temperature guage going nuts

[paul_clark3000]

Has anybody experienced problems with their temp guage in the cabin shooting up to the red when the engine has not properly warmed up? Each time I start it I let it run for a few minutes, than by the time I am half way down the street, the guage starts pointing north! It cannot be the stat because the engine is not warm enough, I am assuming it is the temperaute sender unit but before I go off buying the wrong bits would appreciate any other alternative suggestions

Thanks

[keithskip]

Does it cool down once you've been driving for a bit? Mine does - I try not to let it just sit there running, but sometimes it's unavoidable - gauge goes up high but returns to normal pretty quickly. I've assumed it returns to normal because thermostat opens, esp since I have a higher anti=freeze concentration during the winter.
But I too would welcome some expert comment.

[GreenV8S]

Has anybody experienced problems with their temp guage in the cabin shooting up to the red when the engine has not properly warmed up? Each time I start it I let it run for a few minutes, than by the time I am half way down the street, the guage starts pointing north! It cannot be the stat because the engine is not warm enough, I am assuming it is the temperaute sender unit but before I go off buying the wrong bits would appreciate any other alternative suggestions

Thanks

Could be as simple as a wiring fault causing an open/short circuit when cold, or something like that. But until you know, I'd assume the worst - it could be a real problem.

Do you have a standard TVR serpentine engine? If so, you have no external bypass, and if your stat is working properly with no holes drilled in it, the only circulation round the engine is via the heater matrix. If this is switched off, you may have almost nil water flow, which could cause very high local temperature readings.

Alternatively you may have an air lock causing the pump to stall until you go round a corner, the stat opens or whatever and some more water sloshes in to it. Bleeding the cooling system thoroughly would cure this.

Either way it's potentially bad news because if you are actually getting those high temperatures, you'll also get high thermal stresses which will take their toll on the engine.

Hope this helps,
Peter Humphries (and a green V8S)

[paul_clark3000]

The temp needle does drop after about five minutes - but while you watch the needle in the top end of the red you cant help but worry and be tempted to turn the engine off! The thing is with the stat, it should not open until about 98 degrees, but when you feel the hoses and engine, they are still relatively cool. This would suggest the temp guage does not match the actual engine temperature. However, being a bit of a novice I dont like to assume and would love a bit of assurance my engine is not about to go pop!

[shpub]

Pete there is a bypass fitted to the heater hose in the passenger footwell that allows some flow even when the heater is closed. You can't see it unless you rip out the heater unit etc but it is in there. Numerous mentions of it in the TVR docs. Even in the Griff/Chimaera parts list under heater bypass!

Probably is a faulty sender but could becaused by other problems like a head gasket causing localised heating. Worth assuming there is a problem unless proved otherwise.

Steve

[shpub]

The stat should start to open at around 80ish and not 98! The temps are easy to check with with an IR remote thermometer.

[gideonr]

Had wild temperature guage readings in my old Rover 216 (rather different I know) after driving for 5 mins or so, and this turned out to be the head gasket, so beware.

Chimaera 400HC

[paul_clark3000]

Thanks for the note on impending doom! will check sender unit, but probably wothwhile dropping it in to the garage. Cant wait to see how much a head gasket will set me back!