Is your belt tensioner secured with an allen head or a 19mm socket? On a 103, after you loosen the 19mm holding the belt tensioner snug, you loosen a tensioning rod on top of the tensioner with a 13mm socket. The 103 motors use a special 8mm Stahlwille and ft. long metal rod bent slightly at one end for fan removal. Somehow, you got through this.
If you'd like, I can email you the 103 belt replacement process off the MB CD-Rom. Like Chuck, I don't think this process differs much between the 103/104.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.