Slow crank rate when hot - 2006 911

I’ve owned my 2006 911 Carrera S for about 10 years. Seems like when the car has been driven for over 10 miles, that if I turn off the ignition (maybe to fill gas tank), and try to restart the car, I get a slower crank rate? If the car cools down for a little, the crank rate goes back to normal.

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First, welcome to Carpokes! Please post early and often. Re your car, it sounds like classic starter motor heat soak. It's not a problem unique to Porsches, but the 997 appears to be prone to it. As long as the battery is strong, then it's most likely the starter and starter cable. Age conspires against both, creating more and more electrical resistance. Heat adds to that resistance, especially inside a super hot starter, which makes it hard to crank, even for a healthy battery. If that's your issue, which would be my guess, replacing both the starter and the starter cable is probably wise.

I'm curious if the car starts with the slower crank rate?? When I first read this what immediately came to mind was vapor lock, but if it starts, obviously that is not the issue.

Yes, the car starts rather quick - even with the SLOW turnover rate.

Well, I think Tom probably hit your problem right on the head.

I have a 2005 CarreraS with the same problem, we replaced the wire harness that is connected to the starter solenoid . This cable is got e Y split witch gets corroded in time and is heating up reducing the electricity to pass tru. This fixed my problem.

Yep, common problem with the 997. I replaced both the cable and starter to avoid having to go back in there. Problem fixed.

Very interesting. I have an '06 997 and have had the same issue. I ordered a new Bosch starter today and am wondering if I also need the harness. Is this the harness that runs from the solenoid to both the battery and the alternator? My parts diagram is showing two different ones available: 1) harness;;PR:249 with: Connection point Alternator starter#99760701804 and, 2) harness;;PR:480 with: Connection point Alternator starter #99760701903 Any idea which is the one to go with or are there any differences at all??? Kind of a weird description the way they word things. If I'm going to dive in there, I might as well fix everything I can get my hands on! Any input, much appreciated!

I got my harness at Pelican Parts. Here's the part number: 997 607 019 03 Mine is a Carrera S. Put your car detail in PP website and it will give you correct cable.

Thanks, Michael! Just put in an order with PP. BTW...the two different part #'s are: the 804 is for the automatic, and the 903 is for the manual. No idea why they would be different, but there you go...

Had the same problem with my 08 CS2. Swapped the battery ground cable and the starter, the problem is gone.

Well, this Monday I dove in there to replace the starter and the "Y" cable that runs from the alternator to the starter and then down to the side of the transmission where it connects to the main pos. lead from the battery. For years my 997 has taken about 4 cranks to start, hot or cold. It would turn for about 3-4 seconds but would always fire right up. Last Oct. I was on a road trip (interstate) and after leaving a rest area with a hot engine, there might be a momentary hesitation in the starter not catching at all. I thought this very strange indeed. Acted like a loose connection for a couple of seconds and would then fire up. Anyway, after reading the beginning of this thread, I decided that R&Ring my starter and Y cable was in my future. I'm happy to say that now it takes about 1/2 second to fire up the car. Wicked fast starts now! The job took me about 6 hours total and I'd say that maybe half of that was fighting for access to certain bolts. Porsche did not design these engines well for some repairs, and getting the starter out is one of them. I hope I'll never have to R&R the AOS as that one could be a bear for sure. Easy with the engine out, of course! That said, changing out the starter and this cable is certainly doable and offers great satisfaction to a DIY mechanic like me! Saved a ton of money, and I really like working out in my carport with my dog helping me!

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Based on what you stated, it is not the much talked about cable that runs from the stud at the transmission junction block [passenger side] to the starter and alternator. Exact same problem on a friend's 2005 that I diagnosed. Unfortunately, upon recommendations on a Porsche forum, he had already bought the cable...unnecessarily. If the cable has not been overheated at the crimps and changed color, the issue is elsewhere. I rebuilt his starter and this is what the problem was... https://www.smugmug.com/gallery/n-k4hmS4

In my case, I believe the "Y" cable most definitely was part of the problem. After removal of the cable, I could twist the cable within the end that bolts up to the starter. This is certainly not how it should be. Whether or not the starter was also part of the problem, I can't say. But it makes sense to replace both starter and cable while you're in there.

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Well I believe in testing instead of guessing. I took some voltage drop measurements proving the cable was fine. In a 12V system the maximum allowable voltage drop is 0.5V from source to load. Unfortunately, my 997 friend had already bought the cable and he wanted it installed since he had it. Once we had the cable off, all crimps looked fine of course and he threw out a perfectly good cable. I installed the new cable and those hold-downs running across the back of the engine were a PITA to get to. Still a slow hot start after that, no surprise. I had him replace the starter while I took his old one apart and noted the issue. Jokingly I said, "its not your starter"...just kidding I said a few moments later.

Folks I got the SLOW CRANK when HOT issue SOLVED!!!! It was the starter cable. Got it replaced (parts & labor cost was just under $2,000 here in the Naples, FL area).

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OMG, sorry to say but you got taken.

Actually, I checked with the two Porsche dealers for the price, and TWO auto shops that deal strictly with German cars here in Naples area. Everyone was within $50.

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Service labor and parts is not inexpensive and it's gotten far worse the past couple of years. Glad you got if fixed and that it solved the issue.

The cable itself is around $150+-. I think if a guy was quite skilled, efficient, and had done the job before, it might be a 3 hour job or so with all the right tools. This is one thing that really grinds my gears about Porsche dealers and even the indy shops...their prices are unreal. They mark up parts 3-4X, bill at $250/hour, and that still isn't enough! I do all of my own work to the extent that I can, and I dread the day that I ever need to go to a shop. I do think they took advantage of you but , sadly, that seems to just be standard operating procedure with Porsche mechanics. Shameful, IMO.

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When I replaced that cable on my friend's 2005 997 in 2017, I think it was about $150 and it took me about 3 hours to replace it. Of course we had a lift and all the tools. Of course the owner isn't that technical and bought the "recommendations" on Rennlist to replace that cable, which of course was not the issue. I told him so, but he had it and wanted it installed. So lets do some numbers: at MSRP for the cable (shops pay wholesale), there is profit in it, then 3 hours at a whopping $250 an hour is $750, so we are sitting at well under $1000. By the way, I love working on cars, motorcycles and aircraft and I took my time, so you can do it in less than 3 hours. And $250 an hour? They are an effing mechanic, not a brain surgeon. I'd love to see them do a control systems problem if I threw LaPlace tables at them. Same here, HVAC, plumbing, electrical, concrete work and all to higher standards than those clowns. Same when I was a flight instructor, worked on aircraft that I flew the next day....now that is trust. LOL

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I, too, preferred to test voltage drops to diagnose where the issue was coming from (e.g. starter, alternator cable, battery). My issue ended up being the starter. One thing I have to say about that is I think auto zone sells refurbished starters for the 997. DO NOT BUY THEM. Buy OEM and brand new! Had a refurbished one crap out one week later and it was just double the work to get it out and put in a brand new OEM version... I wouldn't say that you've wasted your time putting in the new alternator cable as the latest version for the 997 is thicker and more robust compared to what the car originally came out of the factory with. So, it was definitely preventative maintenance! During my 997 ownership, I've replaced the starter, installed updated alternator cable, and car battery (Duralast gold). OEM starter should last ~60k miles along with the original old alternator cable. I found that Duralast gold lasts ~3 years which caused me to get a Battery Tender and maintainer. Turns out the 997 draws quite the amount of juice from the battery during each start, so if you want to maximize crank power, definitely look into keeping your battery charged with a Battery Tender and Maintainer!

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+1 on the rebuilt starters from the big chain auto parts stores. I replaced the one on my 944 at least 3 times until I finally learned my lesson. I ended up getting a unit "rebuilt" by Bosch itself, and can vouch for those. It comes in a Bosch box. I put "rebuilt" in quotes because it looked to me like a brand new starter... Entirely different than those sticky black things with loose electrical posts they sell at O'Reilly and AutoZone, etc.

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On the RL forum some years ago: alternator issues and buying rebuilt units. Most of them are rebuilt and if done right, they are as good as new. I noted that even Bosch units, very few parts were replaced. They turned down the slip rings and they are thin to start with. They tested the rectifier pack and reused it. They did replace both bearings and the regulator/brush set and glass beaded the unit. Big deal. Personally I would never turn down slip rings on my lathe; I'd replace them. In fact I used the bearings from WBD (waiglobal) due to the higher temperature grease they use (considering where the alternator is located) and a smoother running bearing. As for having a battery on a charger/maintainer, you'll know the battery will always be charged and will never sulphate. The trouble is, you never know when the battery gets weak and capacity drops over time. It'll always start the vehicle, but if left parked for a day it might not start it then. If you have accessories drawing current, of course I would use it all the time. I spot charge my batteries (unless you are away for months) and monitor the battery voltage. When it drops a few tenths (12.8V to 12.6V), I'll connect the charger/maintainer again for a day and then disconnect it.