Clutch Drag

[peterg]

Me again!
As said before my tuner said that I am suffering from clutch drag, but I don't understand why. Can someone explain?

When driving the clutch engages at the end of travel. When in neutral, if I depress the clutch engine revs drop by about 300 rpm. But why? As the car is in neutral and not engaged to anything why should revs drop off when it is depressed?

The car is fitted with a new MG B clutch in favour of the original item, which I was told isn't quite upto the mark.

Sunny days & smoking exhaust!

Regards, Peter

[Ronald G. Stephenson]

Peter, when clutches wear out, they allow the engine to over-rev when the car is being accelerated. This is called 'slippage'. As to 'drag', if your car did not have the clutch fully engaged you would have slippage. If you are experiencing 'drag', it just may be a wheel cylinder locked up in the apply position. Problems arise when you start swapping parts around from other brands. It would be best to have a specialist look at what is going on. You mentioned the fact that the pedal action has changed, and that may be due to the new clutch/pressure plate requiring more travel to disengage. In some instances, this can be adjusted out, if the linkage is mechanical. If hydraulic, then some serious bore sizes on master and slave cylinders would have to be addressed. Clutches are fairly straightforward, provided the right parts go in for replacement. Let me know what happens. ron

[peterg]

Thanks Ronald,
But this happens when stationary, out of gear. That is why I cannot understand what is happening.
Depressing the clutch pedal shouldn't have any effect, should it?
I don't think 403 clutches are hydraulic or assisted in any way.
Peter

[Ronald G. Stephenson]

Again, the only advice is to get a 'second opinion', as they say in the medical profession. The clutch disc, pressure plate, clutch release bearing and the linkage to the clutch from the pedal needs to be examined. It is likely something simple that has been overlooked in the work. I suspect mis-matched parts not allowing sufficient clearance. I have seen instances where the clutch fork return spring has been left off, causing all sorts of noises,and prematurely wearing out the release bearing. Good luck. Sorry you are having the difficulty. ron

[UHT405]

Peter,

The clutch should engage and disrengage roughly half way up the travel of the pedal. When you say it engages at the end of travel, is that with the pedal near fully up or near fully depressed? If the former, then it could simply be that your clutch mechanism - which is indeed mechanical as you say - is out of adjustment and forcing the clutch pressure plate to operate too soon in the pedal travel. When you operate the clutch, the linkage applies a force to the centre of the clutch pressure plate spring via the release bearing, and that force is reacted through the flywheel and crankshaft to the block via the crankshaft thrust washers. If too excessive force is applied, then the thrust bearing can load up heavily and/or the crank is forced heavily on to the thrust washers in the block - either adds a small load to the engine which at idle could cause a small drop in revs.

I'd suggest checking the clutch adjustment as a first step....

regards

Martin

[Richard]

I have the same effect on my 405. When standing still, out of gear, with the engine idling I then depress the clutch the engine revs drop by about 200-300rpm. My engine idles at about 900rpm so I have never worried too much about this but am also curious to know why and what if anything I can do about it. The clutch is original.

Regards
Richard

[peterg]

Thanks Martin,
The clutch engages when the pedal is nearly fully up. as said, it is a new clutch fitted by a highly regarded Bristol specialist who said that is how modern clutches should operate.

Personally I prefer a clutch that engages a little earlier. It gives me more feel.

Because my tick over is nearer to 750 rpm a loss of 300 rpm puts me close to stalling when the engine is warm.

Regards, Peter

[penman]

Hi
That is certainly not my experience with my everyday car.
I prefer a clutch to start biting quite low as that way the heel can be kept on the floor for fine adjustment of position.
Also a clutch starting to bite near the top is in imminent danger of not having any free play in the mechanism when fully up thus leading to accelerated clutch wear.
The cynic in me asks "Why would a garage set the clutch bite high?".

Originally Posted by peterg

Thanks Martin,
The clutch engages when the pedal is nearly fully up. as said, it is a new clutch fitted by a highly regarded Bristol specialist who said that is how modern clutches should operate.

Personally I prefer a clutch that engages a little earlier. It gives me more feel.

Because my tick over is nearer to 750 rpm a loss of 300 rpm puts me close to stalling when the engine is warm.

Regards, Peter

[Ronald G. Stephenson]

I too, am one of those 'half-way-up' people, and always insist on my preference. I believe that the release bearing needs some free play, and if the pedal engagement is way up, it is usually a sign that it is time for a new clutch disc. Not a lot of material on these things, and a poor driver can destroy one in a short time. The least amount of slippage is best, and I had one everyday driver that had a clutch lasting 180,000 miles, and that is not an exageration.