replacement hex bolts - engine 1984 500 SEL - PeachParts Mercedes-Benz Forum

dloveless · #1 08-27-2003, 12:10 PM

Apologies if this has been covered before... search was unsuccessful.
Am in middle of R&R cylinder heads and know I want to replace at least some of the hex bolts used in attaching alternator. Possibly others also before I get done. Anyone have a good source for these things? Or will over the counter replacements be OK?Thanks.

csnow · #2 08-27-2003, 01:24 PM

Just make sure you use hardened fasteners with an 8.8 or 10.9 grade. Try to get them with the proper length of 'unthreaded' portion whenever possible.

Of course you need the right pitch and size.

There are like a gazillion online fastener suppliers, but unless you really need 10.9/12.9 grades (some MB suspension bits) or stainless, they should be relatively easy to find locally.

Some 'adaptation' may be needed.
Many automotive bolts are 'flange bolts', meaning that they have a flange under the head, so no washer is required. Good hardware stores have these, but most do not, so you may need to add a washer. Sometimes they use 'flanged serrated' bolts, which means there are little teeth under the flanged head to prevent them from loosening. Now these are really hard to find, and a split lock washer should be used in this case.

When comparing fasteners, I often see differences in head thickness. Thicker is better, it most cases, since the corners are less likely to strip. Another difference you sometimes see is in the head diameter. I can't stand when fasteners have odd head sizes like 11mm, 16mm, or 18mm, or undersized heads.

From what I understand, if they also have a DIN rating, these variables are more standardized.

ISO standard allows for smaller heads, and Ansi allows both smaller and thinner heads (compared to DIN). Gotta love those Germans!

Of course, this is from an obsessive sort of guy who travels pretty far out of his way to go to a 'real' hardware store to stock up on overkill fasteners.