On 1/30/2015, Rafael Puga wrote:
.... "Driving my MGA .... it suddenly stopped moving. The engine was running okay but the car stopped moving, it seemed like the clutch was pressed (but it was not)".

Put car on level pavement, hand brake off and transmission in gear (any gear). Look underneath at the propshaft while you roll the car a bit. If the car rolls but the propshaft does not turn, then the disconnect is inside the rear axle. A fairly rare problem here is broken halfshaft, like this:

Much more rare may be a broken differential. Halfshafts and differential can be repaired or replaced without removing the rear axle housing from the car.

If the car rolls and the propshaft turns when in gear, then the disconnect is in the clutch or gearbox. Engine has to come out to repair a clutch. Engine and gearbox have to come out to repair the gearbox.

One more possibility, if the propshaft turns when you roll it and it is in gear. Underneath, right side of the bellhousing, look at the clutch slave cylinder. If it is wet with fluid you may have an easier fix (maybe). There are a coupe of odd conditions that may allow fluid to flow forward but not return. When that happens the clutch slave piston is pushed forward and stays extended. Another push of the clutch pedal pushes the slave piston farther out. After about three pushes the piston may pop out from the end of the slave cylinder and lose all of the fluid. When fully extended like this the slave pushrod can hold the clutch in the disengaged position.

Most common cause of this problem is a clogged rubber flex hose at the slave cylinder. Common failure mode is swelling inside the hose until it closes up inside. This allows fluid to flow forward under high pressure but cannot return. Symptom leading up to this is high force to depress the clutch pedal, but much less pedal force on the return stroke. Solution is to replace the clutch hose and reassemble the slave cylinder. You might consider repacking rubber parts in the slave cylinder or even replacing it.

Be aware that it requires about 200 pounds of force to move the clutch release arm rearward at the bottom end when operating the clutch. You can do this with a 12-inch adjustable wrench to extend length of the arm for leverage. If the slave is stuck in the extended position there will be this kind of force on the trapped pushrod, so you may have a little problem dismounting the slave cylinder.

On 1/31/2015, Rafael Puga wrote:
"It seems a clutch problem, gear do not enter now and strange rattling noise when car is idling and start pressing clutch, noise stops when clutch fully pressed down".

98% chance it is a clutch problem. Best guess is the splined center part of the clutch friction disc has torn loose from the rest of the disc. Next guess is one of the three release arms in the pressure plate assembly is somehow disconnected. When it rattles the release arm is moving quite a bit (rattling about). So the release arm pivot bushing is badly worn, probably also worn pivot bolt. Also possible broken mounting ears on the gearboc front cover (which should hold the pivot bolt). Engine will have to come out to inspect the clutch parts.

On 2/18/2015, Rafael Puga wrote:
"The clutch was the problem. The interesting thing was that a good clutch not used much lost all the rivets holding it.

First time I have ever seen that particular failure. It has to shear off 20 rivets all at once to break like that. Put it on your coffee table for a conversation piece. Install a new clutch disc, and it will never happen again.