I was thinking about clear silicone grease that doesn't dry up. On second thought, be careful that the grease doens't make it into the cooling system.
yes the grease was a bad idea... The permanent siliocon was probably not so bad but i didn't fully test it. I had to go immediatelly so i stopped at the local gas station for a check. Leak!! big leak from the vlave. I applied a decent amount of Teflon (the plumber's one as Mark mentioned, comes as white tape) Since then i got no leaks, no bubbles. All good. So it seems it was the valve after all.
That valve is a bleed point for filling the cooling system. It might be leaking because a tiny bit of dirt has got into it; and I'd try (first time) wipe clean and then seal it with PTFE (plumber's, Teflon) tape. That may be what you have done. Don't seal it up with a permanent silicone sealant.
The leak's probably allowed air to be sucked into the cooling system, and the resulting bubbles and airlocks might be affecting the water flow and confusing the thermostat, various temperature sensors and switches even after the leak itself is fixed. This thread's been there already!
You are right, after all the leaks and the final teflon appliance, it seems that the temps are a bit better. Still no high speed fan. I start to believe that the last mechanic that replaced the switch 5 years ago may have used the single speed one intended for vehicles without air condition.
The other place my J63 once suffered a slow leak was where the pipes connect to the heater matrix, in the cabin rather than in the engine compartment. The main symptom of that is a patch of damp carpet in the right-hand foot well, and that only shows up in colder weather. I trusted the dismal Haynes manual about that, and spent a whole weekend replacing the heater matrix -- a long job for my right-hand-drive model, because the steering column gets in the way. That was useless: the parts which were leaking were two O rings in the connecting joint.
If you have this leak, reply and I'll try to describe how to replace the O rings. It takes about 30 minutes, and parts cost next to nothing. It was years ago so I'll have to renew my memory by touch.
- Mark
Well we are getting in a bigger conversation here ... Unfortunatelly i have no heater connected. No hot air inthe cabin. 5years ago we were playing in Poland. In a jam in the highway the engine got too hot (unfortunatelly i was asleep) and the heater blew off... Coolant all over the cabin... Nasty situation. So we disconnected the hose that comes from the heater and we twisted the second in the place of the first one so we have circulation of the coolant.
So this Espace has a history of high temps. The switch was replaced just before that trip. But i can't recall fan speeds.
Probably the new switch will give the solution i am waiting for.
Thank you both so very much for your help
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i will be reporting.