924Board.org

[SSen100]

As I've put on an earlier thread, my 924's engine seems fine: smooth and no shortage of power. Economy also fine. Vibration doesn't seem to be the engine's fault.

One thing I notice is this: car judders badly in traffic.

When I'm crawling through traffic, there is a lot of judder as I'm letting the clutch out. (At first, I thought I'd left it in 3rd, not 1st, but this wasn't the case.) To keep going, I have to rev the engine hard and slip the clutch - not a great thing to keep having to do!

What could be causing it?
I thought the clutch might be on it's way out but the rest of the time, it seems fine. No sign of slip when changing gear. Garage thinks it's OK. Someone said 924S/944 often have a gearbox bearing problem - could that be relevant here?

I had another theory: fuel starvation. The fuel lines corroded through and the garage replaced them recently. Could it be that there is something wrong with the new lines that cause them to starve the engine of fuel under certain condition? I also get a smell of fuel when the tank is full to 3/4 full but I understand that is normal (but is it safe)?

Any ideas, anyone?

[AznDrgn]

My car seems to do the same thing but of course I have abused the crap out of my tranny and I just figured that I broke a tooth on the ring gear. Now that someone else has the problem I'd say it's a fine tuning problem somewhere but I really don't know as I have not tracked down the problem on my own car. As far as the fuel smell goes it's normal but it's caused but the fuel filler line being old and deteriorated and it is quite an easy fix. If you like sniffing gas fumes and don't pass out too easily it should be fine otherwise change the piece out and your problem should go away.
_________________
-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

[manouchehr]

Have you been driving my car again!?

your description sounds just like my car. near perfect condition, everything smooth except this judder occasionally when letting out the clutch from standstill. judder might not even be the right word. its more like a violent shaking. it only seems to do this when the engine is hot, like when driving in bad traffic and not even all the time then.

same 3/4 tank smell too.

hop someone knows what's going on!

[Sleykin]

Mine does the same. Mostly when backing up. I was told it is normal for these clutches. I got rid of most of the fuel smell by repairing the rear hatch seal. There was a gap about 2" long where the seal joined in back. I got a used seal and cut a piece to fit the gap.
_________________
Glenn Neff
Medford, OR
87' 924S

[edh]

fuel smell is probably from the lines going from the filler to tank - they are accessible from inside the hatch. If you remove the metal cover & tighten up the jubilee clips it may help. (It did on mine)

Fumes through hatch seal are most noticeable when the sunroof is opened - creates lower pressure inside the car & sucks air in from the rear.
_________________
current - '90 944S2, '00 986S,
ex - '90 944 turbo '86 924S, '88 924S

[Smoothie]

I get the judder sometimes too, when driving slower than the car wants to go. Just need to finesse the clutch, but no overreving needed in my case. I wonder if something in your clutch cable or mechanism isn't operating smoothly enough to allow a smooth partial engagement for slow, creeping-along driving. I have the hydraulic clutch, so I'm not familiar with the feel of the cabled clutch. The judder's got to be a combination of play in the driveline and a grabby, and maybe somewhat warped and worn clutch (and the amount of grabbiness constantly changes with temperature of the clutch itself as well as air temp and humidity). Try a partial engagement of the parking brake next time it happens (if you can remember to release it when the speed picks up again.)
_________________
"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Vince Ponz]

My 944 does that in heavy hot traffic. Has done it for years. Finally the rubber clutch gave out.
_________________
"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

[AznDrgn]

mine did it a lot less noticeably once I fixed the timing. The cam crank timing were off by about 3 degrees fixed that and it was a lot less noticeable.
_________________
-'87 Jeep Cherokee 4.0L 6" of lift 33" Super Swampers

-'83 Callaway 944 2.5L turbo, 300HP, 1 of 42 ever made

[Duncan]

I am still very, very interested in any ideas about this 'judder when engaging clutch with hot engine issue' It seems not to be a very rare problem, which my car experiences too. My clutch is now two years old, and it just happens sometimes.

Maybe one of the experts can shine a light on the issue? What basically changes when the engine gets really hot?

Remaining worried,
Duncan

[Ozzie]

Clutch shudder can be caused by
warped flywheel.
bad clutch plate
bad pressure plate.
bad clutch bearing
worn torque tube end
there is a bearing to align the end of the torque tube- could be worn.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[Duncan]

Thanks for your reply,

I am sorry to keep whining about this, but it it the one thing that stands between having the engine rebuild or not (investing the cash that is), point is:

clutch plate is replaced with new
presure plate is replaced with new
release bearing is replaced with new
the bearing in the crankshaft end is replaced with new

all done by an expert mechanic, who has even taken apart the
whole clutch assembly after my complaints to inspect it (about one year after the initial repair) and show me that nothing was wrong (at no cost ).

Clutch is fine 99.9 % of the time, i.e. when the engine is at normal operation temp, but this judder or heavy vibration of the drivetrain only happens SOMETIMES, when the engine is really hot, like when driving in heavy traffic.

I just need someone who is willing to sit down and think really deeply, what actually happens with the drivetrain when the engine is really hot...
Duncan

[RC]

Did you have the flywheel refaced as is recommended by all clutch manufacturers?

A glazed flywheel is the primary contributor to clutch shudder.

An expert mechanic should know that but may not be willing to admit it if it was his negligence. Or was it your economics?

Do some research at clutch sites tech info.

Roger

[Paul]

Motor and tranny mounts shot?
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[Duncan]

Well, when the clutch was done I did not know anything about car mechanics, so did not know the flywheel should be refaced. I vaguely remember from the FAQ that it was advised against resurfacing the flywheel because normal shop machinery can not get a good enough surface finish, or am I wrong? Only with the second clutch disassembly the pilot bearing was replaced on my request, as it was not included in a 'regular clutch job'.

would the flywheel glazing have more effect when hot?

The right hand side motor mount and both tranny mounts (one of which was definitely shot) where replaced, because the mechanic identified those as a possible cause of the judder. It made no difference.


Duncan

[RC]

Refacing a flywheel should be a piece of cake for a GOOD machine shop with MODERN equipment.