Join Date: May 2006
Location: Ely, Cambridgeshire
Car: MG TF 160
Oscillating temperature gauge – solved!
You may remember that I posted about a problem with the coolant temperature gauge: every time I pressed the clutch pedal, the gauge dropped to zero, to rise quite happily as soon as I released the clutch. I expected the problem to be somewhere near the pedal but, having contorted myself to get down there, I found no wires anywhere near the pedal. Next, I removed the black plastic cover under the bonnet, to see if there was a problem near the master cylinder. Nope. No wires there. This really only left one place: the slave cylinder.
Sure enough, this is where the problem was. Basically, the part of the harness holding the cables running to the coolant temperature sensor and the temperature sensor for the ECU run right by the clutch slave cylinder. Now the piston in the cylinder doesn’t move very far with each use of the clutch (maybe an inch) but every time it was used, it waggled this mini-harness back and forth. I guess it got to the point where the wires were severed but the insulation wasn’t and using the clutch bent the cable enough to separate the strands of the conductor. I took apart the connector fitting onto the sensor (what a job) and rewired it with fresh cable and – lo and behold – all is OK. (I also cable-tied the harness out of the way of the clutch!)
So…next time you have your engine cover off, you might like to think about checking the same cables. I don’t know whether it was just that they were misrouted on mine or whether they’re all like that (in which case, duh!).
Hope this helps somebody.