Babalouie's 911 - start on p7

[irsa76]

Dual mass flywheels are the devil. Nice if you drive gently and plan on selling the car before it needs a clutch job. Nasty, read holy hell that's expensive, if you drive it hard. Not sure if the 964 eats the flywheels like Sprinters do, very common for Sprintshift vans to do both the clutch AND dualmass flywheel at the same time.

[Babalouie]

As far as I know, the later-spec Luk flywheels are meant to be ok. They're getting on for 18yrs old now, so I presume they're sorted.

The upgrade to RS-spec conventional flywheel chops 9kg (or something) off the flywheel weight, but I'm not sure I want a light-flywheel. One of the nice things about it now is how tractable it is in traffic.

[Q]

the reality of dual mass flywheels are you can't machine them.
so most are replaced at 60k when you do a clutch plate change.

[Babalouie]

So the key would be to replace the clutch friction plate before it becomes absolutely necessary, so that you can recycle the flywheel?

[Q]

correct.
.....and save $1500 /

[Babalouie]

Hmm...I wonder what are the chances my car is still on its original clutch at 95,000kms.

[Q]

possible, but not probable.
60 000km is typical.........set your calender by it typical.

[Babalouie]

possible, but not probable.
60 000km is typical.........set your calender by it typical.

The previous owner bought it at around the 65km mark, I'll ask him if he remembers

[number8]

Also, the 964 brought some expensive maintenance items which were unknown to earlier 911s, which was that the engine mounts and front suspension bushes need replacing at 100,000kms or 15yrs, and until recently, you had to replace the whole front wishbone and the bushes weren't available separately. Again, this is the same for 993s.

so theres now an alternative to replacing the whole wishbone?

otherwise was going to say, someone like fulcrum might make a suitable bushing you could use

[Babalouie]

so theres now an alternative to replacing the whole wishbone?

Yes, you can now get a few different brands of oem-style rubber bush.

It's a bizarre setup though, the bush isn't solid rubber, but has slits/voids in it, so the outer metal casing is splined and is pressed into the wishbone at a certain orientation. That's prolly why Porsche recommends replacing the whole arm.

Looked like a bit of a pain in the arse, so I got Hamiltons to do it for me

[itsnotagsr]

Cheers for the explaination Babs. Learnt a bit! I'd always heard that the 964 almost bankrupted the company. I thought this was due to the engineering expense and poor sales during the early 90s recession, but now it seems like it was more due to warranty repairs and spare sales seem to have been their saviour!

[Babalouie]

Well Porsche was almost bankrupt when they were developing the 964. At the beginning of the 80s, they were doing very well, and so in the mid 80s they expanded production facilities, total output was more or less trebeled, and all was good. But then in the late 80s, the Deutschmark surged against the USD$ (where half their global output was sold) and everything collapsed.

So when the 964 was on the drawing board, there wasn't much money to spend, and so the styling changes were dictated as only being for the bumperline and below, and the interior largely remained the same. They were aware that the 911 was falling behind the times tho, so they did make an effort to make everything as high-tech as possible beneath the skin (of course, 20yrs later when you restore one, you wish they'd left things well alone...).

When the 964 launched, a big hoo-hah was made of it being 85% mechanically new, but of course that was hard to believe when it looked so similar to the Carrera 3.2. When the 993 was on the drawing board, they were still skint, so the planned re-jig of the roofline was shelved and the interior was mostly unchanged from the 964.

I reckon the warranty costs of the 964 are mainly to do with replacing the early dual mass flywheels, and they prolly pale into comparison with the whole Intermediate Shaft thingo when the Boxter/996 was released.

[irsa76]

correct.
.....and save $1500 /

That's cheaper then the Merc, iirc that was $2000!
Failed dualmass flywheels are easy to pick, they have severe vibration, in my case it shook the whole van.

[Q]

That's cheaper then the Merc..................

....having owned a few of examples of each, I can assure you this ^ is normal !

[Babalouie]

Since I swapped in a new clutch slave cylinder, the gearshift is much better, but occasionally it's still a little sticky when you're knocking it out of gear, so I figure that the master must be sub-optimal too.

But bleeding the master cylinder in a 911 is a bugger of a job...as you will see. first thing I did, was swap out the old master cylinder for the new. In a 911, this entails mucking around the pedal area...


Unscrew the pushrod for the throttle pedal, and it flips down to reveal the wooden board behind.


That removes with a few screws, to reveal the guts of the floor hinged pedals. And there's the clutch master cylinder, mounted vertically next to the clutch pedal, and fed by that 6mm flexible blue hose. It's all wondefully over complicated, with heaps of little balljoints, pushrods, jackshafts and bellcranks where perhaps a cable might have sufficed. But that wouldn't have been as much fun to design I spose


The old master looked ok, and was dry inside the boot, although there had to be something wrong, since everything downstream of it had been renewed, and the gearshift was still quite stiff.


BTW the brake pedal hooks up to a pushrod, which disappears into the front boot, where I presume the master cylinder lives.


The new clutch master, interestingly it's a 993 part number that's provided for 964, and it's also made of alloy instead of the usual steel, so is noticeably light. The outlet is a hardline fitting that goes on the left, and the inlet is a push-fit into that rubber grommet in the middle.


It all buttons up easily enough, but bleeding it was a disaster. First we started off with conventional bleeding, which is to say one person on the clutch pedal, and the other person opening and closing the bleed nipple on the slave cylinder. But even after passing about 300ml of fluid though the system, it still wasn't bled, and each pump of the clutch pedal would only emit a very small squirt of fluid on the slave end.

I reckoned this was because of the unconventional design....the reservoir is in the boot, and is mounted quite low. It then feeds the master cylinder via this long 6mm tube, and because the master is vertical, and the inlet is at the bottom, it has to fill the cylinder from the bottom-up between bleeding strokes, and so I think when you're doing it in the normal manner, the master cylinder only gets half full between pump strokes, and so it never really primes. And after spending a long time bleeding, we didn't get a pedal, so it was back to the drawing board.

So I tried buying a vacuum bleeder next.


You pump the trigger, and it builds a vacuum in that canister, which sucks the fluid out of the bleed nipple. But all I got was this gurgling sound (which I think in clutch language means "HAH!"), and very little fluid coming out. Basically I reckon the lines were too airlocked for the vacuum thingy to do anything. It does seem to work just fine on brake bleeding though. So...time for Plan C.


Interestingly, the 911 has two bleed nipples on each caliper. I did not know this.


I fit all my cars with these gadgets, Speedbleeders, which replace the stock bleed nipples, with special ones which have a one-way valve built in. So you can pump fluid out, but it will never suck fluid (or air) back in on the pedal upstroke. Great for when you can't get someone to help you. But I haven't fitted them to the car, since I mistakenly only ordered four of them


But a memory of working on an old Peugeot 505 way back in uni days gave me an idea. The Pug Haynes manual recommended a weird way of bleeding the slave cylinder. You attached a tube from the nearest brake caliper to the clutch slave, and then by pumping the brake pedal, you pressure-bled the clutch by forcing brake fluid through the caliper bleed nipple, and then backwards through the clutch circuit. The Speedbleeders would make that approach really easy, so I fitted one caliper with them, and ran a tube from the caliper...


To the clutch slave. I then opened both bleed nipples a quarter turn, and slowly began to pump the brake pedal.


And it started to work! You could see the blue brake fluid start to flow into the reservoir, to the accompaniment of some gurgling sounds from the clutch master....the brake and clutch share the same reservoir, so as the fluid returns from the clutch side, it refills the brake-side.


And when the level suddenly dropped a lot, it looked like a big air pocket had been purged.


But after all this...we STILL didn't have a pedal The master was definitely primed, so I thought that the culprit was the slave. It's mounted high, and the hose goes downwards from it. So when we reverse-bleed, it's very effective in moving a column of fluid towards the front of the system, but because air bubbles will try to stay at the top, I reckoned we had an air pocket in the slave.


So I unbolted the slave, and let it hang down. Then it got reverse-bled from the caliper, the idea being that any bubbles would be purged upwards into the hose, and thence along the rest of the system to burp into the reservoir. For good measure, I worked the piston of the slave cylinder by hand to pump any air pockets out of it and up into the hose.


This actually worked too...it did burp, and the level in the reservoir dropped again....but we still didn't have a pedal!

So with the slave refitted, we had a last go at bleeding it conventionally, and with the whole thing primed, this worked too, and some bubbles were purged. And FINALLY we had a pedal.

I would say though...that it still isn't 100%. The gearshift is smoother than ever, but very occasionally seems to stick a little. So I think there are still air pockets in that convoluted system...somewhere. I reckon the issue is that the hardline from master to slave is very long, and has several tight bends, including making an up and down u-turn as it loops above the master and comes back down. So an air bubble might be pushed 4 inches in the right direction when you pump the pedal on a bleeding stroke, but then at the end of the stroke, the bubble goes right back up to where it was again.

Bloody thing...this is a 5min job in the Hako...takes two days on a Porsche and you're still not done