loaded wheels aren't that expensive to make or design. Haha.
I'm actually not totally against it. Yes they did away with tensioners and good riddance. Those things were always noisy and wearing out and not so cheap to replace.
If you're clever you can replace stretch belts with a big screwdriver, or some people use a cable tie. With tensioners you needed a big breaker bar.