[Velocity]

My 968 has developed an intermittent (but still fairly frequent) squealing noise, most noticeable at low speeds.

 

Squeal is definitely associated with rotational speed of wheels (not in engine) - see initial video below.    I suspect it's related to brakes, but it happens without any brake application.    Front rotors and pads were replaced "recently" (a few months ago, but only ~300-400 miles since then).    I have taken temps of all rotors after it was happening and there is not enough variation in rotor temp (temps were <5F variance between paired rotors) for me to think there is a specific caliper/pad sticking.    The car does NOT pull to either side as I suspect it may if there was a sticking rotor either.

 

It is NOT reproducible 100% of the time, but happens often enough to be annoying/concerning - of course, one of the times I could NOT reproduce it was when a friend and I were specifically trying to repro it with the intent of further troubleshooting. 

 

Here's a few videos that might help :

• Initial time I noticed it (June 1) - https://youtu.be/BRLsZR2Rrss
  
• Recent repeat occurrence (different location, more open area, slightly higher speed) - https://youtu.be/8n9t12RHpPQ
  
• Oddly, this video is less than 2 minutes after the above video after stopping at 1 stop sign and one turn - https://youtu.be/tt4UGTs2uqs - note squeal is completely gone at this point (sorry about wind noise).   I arrived home less than 2 minutes after this video and squeal was still completely gone at that point.
  

My plan is to try and repro it again when I have access to a friends lift, get it there ASAP, get all wheels off the ground, then spin each independently to try and isolate it.    

 

Any guesses as to the source?   Something brake related?     Possible wheel bearing going out?   

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[J.Elenbaas]

I think when it's a bearing the sound will not disapear after breaking.

Si i'm going for the brakes.


In the second video you hear it better, and to me that a brake pad scraping against a rotor

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[ds968]

No chance that’s a wheel bearing, IMO, no matter how bad they get that’s not even close to the type of the sound they would produce.  Also extremely unlikely it’s transmission related .   And if it’s not coming from the engine bay where a pulley may be acting up and causing belts to squeal , I’d bet on some brakes components  friction or similar part of the suspension that’s touching or not properly lubed, but hopefully a cheap and easy fix.   Just weird that it doesn’t do it while driving in reverse .. 

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[Kaj Hallstrom]

Sounds like one of the brake pads is slightly touching the rotor magnifying the squeak. Did you replace the two anti-squeak discs when you replaced the pads. or used some ant-squeak spray ?

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[Waylander]

Bet there is a little stone stuck in there somewhere

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[ds968]

Bet there is a little stone stuck in there somewhere

+ 1 .  If you drive over that “rocky” road ( seen in the second video ) often enough, some stone is bound to get wedged in there sooner or later . 

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[J.Elenbaas]

Or oxidation on the rotor, although i never heard it squeling like that after a damp night.

Other possibility that happens a lot is oxidation from the caliper pushing the rvs guiding plates out and maybe pushing the pads against the rotor.

 

Anyway, you have to look for possible problems in the brake/rotor/caliper/pads area.

 

The squeling sounds a bit like steel on steel, but then again it will not disappear after breaking ones.


squeling should be squealing  :closedeyes:

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[ds968]

Just weird it doesn’t happen in reverse ..

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[Velocity]

Sounds like one of the brake pads is slightly touching the rotor magnifying the squeak. Did you replace the two anti-squeak discs when you replaced the pads. or used some ant-squeak spray ?

 

The brake job was done at a mechanic, who pretty much exclusively works on European cars, and is highly recommended (although I have had one other issue with them), so I don't know if they replaced the "antisqueak discs".    This car also has the "Big Red" brake upgrade on front (calipers from a 993 twin turbo) - rotors and pads were ordered for that fitment.   Anyone know if these are the "antisqueak" discs in question (keeping in mind these are NOT stock 968 brakes) - https://www.lindseyracing.com/LR/Porsche...-DAMP.html or https://www.pelicanparts.com/catalog/Sup....htm#item9 (seems to show both 36mm and 44mm)

 

Given all the replies lean that way, looking like I'll be working with a friend to teardown/clean/inspect the front brakes - might as well have these ready when I do in case they were NOT installed.

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[J.Elenbaas]

Yep those are anti squeak discs, but you don't necessarely need them.

I just replaced my brake pads with original Porsche pads (Pagid's) which have anti squeak plates fited on the backside.

I also ordered the anti squeak plates, but that just doesn't fit all together in between the rotors and calipers due to this plate.

 

It was the first time in 30 years i have seen this type of pads, but i like them and they don't squeak.

It's also the first time i went to all original, and not aftermarked

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[Roboman]

I was just wondering about "rim rock" and whether it is a feature of 968s. And if it were, what is the gap created. If yes, could it be possible to use a thin knife or fishing line etc to search for trapped pebbles?


That was probably complete rubbish, but I'm stuck in my chair right now, waiting for the cat to awaken so I can get on with putting up photos/paintings etc in our living room


Okay, well the world of rim rock on Google is dominated by cyclists, a brake repair company called rim rock, and a car sales outlet called Rimrock Cadillac.


I found this YouTube video which comes with a health warning .... the opening shots are a bit of a giveaway as to what is about to follow, but it may be of use.


Time to dislodge the cat and get to work.


Have a good weekend


https://youtu.be/ewlUl2DRk0Y

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[J.Elenbaas]

By the way, if the anti squeal plates are not inserted they will squeal whenever you brake, not every now and then. 

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[pdxmike]

I had this problem. Rear ebrake had a spring that had come loose and was rubbing on the rotor. Only made noise going forward, never in reverse.

 

Should take all of 15 min to remove the rear wheels and rotors to check.

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[Velocity]

I had this problem. Rear ebrake had a spring that had come loose and was rubbing on the rotor. Only made noise going forward, never in reverse.

 

Should take all of 15 min to remove the rear wheels and rotors to check.

 

pdxmike gets the diagnostic win on this one!     

 

Once I had a 2nd person, we could isolate the problem sound to the driver rear wheel - we pulled wheel and rotor and found #2 spring in rearward position from the below diagram loose inside the rotor.   The little "C" clip on the end had snapped off (so spring was just a straight pin out the back).    It had worn a small groove inside the rotor (NOT on braking surface, so rotor is still usable) in the time I've been hearing it.     

 

We tried a few options to repair with existing spring, and also tried to get a temp spring in there but couldn't make anything we had on-hand work, so parts have been ordered (remainder of springs/etc looked pretty old) and will totally replace ebrake parts on rear once those come in.    

 

   

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[Velocity]

Finally completed repairs - I'd rate this a 3/10 in overall difficulty, with the most annoying part of the job getting the new springs all secured in place (took all of 4 hands, but we likely weren't doing it the easiest way) and having to grind the new shoe a bit to get adjuster screw to fit.

 

Original hardware (note missing spring on right side and parking brake shoe loose) :

 

     

 

New hardware on top, old hardware on bottom.   Used Porsche springs and ATE brake shoes (as Porsche were 3x the price) :

 

   

 

There was what appeared to be a datestamp of "92" on the original shoes.

 

Note for anyone doing this job in the future - side springs were easy to compress for removal/insertion with a 10mm socket, newer ones were larger (think we used a 13mm socket).

 

As mentioned above, had to dremel the paint and a bit of the steel off the new shoe to get the adjuster screws to attach properly :

 

   

 

New hardware installed, ready to get brakes back on (the red coloration on the lower shoe is just a reflection or something - they were both black) :

 

   

 

Happy to not have the horrible scraping/squealing noise anymore and hope these last another 28 years!  

 

 

 

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[pdxmike]

Wow - Im glad you got it sorted out and repaired!


Never thought about the age of my parking brake shoes but I would bet most of us are running original equipment - I mean, what is there to wear?

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[Velocity]

Wow - Im glad you got it sorted out and repaired!


Never thought about the age of my parking brake shoes but I would bet most of us are running original equipment - I mean, what is there to wear?

 

I may of been able to get away with just replacing that one spring that broke, but with my luck another one would go in a week, so I replaced all springs, the shoes, and at the adjuster screws (which was likely overkill) on both rear wheels.    Hopefully it's good for another 28 years. ;-)

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