Very strange .......

You all will remember that I changed the "bombs,"
or accumulators along with the shocks.

One of the shocks was useless, so I disected
it, as you have seen pictured earlier in the thread.

I kept both shocks around, since everything that comes
in a yellow - and - black box is expensive.

Since this thread has started, I have aquired another
couple of 456 cars, both 1995 6-speed models.

Yup, all the rear shocks leak !

An extra pair of rear shocks and "bombs" came with one
of the cars, so I took the opportunity to send the
"spare" pair of shocks to Juan Alvarez at Bilstein.

Juan was able to rebuild both shocks for small money
(Like less than $300 the pair, using better-than-new
quality parts)

I then, on a whim, sent the "bombs" to Juan for checking,
and Juan advised:

From: "Alvarez, Juan" <[email protected]>
To: scott guthrie <[email protected]>
Sent: Tuesday, October 16, 2012 6:29 PM
Subject: RE: Ferrari shock accumulator service
Hi Scott,

We have no way of testing these,
theoretically you could hook up
some lines and pressurize it then
dunk it in WATER to check for leeks.

Not recommended since 155 BAR translates into 2245 PSI!!!!!!!!!!!!!

I then asked:



OK Juan.
I will have to hope for the best.
What happens to the system
if the Bombs have an internal
leak, and fill with fluid ?

Scott

Juan replies:

"If the diaphragm has failed then when
the shock starts to compress and displace
the shaft volume the shocks will hydrauliclly lock
and the shocks will only compress part of the way.

Thanks.
------------------------------------

Juan Alvarez"


So: Bite the bullet, and replace both
the shocks AND the bombs if
you see this type of failure.

Scott

PS, Car has been perfect since the repair !

 

From Juan:

Hi Scott,



I was able to finally look at the pictures as well as
read through the thread, good job on the diagnosis.

It’s hard to say what happened, but that type of damage
is consistent with a shock hydraulically locking.

The shocks use a 22mm rod, lots of fluid displacement,
and if the “bomb” failed it could of caused the shock body to rupture.

The wear band more than likely blew apart ,
lots of internal pressure,
causing it to split in to pieces.





Thanks.
------------------------------------

Juan Alvarez

 

I'm glad this thread continues to be of help.

Too bad others have had this same problem,
but it is interesting that with less than
one thousand (1,000) cars built, there has been
at least one failure similar to mine.

I have had three (3) 456 cars
(still have a '95 6-speed)
and I have made it a habit to replace
the "bombs" on all 456 cars, and to
replace/rebuild the rear shocks ASAP.......

Thanks for posting !

Scott

 

Friends:

Some of you have asked about needing
to "bleed" the shocks, sort of like brakes:

I have found on three (3) cars:

No, no need to bleed anything, just drive it,
and it will soon "dissolve" the entrapped air,
and the fluid will be where it needs to be.

NOT like brakes, since the working fluid is
always in circulation, and delivered
at very high pressure....

I usually do fill the shock and the "Bomb"
before bolting stuff together, and run the
car for a while BEFORE driving........

Scott

 

Rob (and others....)

Currently, it seems that the accumulator(s)
are indeed the root of the problem.

It might be best to just replace
them every five(5) years or so.

I have heard NO reports of these shocks
exploding if the accumulator is NOT bad.

Using the BMW "bombs" as a readily-available
source, and minimal labor to install, may be a
good way to extend the life of the
relatively-expensive shocks themselves.

My choice going forward would be to replace shocks
as needed with the wonderful DELTA VEE units,
and then be religious about "bomb replacement."

Just one more thing to do on the ever-reliable 456......

Cheers, Scott