MGB & GT Forum

Does anyone know what is causing this issue and what I should do to fix it? I don’t really want to take the engine gearbox out as I would have to get the local garage to do that and don’t want to spend that money. The car is a 1970 MGB GT 1800.

When the car is cold, the engine starts fine but sometimes I either cannot select a gear or there is a grinding noise as it goes into gear , needing some effort on the gear lever.

If I select a gear ( 1st or reverse) before starting the car, then start her with clutch depressed there is some creep. The picture shows her doing Autotests last weekend. BTW she is rubbish at Autotests due to the heavy steering and rubbish turning circle and I don’t have the skill to swing the back end round the cones. My Midget 1500 is much better for that!

Pumping the clutch pedal several times seems to ease it off but it does not feel spongy and I got the local garage to fit a new master cylinder and they bled the system really well ( with slave cylinder positioned to ensure all air out, so he is convinced there is no air in the system.

I’ve sprayed the linkage from the slave cylinder to the clutch lever with WD40 and more recently lubricating oil and again that helps, especially if I work the pedal a few times.

Once I’ve started the car I can select all forward gears and sometimes reverse with clutch depressed and car stationary. Once I’ve started moving the gear changes get better as the car warms up. Once the problem has cleared the car drives normally until next morning when it may or may not resurface.

It doesn’t feel like the clutch is rusted to the flywheel as I know can happen after standing for a long time, when it is working properly the clutch seems fine. The garage mechanic suggested that it might be rust on the shafts in the selector mechanism but I think that would clear up with use and not get worse again whilst I was using it.

Any thoughts on what I can do or try in order to identify what the problem is and how to fix it?

Any help very much appreciated

My thoughts: take it back to garage, tell them your not happy .Check Any wear in the linkages/pushrod. Get a Gunson Ezebleed and bleed it yourself if garage won't do it,only takes 10 mins.or so. You shouldn't need to pump the pedal. The steering shouldn't feel heavy when moving.

Bleed the air out of the clutch.

X 2

Chris, no matter how many encouragements you receive to bleed the hydrolic or assurances that there is absolutely no air left in the system, there is only one way to be certain; measures the movement of the slave cylinder.
If it is 9.5 mm or more, the hydraulic part is not the cause and there is nothing you can do without removing the engine from the car.

I agree with the others "Air" try this seems to always work

reverse bleed refill into the slave cylinder


good luck
Nick

3 likely problems:

Hydraulic pressure is low…..Air or wear

Linkage mechanism wear….Note attached

Release bearing worn badly ….



NOTE:
The push rod/ clevis for the clutch slave and or the master cylinder linkage may be worn.

Has the problem has gotten worse over time? Remove both cotter/ split pins on the slave and master cylinder and the clevis pins. inspect all of the linkage parts.

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Rankin Barnes
High Point NC
74 Sabrina B

Chris, I have exactly the same issue on my car. In my case I have already confirmed that it is not the hydraulics, even though I have been told a thousand times that it's the hydraulics. The problem is a sticky clutch. It can be "unstuck" the way you describe it: put the car in gear before starting it. Do make sure that you press both the clutch and brake pedals when you start, to avoid any risk of the car lurching forward/backward. Once the car is running you can drive it and change gears during your drive. But after you have stopped and let the car sit for a couple of minutes (or more) it is stuck again. And you have to repeat this starting procedure. When it gets really bad the clutch even gets stuck while you are standing in a traffic jam, or waiting for a traffic light.

To solve this you would need to examine, and most likely replace, the clutch. For which the engine has to come out of the car.

Did the slave cylinder and flex hose get changed at the same time? It certainly sounds as if there is air present and needs to be bled. Reverse-bleed, or vacuum bleed the system.

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I was addicted to the hokey pokey but I turned myself around.

prop-a-gan-da: When a British person takes a close look at something

I use the Eezibleed on both the clutch and the brake MC, on the first it may sometimes require multiple bleeding exercises to drive the last bubbles clinging to the insides of the metal line and the clutch hose finally out and on the brakes airbubbles may remain in the system at first and move to the top of the calipers only after a few weeks of driving. As customary at least for me is that even with an Eezibleed results vary: the last clutch bleeding cost me 3 successive actions, each time with a newly filled reservor with unused fluid or at least a bottle that had not been touched for a number of days

The major problem as I see it, is that the Eezibleed pushes fluid downwards, while the bubbles either cling to parts or even want to move upwards.
After nearly every airbubble seemed finally expelled after a number of tries, the clutch pedal still firmed up even more over the next two weeks

PS In theory reverse bleeding bottom to top could be better, but the thin metal line curves downwards to the banjo junction too, so I wonder

Thanks everyone for your suggestions and observations. I shall work through them all and report back