Could someone measure a 1500 clutch slave pushrod?

[tdskip]

Hi guys - several MGC owners (include me) are struggling with clutch issues getting into reverse. Specifically through either wear or incorrect replacement parts (VB clutch slave cylinder specifically) the clutch is not disengaging and thus you get grinding.

It has been suggested that a Midget 1500 slave pushrod is longer than the MGC one and will provide the necessary travel.

Does anyone have one laying around they could measure? Please please please? Pretty please?

Thanks!

 

[tdskip]

Got them - presented here for sanity checking;

To cover all the bases:

1500: 3 1/4"
1275: 3"
948/1098: 2 1/2"

-Wayne

 

[dklawson]

How does the length of the pushrod affect clutch release if the setup is hydraulic? Are the MGC slave cylinders reaching the end of their travel because the rod is too short?

I anticipate that you can't meaningfully compare the 1500 parts to the A-series parts (Triumph vs BMC).

 

[tdskip]

Yes Doug, compensating for variance in replacement clutch slave and wear in system. Basically just need a bit more throw.

 

[Guest]

Yes Doug, compensating for variance in replacement clutch slave and wear in system. Basically just need a bit more throw.

Rod doesn't matter as slave will only travel so far. It's self adjusting. The only way a longer rod would make a difference is if it was worn so much it pushed the piston out the bore before it released.

Problem w/ the VB 1500 slave is bleeding due to the bleeder being off to the side and not the highest point. What I did on my replacement is take it loose. Point bleeder up to be the highest point. Open bleeder and push slave in w/ screwdriver and hold bottomed out while shutting the bleeder off. Release slave piston to draw in fresh fluid. Open bleeder and push piston back in slave. Do this a few time and when you think you have it, then push the slave in w/ the bleeder closed and that'll back flush any bubble that may be left in the top side out into the m/s res. Leave it pressed in for a monet to let bubble float up before you release SLOWLY so you don't suck the bubbles you just blew out back in.

Worked for me. Thank goodness the Midget slave has more volume than the whole system or you wouldn't be able to do it this way.

 

[tdskip]

Good tip on the bleeder location, easy enough to unbolt it for this.

 

[Guest]

I have a stainless line on mine and it's a pain to move it to the right position. if your master ran dry you'll need to bench bleed it. i got around that by raising the front of the car up on the lift ashigh as I could. M/C has to be level. Don't try that w/ a floor jack. If yours ran dry you'll have to pull it to bench bleed. If I had to pull it I would just install a new one. That way w/ new everythig you won't have to fight it again for a long time. So far I'd have to say it's the hardest thing to do on one of these. I'd rather pull and build an engine.

 

[sparkydave]

Doug and Kelly are correct, a longer pushrod is not going to have any effect since it will have the same amount of travel regardless of how long the pushrod is. A hydraulic clutch is inherently self-adjusting, so the length of the pushrod will make no difference in how far the slave piston travels. Usual problems are a worn pivot bushing on the release arm, a broken pivot pin, or just the fact that bleeding all the air out a 1500 clutch is a PITA. Look for an air bubble caught in the hydraulic hose since it arches higher than the master or the slave. I've never had to bench bleed the master cylinder; when I rebuilt it I just bled the system normally, stomped hard and fast on the pedal a few times to drive the bubble out of the arched hose, and bled again.

Only thing I might note about Kelly's suggestion of removing the slave to bleed it is this: I had a bled system that was working fine. I had to remove the slave briefly, leaving the hydraulics connected, and when I slipped it back in, the dust boot made a tight seal with the pushrod. It worked for two shifts after I put it back in, and then I had to bleed it again. Seems the pushrod acted just like a piston, and it built up a pocket of air under the dust boot as I installed it, so my guess is after I worked the clutch a few times, the air burped its way past the seal.

 

[tdskip]

So help me here guys - the potential travel of the piston is fixed, agreed. But if a longer push rod is used then the effective extension of total reach is extended. I am not getting enough total reach, so a pushrod that is longer will increase my total reach. TR6 folks (like me) use an adjustable pushrod for this reason. What am I missing?

 

[Guest]

You're not getting enough total travel due to the fact air is still in the line being compressed rather than fluid pushing the piston forward. X amount of M/C movment will only give you Y amount of fluid. This fluid is only good for Z amount of slave travel. As the clutch wears, the slave piston is pushed forward by the spring inside thus adjusting itself. The only way the rod would be too short is if the clutch wore so much that the piston was at the end of the slave and fluid was comming out. You still have air in the line. The only way to get more stroke w/ that M/C is to install a slave with a smaller bore and a longer body.

 

[Guest]

Are you saying the rod is too short w/ the slave installed, or it's just not releasing?

 

[tdskip]

Are you saying the rod is too short w/ the slave installed, or it's just not releasing?

Hi there - thanks for the responses and help.

This issue I am trying to work around is that the replacement part (from a certain vendor whose name is similar to a style of architecture) provides a part whose travel is shorter than the factory OEM slave, so to compensate for that I am going to try using a longer push rod.

 

[Guest]

Does the slave mount further back? Is the body shorter? I got mine from them and it was fine.

 

[Guest]

Here's what you can do if you need a longer rod. Go to the hardware store and buy a grade 8 5/16" bolt four inches long. Cut the head off and use a bench grinder to round/smooth the ends to the contour you need and you have a new rod.

 

[tdskip]

Thanks Kelly, remember this is for my MGC not my Bugeye

Good to hear they have good ones for a Sprite! Clever idea on the bolt.

I ordered a 1500 pushrod from Moss, fingers crossed.

Thanks guys!

 

[tdskip]

Hi guys, thought I'd close this out. The actual car in question is my MGC, but I just finished installing the pedal box, connecting the lines and bleeding the slave cylinder with the Midget 1500 push rod.

MGC one is the top (which may or may not be original, but probably is given everything else on the car). Midget 1500 is the bottom.

I now get reverse clean, no grinding. It appears that the combination of fresh cotter pins and the slightly longer slave push rod have done the trick.