Hot shifting issue

[Rasco]

Having an issue getting into gear when the engine is hot an I've stopped the car. It started with an inability to shift into reverse, an tonight spread to all gears.
Today drove on the freeway for an hour, downshifted 5th to 2 nod no issue - came to a stop at the lights and couldn't select any gear. Turned the ignition off and was able to select first (using a bit of muscle). Pumping the clutch makes no difference

Added some thicker engine oil, drove the same route in the cooler night temperature and no gear issue at all

I do have a slight oil leak at the lower front left of the engine and the last mechanic mentioned a slight leak around the gearbox seal

It doesn't seem like a master/slave issue but any pointers to a fix please?

[Pamex]

Could be a few things. I'll forget some here sorry, bit tired. There'll be something blindingly obvious someone who's awake will mention.

First: Have you had any new or suspicious noises?

Was the leak around the rear g/box seal or the one at the front? (It will be coming out of the bellhousing looking like a rear main leak if the front one). Leaks at the front can lead to clutch issues. Leaks at the rear mainly just mean you'll lose oil level in your box.

You mention engine oil. Does the gearbox have enough oil? Some boxes can run just engine oil, but whatever gear oil is recommended for yours is advisable.

You're probably already on top of this, but you definitely have enough clutch fluid? Haven't had to top it up regularly or dramaticaly recently? Have a look if the slave is leaking if so.

There are a few other things, but it gets more technical from here and most of it is a 'tear down the box and find the issue' type thing. I'd look at the above issues first, as most of the further problems I can go into happen when someone hasn't rebuilt the box properly (putting steel syncros where brass ones should be, etc., heat does funny things in these situations) or don't really just happen after the box has been operating properly for a while (such as gears resting against bearings causing binding through the shaft... which means the box will never operate properly from the start).

[93_Clubman]

It doesn't seem like a master/slave issue but any pointers to a fix please?

Sounds like a clutch slave cylinder issue (or may be clutch master cylinder) - it won't necessarily be all that obvious that it's the clutch slave cylinder, so you need to confirm by checking for any brake fluid inside the rubber boot just ahead of the clutch slave cylinder.

[StockNA]

I do have a slight oil leak at the lower front left of the engine and the last mechanic mentioned a slight leak around the gearbox seal

Has the rear main or front main seal ever been replaced? If that leak in the front is your crank seal, quite possible that your rear main seal is gone too causing your clutch to be covered in oil. could be a small leak that happens when the oil is hot and thinner.

Have your synchro's been making any noise recently? Doubtful it would be your synchro's as you can't select any gear, but just a thought.

I would jack the car up, put it on stands and get someone to press the clutch pedal and see if the slave cylinder is doing anything

[Mr Morlock]

If you cannot select its probably not the clutch i.e. if the clutch is not releasing it will make the usual gnashing sound. Sounds like a selector issue. Just take it to a mechanic and get an opinion - they will do a few basic checks and give you some feedback. If the box has to come out for whatever reason then leaks will be addressed.

[93_Clubman]

If you cannot select its probably not the clutch...

But still may be the clutch slave or master cylinder, as not being able to select a gear when hot & stationary is exactly what can happen with a stuffed clutch slave cylinder.

[Rasco]

i've ordered a new master and slave cylinder so hopefully that will fix the issue - some fun new jobs over the Christmas period

first action was to change the gearbox oil but that didn't do anything -

thankyou so much for all of your opinions and advice!