took

I would appreciate some thoughts/suggestions on the following. Car is 96' 993TT

The transmission will not shift into any gear while the engine is running. If I shut the engine off shifting is silky smooth. Starting the engine in 1st gear or any forward gear with the clutch pressed results in the car lurching forward as if the clutch is not pressed in at all. I have run a couple of simple tests on the clutch hydraulic system based on troubleshooting techniques listed in the manual and it checks out OK. First test was to start engine and let idle at least 30 seconds, shut off engine and count the # of pedal actuations before an increase in force is felt. An increase in pedal pressure was right about 20-25 pumps. Manual states that an increase in pedal pressure should be between 10-30 pump actuations. Second test per manual is same as above, except do not actuate the clutch pedal. Wait at least an hour and verify pedal pressure is equal to when the engine is running. This is also OK. I re-bleed the clutch system hoping somehow air got in the system but there no change and no air entrapment observed. Pentosin fluid in both tank reservoirs is within specs. There are no visible Pentosin leaks. The slave cylinder and accumulator were replaced less than 1000 miles ago with original Porsche parts so I have a hard time thinking these are shot. It seems as though the hydraulic system is not building enough pressure to permit gear changes while running??

Funny thing is I had just finished changing the engine oil, transmission and front diff oil as well as a brake fluid flush. After I finished with the fluid changes I backed out of the garage about 15 feet and then forward about 10 feet searching for level ground. I let the car idle up to normal operating temperature and topped up the engine oil. I turned the car off. About 1/2 hour later I went to go for a drive and again backed out of the garage in reverse. Once I pulled the car completely out of the garage I got out of the car putting the transmission in neutral. When I got back in the car and attempted to put the car in reverse the shifter would not go into any gear. I had no problems prior to fluid changes, which has me stumped. Tranny fluid change consisted of Mobil Delvac 75W-90, pumped in about 4.2 to 4.3 liters before seepage out the fill hole occurred.

Any Ideas?

Kyle

No HTwo O

Kyle, wish I could help you. But, if I look back at at a few of your old post, you replaced the slave and accuml. back in late 2007. Is this right? About 3 years ago? And only drove 1,000 miles in that time? It wants to be driven more.

911/Q45

With the engine off, can you hear the clutch disengage(should be a slight clicking)? If not, there are some mechanical parts between the slave and the pressure plate that may have failed, or a flexible hydraulic line may have failed enough to balloon out when pressure is applied, but not failed enough to rupture and leak fluid. If there is clicking, then you may have a bad pressure plate that refuses to disengage. The bad flex hose is the only failure that won't involve dropping the trans.

took

Yes, I can hear the clutch disengage.

took

Its bad enough I hear it from the wife as well...

911/Q45

Probably time to have it towed to Really Mean Garage in Sunnyvale.

ttAmerica RoadsterAWD

Wait! Any chance the disc is stuck to the pressure plate? did you wash your car just prior and left it overnight sitting? I have seen two such examples, mine being one of these.

I washed my 944T on the grass in the evening, left it sitting on the grass and in the morning I had the same, identical problem.

My neighbor owned an Aston Martin. Washed the car on asphalt, sprayed the undercarriage to knock off dust and in the morning it too was stuck.

Here's what I did: pushed car onto the street. With engine off, place car into 1st gear. Turn the engine on...... the car will lurch forward and will be "on" and moving in 1st gear. Push in the clutch and keep it in. Now, rev the accelerator and then slow down until the disc becomes unstuck from the pressure plate. This worked for both me and my neighbor.

Let me know how it goes.

Jaime

budge96

Bleed the slave! Wow sounds archaic!

ca993twin

From the symptoms, I'd say that Jamie is on the right track. If it will shift with the engine off, and not with the engine running, then the clutch is not disengaging. I'd fer sure try the Jamie method for trying to shake it loose before doing anything else.

took

I have re-bleed the slave twice now! Once for good measure, once again after I removed the rectangular rubber cutout on the clutch bell housing to verify that the slave was actuating the throw out bearing while pressing in the clutch. Getting the rubber insert to seat again on the case is impossible with the accumulator in place. I don’t think a second bleed was necessary but I was already in there, so what the heck.
Is there a method to test the slave to make sure it’s not the culprit? Seems as though it not building enough pressure?

budge96

Ok I'll bite where did you flush the brake fluid from? Apparently there's a pressure block up in engine comp ..maybe an air bubble has hindered pressure build up.
I would likely loosen the line on the slave the air may have vacated the cylinder of the slave just not the line...it's long, wait until you get fluid exiting immediately tighten and check pressure..
good luck! Bert

911/Q45

If you read his description, the problem occurred immediately after he had just moved the car, so it's unlikely that the clutch disk rusted to the flywheel. The turbo doesn't use brake fluid, it uses the power steering system to pressurize the slave and it's mostly self bleeding. Time for the shop before you break something expensive.

chris walrod

We assume the clutch pedal feels typical, pressure and feel??

took

Clutch pedal feels normal but at the same time acts as though the clutch is not there at all, if that makes any sense. More specifically as though there is no hydraulic pressure once engine is running, hence not being able to shift. With engine off and pressing in the clutch pedal I hear air coming from the slaves direction, cannot recall if that is normal or not. I have experienced the stiff clutch pedal and leaky reservoir in the trunk before and I am not seeing that.

chris walrod

There is hydraulic pressure generated soley by the clutch master (engine off) just without the hydraulic assist by the stored pressure in the accumulator. With that, you still should be able to feel the clutch action despite it being a difficult pedal.