Originally Posted by daidnik

I'm not sure about how your thermostat housing is on your car (W124?), but the bypass hose usually goes between the thremostat housing and the water pump housing (as on a W108 and many other early models).

Getting the hose is a bit of an artful wrestling match to get the ends over the upper & lower pipes without tearing or abusing the new hose.

If you have the thermostat housing loosened from the cyl head, you can slide it outwards on the studs to increase the distance between the upper & lower pipes a bit and this can help matters, but it also requires dealing with replacing the thermostat housing gasket, so this isn't usually done that way, so then you're back to wrestling and lube.