Idle speed drops when clutch depressed.

[Lakeland997]

I'm just at the stage of starting the engine on my rally car for the first few times.
I haven't been able to run it for long as the heater matrix is leaking but I've noticed that the idle speed drops when I depress the clutch.

Primary gear?
Thrust washers?
Clutch settings?

any ideas please?

[JohnA]

Did you set the diaphragm when you assembled the clutch, you can overload the trust washers especially with a competion cover,this does slow the engine

[ivor badger 2]

release bearing in cover

[Spider]

Crank Thrusts in back to front.

[Lakeland997]

Crank Thrusts in back to front.

Oh dear I hope not
Lets try something simpler first!!!

release bearing in cover

Did you set the diaphragm when you assembled the clutch, you can overload the trust washers especially with a competion cover,this does slow the engine

Do you mean setting the throw out stop on the cover?

[Spider]

Crank Thrusts in back to front.

Oh dear I hope not
Lets try something simpler first!!!

release bearing in cover

Yeap, for sure, but you'd usually hear the release bearing.

[mk1]

My bet will be the easy & simple to solve too much crank overthrow. Adjust the big nut on the end of the china man's hat & all will be well.

I hope.

This can however also be caused by too much thrust washer clearance.

[Lakeland997]

I adjusted the stop nut in accordance with the manual, that is, hold clutch down and screw nut up to cover, release clutch and screw up one further flat of the nut then tighten lock nut.
I will do it again but...
Is there a case for screwing up the nut more than this on a competition clutch (I have orange diaphragm fitted)?
There were no carpets in when doing this, would this increase the clutch travel?

[Lakeland997]

I fixed the heater leak and ran the engine again yesterday.
I noticed that the idle speed drops as soon as the clutch pedal is even slightly depressed. So with very little load on the crank.
I went back through my engine build images and as far as I can see I'm pretty sure I put the thrust washers in the right way round (but we won't eliminate the possibility just yet).
I'm thinking that it seems to be as soon as the release bearing touches the cover so before I lift the full engine out I'll take the clutch cover off and have a look.
Watch this space for a further exciting instalment...

Here's the reason for the heater leak...
I'm using the later SPi heater.
On the left is one of the alloy outlets that I'd originally fitted. Purchased from eBay.
On the right are the brass ones that solved the problem. Purchased from Minispares.
Check out the size of the o-ring in each case.
Here endeth the lesson.

IMG_2411.jpg

[LarryLebel]

Look at the crankshaft fan belt pulley when you depress the clutch. If it moves at all the crank thrust bearings are duff. The slowing of the engine is drag of the pistons when the crank displaces sideways.

[ivor badger 2]

Look at the crankshaft fan belt pulley when you depress the clutch. If it moves at all the crank thrust bearings are duff. The slowing of the engine is drag of the pistons when the crank displaces sideways.

That would assume that someone who photographed building the engine did not check the end float on the crank.

[Vegard]

Welcome to the club!

[ianh1968]

I had the same problem and measured 0.015" of endfloat...

Can I join the club as well?

dscf0073.jpg

... and yes, this was the "copper" side!

As JohnA has already suggested in the second post,
was the clutch properly set up, ie was the diaphragm installed "flat"?

viewtopic.php?f=3&t=8141

The first post by "R&R" summarises things quite nicely...
Much of the first section of the thread is totally confused information,
but later on "more correct" details emerge...

Ian

[Lakeland997]

Ok so I got the clutch housing cover off today.

The flywheel and clutch was purchased complete from a single supplier already assembled and set up.
The diaphragm spring does appear to be flat and the straps are too.

I'm thinking firstly that it might be a duff release bearing (although everything here was new).
There is some significant marking/groove on the clutch cover where the release bearing touches but it's not severe. However I've probably depressed the clutch less than 20 times with the engine running since the build. Should it have already caused such a mark?
There are also small metal particles on the bearing itself that appear to have come from the clutch cover.

When I turn the bearing I can feel a little roughness as if the balls are damaged but I can't say if it's enough to cause the engine to slow but then again perhaps the bearing behaves differently under load.

I guess I haven't much to lose by replacing the release bearing and putting it back together for a quick trial because the next investigation probably means taking the engine out to check the thrust bearings.

IMG_2453.jpg

IMG_2460.jpg

IMG_2461.jpg

[ivor badger 2]

There shouldn't be any roughness in the bearing. The flywheel bolt under the release plate looks as if there is no clearance to allow the clutch to clear. The photo is not terribly clear, so any chance of a photo with the plate removed?

[Richspec]

http://www.mk1-forum.net/viewtopic.php?f=3&t=187

[Spider]

A little while back we were being supplied Diaphragms in which the centre plate for the release bearing to run on were really soft, it looks like you have one like that. Check it with a file, it shouldn't make a mark on it. The old ones were very hard.

See if you can get a hold of the old style 3W5/8 thrust bearing, they are considerably better than those light duty things. The 3W5/8 are still manufactured and available new, but few places keep them.

[minimans]

If you suspect the washers are in backward DON"T continue to run the engine! You will destroy the crank thrust faces..........

[ivor badger 2]

http://www.mk1-forum.net/viewtopic.php?f=3&t=187

It looks like we have a winner

[ianh1968]

http://www.mk1-forum.net/viewtopic.php?f=3&t=187

It looks like we have a winner

... and that definitely the thrust washers/endfloat should be checked.

This can be done with the engine still in the car, as you already have
the clutch cover off.

1) Get an engineer's dial gauge with a mag-base and some suitable mounting rods.
2) Stick the mag-base to the engine block, say, where the engine steady arm goes.
3) Build up your gauge/rods etc so that the dial probe touches the flywheel, preferably at a 90 degree angle.
4) Get a copper mallet and whack the flywheel centre bolt so that the crank is pushed up towards the radiator end.
5) Zero the dial gauge.
6) Get the copper mallet and whack the pulley end of the crankshaft towards the flywheel end.
7) What you end up with on the gauge will be APPROXIMATELY what your endfloat is.

You may want to modify this procedure, but you should get the general idea...

If the diaphragm thrust plate has been contacting the flywheel mounting bolt,
IT IS ALMOST CERTAIN that there will be considerable wear on the thrust washers.

Unfortunately the usual disclaimer of:
"If our tuning parts fuck up your engine, tough, don't blame us..."
will probably apply here...


Ian