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MG MGB Technical - I can't move!

I recently aquired a '70 MGB and have made it a winter project. I converted the charging system to AC-Delco, rebuilt brakes, etc; The clutch slave cylinder still needs rebuilt but anyway, I started it yesterday while in gear to see if I get any wheel spin (it's up on stands right now)and I get nothing. I ran it through all the gears while running (thinking I'd at least get some gear chatter while trying to shift) and I go into all the gears with no resistance due to engine rev. Any thoughts on where I should start looking for problems? Rear axle turns when I move the driveshaft so the pumpkin gears are O.K.
Keith

Keith, You mentioned it has a drive shaft, if you put the transmission in gear can you turn the drive shaft?
If it does, try all gears including reverve, you should be able to turn the drive shaft with the transmission in neutral but not turn in any gear. Let us know what happens. By the way, did you have wheels on the car when you were shifting the tranny and running the engine? Clifton
Clifton Gordon

Keith. Tagging on to what Clifton recommends, first, did the drive shaft turn when you had the engine running and the transmission in gear? If it was, then you have a problem in the rear end. If not, you have a problem in the transmission or clutch. There are two clutch related problems which could cause this sympton. Either the clutch plate (driven plate) could be slipping or the pressure plate is not holding the clutch plate against the flywheel. You handle either of those problems by pulling the engine, surfacing the flywheel and installing a new clutch plate, pressure plate and throwout bearing. You would probably want to rebuild the clutch master and slave cylinders and replace the flex line while you are at it.

The way to check for bad clutch is to put the car in gear with the rear end up on jack stands, then try to turn the drive shaft by hand (engine should be off). If you can turn the drive shaft, the clutch or something inside the transmission is bad. Further troubleshooting requires removal of the engine and transmsission and a physical inspection to see what is there.

If the drive shaft is turning when the engine is running and the transmission in gear, you should see the wheels turn, but not as much as you would expect. I had one car that I installed a new clutch into, which I tried to run while up on jack stands. The rear wheels moved rather slowly, I could stop either wheel by carefully putting drag on it and, when lowered to the ground, the car ran well for many years. So, if the drive shaft is being turned by the engine, I would delay my troubleshooting until it was time to put the car on the ground. Then, if there is a problem, you can address that exact problem rather than this more general one. Les
Les Bengtson

Keith

Just - if I may - to add to Les's advice - if there is no drive check that the clutch is not being held out by a seized slave cylinder, byu undoing it - 2 bolts hold it to bell housing

Chris
chris

Thank you all who have responded so far. I will check on these things tonight and let you know my findings tomorrow.
Keith

Well, thanks to your help and getting my hands dirty, I traced the problem to the slave cylinder. Seems that somehow pressure forced the piston out of the cylinder and had cocked it sideways in the bore. This bound up the cylinder in the release position and had the clutch disengaged. As soon as I pulled the retainer bolts and freed the cylinder the clutch engaged and driveline locked in. All is well in the great white north again :-) Oh, and to Clifton, yes the wheels were off the car, but I have quite an elaborate jack stand system which secures directly into the concrete floor and secures the vehicle so it is solidly braced. Thanks for your observations. I'm still new to the MGB game but well seasoned in auto mechanics. I'll be on this BB cruisin' somewhere. Thanks to all for your help.
Keith

Keith, Glad you got it figured out. I was thinking a spinning axle without the wheels may mask/hide the effects of shifting gears as there would be very little rotating mass. Regards, Clifton
Clifton Gordon

I also recently acquired a 74 MGB and have been doing about the same thing - replacing the brakes, alternator, etc. When I have my clutch pedal pushed all the way down and in gear, the gears will eventually engage. The clutch hose looks like its bad, so I was going to replace the clutch hose and the slave cylinder. Are there any tricks to this, or is it pretty straight forward?
Thom Patrick

I guess Chris gets the award for this solution. Great reading!

BarryQ
73B
B.J. Quartermaine

Clifton, good point on the raised vehicle situation. And to Thom, it's pretty straight forward. One short hose going from the slave cylinder to a union(same as a front caliper hose)then onto the master cylinder. Loosen but don't remove the hose at the slave cylinder before you remove it from the tranny (much easier than putting the cylinder in a vise and possibly damaging it as it's aluminum). Pull the cotter pin, washer and clevis pin from actuating rod and remove the two bolts retain the slave cylinder to the tranny. And...tada.
Keith

Thom. There are all kinds of "tricks" with this job. Nothing really tricky, but the area around the junction between the flex line and the hard line is difficult to get into. For me, disconnecting the battery, then removing the starter makes the job a great deal easier. The fitting on the hard line is a standard 7/16" fitting. Make sure you use a line wrench to loosen and tighten the fittings. The junction between the hard line and flex line should be un-done first, then loosen the flex line going into the slave cylinder. Where the flex line goes into the slave cylinder, there will be a copper washer between the cylinder and the fitting on the line. You should either fit a new copper washer or anneal the old one before re-use. The copper washer do not come with the hoses and must be ordered seperately.

I examine the internals of the slave cylinder before deciding whether to rebuild or replace. Frequently, rebuilding is an option. There are two type of clutch master cylinder, but only one type of slave cylinder. If you rebuild or replace the slave cylinder you will want to also remove, inspect and rebuild/replace the master cylinder. The Moss Motors catalog tells you how to identify which master cylinder you have and gives the correct part numbers for the rebuild kits.

There are several pushrods, clevis pins (the small round rod with a cap on one end and a hole for the cotter pin/split pin on the other that are used to hold parts together) and actuating pieces. You have one piece with a hole in it and another piece with kind of a U shape which fits over the first piece and they are joined by a clevis pin. These are the brake pedal and clutch master cylinder push rod and the slave cylinder push rod and clutch fork. Inspect all of the pins and holes for wear and ovaling. Replace the parts as necessary. I have seen the problem you describe caused by a worn MC pushrod when the rest of the system was good. So, check, rebuild, bleed the system (pain in the neck) and plan on it taking much longer than you would expect. First time is always a bear. Les
Les Bengtson

This thread was discussed between 27/01/2003 and 28/01/2003

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