vilhelm

I have a slow oil drip coming from the left rear strut where it attaches to the axle ***'y. I have cleaned it up at it appears to be coming around the bushing at the attachment point.
are these struts oil filled...the oil smells like motor oil. It is dripping about 1-2 drips per hour. can the strut leak oil like this?

horst

At the rear, these are not struts. They are shock absorbers. And yes- they have oil that is pushed back and forth through a valve arrangement to dampen shock. I would really clean the whole area vey well, and then re-check. It may be oil thrown on the shock from somewhere above. BTW, of all the struts /shocks on the car the one on the left rear is the one most likely to fail. It lives adjacent to the catalytic converter, and gets a lot of heat. It is concievable that this unit has failing seals, or perhaps it was subjected to pretty violent compression and rebound. If it is leaking, when you remove it, you will no doubt be surprised as to how little force is needed for it to move in/out.

Adrian

Dear Bruce,
I assume that the rear shocks are the originals. If one is leaking like this you need to get it removed and replaced or repaired. If the shock absorber collapses you may well find yourself in an uncomfortable position and at any speed the result may be some structural damage. A little weep is one thing a leak is another and believe me you have a leak not a weep,
Ciao,
Adrian
911C4

PS: I hope that the oil is coming from the shock. Horsts advice is very good but engine oil is a lot more expensive if that is dripping out to fix. I hope that it is shock oil.

vilhelm

The streets here in Houston can get rough. So..I'm hoping it is just the shock.
Should these be replaced as a set? Both rear shocks at the same time?

horst

they absolutely should be replaced as a set. If it were me, I would use this as a justification with wifey that it is imperitive to replace front struts and rear shocks with Bilsteins. Tell her it is a major safety issue, and if she really loved you she would get you these for Christmas.

Roland Kunz

Hello

The left side is to far away from any engineoil. Shock oil can smeel different ways but mostly they smell a bit fishy.
Most Porsche shockabsorbers are gas loaded and therefore they will leak even while unused.

Always renew a pair and if you lowered the car get the RS bump stops and have the axles checked and dailed in when you are at that point.

Grüsse

vilhelm

It's confirmed..the left rear shock is leaking. I just had a quote to replace both rear shocks and allign for $1100.00. The book has this job at 3 hrs labor...at $92/hr. Is $700.00 reasonable for new shocks?. I see Pelican has a pair of Koni shocks for $400.00

Is this a DIY job?

horst

yes, it is a DIY job, but the left one is a bit of a pain. I really don't know if I would just replace the rears. Probably ok, since you are replacing both on the same axel, but I would wonder how the balance would be with Konis on one end, and (probably Boge or Sachs) on the other. I would replace them all, but that's just me. These things affect handling, and I just don't need something strange to happen on a high speed twisty. How much deductable do you carry, and how much is a pair of new fronts?

vilhelm

I guess I take a look and see what is on there now. Before I see how much my wife loves me and wants to do for me for Christmas.

Michael Delaney

Roland, You mentioned gas leaking from the shocks over time. I've always wondered if shocks of oil or gas variety have a shelf life. Seems like if they do one should be able to check some kind of date stamp. Is there such a thing? Roy

Bill Gregory

Here are two data points: I just bought Porsche Carrera RS rear shocks at $190 each. Bilstein's can be had for around $120 each. Check www.shox.com and get a quote on whatever non-Porsche shock you're looking for (they have free shipping on Koni's). Try Hendrick Porsche at 800-315-8193 if you're looking for a Porsche shock, as they discount 20%-30%.

You can do it yourself, if you're moderately mechanically oriented, and observe good safety practices when working with compressed springs. The basic procedure after you raise the rear end up is to undo the bottom bolt holding each shock in. It's torqued to 147 ft lbs, and probably hasn't been loosened in 10 years, so it doesn't undo easily. Once you get it loosened, leave it in, remove the airfilter and housing on the right and fan on the left. Remove the 3 nuts and washers at the top of each shock tower. Pull out the bolt at the bottom and remove the shock/spring assembly. Attach your spring compressors to each side of the spring, (be careful here) compress it, undo the nut at the top of the shock, and pull the whole thing apart. Keep the washers at the top of the shock mount in order so you know which goes where, as they are concave washers. Before you start make sure your torque wrench goes to at least 150 ft lbs, so you can reinstall the bottom bolt.

I agree with Horst, either replace it with what you have there now, or upgrade all 4. "Basic" guidance: If you have stock springs, stick with stock shocks/struts. If you upgrade to sports springs, also upgrade to appropriate sport shocks.

Roland Kunz

Hello

Replacing rear shocks can be done by DIY however the C4 rear springs ( orange ) have more preload then the C2 units ( black with color code rings ). So it can be you have to use a tool to preload the unit to screw up the nut. Cornerbalancing is very important to a 964 especially a C4 needs to be surefootet as the computer reacts to Porsche setet paramter and doesnīt have enough reaction time to compensate a crocked up seting. So if the thing never was touched before or you know for sure that the setings where correct you go this way: messure the distance from the nutflange to the end from the threadtube. Clean the thread and then mark the position from the nut to the tube so you can reset it later to exact the same position. Then unscrew the nut. It will not work if you have to much load from the coil plus dirt inside the thread so donīt overdoo and destroy the ringnut. Try if you can turn the ringnut upwards so the dirt will come out from the threads. Or bring the parts to a local car mechanic and let him handle that.

After you changed the shock you return everything to the old position.

the same can be done with units who are sure out from aligment so you donīt worse it.

And yes the upper 3 nuts inside the enginebay are iky to get to.
Whenever the "steam" comes up I think about servicing other Supercars and then I tank porsche you could see the parts and have nearly direct access to them.

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Off topic:

Hey why Italian Car mechanics are great lovers ? They are used to fiddle in dark, thight holes without a chance to look at it.

( Hope donīt get kicked from the board now and lets see when this will show up on the Ferrarilist )

Oh why do italian mechanics have to fiddle in the dark ? Marelli got "aid" from Lucas.
They stole the prototypes when the romeans ruled the brits.

Why didnīt germans copyed the Lucas Prototypes ? Well we sat on the other side from the wall ( Limes ).

Why are all british and italian cars small tiny mobiles ?
They used the roads constructet from the romeians and those had a specific track wide.
This track wide was two horses butts on a chariot.
And why are german and french cars a bit wider ?
becourse they didnīt had horses, they used oxes.
And why american cars have even wider tracks ?
Well the problem was that the people siting on the bench had big sombreros or hats and also wheapons if someone came to close.
And why are japanese cars even smaller the the italians ?
1) Rome didnīt had been there
2) they didnīt use horses they had enough manpower
3) it makes the country look bigger

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be prepared to replace the bearing or the dustcover, bumpstop, ringnut. Have it on hand or enough time to organize them if needed.

The Konis are nice shocks. Somewhere close to the factory Boge Sport but not as good as the Bilsteins with H&R ( RS ) setup.

Konis where used from RUF for "normal" street cars. Only the Killer cars got Bilsteins. However RUF and many other Tuners let manufacture there own specific shock.
Gemballa for example had 4 rear shocks for the Avalance suiting to different heavy tires and different staate delivery

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Indeed some parts have a store time and Porsche will junk them if they get overaged.

Well known are the hood gassprings who are stored only 2 Years and then get send the recycler yet some recycler seem to recycle them by resaleing.

Each important Porsche part has a Production stamp. If you open the engine you can control the build date from the bearings, the pistons, cylinders, Flywheel,....

Now back to the shocks.
Each manufactorer has a technical spec sheet also showing recomended storing times and procedures.

If they are new they are packed well and will be good a very long time in normal humidity storage. However it is always recomended to store oil or gas shocks with the big end showing up. The reason is that the gas will allways be in the upper chamber and the oil will allways be down on the sealing package from the unit where it keeps the seal soft.

This storage is even more recomended on used units.

We worked a lot with NOS and never had a failed Bilstein unit. However the Boge niveaumat are very critical either in Porsche 911 or in Mercedes usage.
However the DeCarbon rear shocks for the 911 Niveau option never showed similar problems.

Also the Koni Gas Struts for Ferraris seem to give up sooner then when they where used 30 years ago in the same application. So overstoreing can be a part from the problem.

Grüsse