Hello.
My car's clutch looses pressure when pushed to floor.
For example I can drive the car with quick gear switches but when clutch is on the floor for more than 3-4 seconds it sticks, although it does not happen every time. I have only encountered the problem with 1st, 2nd and reverse gears.
Clutch fluid reservoir has been full all the time. My mechanic changed the clutch fluid but it did not have any effects.
I do not have good knowledge of the hydraulic system but it seems that when this happens, the slave cylinder which moves the fork I assume, slowly comes back to it's idle position.
The question here is which part is faulty? Master cylinder, slave cylinder or something else?
Thanks for your answers.

Car model: Honda Accord
Year: 2000
Region: EU

 

Get under the dash and look at where the clutch pedal rod goes through the firewall. There should be a boot, if it is not wet, pull it back and see if there is any wetness on the firewall or inside the boot.
If there is wetness/fluid then the Clutch Master Cylinder is most likely leaking and will need to be replaced.

 

also pull back the boot at the slave cylinder and see if it's leaking there...if either is leaking it's best to replace both at the same time

 

Master cylinder's boot had some fluid (black colored old fluid) but not really much in my opinion and it is kinda hard to pull back. Slave cylinder's boot had really just dirt on it, I guess I should try it also when the clutch is on the floor.
I decided to try drive a little and pushing clutch and switching gears, for the first 5 minutes there were no problems. Then I heard "scratching" noise when the clutch pedal was fully pushed to floor. In my opinion the noise comes from the master cylinder or from that area.
I had heard that sound before, right after the fluid was changed and when it happens the clutch sticks.
So at the moment the clutch sticks when that scratching noise starts.
I'm on a tight budget here so I really would not like to start replacing too many parts

 

Scratching sound is the failed seal.
FWIW, when bleeding hydraulic systems, try to vacuum bleed the system rather than using the pedal to stroke(brake and clutch).
When the system is opened to bleed the pedal will travel further than normal, this pushes the piston past its normal throw. Normal area of usage will be smooth and polished from usage, there will be crud and corrosion past the normally traveled(polished) area. This will damage the seals on the piston and they will no longer seal, failing the MC.

 

They did vacuum bleed it. So most likely the seals on master cylinder are damaged. My mechanic said that it would be cheaper to just replace the part than try to replace the seals.
Master cylinder will be changed next Thursday so we will see then. Let's just hope it fixes the problems.
Thanks for your answers and I will update the situation after that.