Been to two shops and no luck, this is my last option

[Skatike27]

Year-1994
Engine- 4.0 v6
Trans-Mazda M5OD-R1
Drivetrain- 4x4
Transfer case-manual

Heres the deal. Truck began shifting hard. I had not replaced the fluid since I bought the truck in the transmission.

So I replaced it with Valvoline Multipurpose ATF, it stated that it meets the Mercon specs needed for the transmission.

This helped the shifting when cold or when going for short drives.

Went for a 150 mile drive that required no shifting or stopping, the truck stayed in overdrive the entire 150 mile stretch. When I left the highway and was on the off ramp I put the truck in neutral and coasted to the stop light. The light turned green, I clutched to the floor and hit a "wall" as I tried to put it into first, then hit a "wall" as I tried 2nd, 3rd, 4th, OD. I wound up shutting off the truck and pushing it hard into gear with the clutch depressed, then starting the truck up.

Now, I got home and immediately checked my transmission level. It was just fine, I checked my transfer case and that was just fine also.

So I took it for a drive and it drove fine and shifted nice and smooth.

So I have been driving it 6 short low speed miles to work and back everyday this last week. No problems shifts great. So I got curious. I went for a drive and beat on it. Getting the motor and trans up in the Rpms and getting the transmission hot, immediately the "wall" came back. I once again checked all the fluids and they were fine.

I did notice this though. When i was in the garage, transmission hot, transmission in first gear (by the way the truck will shift into all gears when the motor is off and clutch pushed in, no problems) and then started the truck. When I let the clutch out, so from the floor, I only had to let it out about a 1/4 of the way to get full engagement of the clutch. When normally or when cold, i have to let it out till about half to get it to engage.

The next thing i did was crawl under the truck and pull the viewing window off and look at the slave cylinder in action. With the truck off, I had a friend push the clutch in to the floor and watched the slave cylinder, If I had to say the distance it traveled I would guess a 1/2" and thats all. This seemed like a low amount of travel to me.

The clutch fluid reservoir stays full and does not empty, therefore this leads me to believe that there is not a leak in the system. Unless, there is an internal seal that has gone bad. I was thinking of bleeding the system just for the heck of it to see if that made a difference but have not had the time.

The main factor to remember in all of this is that this problem is time and heat sensitive.

Now to this date, I have taken it to two dealerships, with the trans warm to have them do a "diagnostic test" needless to say, $500 later, none of them were able to "safely" say what the problem is.

I am a college student and can not afford to just have someone taking things apart till they find the problem, so I am coming to you all. Hopefully someone has had this problem or knows what is going wrong.

Thank you all,
Thomas

[wakingtowinter]

Based on the fact that you're finding it hard to put into gear - feels like pushing against "a wall", and the fact that you say there is little clutch travel, I would guess you have air in the clutch hydraulic system somewhere. And probably a leak. Here's what I would do:

1. check your clutch fluid reservoir. Is it empty?
2. If it is, try filling the reservoir and bleeding the clutch system.
3. Try to locate the leak - there are only three possibilities: slave cylinder, master cylinder or hydraulic hard line connecting the two. Take a look in the inspection port again and see if you can see or feel any brake fluid in there. Also take a look at the coupling where the line goes into the slave and see if there is brake fluid leaking there. I think the best time to check this would be after bleeding and driving the vehicle around a bit. But if I had to bet on it, I'd say the slave cylinder is going bad. That seems to be the most common failure. Good luck!

[Skatike27]

The clutch fluid reservoir is full and does not empty, therefore this leads me to believe that there is not a leak in the system. Unless, there is an internal seal that has gone bad.

I was thinking of bleeding the system just for the heck of it to see if that made a difference but have not had the time.

The main factor to remember in all of this is that this problem is time and heat sensitive.

Thanks for your input,
Thomas.

[cavedweller]

Could the slave be the culpret here ?

[alwaysFlOoReD]

Just a guess;
Moisture/air in your fluid; as it heats up, the air expands, creating a "soft' pedal. Bleed out/replace the fluid in your system and I bet the problem goes away.

Richard

[pcollins]

Just because you cant see the fluid loss, doesn't mean it isn't leaking. My slave did have an internal seal go bad where it didn't lose enough fluid to SEE, but it made a problem for sure.

[Skatike27]

Both alwaysFlOored and pcollins good guesses.

I was wondering if the fluid was just old and worn out. I'm not sure if the fluid can technically "go bad" but it was a thought that crossed my mind. I'm not sure how air or moisture could have all of a sudden gotten into the line to cause it to fail either but I think I will attempt to bleed the line tonight.

I was honestly wondering if the slave or master was failing with an internal leak. Any thoughts on how I could do a test in my garage?

Thank you all for your help so far,
Thomas

[gribly]

Piston blowby. Either the master cylinder or the slave cylinder. I'd replace the master first, since it's easier to get to. The dealers that looked at it fail at diagnostics, sorry.

[4x4junkie]

I suspect there's a little bit of air in the system. I would certainly try bleeding it before doing anything else (might take some forceful action to expel any air that lodges at the top of the MC near where the hydraulic hose connects).

[schmoo]

i know i am going to get yelled at again for this,
but i'll try again.
bleeding is not a normal part of the maintenance
for this system. air getting into the slave IS normal.
the air is supposed to go out the line and vent from
the master cylinder. in order for that to happen,
there has to be enough fluid moving back and forth
to keep the air purged. if your master cylinder is
bad, or the clutch pedal is bent, you don't get
enough fluid movement. on mine, i straightened
the pedal by twisting it clockwise (looking
from bottom) and put a dimple in the floor where
the pedal hits to give more stroke. that was 8 years
ago, and it still works fine.

[Skatike27]

It appears as though the problem has been fixed... I bled the clutch lines last night, had some black fluid come out. Ran out all that black fluid out and put in new clean golden dot 3 brake fluid. Appears to have helped, got the transmission hot and had no problem shifting. I'm going on a road trip this weekend so we will see what happens. I will report back Monday.

Thanks again for all the input.
Thomas

[4x4junkie]

Originally Posted by schmoo

i know i am going to get yelled at again for this,
but i'll try again.
bleeding is not a normal part of the maintenance
for this system. air getting into the slave IS normal.
the air is supposed to go out the line and vent from
the master cylinder. in order for that to happen,
there has to be enough fluid moving back and forth
to keep the air purged. if your master cylinder is
bad, or the clutch pedal is bent, you don't get
enough fluid movement. on mine, i straightened
the pedal by twisting it clockwise (looking
from bottom) and put a dimple in the floor where
the pedal hits to give more stroke. that was 8 years
ago, and it still works fine.

Can you explain how air would enter the slave, and if the air is supposed to vent out the master like you say (up through the reservoir?) how is that air then supposed to get out past the sealed diaphragm that is inside the reservoir?