A real noggin scratcher...

[Morris]

On my way home from work yesterday in stop and go traffic, I said to myself, "Wow. This car is really running and driving well. I think I am getting close to having it dialed in. It's getting good mileage, making good power and running smoothly. Everything is nice and tight, too. Especially the clutch."

45 seconds later the clutch went out. Or rather, the clutch pedal started getting closer and closer to the floor before engaging the clutch. When I had no more clutch at all, I ground it into second, took the first available exit, and found a safe place to park. After making a few calls to let people know I was going to be late, I inspected the car. Granted, the thoroughness of inspection I can execute in a parking lot is limited, but I could find no signs of leaking brake fluid. All the parts and pieces where were they should be, and the reservoir on my brand new master was full of fluid. The fluid, which was completely replaced a few months ago was rather brown. Other than that, I could not find anything unusual. I hoped back into the car, pumped the pedal about ten times and got full pressure back. I drove the car around for the rest of the evening without issue.

Any idea what the heck happened?

 

[smaceng]

I think you will find that a more closer examination will find that either the new clutch master cylinder is leaking around the piston, or the slave cylinder is leaking. 95% of the time, it is one of the above. Why this happens so often in British cars I do not know. I have never replaced a slave or a clutch master in a Japanese car.
Scott in CA

 

[JPSmit]

On my way home from work yesterday in stop and go traffic, I said to myself, "Wow. This car is really running and driving well. I think I am getting close to having it dialed in. It's getting good mileage, making good power and running smoothly. Everything is nice and tight, too. Especially the clutch."



Any idea what the heck happened?

Yes, I know exactly what happened, you thought the above thought! Right up there with "Gee the traffic seems light today, I think I'll be early." and "I'm sure the officer didn't notice." (which I myself accidently thought earlier this week )

Happy thoughts work at Disney and in Neverland but for LBC's the only option is grumpy dangerous thoughts like "Gee, this car is running like cr*p today." or "Is that a misfire?" or "I think the brakes are getting soft." Then and only then will you be able to reliably drive your car and hate every minute of it the way the manufacturer intended.

sheesh. :madder:

 

[Deleted member 8987]

If the fluid is at the same general height, you can usually rule out the slave. When the slave goes, fluid leaks past the seal, and it goes out on the ground, refilling the master from the reservoir each pump of the pedal, dropping the reservoir level.
The "rather brown" comment is bothersome...not worrisome, just bothersome. You didn't mix fluid types, did you?

 

[RyanBez]

I notice you are in Austin, any chance the fluid started to boil? Hot day in stop and go, just a thought. Explains why letting it sit for a bit and it fixed itself.

 

[Morris]

I did not mix fluid types.

I was wondering if the issue might be boiling fluid. However, I have been through much worse traffic and heat without experiencing clutch troubles. The exhaust pipe does pass near the slave... perhaps that played part?

 

[Billm]

Slit some plastic tubing (1/2" or so) and slide it over the clutch line. See if it helps.
BillM

 

[Westfield_XI]

On my way home from work yesterday in stop and go traffic, I said to myself, "Wow. This car is really running and driving well. I think I am getting close to having it dialed in. It's getting good mileage, making good power and running smoothly. Everything is nice and tight, too. Especially the clutch."



Any idea what the heck happened?

Yes, I know exactly what happened, you thought the above thought! Right up there with "Gee the traffic seems light today, I think I'll be early." and "I'm sure the officer didn't notice." (which I myself accidently thought earlier this week )

Happy thoughts work at Disney and in Neverland but for LBC's the only option is grumpy dangerous thoughts like "Gee, this car is running like cr*p today." or "Is that a misfire?" or "I think the brakes are getting soft." Then and only then will you be able to reliably drive your car and hate every minute of it the way the manufacturer intended.

sheesh. :madder:

I wonder why a man who owns an MG, a Vauxhall and a Fiat would have an attitude like that?

 

[JPSmit]

On my way home from work yesterday in stop and go traffic, I said to myself, "Wow. This car is really running and driving well. I think I am getting close to having it dialed in. It's getting good mileage, making good power and running smoothly. Everything is nice and tight, too. Especially the clutch."



Any idea what the heck happened?

Yes, I know exactly what happened, you thought the above thought! Right up there with "Gee the traffic seems light today, I think I'll be early." and "I'm sure the officer didn't notice." (which I myself accidently thought earlier this week )

Happy thoughts work at Disney and in Neverland but for LBC's the only option is grumpy dangerous thoughts like "Gee, this car is running like cr*p today." or "Is that a misfire?" or "I think the brakes are getting soft." Then and only then will you be able to reliably drive your car and hate every minute of it the way the manufacturer intended.

sheesh. :madder:

I wonder why a man who owns an MG, a Vauxhall and a Fiat would have an attitude like that?

 

[bug_sixty]

huh maybe bleeding issue somewhere..air pocket that worked its way through

 

[RyanBez]

huh maybe bleeding issue somewhere..air pocket that worked its way through

If it was an airpocket it wouldn't disappear unless there is a leak which I think you find. Do you have a single or twin M/C the air pocket could be switching between brakes and clutch possibly? But I wouldn't think air pocket imo.

 

[Deleted member 8987]

What year and what engine?
Any chance the exhaust is close to the slave or the pipe to the slave? The only time in my life I have ever had hydraulic clutch issues was on a logging road, slow grind, and the exhaust heated the slave, boiled the fluid. Depending on the layout of the feed pipe, air runs uphill, so any air bubbles could have migrated back to the master and vented in the reservoir.
Just a thought.

 

[Morris]

It's a 1500. Typically when air bubbles get in the clutch line it takes an act of congress to get them out. But I guess anything is possible.

 

[Deleted member 8987]

Okay, on a 1500, does your exhaust go straight back or cross under near the bell housing?
Is the exhaust close the the slave at any point?

 

[RyanBez]

I did not mix fluid types.

I was wondering if the issue might be boiling fluid. However, I have been through much worse traffic and heat without experiencing clutch troubles. The exhaust pipe does pass near the slave... perhaps that played part?

Looks like it does. Seems like a logical explanation.

 

[regularman]

In those situations you have to learn the quick pump of the clutch pedal to get it in gear just to get you home. If you shift at the right rpm you can do without the clutch.

 

[Guest]

Morris, new m/c is bad. No way you boiled fluid. Mine gets hotter than yours and it's never happened. Change the m/c and blow out lines and s/c.

Do final bled by removing s/c, point bleeder up, open and compress slave. Close bled before release and repeat. once you have no more air comming out, compress slave w/ bleeder shut for final purge of any air through line and out into res.

 

[racingenglishcars]

I think you will find that a more closer examination will find that either the new clutch master cylinder is leaking around the piston, or the slave cylinder is leaking. 95% of the time, it is one of the above. Why this happens so often in British cars I do not know. I have never replaced a slave or a clutch master in a Japanese car.
Scott in CA

Funny thing about that. I have been wondering for the last 25 years when I will have to change the slave cylinder in my Land Rover. I did actually change it once back in the early 80's