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Discussion Starter · #1 ·
I’m getting some clutch drag on my my recently installed M41.

But it only happens when the engine is hot or has been running for a while.

All of the lines are all new, and were bled when installed.

I’m wondering if the soft line between the master and slave is getting hot and ballooning? i might replace it with steel braided line and see if it’s still an issue.

any other thoughts on what might be the issue? synchros on the way out?
 

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Clutch drag as in it shifts in to first just fine when cold; but, balks or grinds when going into first when hot?

When cold, the viscosity of the oil in the transmission and the grease on the input shaft can create enough drag that a slightly dragging clutch will not spin the input shaft (leading to balking / grinding going into first gear). Once things warm up the viscosity of the lubricants is reduced and the drag reduces which makes it easier to spin the input shaft leading to your problems. That is why you may have the 'only when hot' problem. It only takes a slight amount of drag to create this problem.

If so, when hot check to make sure that you are getting the correct throw on the fork where it contacts the slave cylinder. That would indicate whether the problem is on the hydraulics side or inside the bell housing somewhere. I don't have the specs for the Amazon throw so you may have to dig for that info.

If you have a hydraulic operating mechanism I think that means an earlier B18??? I am not familiar with the clutch fork arrangement. If the fork is similar to the fork on the 140 the fork can suffer a number of problems which lead to release problems. The early 140 forks were known to develop small cracks in the arm leading to flexing and lost motion. The pins on the fork that engage the throw out bearing can wear leading to lost motion and the ball / pivot point for the fork can wear also leading to lost motion. There is also the possibility that the fork is bent which can lead to lost motion.

If you did work on the clutch, make sure that you got the correct release bearing. There are Sachs and a Borg & Beck clutches and the release bearing are not compatible. I don't know how bad the non compatibility issue is (i.e. they wont fit in the friction disc or they just cause problems). I have never had the mix up; but, it might be something to check.

Did you replace the pilot bearing? Any chance the pilot bearing is dragging slightly or there is an alignment problem causing the bearing to drag? Again, a slight amount of drag at the pilot bearing could cause the balking to materialize once the transmission oil warms up.
 

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Discussion Starter · #3 ·
Thanks for the info!

About 6 months ago, I converted a BW35 to M41 + J-type OD, and all of the available parts were sourced new, anything old was inspected before installation. Its a Sachs clutch with the proper release bearing, and ball on the fork is new. The drag is a recent development, it gives a slight grind going into first or reverse when hot. I've adjusted the throw once (but with the engine cold), thinking that things might have "settled in" after the install. It sorted out the problem for a few weeks, but then the issue has started again, so it might be something else.
 

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I never had this problem on my 140 or 240; but, I did have what appears to be almost exactly the same problem on my 745 turbo which, in a world of coincidences, materialized after the clutch was replaced. As soon as the clutch / transmission got hot it would sometimes become exceedingly hard to shift into first gear at a stop. The severity of the problem was highly variable. Sometimes just a tiny balk / grind and sometimes a complete block going into first.

Replaced the master and slave and bled a number of times. Sometimes seemed to help and then sometimes no improvement at all. The transmission was off twice to inspect for problems on the input shaft, clutch release bearing, pilot bearing, fork - nothing was ever found. One mechanic suggest a possible weird alignment problem with the pilot bearing causing it to drag; but, there were never any odd noises. Finally sold the car and I told the buyer that it had 'sometime' issues shifting into 1st; but, on the test drive it shifted normally for a vehicle with around 200,000 km on it.

Just about all clutches seem to have a tiny amount of drag. If the drag is not so tiny and the first gear synchros are tired, then it becomes a bigger problem. You could try some Red Line MTL in the transmission to see if that helps improve the operation of the first gear synchros. I use Red Line MTL in my M41 and it shifts smoothly although I have minimal to no drag on the clutch because I have no recollection of ever getting a grind going into reverse (it will block sometimes; but, no grinding).

I assume the M41 is 'new to you'. Were the internals inspected or do you have any knowledge of how it operated prior to being installed in the Amazon?
 

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Thanks for the info!

About 6 months ago, I converted a BW35 to M41 + J-type OD, and all of the available parts were sourced new, anything old was inspected before installation. Its a Sachs clutch with the proper release bearing, and ball on the fork is new. The drag is a recent development, it gives a slight grind going into first or reverse when hot. I've adjusted the throw once (but with the engine cold), thinking that things might have "settled in" after the install. It sorted out the problem for a few weeks, but then the issue has started again, so it might be something else.
I don't know anything about your M41 but with my Porsche 356 a slight grind going into reverse indicated the clutch was not fully disengaged. I adjusted the cable and like you it was good for a few weeks and then started again. Found out the cable was starting to break and kept getting longer. Replaced the cable and all was good.Who knows?
 

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Discussion Starter · #6 ·
Just to clarify, this is the earlier hydraulic system, so no cables.

I've had a brake hose on a motorcycle get too hot and balloon under pressure, reducing the line pressure. While its a possibility here, I think it is unlikely.
 

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How old are your master and slave cylinders? Could one (or both) be bypassing when hot?
 

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Just to clarify, this is the earlier hydraulic system, so no cables.

I've had a brake hose on a motorcycle get too hot and balloon under pressure, reducing the line pressure. While its a possibility here, I think it is unlikely.
Thanks :thumbup:
 

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Just to clarify, this is the earlier hydraulic system, so no cables.

I've had a brake hose on a motorcycle get too hot and balloon under pressure, reducing the line pressure. While its a possibility here, I think it is unlikely.
The hydraulic pressure in the clutch system is much, much lower than the pressures in the brake system so hose distortion is unlikely unless it is in really bad shape or really cheap. The ultimate confirmation would be to check the throw at the slave cylinder under hot and cold conditions. If the throw does not change then your hot / cold problem does not originate in the hydraulics.
 

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35;

Following with interest...not too much to add, but I agree with good info by 142G: Compare adjustment and action of Throw-out Rod at cold and hot!

Good Hunting
 

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Discussion Starter · #11 ·
Both the master and slave are brand new from VP.

I'll check the throw both hot and cold and see if there is a difference.
 

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35;

...now I have something to add...! Are those replacement master and slave cylinders made by Girling? Be aware, brand new inexpensive, (so mighty tempting to replace the old and "be done with it") hydraulic components, being china **** counterfeit knock-offs, have been known to have weird (and any number of) problems, including possibly being the source of your symptoms...so when you run out of things to check, try some troubleshooting by substitution...reinstall old master and slave, one at a time, and see if symptom remain or change...

Good Hunting
 

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Discussion Starter · #13 ·
a quick follow up:

I should have mentioned that I'm running a Willlwood clutch master, Wilwood slave and Willwood pedal setup.

I double and triple checked the thorw... everything measured up fine. But the clutch grab was pretty low on the pedal action (i prefer it pretty low), so i backed that out a bit and it solved the problem.

My guess is that after things broke in, i was *right* at the point where the clutch would release fine when cold, but when everything warmed up, there was some bite on the clutch.
 

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Yeah if engagement is right off the floor, you're at the ragged edge of dragging. Ideally it's just a bit off the floor. High is the opposite problem.

Glad you got it worked out, and thanks for posting the followup.
 
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