Clutch Life - PeachParts Mercedes-Benz Forum

Simpler=Better · #1 03-06-2015, 08:24 AM

So I got my truck at 160k, now she's at 235k. As far as I know, it's the factory clutch (PO sold it because he didn't want to throw $$ at ball joints

).
I suck out the clutch reservoir every spring and refill with fresh DOT4, no other maintenance.

I've smoked it 3-4 times when in a pinch (as in smell and visible smoke), and when I've needed to slip it (trailer, getting another car unstuck, etc.) I slip it.
Otherwise I take it really easy on takeoff, and rev match/shift without it.

So...as I was rocking the truck free this morning, I started to wonder-how much am I tempting fate? If it goes, I'll be riding my lawn mower to work.

Air&Road · #2 03-06-2015, 09:05 AM

With well over a million miles of clutch experience, I believe that clutch life is HUGELY determined by how it is used. It sounds like you are onto the most important key to it and that is preventing heat. Under any load slip the clutch with the lowest RPM and load as possible to get to a point where the clutch pedal is released, thus having solid connection as soon as possible without lugging the engine.

In more severe loading like you describe, you have to do what you have to do, but just try to produce as little heat as possible.

BTW, as far as the hydraulics go, you would be much better served to use an assistant at the pedal so you could flush a few stroke of fluid through the system.

Hope this helps.

barry12345 · #3 03-06-2015, 10:13 AM

Simply a wear item. Treating it easy generally is the normal way to extend the life but they will still eventually wear out as they were designed to.

spdrun · #4 03-06-2015, 11:54 AM

I still had the original clutch disk in the 240D at about 250k miles. It finally failed via the release bearing self-disassembling, not via wear of the wear surfaces.

Can't Know · #5 03-06-2015, 01:18 PM

235K is impressive for a clutch in a passenger truck, particularly one you use for towing.

The old, traditional test for the clutch is a simple one. Tested at normal operating temperpature, put the front bumper firmly against an immovable object (or have a helper to stick a foot over firmly on the brake pedal) and set the parking brake fully, then put it in 4th (not OD, just whatever is next down from OD), rev it to 3,500 or so, then slip your foot off the clutch pedal (no gradual release, immediate, full engagment). To pass the test the engine should die IMMEDIATELY. If it bogs and starts to rev back up, obviously get off the gas pedal and push the clutch pedal down, and start planning for replacement.

That said, if you're planning to keep the truck, I'd just plan to replace it anyway. It's not the toughest job you'll ever do, and then you're good for another 235K or so.

Do the works when you do it, pressure plate, clutch plate, TO bearing, pilot bushing. It just sucks to have to go in and re-do one of those later, since all the labor is the same.

t walgamuth · #6 03-06-2015, 02:15 PM

Quote:

Originally Posted by Can't Know

235K is impressive for a clutch in a passenger truck, particularly one you use for towing.

The old, traditional test for the clutch is a simple one. Tested at normal operating temperpature, put the front bumper firmly against an immovable object (or have a helper to stick a foot over firmly on the brake pedal) and set the parking brake fully, then put it in 4th (not OD, just whatever is next down from OD), rev it to 3,500 or so, then slip your foot off the clutch pedal (no gradual release, immediate, full engagment). To pass the test the engine should die IMMEDIATELY. If it bogs and starts to rev back up, obviously get off the gas pedal and push the clutch pedal down, and start planning for replacement.

That said, if you're planning to keep the truck, I'd just plan to replace it anyway. It's not the toughest job you'll ever do, and then you're good for another 235K or so.

Do the works when you do it, pressure plate, clutch plate, TO bearing, pilot bushing. It just sucks to have to go in and re-do one of those later, since all the labor is the same.

I would never test a clutch like that (in my own car

).

97 SL320 · #7 03-06-2015, 07:29 PM

Quote:

Originally Posted by Can't Know

The old, traditional test for the clutch is a simple one. Tested at normal operating temperpature, put the front bumper firmly against an immovable object (or have a helper to stick a foot over firmly on the brake pedal) and set the parking brake fully, then put it in 4th (not OD, just whatever is next down from OD), rev it to 3,500 or so, then slip your foot off the clutch pedal (no gradual release, immediate, full engagment). To pass the test the engine should die IMMEDIATELY. If it bogs and starts to rev back up, obviously get off the gas pedal and push the clutch pedal down, and start planning for replacement.

Ug! there is a better way to do this. 3rd or 4th gear 1/2 throttle up hill at a speed just above lugging the engine, push the clutch down until it slips, motor flares to 2,500 let clutch up normally ( don't dump ) motor should rapidly pull back down to preslip speed.

As for clutch life, some of these has a self adjusting pressure plate that gives a variable height peddle as it malfunctions. No, not the auto adjusting release bearing but actual springs / wedges in the clutch cover apparently intended to reduce clutch release cylinder wear. This can be replaced with a regular clutch cover

The release bearing hydraulic unit is self adjusting and can leak.

Changing the clutch on this is easy and new clutch parts not expensive even for OE like Valeo or LUK. Be sure to get the flywheel resurfaced, a warped flywheel will cause the clutch to drag. Also change the master and slave hydraulic unit at the same time. I'm big on lifeing parts and changing them near end of life rather than waiting for something to break at random.

Simpler=Better · #8 03-06-2015, 01:41 PM

My fears are absolved, I'll wait until she pops and then replace. I do have a nice Fidanza flywheel that might fit...

mytmousemalibu · #9 03-06-2015, 02:27 PM

What kind of truck out of curiosity?

For what its worth, I've driven mostly manuals my whole life, I prefer them. And worked in a range of professional auto repair facilities namely on BMW's. I've changed a lot of them! Clutches seen to fall into 2 categories when the actual clutch fails. One is they just become so worn they can't hold the power and they slip, pretty simple. The other is somewhere close to or within that realm of wear, the friction lining becomes so thin/weak it shears away from the rivets and usually jams up in the pressure plate and then the dang thing won't disengage no matter what you do, pedal pressed hard to the floor! I've changed a bunch that did that! You probably already know this but always replace the pressure plate, pilot bearing, throw-out bearing, etc. Get an entire clutch kit. The LuK Repsets are excellent kits if available. I also recommend having your flywheel resurfaced if it has a lot of heat marks, grooves, crazing. Sometimes getting the last miles out of a clutch means the rivets end up eating away at you flywheel.

Simpler=Better · #10 03-06-2015, 03:57 PM

1998 Ranger, 2.5L SOHC, M5OD, 2wd. The littlest of little trucks.

mytmousemalibu · #11 03-06-2015, 09:53 PM

Quote:

Originally Posted by Simpler=Better

1998 Ranger, 2.5L SOHC, M5OD, 2wd. The littlest of little trucks.

Ah! I had a 93' Ranger, 4.0L 2wd, M5OD and had also done a clutch in it plus a clutch in my friends which was about the same as yours. Its not too bad of a job but the slave cylinder in those trucks tends to suck. Its internal to the bellhousing and mostly plastic. The hyd. line going to it can be a pain in the @ss to release too. Theres a special tool but its not that great. You have to push a plastic sleeve into the coupler to release the line. I had to replace the slave unit twice because they wouldn't hold a bleed, after a while the thing would gradually suck in air and with the clutch pedal to the floor, the clutch would drag enough it would be very hard to get into gear while stopped. If yours works good in that regard, leave it be and keep a spare. You can replace the bearing on it. Also check/replace the shifter bushing halves and pins, very commonly trashed on these Mazda 5spds. If you have any Q's let me know, I have more experience on these than I would like

KarTek · #12 03-06-2015, 11:04 PM

Every clutch I've ever had has worn out very slowly and has announced it's demise WELL before it was unusable.

For example, this evening I was driving the F250 and I sensed that the clutch was slipping a little in 4th gear. I have about 125,000 miles on this awful metallic clutch and I'm overjoyed that I can finally replace it with something semi-organic.

97 SL320 · #13 03-07-2015, 11:23 AM

Quote:

Originally Posted by KarTek

Every clutch I've ever had has worn out very slowly and has announced it's demise WELL before it was unusable.

Yes that generally happens.

The biggest issue with a high mile clutch cover is fatigue of the diaphragm spring, when this cracks all clamping force is instantaneously lost with no warning. No clamping load = no drive.

Many older clutches used coil springs and it you lost a spring or two the car would still drive.

KarTek · #14 03-07-2015, 04:47 PM

Quote:

Originally Posted by 97 SL320

Yes that generally happens.

The biggest issue with a high mile clutch cover is fatigue of the diaphragm spring, when this cracks all clamping force is instantaneously lost with no warning. No clamping load = no drive.

Many older clutches used coil springs and it you lost a spring or two the car would still drive.

True, I can't remember if this clutch has a diaphragm or coil springs. I do know that I had to remove the pedal assist spring when I swapped clutches because the pedal pressure was far too light and I couldn't get a smooth engagement, especially when pulling a heavy load.

t walgamuth · #15 03-07-2015, 07:03 PM

The best way to test a clutch is to just wait until it starts slipping on the highway when you pull a hill. That is the most leverage the weight of the vehicle has on the clutch. When that happens just back off a bit and go down a gear if necessary. Treated this way your clutch will last easily until you can change it at a convenient time and place.