[anthonymaher]

Hi Forum;



I have been working through the standard maintenence issues with <acronym title='model year'>MY</acronym> 968, with much help and guidance from this site.



<acronym title='model year'>MY</acronym> '94 has about 78k on it, with the M030 option and limited slip. The car is a daily driver, and while there are some stretches of road in Washington DC that feel like <acronym title='model year'>MY</acronym> teeth are shaking loose with the suspension, for the most part I really enjoy the way the car handles. I have replaced the usual components on the suspension; new OEM rotors, pads, hydraulic lines, along with master/slave with the brakes and clutch.



There are currently no obvious problems with the steering and suspension; there are a few clunks underneath, but I am mostly approaching this from a preventive maintence point of view. Understand that <acronym title='model year'>MY</acronym> point of reference for suspensions is based on mid-century British sports cars, where new rubber bushings, sleeves and thick hypoid oil fixes a lot of sins.



<acronym title='model year'>MY</acronym> question is, after doing the obvious replacement of rubber, hydraulics and brakes, what is a logical approach to the next level of maintenence? I dont know if this is any different for the sport suspension, but I do not have another 968 to compare it against, so here is what i was looking at:



1. Bushings: The bushings are hard, I assume derlin? No idea if they are original or changed by the <acronym title='previous owner'>PO</acronym>. Should I replace them all? If so, should it be derlin or something else?

2. Parking Brake: I rarely use it now, and agree with many that it is pretty marginal and has the potential for disaster. Other than replacing the pads and pins and not use it much, i was going to leave it alone.

3. Wheel bearings: I was planning on replacing since it is a fairly inexpensive exercise.

4. Struts: The car does not feel in any way soft or bouncy, but is that a good indicator of wear on this suspension? Any tips to determine what kind of shape the original Koni's are in, or just leave them alone?

5. Power steering pump: It's a little leaky, and I was planning on replacing with a rebuilt unit

6. Rack: No major issues with visual inspection. Anything else to be aware of?



Thanks for any input and guidance

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[flash]

delrin can be a great bushing, but requires maintenance (like grease) to keep it quiet - then as a result of the grease, you need to prevent them from moving when they are on the sway bar



definitely fix the pump - leaks will destroy the rubber components

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[gcb729]

I had some clunks in <acronym title='model year'>MY</acronym> 93 and replaced the camber block bushings (front lower control arm, rear bushing) for the cure. I am not certain if the M030 option on the 968 is so, but on <acronym title='model year'>MY</acronym> 944 Turbo S with the M030 option the suspension bushings were of harder rubber. Delrin gives a secure feeling, but it will only add to the harshness of the suspension. I find it very hard to bounce test the suspension on our cars, since they are relatively stiffly sprung and have limited travel suspension as stock, especially yours. You could go through adjusting the rebound rate on your shocks and see if this suits your liking.



+1 on power steering leak repairs. That leaky pump may actually be the hose from the reservoir to the pump - Clean and dry, then diagnose (the first rule of engineering prevails - gravity migrates fluid downhill) I've been migrating <acronym title='model year'>MY</acronym> cars to Pentosin hydraulic fluid, getting away from ATF as I repair various leaks in this system. I know what the owner manual says, ATF is the fluid. (Owners manuals are the Best Available Information at the Time of Printing - Subject to Change) If you consider the evolution of automotive fluids these days, along with the TSB associated with vehicles that do change what is in the owners manual, one such TSB from VW that states ATF prematurely erodes seals within the ZF steering systems and Pentosin fluid is to be used, along with <acronym title='model year'>MY</acronym> personal experience with owning two of these cars, both with the patented power steering leaks, along with modern Porsche vehicles being delivered with Pentosin fluid. I need no more convincing. Anyone else concur.

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[flash]

just for the sake of clarity, the rear bushing is the caster, not camber block bushing - it has an eccentric that allows caster adjustment - camber adjustment is at the strut - they changed the design of that bushing over the years to firm up the connection point - that particular bushing can be responsible for a lot of suspension issues

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[gcb729]

Thanks for the correction, I bow to thee.

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[flash]

lol - no need for that - i just wanted to make sure that others reading this stuff later were properly informed - a large part of the purpose of this site is to provide a research resource for others

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[chudson]

Hey gcb729 - that Pentosin suggestion is certainly of interest.



Being an automotive professional I generally err on the side of the engineers who designed the system and their recommendations at the time. I've been stocking Pentosin since the early 80s. It may have been around much longer than that. <acronym title='model year'>MY</acronym> point is that it was available to both the ZF and Porsche engineers at the time of the design, yet they chose Dexron ATF for this application.



I remember Dexron would do damage / cause leaks in 80s vintage Audi power steering systems that were ZF and specified Pentosin. <acronym title='model year'>MY</acronym> fear would be that some seal in <acronym title='model year'>MY</acronym> 18 year old ZF Dexron system may not be designed for exposure to the Pentosin. I'm neither a mechanical nor lubricant engineer, but assume that ZF specified different fluids for some reason. What information have you found?



Dexron has also seen a lot of development over the years. We can only assume / hope that it causes no issues with our old seals. I just preformed a system flush to mine. Time will tell.........



Sorry, I did not type type "<acronym title='model year'>MY</acronym>" in all caps. For some reason I can't edit it???



Flash, it that a software thing thinking the intent is Model Year? <acronym title='model year'>MY</acronym> is in all caps in the previous post also.

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[flash]

i pulled all the posts about "my" as clearly it is a local problem



back on topic now

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[gcb729]

Yes Flash "My" comes up "MY" in "my" posts as well. My, my, my that sure is alot of my. I thought it might be a built in tool to get us all to refer to our vehicles beginning with Model Year (MY). At first I thought it might be some unconscious idiosyncracy on my part giving myself undue importance by highlighting "My" in my posts with MY, but that's just not me. Then I thought it was just my usual fat fingers, but then I read the above posts and just knew I wasn't just having one of those moments. Mystery solved, I feel better now. Back on topic, I promise.



ON TOPIC



I'm a self proclaimed automotive professional (the worse kind) as well, I might also add that I will take that past hundred years or so of climate data and project these results into it to several billion years of earth building and swear it is Global Warming, is certainly completely man caused, and I'll get my beach front property back in AZ instead on the shores of the Colorado River OR I believe climate change is a reality, after all a couple of ice ages occurred, smoldering tar pits, ravaging volcanos certainly have prevailed. No, no, no I promised back on topic.



ON TOPIC - PROMISE



I own too many low level Porsches, I play with them, service them, repair them. 1983 944's to 94 968 with other front engine water cooled beast inbetween - I like them, alot. Each one has presented "the pattern failure" , swollen, leaky inlet hose (reservoir to pump), leaky intermediate hose (rack return line to cooler coil), leaky return line (cooler to reservoir) and rack leaks. In other words if it is a rubber hose/seal - metal/hard surface fitting interface there is or will exist a deteriorated rubber hose and ensuing leak, not exactly a full blown leak, but drippy ouzo (spicy leak) ooze. An odd similarity to all these leaks is the general low pressure nature of the leaking areas, I have (in my humble ownership) had no pressure side hose failures or any issues. I have ASE Master Tech certification (so what, I can read, then regurgitate answers), my base discipline is a Mining Engineer (so what, I can blow stuff up, move it, process it and make some money), but as I'm "upfixin" one of my Porsches (strickly for soothing purposes only) I can't help but analyze things - like what I call these "pattern failures". I read once, do not ask me to cite my reference, in my time as an automotive shop owner I was the technical information source for the shop techs. I was getting really familiar with all the specialty fluids being introduced by the manufacturers and came across a TSB for VW requiring Pentosin (or a fluid meeting the formulation for Pentosin) in the ZF steering systems due to rubber degradation. This would have to be for early to mid MY 2000's VW vehicles (if memory is firing on all 4 large cylinders), but I'm sure I read it. I'm sure that I'm NOT sure about this use of Pentosin (CHF202 or CHF11, I beleive) in my/our older 80's & 90's vehicles. The pattern failure might just be the age of these cars, or some owners lack of proper PM services, but I focus on the pressure side of the system with minimal issues and the inherent material difference between the High Pressure and Low Pressure hose construction and surmise there could be an issue. I have braved the new frontier and have or will be Pentosinizing my cars (ah, the test lab rat) and just wanted to share my or is that MY thoughts. Additionally, I was wondering if anyone else had similar inklings.



OFF TOPIC



Flash, please include a spell check in the post section so that poor, lazy semiliterates such as my self can feel assured our spelling is correct, it doesn't do much for our grammar, but oh well. Cheers fellow 968ers.

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[flash]

There is already a spell check here. At least, I see one. Maybe it's a browser thing? That could be where your "my" problem is coming from too.



back on topic



something to look at is the uppermost bearing in the strut itself - these tend to wear, and allow side to side play, which affects the handling, makes noise, yada yada

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[williamoss]

on the same topic but a new question..............



My 968 from RS barn came with the M030, limited slip. This past weekend at Packwood Washington I did an Evolution School for auto cross. I highly recommend this school as it is taught by Nation Champ drivers. Anyway one of the instructor suggested that with 36 pounds of air in all 4 tires my car had a over steering problem This was a feeling I have had for months but did not know what to call it. I felt as if the front end was always about to brake away. His solution at the track was to lower the air pressure in the rear by 2 pounds. it worked great and the front end now feels firm to the ground



So do I keep the pressures lower in the rear during street driving as well at auto crossing which might burn up the rear tires quicker, or do I play with the rear springs to try to get a better weight ratio to eliminate the over steering problems?



Will wheel spacers help in over steering?

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[williamoss]

Regrading spell checking



When I use it it shows a word in question and suggestions of what to do with it but it does not highlight the word in the paragraph, so I find it difficult to figure out which word it is trying to correct. Is there a fix for this problem in the new software?

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[flash]

the front end breaking away is understeer, not oversteer



you always let a couple of pounds out for track days - that's because they heat up more



i think spell check is a browser thing, not part of the software - mine picks it up word by word

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[chudson]

Hey gcb729



I'm with you on the VW TSB and probably actually have it somewhere. We have had similar paths. I'm also an ASE Master Tech / 30+ years. I just would like to see Porsche adopting the VW philosophy in print (for older models) before I start feeding the 968 Pentosin. It may hurt nothing and indeed may help, but my 18 year old specimen is still bone dry with Dexron. I'm gonna roll the dice that it stays that way. Keep us posted on how your does on the green juice.



Yes, speel chek wud be wunderfol

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[banditsc]

Interestingly it appears that Pentosin is the Porsche reconfigured replacement for our cars. A little digging turned up a TSB for the 964/993 which use basically the same system as ours. It says to use Pentosin CHF 11S which has now been superseded by CHF 202.





Steering Gear - New Type Oil

Group 4

Number 9606

Model

6 Cyl.

Part Identifier 4800

June 11, 1996

Subject:

New Type Oil for Steering Gear

ATTENTION:

Service Manager / Service Technician

Model Affected:

911 Carrera 2 and 4, Model Years 1989 to 1994,

911 Turbo, Model Years 1991, 1992 and 1994, and

911 Carrera (993) 1995 Model Year on

Concern:

In production, the power assist steering system is now filled with Pentosin CHF 11S fluid (green in color).

General Information:

From the following VIN numbers, the power assist steering system is factory filled with Pentosin CHF 11S fluid:

As of March 25, 1996 from VIN:

99 9 TS 32 3082 Coupe

99 3 TS 34 1781 Cabriolet

99 8 TS 38 5439 Targa

Pentosin has been selected for use because of better and more uniform viscosity behavior at low ambient temperatures.

Vehicles of the model types affected produced before the above mentioned VIN numbers used ATF in the power assisted steering system. It is now permitted to use Pentosin CHF 11S in these vehicles as well.

ATF fluid and Pentosin CHF 11S fluid can be mixed. In vehicles produced before the above mentioned VIN numbers, Pentosin CHF 11S fluid can be used to top off the fluid reservoir.

The 1996 911 Turbo uses Pentosin CHF 11S fluid in the steering and hydraulic assisted clutch systems. In this system, ATF must not be mixed with Pentosin CHF 11S.

Vehicles having repairs made to the steering gear that involve loss of the steering fluid should be refilled with Pentosin CHF 11S fluid.

Parts Information:

Pentosin CHF 11S fluid (1 Liter), part number - 000 043 203 33

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[RS Barn]

Getting back to MO30 suspension maintaince.

I have found almost all MO30 coil- over rear shocks have a hydraulic problem . Debris gets into the valving discs and causes hydraulic lock. If you remove shocks, ,take off springs and compress (or try to) there is a problem. They usually move an inch or so and then hydraulic lock. This will cause a jouncy ride over small sharp bumps and can really upset car in corners with bumps.

The fix is to test and then send to Tru Choice for a rebuild and dyno.

These cars are firm to start with and only get worse with hyd problem. if you drive one all the time you may have been living with a problem you though was normal.

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[chudson]

Josh - good find. Interesting that it only claims to improve behavior at low temps and not seal longevity.



Pete - Tru Choice preferred over Koni? If so why? I have a set that will compress, but it ain't easy!

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[RS Barn]

True Cchoice is the US repair facility for Koni as far as I know. that's where i've sent all my stuff for years.

Back to MO30 rear shocks.I believe they have 15-20% more compression damping than any other shock I have worked with and that;s not a good thing for street cars-

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[chudson]

Pete - thanx. I had previously contacted Koni's service department regarding sending mine in but they didn't give any hint that anyone other than them would be doing them.



Back to M030 I agree with your statement above. How do you feel the fronts compare to other performance shocks?

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[pure&amp;simple]

[quote name='williamoss' timestamp='1314030261' post='114548']

So do I keep the pressures lower in the rear during street driving as well at auto crossing which might burn up the rear tires quicker, or do I play with the rear springs to try to get a better weight ratio to eliminate the over steering problems? Will wheel spacers help in over steering?

[/quote]



Lower tire pressure in the rear is a good quick fix. Do you know your alignment settings? You might try increasing the amount of negative camber in the rear (or reducing it in the front). You should ensure you're driving on a good alignment before playing with spring rates. Spacers in the front will increase oversteer, while spacers in the rear will decrease it. There is a small chance that the oversteer problem could also be an issue with your shocks... what shocks are you using? are they relatively new? What are your current spring rates?

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