Suspension parts refresh and Zinc plating (continued)

[Costa P]

The first part of this write up is on my project page, refer post#112
930 rebuild – The revival of my mothballed project

Originally Posted by Costa P

Well…while I’m in there, might as well do some cosmetic freshening ups!

After the application of a variety of power tools with steel brushes ...voila!


.
.
.



Making good progress to get everything prepared and ready for replating.

It has been a while since my last update. In the meantime, I’ve slowly been completing various tasks and the results are coming to fruition.

The suspension parts are back from Zinc plating (more about that in a moment)…but first ill share some more pics from the preparation effort:

I have brushed and prepped all parts for plating, as can be seen from the suspension bolts.
I must admit that it has taken many more hours than what I initially imagined.
It is also work that is not the most gratifying at the time, in fact quite frustrating. The rewards though are reaped at the end, once you see the result of the final plated parts…more about that in a moment.


The strut upper mounting required attention next. Firstly, the old rubbers were trimmed and pressed out. The fresh ER replacement rubbers are awaiting installation





In the previous pictures, you may have observed that some of the weld nuts have detached.
Upon closer inspection, I realised that the root cause for this is over tightening of the cap screws that hold the upper strut mount against the body.
Over the years, the various PO’s and shops that conduct wheel alignment have been overtightening (over torqueing) these bolts and causing the plate to distort and pull into the rectangular apertures in the body (refer next picture).
The rectangular witness marks around the holes are clearly visible.


After closer inspection of the schnorr locking washers (serrated washers) which are used together with the above mentioned cap screws, I realised that they were completely blunt and flattened.
Even their original “belleville washer” shape was completely flattened.
My deduction is that:

a) The schnorr washers have never been replaced and therefore are no longer able execute their task of preventing the cap screws from vibrating loose.
I suspect that this would result in a vicious cycle of the wheel alignment that goes off which is followed by another round of wheel alignment and tightening the cr#p out of the said bolts!

b) The deformation of the upper strut mount (rectangular witness marks and bulging of material) would play havoc during wheel alignment and setting of camber.
The bulge that has formed would have the tendency of self locating in the body as soon as you tighten the cap screws!

Long story short, iv had to repair the bulge by pressing it back. Once the shape had been restored, the weld nuts were tacked back into place.
The end result is visible in the pics of the freshly zinc plated parts (coming up next).



more pictures coming up...

[Costa P]

[540964]

Very nice.

[Costa P]

A lot has been said and opinions differ regarding the need for baking (to mitigate Hydrogen embrittlement) of our beloved Porsche parts after the zinc plating process…

I’v read up and considered multiple perspectives and decided the following way forward for my parts:
a) Yes, hydrogen embrittlement is a real thing…..it is not a hoax and it is not paranoia.
b) The rule of thumb is that parts that are grade 10.9 and above should avoid undergoing zinc plating because of the risk of failure as a result of hydrogen embrittlement.
c) If you insist to proceed with Zinc plating, then you need to bake after zinc plating to “de-embrittle”. You are warned though, that the baking process DOES NOT guarantee against failure as a result of hydrogen embrittlement!
Note: The special Porsche eccentric bolts for the spring plates are grade 10.9!

d) My special request to the Zinc plating company was to "De-embrittle (bake) at 190deg celsius for 8 hours within 60 minutes of processing"

[Costa P]

The trailing arms received a lot of TLC too.
A total of 3 hours each, of hand brushing/scrubbing with Prepsol cleaner and pressure washing!