Hi,
1990, 190E, 2.6, 164K. After reading several posts in this forum, I initiated a timing chain tensioner replacement. I was able to open the tensioner housing, then the old spring without removing the air pump for exhaust (I exactly don't know the name of the part, its located above the alternator and connected with the serpentine belt).

After putting the tensioner housing, then plunger and then spring I am not able to put back the outer nut (12mm hex), its just too difficult to put the nut back to thread against the pressure of the spring.

Plz advice how to resolve the problem. Do I need to loose serpentine belt tensioner>loose belt> take out air pump and then try to put back the chain tensioner outer nut?

How to open the air pump for exhaust?

Any help will be highly appreciated.

Thanks