I am replacing the vacuum pump on my '82 240d and I have gotten all the bolts out except the bottom one, does anyone know of a trick to access it?

Also I took the fan and fan pulley off to more easily access the pump. I was trying to put the fan and pulley back on and the belt is not tight, what do I need to do to tighten it?

Any suggestions would be much appreciated. Thanks!

Are you using an Allen tool that fits on a Socket Wrench or are you using a regular Allen Wrench? You might have to use which ever one works best. Besure to clean all of the dirt out of the Allen Head hole on the bolt so that what ever tool you use goes all the way in.

All of your belts need to be properly tightened. There are Belt Tension Gauges sold but I think most people just push on the belt and make a subjective judgement for themselves (I do).
So with out some sort of gauge or Factory Manual to go by the belt needs to be just tight enough not to slip under load.

__________________
84 300D, 82 Volvo 244Gl Diesel

Regarding that bottom bolt, are you simply having trouble reaching it,
or is it giving you trouble (too tight) ?

Because Diesel811 is right, you may need to switch to spcket based Allen.

Second: belt tightening is pretty much the same on al under hood components.
The pivot bolts need to be lossened, and not much needed at all.
And then the lock.sliding bolt.
Then each accessory has a tightening bolt the pulls the item to
the desired tension, then you go and tighten the pivot bolt and the
sliding bolt.
Your alternator, power steering pump, and AC compressor all have this.
Pivot, Lock/slide, tensioner.

Which device shares the belt with the fan ?

__________________
80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

I bought more allen wrenches and was able to take off the vacuum pump and put the new one in. Now I have everything back together but the belt for the fan and alternator(I think) has a lot of slack. I can't quite figure out how to tighten the belt.