Temp guage-massive swings in readings!!!!

[ianrut]

Hi to all,new owner of 5ltr chim-superb!All was well for first 1000 miles(about a week!)now temp guage readings swing from 70-110 even whilst driving.Used to read around 90.System seems fine,new rad,water levels ok,fans cut in.Car is 96,anyone with any ideas?The sun is shining and the next 1000 miles awaits...
Thanks in advance.

[smb]

How quickly does the guage swing?, if it's seconds from top to bottom or vice versa likely to be a breakdown/short of the sensor wire or sensor. If it's more gradualy, could be thermostat but from the symptoms ( assuming it goes up and down) likely electrical

[ianrut]

Speed of swing varies,sometimes it will hold steady other times whilst stationary the needle will actually flicker +/- 10c.On normal route this morning guage registered above 90c at a point where normally the engine was barely warm!!

[smb]

Probably electrical if it moves that quickly. It's normal in a TVR for the guage to move higher once the car is staionary , but never over the 95-100 level ( depends on car and guage accuracy). If flickering, rapidly between two points it's likely to be either sender, wire from sender breaking down or gauge.

Changing the sender is fairly cheap and easy if you don't want it diagnosed by someone. The others require alittle more effort.
EDITED to ask - do any other gauges flicker? if yes perhaps you have an electrical voltage problem

>> Edited by smb on Saturday 5th July 09:03

[Q35]

Had the same problem with my 97 4.0L, changed the sender near to the base of distributer problem solved.

[GreenV8S]

Could be a duff sensor (possibly a check with a volt meter would confirm), wiring fault, or perhaps an air lock. Air lock is the least likely but most worrying since it means your engine really is seeing massive temperature swing (which will do the heads no good at all). So I'd start by checking the level and bleeding if I were you, just in case.