Can a failing DMF have symptoms of a slipping clutch?

[podwin]

I bought a diesel recently which had a new clutch 20,000 miles ago.

However it slips sometimes, and when under load I can hear a metallic knocking sound, but not sure if that is the normal diesel knock.

Would a DMF make this sound, and slip like a clutch?

[TooLateForAName]

Does sound like the DMF should have been done with the clutch....

[podwin]

Thanks, no evidence of that being done though.

Is it OK just to replace the DMF now? Or should it be done with a new clutch?

[mygoldfishbowl]

A new clutch as well unfortunately. The worn flywheel will have adversely worn the clutch.

[Krikkit]

Compared to the cost of a DMF and taking the box off etc, a new clutch is well worth buying!

[eltax91]

What car?

[podwin]

A 1.5 Qashqai.

It slips in the higher gears, only when it's warm though.

[mygoldfishbowl]

...and while you're in there change the crankshaft oil seal.

[ShaunTheSheep]

podwin said:

A 1.5 Qashqai.

It slips in the higher gears, only when it's warm though.

Torque produced doesn't change by an appreciable amount depending on whether the car is warm. Or do you mean when the clutch is warm - say after riding it at some traffic lights (tut tut! ;-) ?

If slipping is related to engine temperature, or how long the car has been driven, i'd be wondering if the slipping clutch is just a symptom of something else. That is to say, you could replace the clutch, which surely needs doing, but suffer the same fault again because the cause has not been rectified.

[HertsBiker]

mygoldfishbowl said:

...and while you're in there change the crankshaft oil seal.

Very much this. Oily clutches judder.

[podwin]

ShaunTheSheep said:

If slipping is related to engine temperature, or how long the car has been driven, i'd be wondering if the slipping clutch is just a symptom of something else. That is to say, you could replace the clutch, which surely needs doing, but suffer the same fault again because the cause has not been rectified.

I have thought this, that the fault may not be solved. When it is slipping it is accompanied with a metallic knocking noise which made me think of the DMF.

In the summer, it would slip as soon as I got on the motorway (within 5 mins) when it was 30 degrees.

But when it is cold it seems to behave, in the mornings it never does it (~12 degrees), even when I try to provoke it by accelerating in 6th up a hill from 50mph.

Doing the same journey at 4pm it may or may not slip depending how hot it is outside.

When it is slipping it is only at motorway speeds in 4th, 5th or 6th, there is no judder, and it is fine in town.

The only time I got it to slip when it wasn't a warm day, was an hours drive from Wales, overtaking many caravens on the B Roads.

I have tried Googling and have found similar problems in forums from several makes, but they never come back to say how they solved it.

Some advice I did notice was a bad master cylinder, how would that be the cause? I've never understood master / slave cylinder stuff.

[Turkey]

The slip could perhaps be the master or slave sticking when the car is hot, and not disengaging the clutch properly, but I this is quite an unlikely failure moode for clutch hydraulics (would depend on the exact design of the parts on the DCI though).

I just saw this thread, where a Megane owner had a crankshaft oil seal leak causing slip and DMF damage, hope it's not this problem: http://www.renaultforums.co.uk/archive/index.php/t...

[ShaunTheSheep]

podwin said:

When it is slipping it is accompanied with a metallic knocking noise which made me think of the DMF.

Sounds likely, can you feel it through the clutch pedal at all?

podwin said:

In the summer, it would slip as soon as I got on the motorway (within 5 mins) when it was 30 degrees.

But when it is cold it seems to behave, in the mornings it never does it (~12 degrees), even when I try to provoke it by accelerating in 6th up a hill from 50mph.

That's only 20 degrees difference, the clutch in normal operation will see greater temperature differences than that, up to 120 degree C differences according to t'internet.

Is there something else that could be affected by temperature? Others have mentioned an oil seal, that's possible i guess. The seal could become more malleable, to the point of letting warm (thin) oil out when ambient temperature is warm enough. I know from working on my Rx8 that the rubber hoses under the bonnet are a bugger to work with (stiff, zero give in them) in the winter months but are no hassle in the summer, i live in Scotland so that's only around 18 degrees difference in ambient.

Either way it sounds interesting. If you're ever in North Lanarkshire i'm happy to lend a shot of my boroscope for a peek in at the clutch to see what's happening!

[podwin]

Turkey said:

I just saw this thread, where a Megane owner had a crankshaft oil seal leak causing slip and DMF damage, hope it's not this problem: http://www.renaultforums.co.uk/archive/index.php/t...

I have thought about oil contamination, but thought it would be a constant, thanks for the input.

[podwin]

ShaunTheSheep said:

That's only 20 degrees difference, the clutch in normal operation will see greater temperature differences than that, up to 120 degree C differences according to t'internet.

I know, it doesn't make sense does it?

Thanks.

[podwin]

Stuck on the m62 unable to select a gear.

There was no slipping, the clutch peddle just doesn't do anything. What does that mean?

Waiting for recovery

[anonymous-user]

That means your DMF is fked and probably the clutch as well.

Happened to me too - the whole assembly had completely seized up when they removed it.

[podwin]

Oh lovely

[littleredrooster]

podwin said:

Stuck on the m62 unable to select a gear.

There was no slipping, the clutch peddle just doesn't do anything. What does that mean?

Waiting for recovery

Problem with master cylinder, slave cylinder or DMF, insufficient info for full interweb dognoses.

*pedal*, btw...unless you're selling something.

[podwin]

Drives fine once it is in gear.

Thanks for the spelling.