Clutch slipping opinions

[dhg1337]

The other day I drove a early 70s 911 with a stock SC motor in it for sale. Nice guy, nice car, very honest about the car, spent allot of money having general Porsche repairs done by others. It was estimated the clutch had 35-40k miles on the clutch.

So I am test driving it with the owner, I mention to him I am going to test the clutch for slipping. We are going up a slight incline in 3rd gear at 3k rpm's, I push the gas pedal to the floor( not much power but ok it was missfiring a little) then I very quickly pushed down the clutch, the rpms rose about 1k by the time the clutch was fully re-engaged. From there the rpm's continued to rise to redline. The car was not accelerating. Then a horrible clutch burning smell engulfed the inside of the car.Now this all happened in a matter of seconds. I turn to the owner and immediately tell him his clutch is fried, it did not seem out of adjustment. He recently paid $2600 to have one head stud replaced, we wondered if the shop inspected the clutch while apart.

I have done this thousands of times to my cars and motorcycles on a regular basis to make sure the clutch is not slipping. Also on cars I am buying. The clutch either bites or slips, period.
This brief test on a low hp car to me does not seem harsh.


Anyway, his shop said the clutch was 50% when they had it apart for the last repair and was fine. The shop said what I did was enough to ruin a perfectly good clutch in a matter of moments. Give me a break, that's the stupidest thing I ever heard.

Anyone that works on their own car,want to chime in, maybe I am wrong.

[Eagledriver]

Remind me to never let you test drive my car. WTF are you thinking. If you can floor the car without the clutch slipping on acceleration then the clutch is fine. If you push in the pedal and the clutch slips, it will heat up and might keep slipping. I've driven cars with slipping clutches before and it's obvious.

-Andy

[timmy2]

I agree with Andy,
My '88 Celica GT Convertible daily driver was giving signs of slippage the other day. The engine would rev faster than car would accelerate. I realized I had over revved and dumped the clutch accidentally when leaving work. I drove it home gently,parked it in my garage, adjusted the clutch freeplay, let it cool down overnight and she drives fine now.
The Factory Toyota manual even says a hot clutch/pressure plate can slip like that and to let it cool off!.
You'd be replacing my clutch if you did that in any of my vehicles.....

[Newlin4141]

At the risk of this becoming a publicly-aired he-said / he-said thing, with all due respect, this is not an accurate account of what happened.

Here's what I saw from the passenger seat: We turn south on Winchester from Lark (in Los Gatos). There's no incline here. I don't know if this even matters, but it's flat. Anyway, we get up to 20 - 30MPH and the potential buyer says, "Okay I'm going to do something now to test your clutch." He shifts her into third, puts the throttle to the floor for about a second and a half, then stands on the clutch until the motor revs past 5k (I'm quite certain of this part because it startled me!), then he side-steps the clutch. Motor redlines for another second and a half and even goes *past* the redline, which was a first for me. I'd never driven the car that hard. He backs off. Car fills with the expensive smell of burning clutch. "Your clutch is fried," he says. "What?" "Yeah, your clutch is bad. Watch." Same thing again: He slows the car down, still in third gear, now going ~20 MPH up a slight incline at this point, throttle to the floor, clutch goes down, motor revs to 4k, then 5k, then he pops the clutch a second time. Right foot down. RPMs blow past the redline again. Guess my rev limiter doesn't work, either. Great.

My shop did repair two head studs, but a laundry list of other things. I don't know why, dhg1337, would say it was just a head stud. He looked at the receipt twice! Car had an oil and filter change, replaced a couple gaskets (one was a head gasket, the other I can't read from the receipt), valve adjustment on passenger side, they adjusted cam something (again, great mechanics, bad hand-writing), there's a new oil thermostat, fuel accumulator, a couple hoses and they removed the front oil cooler, cleaned and flushed it completely, removed the pipes to the oil cooler and flushed those. It's all there. Anyway, it wasn't "$2600 to have one head stud replaced." These guys have worked on this car for the last 20 years (I have receipts) and are awesome. Every time she went to them, both the previous owner and I would spare no expense to have them fix whatever was needed. If the car needed a new clutch, one of the two mechanics who looked at it would have told me, and a new clutch would have gone in. They're what? $500 - $600 in parts? Motor's already out. No brainer.

Incidentally, the car went back to the shop the next morning (today) to have this clutch sorted, meanwhile someone came by who'd heard about the car, did his own inspection, drove it, and bought it before lunch. The buyer will likely replace the clutch. Or maybe not, I don't know. Nor do I know if dhg137 was responsible for frying it. I'm not a mechanic. Here's what I do know: If I was to test drive someone's sweet mid-70s P-car, I'd take it out and gingerly drive it to see how it feels. If I had any questions as to the strength of the clutch, I'd ask the guys who just had the motor out. From my perspective, dumping a clutch at 5 grand in third going 20 - 30MPG seems like a pretty violent way to test a stranger's vintage car. Just my take.

[Quicksilver]

I'm trying to figure out where in the universe some idiot comes up with a "Lets slip the crap out of the clutch" as a test for a clutch... and then decides to do this to someone else's car.
Gee, it is so surprising that after you make a concerted effort to glaze the clutch that the coefficient of friction would be reduced to the point were it might slip. If you did that ONCE with a brand new vintage multidisk racing clutch you would destroy it. If Newlin4141 is lucky it will be normal after the glaze has worn off.

Dumb,
Dumb,
Dumb...

A Porsche isn't a drag car. That type of stupid abuse is something you do in a drag car with the full knowledge that you are going to have to replace the brand new clutch very very soon.

A slipping clutch can be diagnosed with minimal slippage as you apply power. Hell, a diaphragm clutch can slip because the disk is too thick! I have seem more then one car that had clutches that slipped until they wore in a bit.

[Newlin4141]

Originally Posted by Quicksilver

I'm trying to figure out where in the universe some idiot comes up with a "Lets slip the crap out of the clutch" as a test for a clutch... and then decides to do this to someone else's car.

TWICE!

Perhaps I'm the idiot for letting someone who seemed to know Porsches drive my car without having cash in hand (my hand).

Expensive lesson. Live and learn.

[Porchcar guy]

What is even more interesting is that the driver/potential buyer started a thread to ask if he was wrong...in a simple word ...YES !

[tobluforu]

I know one thing, i'm not taking any advice from 1337

[CCM911]

I would just die if someone did that to my car! Just poor manners.

[timchar]

If you had to discount your sale price due to this obvious clutch abuse, this guy should reimburse you. I'm blown away someone would "test" a clutch in this manner... Guess the culprit who started this thread got his answer. I think he quietly snuck out the back door.......

[vulcan300]

If I was selling my car and someone did that I'd have a hard time resisting the urge to punch them square in the nose!

[Newlin4141]

Originally Posted by timchar

If you had to discount your sale price due to this obvious clutch abuse, this guy should reimburse you. I'm blown away someone would "test" a clutch in this manner... Guess the culprit who started this thread got his answer. I think he quietly snuck out the back door.......

Reimbursement, now that's interesting. I did sell it for a reduced price. Or, that's the plan. I'm supposed to pick up the check in 20 minutes. Will update later today with exact details.

Here's the car for reference.

[vulcan300]

Your car is gorgeous and being sold way too cheap IMHO.

[wjfk32]

Newlin4141

Dude....

WTF--JUST HAPPENDED????......Pull over and let him out of ze car.........period...

U drive my car once you pay me........

Wow!! beautiful car


Walt

[timchar]

Your car is beautiful and very well cared for.. maybe the clutch killer will find some morals and pay what's fair...i feel for ya brother....

[manbridge 74]

For relevance a standard clutch test would consist of this IMO....

-Letting the clutch out in gear and seeing if car stalls instantly.
-Finding a steep hill and, using one gear higher than normal, floor it.

If no slippage is seen in either test, clutch is good.

And maybe one should sell a 911 like a sportbike? Ie, no test drives/rides. You could probably make rare exceptions to this, but a sad situation as seen here might be avoided.

[Newlin4141]

Wow, after reading all this, I feel sorta ill. What a bummer.

Sold the car today for $13,000 after I disclosed to the buyer what this donkey did to her clutch.

Expensive lesson of the day: You want to test drive my Porsche, I'll hold the money.

[Christien]

If I did that to your car, I'd be writing you a cheque for $1500. That should cover the cost of engine/tranny removal/replacement and a new clutch disc. But then again, I would never do that to your car. Or mine. But particularly someone else's. If I were you on that test drive, I'd tell the guy to pull over, get the f#ck out, and leave him at the side of the road. Find your own way back.

You don't thrash someone else's car under the pretence of "testing". Asshat.

[yelcab1]

Nobody touches my clutch, especially you!

[DaveE]

At least he didn't run it into a tree to check out the seat belts.....