Clutch bleeding

[eejay56]

Does anyone have any tips or tricks for bleeding the clutch on a late Spitfire? Mine seems to not be fully disengaging, I thought I got it when I reassembled everything but apparently not. The master cylinder is rebuilt and slave is new as is the clutch.

 

[sp53]

In the 70’s and In another lifetime full of toil and bluff, I owned a 71 spitfire and had a similar problem. The popular opinion was that the clutch rod was to short, so they actually had this little piece you could put on the rod or just drive it for a couple of hundred miles until the new surface of the clutch wore down. I know it sounds strange and perhaps some member will tell me that my experience is not true. However, what I did was drive the thing for a week and it got better. I guess a guy could make an adjusting rod also.

 

[eejay56]

I've got over a thousand miles since the rebuild and it's getting worse not better.

 

[IanF]

When we did the trans swap in Robyn's car, I had a heck of a time getting the clutch to feel right. Would grab very low in the travel if it would disengage at all. I must have tried bleeding it a 1/2 dozen times.

It turned out to be air in the line/slave after all. I got it out by removing the slave from the bell housing, angling it down slightly so the bleeder screw was the absolute highest point and then bleeding again. Fortunately, a one-person job with the trans cover removed. There was one last bubble of air and it's been fine ever since.

 

[eejay56]

That's not what I wanted to hear Ian. I wanted someone to say "Oh, don't you know about the secret way to get to it and get all the air out without pulling the tranny tunnel." I guess if I gotta, I gotta. Pulling the slave to tilt it up sounds like a good trick though, I'll try it. By the way did you ever get that dash made? Don't bother sending those pieces back. Piece O' Spit had one with good wood.

 

[emmett1010]

Hello:
I've never had any luck rebuilding hydraulics.
If, and thats a big if--you hone ALL the pitting out, the bore is qite a bit larger--
These systems have no margin for error--
Try a new master,
good luck, Emmett

 

[TR4]

I too had to remove the slave from its bracket to bleed all the air out. I used the EZ Bleed system so was an easy one man job. I believe all of the Big 3 carry it. Sells for around $15 if I remember correctly. Worth the cash IMO.

 

[Guest]

The way I've always done Spits and Midgets was to go buy a cheap oil squirt can... fill with brake fluid..... affix a hose to the end of the can nozzle, and the other end to the slave bleed screw (opened of course!) Then, I pump fluid backwards up through the sysetem vigorously. I still had to pump the pedal enthusiastically and repeat several times, but it always worked. ... Sherman Bird.. owner Avian Automotive, ASE Master Certified, L-1 Advanced Engine Performance Specialist.... 33 years professional experience.

 

[Adrio]

I had a similar problem with my TR4. I repeated the bleed thing a few times and even just opened the bleed screw and let the fluid flow for a bit while pouring some in the top. In the end the bubble finally got out.

I like the idea of moving the slave to but the nipple at the high spot. I wonder if you could do the same on a very steep hill without having to remove your tunnel?

 

[IanF]

I did try bleeding with the rear of the car on stands and the front wheels on the floor, but that didn't seem to help. Maybe you'll have better luck?

To be honest, I can't imagine trying to bleed the slave with the tunnel cover <span style="font-style: italic">on</span>... wow... can barely see the thing from underneath... :crazy:

Unfortunately, I haven't made much progress with the dash panels. The first attempt failed (crap plywood) and then it became too much of a rush to get the car finished. I definitely want to make something especially now with two cars... boy is that turn signal light location annoying...

 

[gjh2007]

If you don't have a MityVac, get one, they have all kind of uses. Great for bleeding any hydraulics, or flushing the fluid in your brake system. Can also be used for pressurising cooling systems to check for leaks, or checking vaccum system... or...

https://www.mityvac.com/

 

[eejay56]

OK all the air is out(thanks Ian) and I'm still having problems. It's as if like sp53 said the clutch rod is too short. Here is my stupid question that shows my poor observation skills, I've been driving this car for 2 years and should know but shouldn't the clutch go to the floor? It goes about halfway and stops solid no mushiness at all. If I push the slave piston all the way back in the cylinder the pedal goes all the way to the floor but when it's all put together the piston hits the stop at the end before the clutch is fully engaged.

 

[Adrio]

This is way out there so please don't be offended. Could the slave be mounted on the wrong side of the flange. I can't remember which side it should be on but if the "wrong" side is such that it moves the slave farther from the lever then it would have the same result as the rod being too short.

 

[sp53]

Well now it is starting to sound like you have the clutch disc in backwards. ( do not ask how I know) When you put the disc in did you make sure the flat side of the disc is facing the flywheel? Because if you did not, there is a small collar that will hit the plate before the disc. Does the clutch work at all or are you double clutching this thing every time you shift?

 

[Mark Jones]

It could be that the hole in the push rod has become elongated and the push rod pin has a grove in it, which is not allowing the clutch to fully disengage. I had the situation where the clutch was not being fully disengage; the car would creep forward if I took my foot of the brake. I did find both the push road and the pin worn and by replacing these pieces the clutch now fully diengages.

 

[eejay56]

Here is the complete history. My tranny has been crunchy in first for a long time but that was a syncro problem not clutch. I rebuilt the master and slave cylinders a year ago. No problem. This spring when I rebuilt the engine I replaced clutch plate, pressure plate, and bearing (AP Driveline BPNW part no. KT8917) The first day I got it running the clutch pedal wore though at the pin to the master. I replaced it with a used one that has some wear at the hole but it's shimmed and there is no slop there.I have almost 3000 miles since then with no problem. gradually the clutch has gotten worse until now it never fully disengages. It creeps with the clutch in and dies if I stop in gear. Double clutching is required. The pedal is firm not mushy and stops solid a couple of inches from the floor. I've pulled both cylinders and cleaned them and examined the bores. With the slave out I can push the cylinder all the way back and the pedal goes to the floor so there is not a problem with the linkage. Last weekend I pulled the tranny to see if I could see a problem with the clutch. While it was out I replaced it with my spare tranny swapping the clutch release lever to keep my new bearing. It was OK for about 100 miles now is bad again. I don't think the clutch plate is in backwards. I guess I'll pull the tranny again this weekend and examine the clutch some more. I can move the clutch rod about 1 to 1 1/2 inches in and out.

 

[eejay56]

Someone on the Spitfire and GT6 Magazine forum is having a very similar issue and someone suggested a problem with the thrust washers. They were replaced in the rebuild and I can't move the pulley but I'll pull the oil pan first to check that before the transmission (it's a lot easier). It was 100 here yesterday and supposed to hit 100 today and tomorrow and my garage is full of my parts car so I have to work in my driveway

 

[eejay56]

It's fixed. The pin that holds the clutch lever rode up and out of the hole on the bottom so the lever was cockeyed.

 

[hilsideser]

Did you build a tent over the car for shade cover? Yikes!