740 (B200E/M47) Clutch pedal operating too low?

[eeedelli]

Hi folks,

My pre-facelift 740 estate (B200E/M47) is causing some head scratching. I don’t know whether this has been a gradual thing that I’ve only just noticed or whether it’s gone relatively quickly. Either way, I’m aware of this issue now and am concerned that it might soon leave me stranded.

The problem is that the biting point on the clutch now occurs when the pedal is almost at the floor. The first couple of inches of pedal travel has no resistance but then it feels ‘normal’ as it goes down. (Once engaged, transmission is fine - there doesn't seem to be any clutch slip etc. and I'd be surprised if it's worn, though there is sometimes some judder in 1st and reverse, which also afflicts my cousin's 740 and we've never been able to work out what's causing it, despite changing his engine mounts and all sorts. That always seems to be roadwheel speed dependent (about ½mph) so I suspect possibly more to do with rear mounting bushes.)

The clutch fork is moving throughout the whole of the pedal travel. (I thought at first that it might somehow have got an airlock, possibly from when I had to put new seals in the master cylinder a few months ago, which would mean it was initially compressing the air rather than moving the fork but, no, it’s moving throughout, according to my cousin who watched it as I pressed it through the ‘floppy’ section for the top couple of inches and, once that was established, carried on to the floor.) There’s no sign of leaks and the fluid in the reservoir is full.

It’s never had the proper operating rod on the slave cylinder ever since I’ve owned it these last 19 years (a bolt acts as a substitute) since the ‘pip’ that clips into the fork is missing. (The same thing happened to my cousin with his 740 last year when it just popped out on the road somewhere and left him stranded. Fortunately, I was there in my 940 as well and was able to tow him home where he also went for a bolt substitute.)

He suspects the finger springs in the centre of the pressure plate might be going weak after a good few years of use. I’m very ‘old school’ and automatically double-declutch everything, which wears the clutch driven plate and the brakes less (as it provides engine braking) but doubles the number of clutch release operations, of course.

I suggested that it could be that the bolt used to replace the original operating rod is a bit shorter than it should be but that would mean it must have been like this for years and I’ve only noticed it recently, which is possible, though I do seem to have noticed an increase in the number of occasions on which I’ve gone to throw it into reverse or first and found I hadn’t depressed the clutch far enough, resulting in some embarrisingly noisy grinding! (Unlike some drivers that I hear, I always wait a few seconds for the shafts to stop rotating before trying to engage 1st or reverse, so it always comes as an unpleasant surprise if there's any grinding at all.)

Any suggestions?

Ta,
David.

[940volvoman]

I would recommend replacing,or at the very least servicing and bleeding the clutch slave cylinder.maybe even the clutch master cylinder,too.

[eeedelli]

Originally Posted by 940volvoman

I would recommend replacing,or at the very least servicing and bleeding the clutch slave cylinder.maybe even the clutch master cylinder,too.

I rebuilt the master cylinder only a few months ago with new seals and bled the system then. There's no sign of any leakage from the slave and the fluid reservoir remains full to the brim.

As I mentioned, the fork moves throughout the whole of the pedal stroke so it doesn't look as though there's air in the system anyway. (That was my first thought and the first check.) If there was any air in there, I think the floppy first few inches of pedal travel would be busy compressing the air bubble rather than moving the fork ... but it moves the fork.

It's as if the fork is too far away and has to move through an area where it's not actually making any contact with anything before it reaches the point where it is ... but I don't see how that could have developed.

[martin calva]

Originally Posted by eeedelli

Any suggestions?

Ta,
David.

My 940 had the clutch pedal going almost to the floor to disengage. The local garage (owner is former Volvo manager) said that the only remedy was a new clutch, as there is no adjustment. The car had done 530,000 km almost certainly on the original clutch.

I got the local garage to replace the gearbox (3rd gear kaput) and he replaced the clutch at the same time. Works like new now.

[360beast]

Originally Posted by martin calva

My 940 had the clutch pedal going almost to the floor to disengage. The local garage (owner is former Volvo manager) said that the only remedy was a new clutch, as there is no adjustment. The car had done 530,000 km almost certainly on the original clutch.

I got the local garage to replace the gearbox (3rd gear kaput) and he replaced the clutch at the same time. Works like new now.

Did you keep the original gearbox? They can be repaired as it is most likely the stop ring needs welding in place.

[TonyS9]

On my 940 I originally had the clutch master cyclinder push rod hole with a worn slot in it, making for crunchy gear changes. It only takes 1-2mm to lose most of your travel due to the long lever. The easy way to detect this is to lift the clutch with your toe, I had maybe 1" of travel upwards, after fixing this is down to a few mm.

The pedal and master cylinder are plastic with a metal pin (older cars like the 240 are metal). It doesn't seem to affect every car but some seem to get it, maybe if its not lubricated correctly. My car seemed to have it from near the start, as the records have evidence of clutch bleeding, but the dealer didn't get to the bottom of it. Its been fine for many years after replacing with a used master.

[eeedelli]

Originally Posted by TonyS9

On my 940 I originally had the clutch master cyclinder push rod hole with a worn slot in it, making for crunchy gear changes. It only takes 1-2mm to lose most of your travel due to the long lever. The easy way to detect this is to lift the clutch with your toe, I had maybe 1" of travel upwards, after fixing this is down to a few mm.

The pedal and master cylinder are plastic with a metal pin (older cars like the 240 are metal). It doesn't seem to affect every car but some seem to get it, maybe if its not lubricated correctly. My car seemed to have it from near the start, as the records have evidence of clutch bleeding, but the dealer didn't get to the bottom of it. Its been fine for many years after replacing with a used master.

Ooh! That's an interesting point, though I'm not quite sure I understand where you mean. Do you mean the hole in the top of the pedal's arm itself (which a pin passes through to couple that to the master cylinder's operating rod) or do you mean the axis about which the pedal operates?

When you say you had 1" of upward travel, do you mean before the pedal became more (normally) stiff (i.e. before it's actually doing something) or do you mean from the null position? (Isn't it pulled back up with a spring though, or does it only get pushed back by the fork's spring returning the slave cylinder? Can't quite remember now.)

Also, I'm not sure I follow you about the "pedal and master cylinder are plastic". The pedal is certainly plastic but I've never seen a plastic master cylinder (apart from the unpressurised reservoir on top of the brake master cylinder).

My gut reaction at the moment is that it's the clutch master cylinder seals going again. When they failed 9 months ago, I was fooled at first because the fork would still move (albeit not enough, which I hadn't realised) but just one day later when looking at it again, there was no movement of the fork at all, which confirmed it.

I haven't used it this week and have just gone out to see whether it's done the same trick but it seems to be the same as it was last week. However, the seals that were sent last time were from 'Professional Parts Sweden' which, reading other threads elsewhere about the quality of their rubber components might be renamed 'Unprofessional parts, China'!

I have another set on order which should be by AutoFren (Spanish company) in case I need to change them again and I'm trying to avoid using it until I am ready to do that. (Also, I'm waiting for a wheel to be machined for my camper van, which I don't want to block in with the 740 as the van is due for its annual MOT test, so I'm a bit stuck all round at present and leaving the 740 in the street ... and the weather has been (and is set to continue being) awful! <sigh>

[eeedelli]

Well now I’m flummoxed – again!

The repair on the camper van wheel kept getting put back by the machine shop and I only finally got it all back together and through MOT last week, so have only now been able to get the 740 in front of it to work on.

Lo and behold, when I went to move it off the pavement after sitting there for a month, the pedal had no resistance at all and I couldn’t engage any gear after starting.

“Ah ha!” I thought, “It must therefore be the master cylinder again.” There was no sign of any leaks from anywhere and the reservoir was still full but I tried re-bleeding it in-situ. Despite not noticing any air bubbles, it restored it to its previous sub-optimal condition (floppy first couple of inches and bite point ¾” off the floor) but sufficient for me to drive it into the back yard to work on.

I’ve pulled out the “Professional Parts Sweden” seals from 9 months ago (which I suspected might have been of poor composition rubber) and replaced them with the new “AutoFren” ones, noting that the former had already worn down to 19.7mm diameter (which you’d think would be sufficient for a 19mm bore, though the front (pressure) one didn’t seem to have much ‘lip’ left compared to the new one at about 20.5mm).

Again, I checked the cylinder and noted that it was, generally, mirror polished, though with very slight dullness where the pressure seal sits at rest. (Examining with a magnifying glass did show up some tiny scores there so perhaps I’m on a hiding to nothing with seals now – maybe a new cylinder is the answer?)

I’ve just wrestled it back on the car and now find that operation is fairly progressive in terms of feel but still very ‘soft’ for the first inch or so … but the bite point is still happening only about ¾” off the floor, which seems far too low to me.

Given that I clearly had a hydraulic problem (couldn’t engage gear after leaving it standing for several weeks and re-bleeding changed that), I’m at a bit of a loss to know what to do now. I don’t really want to risk using it and end up getting stranded but I’m now not sure whether it’s actually ok as it is.

Equally, I don’t want to shell out on a new cylinder only to find that it’s the same … and very much likewise for a clutch! (The cylinder I can just about manage but there’s no way I can do the clutch itself … with my joint problems, without a proper ramp and having to work outdoors at this time of year in an area that often ends up with large puddles of standing water around the place or, at best until next summer, muddy water squirting up between the flags as you move around on them.)

Btw, this is on a B200E which, I gather, has a 216mm clutch, vs 229mm on all the others, so I’m wondering whether the lightness (compared with my cousin’s B230E, which is much stiffer) is normal after all (*) … but that still leaves the ‘soft’ first inch and the low bite point to puzzle over.
(*) Having said that, I notice that all suppliers now seem to list only the 229mm version even for the B200E, so I might already have one that size anyway without knowing - though I see from the Classic Swede site that it suggests that I'd need to replace the flywheel with a dished one (presumably from the B230E) to accommodate that - but the catcar.info parts website lists 1317359 as the flywheel for both B200E and B230E, so now I have no idea what's in there or whether I already have what's required!

Perhaps Martin’s solution and a new clutch is the answer but it all seems suspiciously coincidental that I’ve had both hydraulic *and* mechanical clutch problems simultaneously.

Also, having re-read Tony's reply about the 'worn slot' in the plastic parts, I now see what that meant and have checked. There's less than ¼" of upward travel when lifted so I don't think that's the problem here.

Any suggestions?

[TonyS9]

Good you figured out and checked the plastic stuff.

On the clutch plate, I wasn't aware the 700/900 used a 216m plate, but I can confirm that the 360 B200E/K uses a 210mm disk with a 229m dogdish flywheel. Both use the m46M47 gearbox, but different splines, and a different bell housing.

Although its worth noting a 360 B200E is slightly different to a 700 B200E.

The turbo with M46 uses a 229mm friction disk and a higher pressure cover plate. The turbo cover plate fits in the 360 although you need to trim it a tiny bit.

So you can fit whatever clutch you want if you have some different requirements.

[eeedelli]

Thanks for the reply Tony. It’s all been a bit difficult to know what to do, with so many variants and combinations that might be in there etc!

However, in the meantime, there has been some progress which I was just about to post up.

My cousin came down and we decided to re-bleed the system. Despite having used a pressure bleeder, he surmised that a constant but *relatively* slow flow rate during bleeding might still have left some air in the long horizontal pipe that goes up and over the top of the bulkhead (firewall) before dropping down to the slave cylinder. (Remember I’m RHD here!)

He was right! Another bleed with the pressure bleeder but combined with multiple rapid flooring strokes of the pedal expelled some more air! The result is that the floppiness of the first inch or so disappeared. Hurrah!

However, the bite point still starts about ¾-1” above the floor. That led us to compare it with his (albeit a B230E/M46). On full pedal throw, his slave cylinder stroke is about 25mm (~1”) whereas mine is 17mm (<¾”). We concluded that there are only two possibilities for this difference. (1) The finger springs in the clutch have weakened and are not pushing the slave fully back or (2) I’ve previously accidentally fitted a larger diameter slave cyl when I last replaced it a few years ago and hadn’t noticed the low bite point … but had noticed the recent onset of floppiness at the top, which drew my attention to the rapidly failing seals again… and then then to the low bite point when I started to look at the problem.

As the ‘at rest’ distance of the fork to the slave cyl bracket is the same on both, option 1 seems unlikely (though with it effectively being’ self-adjusting’, that’s not guaranteed), so that leaves option 2 as probably the more likely one.

Since the rest position is the same, the displacement must be entirely down to the relative volumes of the master and slave cylinder. If I were to fit a smaller (i.e. probably correct) diameter slave, the stroke length would increase, so the bite point would be higher up on the pedal. I’m almost certain I got the 22.2mm version when I last had to change it. The chances are that I should have got the 20.64mm version. Working out the volume displacement suggests that this would increase the stroke to about 20mm – not quite as far as his but going in the right direction. I haven’t measured the pedal to pivot and pivot to master cyl pin distances but I would hazard a guess that it’s about a 12 to 1 ratio, so the extra 3mm stroke would mean that the start of the biting point would be around 36mm (~1½”) higher than it is now, meaning it would be about 2¼-2½” above the floor, which is starting to sound more sensible.

To check that the replacement seals were ok, I wedged a plank of wood between the clutch pedal (when touching the floor) and the underside of the seat floor (600mm exactly), started the engine and checked I could engage 1st and reverse. I left it there for 15 mins, came back and did it again. No change. If the new seals (or the one-way valve) in the master cylinder had been leaking, the slave would have gradually returned and engagement would have been impossible.

The final check is for me now to leave it a few days and try it again and see that there’s no deterioration. If there isn’t I’ll start using it again tentatively and see how it goes!