Clutch slave cylinder problem

Defender 90 300tdi
Refitting the clutch slave cylinder my problem is that it doesn't want to bolt up tightly to bell housing..gap of about 15mm! The push rod seem to be protruding too far...from the bell housing it sticks out about 20 - 25mm. This seems too much for the slave cyl spring too compress. Can any one help? Has something moved in clutch region, when cylinder was removed to cause this?
John

If anyone out there has access to a bellhousing..can you measure how far the pushrod extends beyond the mating surface, when it is fully in..is about 25mm or less?

Have you checked the old slave against the new one to see how far back the piston sits from the mating surface?

I am sure when I ordered mine there was a question ref the pushrod length, as there appear to be different lengths. So I was sure to measure the distance of the old slave to the new slave.

Cheers

I am re-using the old cylinder..just the rubber has been replaced, so its the part.
Is a lot of force needed to get it in place?

Problem solved...Both master and slave cylinders have exact same diameter bores. When i disassembled them both pistons with springs were beside each other and i put the one for master (minus its valve) in the slave cylinder! It fitted fine, except its piston head is flat whereas the slaves head has a large recess to accommodate the pushrod...thats why it wouldnt mate with bell housing. moral of the story: when disassembling keep all parts in separate labeled containers. Hope this helps someone in the future.
Thanks
John

Classic mistake, give yourself a pat on the back for sorting it and a slap on the mush for doing it in the first place.
Any one who has been spannering some time will have done similar. Know I have. Cheers John.