This topic has probably been discussed on the forum before, but let's just say: RR P 38, at least the older ones have a plastic 8 mm hose between the radiator and the expansion tank, which came off while driving. I didn't notice it, no warning lights or temperature gauge showed anything unusual. My drive was quite short, only 15 km. I did a little work around the house. When I tried to go back, the car wouldn't start. After opening the hood, I saw that the area of the expansion tank was wet and the mentioned plastic pipe had detached from the tank. After temporarily adding water, which took about 4 liters, and reconnecting the disconnected plastic hose, the car started and I was able to get back home. "check engine" light stays on all the way. After checking at home, I noticed that the reason for the hose coming off was that the plastic tube in question had broken under the hose clamp. Now that plastic hose has been completely replaced with a rubber hose that can withstand the required amount of liquid and heat. Acknowledgment of the Nanocom fault light.
I recommend: If someone is using that plastic hose, replace it with a rubber hose as soon as possible.
If my trip had been longer, the engine could have been damaged and it would have been an expensive pleasure...

Just to add, run the hose up along and around the side of the battery like the later 38's do. It bleeds much quicker that way
The early ones like my 99 had the pipe go down and behind the battery.

The plastic pipe is 20+ years old & while originally flexible is now stiff & as I know to my cost can easily shatter unless you handle it very delicately when blowing through to ensure it is patent. I made a emergency repair with a length of 1/2" garden hosepipe & two jubilee clips. It lasted for the 200 miles home although the hosepipe was nearer 1" by the time I arrived. It's now been replaced with this nice 8mm silicone rubber hose. It comes in black or a natty blue.