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Super Minx clutch losing pressure
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TriciaS



Joined: 17 Nov 2016
Posts: 62

PostPosted: Sat Aug 19, 2017 2:21 pm    Post subject: Reply with quote

[quote="peterwpg"]Re post from Jaguar/Peter above. Could this be the answer. The "firmness" that TriciaS refers to may be unwanted firmness and is causing over movement of the clutch.

I am really confused that you don't understand when I say firmness of the pedal, it is quite obvious that you need a firmness to the pedal and without it being firm is when it is straight to the floor, firmness means pressure is there and lose firmness means pedal goes straight to floor with no pressure, just want to clear that up as it was annoying me that you think firmness is a problem
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TriciaS



Joined: 17 Nov 2016
Posts: 62

PostPosted: Sat Aug 19, 2017 3:15 pm    Post subject: Reply with quote

peter scott wrote:
Gentlemen, you appear to be ignoring Tricia's statement that the problem only occurs when the engine is running. (Or have I misunderstood her?)

Peter

you are correct the problem is only when the engine is running, now we have movement of the crankshaft as the engine is started with foot on clutch pedal does this mean it is beyond repair, there is no movement with engine off
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peterwpg



Joined: 10 Apr 2008
Posts: 2223
Location: New Brunswick. Canada

PostPosted: Sat Aug 19, 2017 4:35 pm    Post subject: Reply with quote

I don't think this is the kind of thing anyone at OCC wanted to hear.

The crankshaft moving, is a little alarming and may point to excessive overthrow of the clutch.

From what you say about the hydraulic pipe, and knowing that the clutch and engine has been "fiddled with", there has to be doubt about the quality of previous work.

I am clear out of ideas or suggestions, given your own maintenance limitations.

Regards

Peter L
New Brunswick
Canada
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TriciaS



Joined: 17 Nov 2016
Posts: 62

PostPosted: Sat Aug 19, 2017 5:01 pm    Post subject: Reply with quote

I have been having a bit of a read about crankshaft washers and we are possibly thinking of attempting to change them ourselves with the engine still in the car, it sounds simple enough to do although I need to read more and hopefully get some advice on best way to decide if I need larger washers and how to work out the size required. The movement in the crank is only 3/32th of an inch but how to work that into the washers I don't get yet but will keep reading and not touch until I understand it a bit more, just got to keep another half busy so as he doesn't start dismantling before I know what to order and if it definitely can be done with engine in car.
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peter scott



Joined: 18 Dec 2007
Posts: 5981
Location: Edinburgh

PostPosted: Sat Aug 19, 2017 5:25 pm    Post subject: Reply with quote

Hi Tricia,

Assuming that it still has thrust washers then you measure the gap using feeler gauges. The end float should be between 2 to 4 thousands of an inch (0.05 to 0.1 mm)

Peter
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peterwpg



Joined: 10 Apr 2008
Posts: 2223
Location: New Brunswick. Canada

PostPosted: Sat Aug 19, 2017 5:31 pm    Post subject: Reply with quote

Tricia S. Please stop there. I don't believe the problem is the washers.

There may be crankshaft movement, but it is possible that something else caused the washers to wear and that something could very well be the excessive overthrow of the clutch, maybe wrong hydraulics, wrong clutch bearing, wrong clutch, assembly problems.

I don't have first hand experience of your engine, but would not try to do it at this stage.
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TriciaS



Joined: 17 Nov 2016
Posts: 62

PostPosted: Sat Aug 19, 2017 5:58 pm    Post subject: Reply with quote

peterwpg wrote:
Tricia S. Please stop there. I don't believe the problem is the washers.

There may be crankshaft movement, but it is possible that something else caused the washers to wear and that something could very well be the excessive overthrow of the clutch, maybe wrong hydraulics, wrong clutch bearing, wrong clutch, assembly problems.

I don't have first-hand experience of your engine but would not try to do it at this stage.

I still am looking at getting another push rod, as I said in earlier post the new slave is slightly longer than the old one so I presume this could cause what you call throwout as the word doesn't mean anything to me as not looked up meaning of the word yet but did say that where they had the slave meant the piston came too far out the bore so we moved it to the other side of the lip of the bell-housing.
I will not be dropping gearbox and doing anything to the clutch itself as done far too many in recent years and find it too hard now old and weak arms.
I wonder if you think 3/32th is not much movement to cause the 4 inch difference in the measurements we did the other week but as you cannot tell me what sort of movement it should be then I can only go by other symptoms of revs dropping when clutch pressed as a sign it is the crankshaft, I am waffling now and losing my concentration so will take a break from thinking for half hour or so haha.
oh it is very hard to pull the crankshaft to get it to move but it moves with the engine off now too I think the same amount whether engine on or off but will check again tomorrow
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Jaguar



Joined: 24 Jan 2013
Posts: 19
Location: The Netherlands

PostPosted: Sat Aug 19, 2017 6:00 pm    Post subject: Reply with quote

Hi Tricia,

Just like the peterwpg I don't believe that the thrust washers are the problem. As I wrote before if the movement of the crank shaft is that much you should have a very low oil pressure at idle (is the oil warning light burning?) and there should be a very significant drop of engine revolutions when you press the clutch pedal.
I don't doubt you have crankshaft movement, but it doesn't explain your clutch problem. By the way changing the thrust washers is quite easy without having to take the engine out. You have to remove the sump pan and after that you remove the concerning main bearing caps. Then you can move the thrust washers out op their position if they have not already fallen in the sump pan.
Oh and when measuring crankshaft movement with the eye the engine must be idling. If you want to measure it without the engine running use a dial indicator and yes the movement you have registrated is quite much. Are you sure about this measurement?
If you are going to replace the thrust washers check that condition of the crank shaft at the place were the have contact with the thrust washers and the same is necessary when it regards the engine block at the other side. Worn thrust washers is a serious case which unattended can lead to destroying both the crankshaft and the engine block.

Peter R.
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peter scott



Joined: 18 Dec 2007
Posts: 5981
Location: Edinburgh

PostPosted: Sat Aug 19, 2017 6:57 pm    Post subject: Reply with quote

Has the clutch ever worked correctly in your ownership or did you buy it with the problem?

The Super Minx thrust washers are on either side of the centre main bearing. Yes, draining the oil and removing the sump is a messy business and working from underneath with oil dipping on your face is not pleasant but it's not difficult.

Having removed the sump you will need to remove the bearing cap from the centre main and then lever the crankshaft back or forward to discover its movement. Pushing feeler gauges into the gap you will be able to assess the end float. If you need to renew the thrust washers they can be pushed around the shaft to get them to the bottom and prised out with a small screw driver.

When you remove the bearing cap mark it so that you can replace it the correct way round.

Peter



p.s. I can't think of anything else that would cause your problem but having said that, back in the early 1970s my Sunbeam Alpine had a rattle coming from the clutch area. I thought it must be a broken finger from the diaphragm spring. I took the engine out and replaced the complete clutch assembly but unfortunately there were no broken fingers. When I restarted the engine the rattle was still there! I then discovered that it was the separating plate inside the exhaust pipe Y piece had come loose! It is located beside the bellhousing. Embarassed
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47Jag



Joined: 26 Jun 2008
Posts: 1458
Location: Bothwell, Scotland

PostPosted: Sat Aug 19, 2017 7:44 pm    Post subject: Reply with quote

Peterwg & Jaguar,

If the 3/32" measurement is accurate then this is about the thickness of a thrust washer. So it is conceivable that a thrust washer has collapsed. I can't see how it could drop out though since they sit in a recess in the bearing cap. This would tie in with the revs dropping. If it has worn out then I would expect some damage to the thrust faces of the crankshaft. Sad

Art
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peter scott



Joined: 18 Dec 2007
Posts: 5981
Location: Edinburgh

PostPosted: Sat Aug 19, 2017 8:03 pm    Post subject: Reply with quote

If the car was bought with this fault it's possible that someone forgot to include the thrust washers when assembling the engine.

Peter
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MVPeters



Joined: 28 Aug 2008
Posts: 635
Location: Northern MA, USA

PostPosted: Sat Aug 19, 2017 8:34 pm    Post subject: Reply with quote

Tricia

This seems to have us all baffled!
I can't help but think that the quickest, easiest & cheapest way to find out what's going on is to get the car up on a lift & have an elderly mechanic look at it.

Having said that, here's a couple of my thoughts:
A good article on clutches here: http://www.novak-adapt.com/knowledge/clutches-etc

Is the new, longer, slave cylinder the correct bore diameter to match the master?
Does the clutch dis-engage with just a small depression of the pedal - ie not all the way to the floor?
Is it possible the clutch diaphragm is going 'over-centre'?

No matter what the answers, I can't see any connection with the engine running or not.

re the thrust washers: that should not be an expensive diagnosis or fix either. Are the washers relatively easy to get?

These are nice, usable, comfortable cars - please try to hang on to it!
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Jaguar



Joined: 24 Jan 2013
Posts: 19
Location: The Netherlands

PostPosted: Sun Aug 20, 2017 9:29 am    Post subject: Reply with quote

One correction on the end float, indeed if it regards a 1592 cc engine it should be between .002 and .004 inch, but if it regards a 1725 cc engine (like the one which is insttalled in a Super Minx MK IV the end float must be between .002 and .008 inch.
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1320
Location: Above the snow line in old Monmouthshire

PostPosted: Sun Aug 20, 2017 4:03 pm    Post subject: Reply with quote

MVPeters wrote:


re the thrust washers: that should not be an expensive diagnosis or fix either. Are the washers relatively easy to get?


Even if not, they're hardly impossible to make from scratch.
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Jaguar



Joined: 24 Jan 2013
Posts: 19
Location: The Netherlands

PostPosted: Mon Aug 21, 2017 10:57 am    Post subject: Reply with quote

Hi Tricia,

While you already have found out that the slave was installed at the wrong side of the gearbox, which is a commom made mistake, there is another mistake that is made frequently and that is the position of the bleeding screw.
The appropiate position of this bleeding screw is at the top of the slave while the lining from the master is at the bottom of the slave and certainly not the other way around. If the bleeding screw is at the bottom of the slave bleeding becomes a nightmare and one never gets the required result.
Although I see no connection with the problem you have described, it is worthwile checking this, it won't take more than a minute.

Peter R.
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