The pipe from the gearbox to the left side of the oil cooler on the manual v8 had seized so I needed a new cooler and pipe. The smaller cooler is NLA and the Bearmach was out of stock so had to choose a Britpart replacement. I don't know why but the left hand thread on the cooler takes a 27mm nut and the right hand takes a 24mm nut. That's the same as the engine oil cooler.

Britcar supplied a new cooler and LR original pipe but the LR pipe came with a 24mm nut. Britcar were very helpful and spoke to LR who said try a different pipe but with the same result. I took the pipe to our local Pirtek and asked them to change the flexible hose for one with the correct fitting from an engine oil cooler pipe but there was a lot of tooth sucking and "we can't recrimp old pipes" - even though they were new! In the end Duncan at Britcar, took an engine oil cooler pipe which has the correct nut on to his, next door, Pirtek and they changed the pipe over with no problem. So big thanks to Britcar who did all that at no cost to me and £70 to Pirtek.

Are the threads at the cooler LH? I tried removing the gearbox and engine coolers from a parts P38 and destroyed them. I thought they were badly seized, but maybe I was turning the wrong way?

No, they just corrode together with the steel nut and the aluminium thread on the cooler. I tried everything to get them apart. Soaking, heating, freezing and in the end just sheared the threaded part of the cooler clean off. Why they put two different size threads on is anyone's guess as even I couldn't get them the wrong way round.

DavidAll wrote:

The pipe from the gearbox to the left side of the oil cooler on the manual v8 had seized so I needed a new cooler and pipe. I don't know why but the left hand thread on the cooler takes a 27mm nut and the right hand takes a 24mm nut

I initially read it as the 'left hand thread' meaning the thread was left handed then realised David was talking about the thread on the left hand side. So no, the threads are standard right hand thread, just a different size from side to side.

ok, at least I wasn't completely out to lunch. What do we do if we ever need to replace a hose? Like David, I was hoping I would be able to use heat if I need to get the hoses off the cooler another time. Do we need to buy a new cooler at the same time as a pair of hoses?

That's what I did with the engine oil cooler as I figured they wouldn't come undone.

This is a common problem and we do deal with this all the time, it happens also in AC radiators and steering cooler lines.
Sometimes no matter how much you go at it, it will not budge, and if you break/twist the radiator/cooler end, you're done for.

On our projects, with the AC and steering pipes, I have found is much easier to undo them at the "far end" - say by the AC compressor, by the steering pump, and so on. Usually the "far end" is closer to heat/more protected area in the engine bay, and thus saved from the muck, salt and rust of being up in the front. Yes, it is much more work, and sometimes removing the pipes requires to dismantle other components and/or great feats of athletic prowess (with associated colorful language) but you save the cooler to start with ...

Other options include to "break" the nut, and thus save the threaded section. Then you can fit another new nut.
You can also cut the pipe somewhere else, remove the cooler, and work on the bench with full access from all sides. The two parts of the pipe can be again welded by anyone capable of. We have one guy that even "rebuilds" rusted/corroded parts of the pipes (usually by the rubber mounting points where muck sets in), then you save the pipe (for some cars are very expensive or non available).
For very thin ones (say, brake pipes) we just cut the ends, get the overall length, then make a new one with new threads ... and bend it carefully following the contours of the original one. Lots of work :-)