Motorraum: '90 750iL Elektrofrage- soll Samstag schrauben

[Erich]

Auf dem US Roadfly hatte einer sich gemeldet, der durch Zufall hier in Tokyo wohnt. Habe ihm angeboten, da mal ein bischen zu helfen mit Kollege Mike.

Endlich kann ich auch mal einem am Auto direkt helfen

Hier mal die Kopie seiner Meldung:
This afternoon for the first time, I started my car and the engine had this vibration and it sounded low pitched. I thought maybe I was in limp mode so I popped the hood to check. Both sides were running. So I shut the car off.
Now a little history:
Just prior to starting I checked the fluids and added about a liter of water to the resovoir tank. (Note: I had recieved a check coolant level in the past couple months and have been topping up) I can not see any coolant leaks and I am afraid it could be a head gasket? The oil level hasn't changed nor is there any usual signs of coolant and oil mixing (ie white sludge under oil cap, frothy oil on dipstick)I couldn't smell any coolant burning nor was there any on the ground. I started it up again and noticed a little bit of white exhaust (I live in Tokyo and the temp is above 0 celcius but still a little cool) After warm up the white exhaust disappeared. I think this is normal. The engine still has the vibration, and after driving around the block and letting the engine warm up the temp gauge reads normal (12 o'clock), with no overheating problems prior.
In the past month I changed the catalytic converter on the left side, from the exhaust manifold to the muffler with a non OEM part (BMW after market part bought from ArizonaAZ)The catalyizer did not have a spot on the pipe to insert the exhaust temp sensor. I doubt however, this could be the problem as there have been no instances of this vibration until today. The funny thing is that I drove the car this morning and aside from it being cold from the night before it ran normally.
Does anyone have any ideas on what I should be looking for? I know I have to find the coolant leak, but is that the probable source of the problem?


Dann hat er mir jetzt noch per email folgendes geschickt:

When the garage installed the cat they showed me on the lift and the O2
sensor is installed but further down the pipe close to the muffler is a wire
with a sensor on it the garage called it an
exhaust temp sensor.
----------------------------------------------------

Kuehlwasserverlust ist klar, keine Frage. Muessen wir suchen.

Aber was ist mit diesem exhaust Temperature Sensor der hinten kurz vor dem Endschalldaempfer sitzen soll?
Hat dieser Temp-fuehler dort irgend etwas mit dem Motormanagement zu tun?

Wenn dieser nun nicht drin ist an dem Auspuff, den er aus USA importiert hat, wie kann sich das auswirken auf das Motormanagement und was kann man evtl. machen.

 geht hier um die Nummer 28, Temperatursensor.