How Flush Clutch Fluid?

[SubLGT]

Is a "gravity flush" an acceptable way to flush old fluid from the reservoir and clutch slave cylinder? As long as I don't allow the reservoir to run dry, I can't see a problem with it.

The service manual recommends the two person method, with one person under the car at the bleeder screw, and another person at the pedal, very similar to manual flushing/bleeding of brakes (i.e. push on pedal--open and close bleeder--release pedal)

 

[demarpaint]

A gravity flush is how I do my Ford van slave cylinder. I over fill it and open the bleeder just a bit, then come out from under it and keep pouring brake fluid in. Toward the end I'll over fill it, crawl under and tighten the bleeder. Then extract any extra to get it to the full mark. I'll run a pint through it once every two years. If my wife is around when I crawl back under she'll tell me when it's at the full mark and I'll tighten the bleeder.

As you said, don't let it run dry!

 

[Tosh]

Suck the reservoir dry first and refill it; no sense pulling dirty fluid through.
I always use the helper method as there's way more agitation/turbulence/flushing action when pushing the pedal.

 

[demarpaint]

Originally Posted By: Tosh
Suck the reservoir dry first and refill it; no sense pulling dirty fluid through.
I always use the helper method as there's way more agitation/turbulence/flushing action when pushing the pedal.


My resistor holds less than two ounces of fluid, so I don't usually bother. When I remove the rubber cup under the cap there's very little fluid in there.

 

[DoubleWasp]

I can tell you from a lot of experience that there are some clutch systems that will not blues without doing the pedal-pressure method.

Don't know exactly why, but I've seen people go through a 32 Oz. bottle trying to gravity bleed, only to fail until the pedal method was used.

 

[demarpaint]

Originally Posted By: DoubleWasp
I can tell you from a lot of experience that there are some clutch systems that will not blues without doing the pedal-pressure method.

Don't know exactly why, but I've seen people go through a 32 Oz. bottle trying to gravity bleed, only to fail until the pedal method was used.


I guess it depends on the slave cylinder and clutch setup itself then. I heard some had to be reverse bled. Not the case with my Ford. I don't see why if no air gets into the system why gravity bleeding it to refresh the fluid would be a problem. But I could be learning something new today.

 

[Kawiguy454]

this is why a good method is to gravity bleed using a clear tubing from bleeder into a soda bottle with the end submerged. you can pump the pedal without drawing air back into the system.

 

[skyactiv]

Do yourself a huge favor and buy a speed bleeder. It will be under $15 shipped. You can use a Mitivac vacuum pump but it will still be a PITA.

 

[skyactiv]

https://www.rallysportdirect.com/part/br...CFYc1aQodoewJ_A

 

[69GTX]

I just use the 1 man "Ranger" method. When I first bought by manual transmission 1999 the clutch fluid was a little dark. It could have been the original fluid and 13 yrs old. I "rangered" about half an 8 oz bottle of brake fluid through it and it cleaned up perfectly. It never turned dark again. Now I do this annually just to keep it fresh. For those that race their cars often, they may need to clean up the fluid quite frequently.

The Ranger Protocol

 

[andyd]

The old BMWs, you unbolted the slave and pumped on the push rod. Bugs and 3 on the trees used mechanical linkage that was adjustable. Gravity bleed should work fine in a working system.

 

[demarpaint]

Originally Posted By: 69GTX
I just use the 1 man "Ranger" method. When I first bought by manual transmission 1999 the clutch fluid was a little dark. It could have been the original fluid and 13 yrs old. I "rangered" about half an 8 oz bottle of brake fluid through it and it cleaned up perfectly. It never turned dark again. Now I do this annually just to keep it fresh. For those that race their cars often, they may need to clean up the fluid quite frequently.

The Ranger Protocol


I'm going to give it a try on my van. I like the idea of not having to crawl under it and open the bleeder.

 

[DoubleWasp]

Originally Posted By: demarpaint

I guess it depends on the slave cylinder and clutch setup itself then. I heard some had to be reverse bled. Not the case with my Ford. I don't see why if no air gets into the system why gravity bleeding it to refresh the fluid would be a problem. But I could be learning something new today.



Gravity bleeding to refresh should be no issue. But if the system is opened, it can get crazy.

 

[demarpaint]

Originally Posted By: DoubleWasp
Originally Posted By: demarpaint

I guess it depends on the slave cylinder and clutch setup itself then. I heard some had to be reverse bled. Not the case with my Ford. I don't see why if no air gets into the system why gravity bleeding it to refresh the fluid would be a problem. But I could be learning something new today.



Gravity bleeding to refresh should be no issue. But if the system is opened, it can get crazy.


Absolutely!

What do you think of the Ranger method? I like the simplicity and the fact that I don't have to open the bleeder. I just can't wrap my head around how by not opening the bleeder all the old fluid and junk is going to come out. Gravity bleeding has worked for me for over 3 decades now, but I'm always up to a new and easier way.

 

[SHOZ]

My slave is on the Gen Coupe is a stupid design. It's a concentric slave so it sits in front of the clutch. Only one pipe in with the bleeder about 8 inches before the slave. I can't get all the air out or the slave itself is defective or or the clutch disc is mismatched to the slave.

Tried vacuum bleeding along with the ten pumps, hold the pedal down and then open the bleeder.

Gravity bleed on it would just drain the master cylinder.

 

[bdcardinal]

There is no bleeder on the Mustang. You fill the reservoir, brake master in my case, and pump the clutch pedal a billion or so times to bleed it. I am going to divorce the reservoir with a 04 GTO one and I might get a McLeod clutch line with a bleeder valve.

 

[SubLGT]

Originally Posted By: 69GTX
I just use the 1 man "Ranger" method. When I first bought by manual transmission 1999 the clutch fluid was a little dark. It could have been the original fluid and 13 yrs old. I "rangered" about half an 8 oz bottle of brake fluid through it and it cleaned up perfectly. It never turned dark again. Now I do this annually just to keep it fresh...


I have used a similar method once a year for my power steering fluid, but I did not think it would work with clutch fluid since there is no pump circulating the fluid.

 

[69GTX]

Originally Posted By: SubLGT
Originally Posted By: 69GTX
I just use the 1 man "Ranger" method. When I first bought by manual transmission 1999 the clutch fluid was a little dark. It could have been the original fluid and 13 yrs old. I "rangered" about half an 8 oz bottle of brake fluid through it and it cleaned up perfectly. It never turned dark again. Now I do this annually just to keep it fresh...


I have used a similar method once a year for my power steering fluid, but I did not think it would work with clutch fluid since there is no pump circulating the fluid.


The "pumps" are the hydraulic cylinders in the system pushing the fluid around on each cycle of the clutch pedal. It's nowhere near the size of a car's brake system either, just a single circuit only a few feet long. I doubt the entire system holds more than 4-8 oz of fluid. The Ranger guy recommends about 30 clutch pedal pumps for every reservoir change. Don't believe me then. I've been doing it for 4 years and the first time it cleaned up the dirty fluid within 2 refills....or 15 minutes. The Ranger guy is a Corvette racer with tons of passes down the strip every season. Don't believe him either even though it's shown to work on his video. I spend no more than 30 minutes per year doing this. And I do it with my power steering fluid as well.

Ranger's website - he's held some class speed records along the way

 

[69GTX]

Additional Ranger method info not on the video including how clutch fluid circulates

 

[DoubleWasp]

Originally Posted By: demarpaint
Originally Posted By: DoubleWasp
Originally Posted By: demarpaint

I guess it depends on the slave cylinder and clutch setup itself then. I heard some had to be reverse bled. Not the case with my Ford. I don't see why if no air gets into the system why gravity bleeding it to refresh the fluid would be a problem. But I could be learning something new today.



Gravity bleeding to refresh should be no issue. But if the system is opened, it can get crazy.


Absolutely!

What do you think of the Ranger method? I like the simplicity and the fact that I don't have to open the bleeder. I just can't wrap my head around how by not opening the bleeder all the old fluid and junk is going to come out. Gravity bleeding has worked for me for over 3 decades now, but I'm always up to a new and easier way.


It looks really good to me. I think I'm going to try that on the next truck clutch that comes up, and then Crack the bleeder to see if it really was able to exchange all of the fluid.