I like to test the skills of the experts here and am very impressed with what you know !! So, they are back. I opened the bonnet on the P38 to check water etc and found myself being stared down by two pairs of eyes. Two Rats had decided to move in because contrary to popular opinion the Rain in Spain does not stay on the plain. They had returned to their popular nesting site against the bulkhead behind the coolant reservoir and conveniently positioned to eat the wires that come past out of the bulkhead. Well I repaired these before and I have not got down to inspect the wiring yet but having jumped in the car and turned on the ignition I get a warning - Gearbox Overheat-check handbook. Obviously the engine had not been run so no overheating possible. So Gilbert and others, what do you think ? Is it just a wire eaten through ?
I had not considered the Battery as a problem. It does not appear to be in bad order. I would have thought that the newly arrived rats doing something to wires is most likely. Presumably there is a temp sensor in the gearbox and if so where would the wiring be ? If I find and fix the problem will I have to reset CPU to cancel the problem message ?
Gearbox overheat is usually the sensor on the cooler failing. The sensor goes open circuit when it reaches the predefined 'I'm too hot' temperature - I don't know what it is off the top of my head.
Anyway - they fail quite regularly. Mine is intermittently dodgy, claiming overheat at random (even when cold), so it is unplugged and I've bridged the terminals of the plug until I get a replacement.
You might be lucky and its the sensor at fault... or one of your ratty friends has chewed through the wiring, and its now open circuit... thus bringing up the fault. I highly doubt low battery voltage would bring up just gearbox overheat and show no other signs of low voltage. Gearbox fault on the other hand, IS a common sign of low battery voltage.
Repair the wiring or replace the sensor (whichever appears to be at fault, short the plug on the vehicle side of the loom to test), and the message will go away - nothing needs resetting.
On a V8, the cooler can just about be seen down the side of the gearbox cooler. The plug for the sensor is blue and on leads.
Thanks Sloth - that seems to fit the bill - the rats had built the start of the nest using the plastic/rubber air blocks near the bonnet hinge and olive twigs. They did this in the last day or two! When I get the energy and rain stops I'm going to have a search and remove the rest of the nest. Didn't realise there was a cooler for the gearbox or sensor or where it was. Will have to track the wiring as I have no idea where it runs. Does it go into the fuse box ?
I don't believe so - straight to the becm. It only brings up the message - it doesn't actually change the operation of gearbox or engine at all. Just a warning really.
As virtually all the wiring between the engine bay and the rest of the car goes through that big bundle under the coolant reservoir, it's quite possible your new lodgers have had a nibble and hit the wire to the temperature sensor.
Yes Gilbert thanks - makes sense - that was a bundle I repaired before - it has some damage again but see my pic - what is that black round dome thing with the yellow bookmark on ? It has a tough rubber hose coming out and passes under the brake master servo - the rubber/plastic pipe has had some damage from nibbles 
That is the pressure accumulator for the brakes. It has two pipes, a flexible one from the brake reservoir and another high pressure one to the ABS modulator. For a man that lives on the top of a mountain, a problem there could be, errm, interesting. Stopping a P38 with no power braking needs both feet on the pedal on the flat.....
Ohhhhh ! then the nibbled bit is just where the flexible one goes under the reservoir, I suppose I can just replace the flexible bit if I have to ? Is it a simple job for a guy who can wield a spanner ? I'm surprised at how many things under the bonnet I don't know anything about - and I used to rebuild the old engines that we grew up on ..........
You can see the flexi one from the reservoir, the one with the cloth braided cover. That's the low pressure side so can be easily replaced but it's the other one that is a high pressure line (about 15 bar if I remember right) which needs to be replaced with the proper thing. You can't just bung a bit of pipe in with a couple of jubilee clips. It has metal ends to it with a flexi section in the middle and part number is ANR3321 (LHD) or ANR3322 (RHD).
Ok Gilbert - I think they have got through what must be the outer cover when I looked with the torch but there is no leakage. I can see that the high pressure side with metal junction is the 3/8 diameter pipe that appears pointed to in my pic by the yellow triangle pointer on the top of the dome and then goes out of sight below the reservoir? . Raining again so it will have to wait but that is just when the little blighters seek a home in the P38 !
I have marked the nibbled pipe with A - the pipe B is not a problem. But where does the A lead to as I can only see it goes out of sight under the reservoir stuff. !
Not sure how to make pic appear if one adds in the edit so putting it in again ! 
I can see now that A is the high pressure side with nibbles and is not easily available from suppliers. Perhaps it will have to be a scrap part. Also, looks like a major job to remove that whole metal gadget under the reservoir !
Another useful modification would be to add a dish of rat poison to that area ;-)
Have tried that - they seem to come back for more and it blows around the engine. I have two rat traps - the wood and spring kind but they seem to avoid them - these spanish rats are very clever ......my dogs chase them up olive trees and usually I have to climb up and rescue the dog !!! You can see the action here https://youtu.be/Q2SURpmUltk
Have bought a replacement pipe from Bob at Hi-Range for £20 in case. He always seems to have spares when I call. tel 01283792302
The one thing I have found that seems to make under the bonnet less than a rat's des res is WD40. I had a rat problem but none since liberally spraying WD around. So it works with Manila rats but no guarantee with Spanish ones!
Thanks George - will try - but here so dusty the under bonnet area is like a sand pit. Here is a pic of 'work in progress' - taken two days to repair the same area as before. 
super4 wrote:
I can see now that A is the high pressure side with nibbles and is not easily available from suppliers. Perhaps it will have to be a scrap part. Also, looks like a major job to remove that whole metal gadget under the reservoir !
On the laptop, so now I can see the pics!
As said, that's the HP side that goes into the modulator (the "metal gadget") which is easy enough to remove, just a pig to replace. However, the pipe should be accessible without going to those lengths. It's a banjo fitting on the side of the modulator, right hand side as you look at it from the front.
It's easy to unbolt the ABS pump and replace the pipe at that end although, IIRC, it can be done in-situ.
Whatever you do, please remember to depressurise the system before undoing anything!
"Depressurise the brake system by turning the ignition to the off position and slowly press the brake pedal through its full travel 30 times. Leave for about 10 seconds and then depress a further 4 times. This will depressurise the system."
Hi George - not as bad as first feared. I mistook some of the casings they had chewed as part of the high pressure pipe and when I got all the rubbish out found that they had only attacked the main loom and eaten through the repairs I did before. Only one wire was eaten - the Gearbox Overheat warning and having repaired that the message has gone from the dashboard. That corner on my RHD P38 is a perfect nesting site and I have to find some way of covering the loom or making the area a forbidden zone. Last year they attacked the injector leads and I repaired those hoping I did it right because the addition of LPG injector leads make it a right buggers muddle. If I got one wrong (ie. 2) would it cause my current poor performance and reluctance to change down when needed on the auto gearbox ?