"Rattle" at 2,000 RPM

[OscarAH1W 1]

I am completely flummoxed by this noise I am getting in my 2004 Turbo Cab.  A couple nights ago while driving home with the top down, I noticed a rattle different from the normal sound of the motor and not accelerating/decelerating with changes in engine RPM.  It occurred at 1800-2000 rpm and was most noticeable when decelerating in 2nd gear in my neighborhood at slow speeds (~20MPH)...  with a helper on the throttle and the engine compartment open, it sounds like it is coming from the right side-top of the engine, around the Hydraulic reservoir.  Putting a spanner/wrench on the component and up to the temple seems to have confirmed this as the source.  I checked my manual and the Pentosin level (mid range on the HOT side of the dipstick at operating temp)  I realize that Porsche recommends checking at 20C but I live in Texas now and that won't happen until November.  Just out of curiosity I looked at the clutch reservoir up front and after removing the gooey trim cover, found it leaking (Seeping) from the recently replaced cap and appearing to be overfilled.  The car has never really been operated in the 8 years I have had it in particularly high average temperatures, so I am hoping that the front is thermal expansion.  Any thoughts on this matter are greatly appreciated... Loren?  What Say You??

 

Thanks in advance,

 

[Loren 2,131 2 Vehicles]

Could be worn out or the bearing got dry and then was likely damaged by running the pump dry.

I have seen a few of the PS units lose fluid and then seize up or worse start a fire.

best remove the belt and check for wobble and smoothness - of all pulleys.

[Danyol 2]

Fluid transfer and overflow to the front reservoir is typically a slave cylinder issue. 

[Loren 2,131 2 Vehicles]

I thought he was talking about the PS reservoir on the engine -- perhaps he can clarify.

[DBJoe996 62]

Take a turkey baster and suck  some of the brake/clutch fluid out of the reservoir to return it to a normal level....then keep an eye on it.

Agree with Loren completely.  If the power steering pump is making a rattle noise, remove the serpentine belt and check the pulley for play and smoothness.  Check all the other pulleys as well, including the water pump.  Good time to put on a new serpentine belt and replace the air filter.

[OscarAH1W 1]

Agree with all.  Checked the Pentosin this morning and fluid level in the PS reservoir is spot on.  I'll pull some fluid out of the front reservoir and keep a closer eye on that.  I think I may be getting the start of a slave cylinder issue again (replaced at 30,000-ish miles, now have ~58K on the car) as I have a little creak that I can feel in the clutch pedal.  I'll pull the air box and check all the pulleys and advise with what I find.  Thanks everyone!

[wizard 21]

Odd. A Porsche clutch slave cylinder should last a lot longer than 30,000 miles. Unless I'm misunderstanding, neither the clutch nor the power steering has anything to do with engine speed ... in 2nd gear.

 

With the car at a standstill and the engine running, do you hear anything when the steering wheel is turned full lock in both directions? Likewise, when depressing the clutch?

 

 

[OscarAH1W 1]

To avoid confusion, I think there are two different issues... disregard my thoughts on the slave cylinder for now...  separate issue (if it even is an issue).  Drove the car a few miles at low RPM this morning and the clicking is most noticeable in 2nd gear when the clutch is engaged and the car is moving.  For whatever reason I think 2nd gear provides the right engine RPM and vehicle speed speed so the wind noise and engine noise are low enough to hear the clicking or rattle.  Even then it is very difficult to discern.  I have been able to recreate it while stopped with the clutch in (disengaged), but it appears to go away when the clutch is disengaged and the car is moving, like if I were stopping at a stop sign...  Got the air box off and am waiting for the compartment to cool down before I pull the belt and check the pulleys.

[OscarAH1W 1]

Quote

 

Okay all, after being out of town all last week I was able to take a more directed look at this problem.  I loosened the serpentine belt and checked the pulleys.  No play anywhere except for the AC compressor wheel which had an almost imperceptible amount of play, but I would think that would be due to the clutch.  Also there was just a hint of play on the deflector pulley on the left side of the engine.  Drove around the neighborhood some more to check out the clicking/rattling noise and driving with the top down, the sound is DEFINITELY manifested on the right (passenger) side of the car.  You can hear it best (at the 1800-2000 RPM) if you kinda cock your head behind the passenger seat...  I bought an engine stethoscope and used it with the engine idling and nothing I touched with it sounded out of sorts.  I rechecked the pentosin in the main reservoir and at operating temp it was still at the COLD mark so I added more and drove it around a bit to heat up and circulate... now the fluid level at operating temp reads about mid-way between the COLD and HOT MAX marks on the dipstick... not an exact estimate since the marks are on opposite sides...  Drove it again and the noise somehow seems quieter but is still there... but that may just be in my head after straining to hear it so much...  any more ideas??

[OscarAH1W 1]

Update:  Took it to the local shop and they diagnosed the water pump bearing as definitely being bad.  They quoted me $1700 to do the water pump and said it could be timing chains, which I don't believe for a second on this car with 59K miles.  ESPECIALLY when they quoted $600+ for the parts and I can get a Factory Water Pump for $274.  I ordered the thermostat as well as the turbo seals, etc per the Porsche Repair Manual, which this place did not quote in their exorbitant price.  They also quoted me the 60,000 mile major maintenance (which I performed myself at 30K) for $1900 more.  In the breakdown they wanted $740 to change the plugs, LOL... with 50% markup on Porsche parts (instead of Bosch or Beru) they were quoting over 4 hours labor and I have done it myself in well under 3.  The bumper cover would already be off for the water pump!  I purchased all the parts to do both jobs for $450. (Went with OEM water pump since it is the same thing Porsche slaps in one of their boxes).  I am going to have a long conversation with these people about what they charge.  Their labor rate is fine but the time they are quoting and the 50% markup over what I can source factory parts for (they should be able to get them cheaper than I can) has me suspect of their practices.

 

I HATE UP-SELLING!!!!

[JFP in PA 582]

You need to understand how a shop works.  The labor rate is split between the shop and the tech, but with the shop having the largest sunk costs in the facility, they need to make it up on the parts via markup on parts that Porsche already overcharges for, or they could not keep their doors open (it is not unusual for a shop to have a monthly electric bill in the hundreds of dollars, even before they switch the AC on; and that is just the start of monthly shop overhead costs.  If they have a PIWIS, that is setting them back $1500 a month just to have it sitting there).  While a 50% may be slightly high for parts markup, it is not completely out of line for a well equipped and staffed shop.

[DBJoe996 62]

I learned something new the other day.  The standard stock 996 and the Turbo differ in the clutch slave cylinder setup.  Turns out that the turbo has a low pressure feed from the clutch/brake master cylinder, and a high pressure feed from the power steering pump, and both systems use Pentosin fluid.  They both work to operate the clutch slave cylinder.  So it is possible that since the power steering pump plays a role in your Turbo and could be leading to a noise related to clutch operation.

 

As well, there could be a leak from the high pressure side of the clutch slave cylinder to the low pressure side, thereby resulting in overfill of the frunk reservoir.  Just a thought.

Edited July 20, 2018 by DBJoe996

[OscarAH1W 1]

I disagree that I don't understand how a shop works.  I'm not going to explain my background and you likely don't (and shouldn't) care anyway so I'll leave it at this:  If an independent shop costs the same for repairs as taking it to the Porsche dealership, except that the independent shop gives me a ride home in a Prius and the dealer gives me a new Macan to tear around in along with a better warranty on the parts and labor, what possible reason could there be for me to take my business to the independent shop?