Temperature Gauge Always Reads HOT??

slash2000

Hi,

The temperatur gauge on my 94 corolla read very hot, even if the engine is cold. When the engine is running (cold engine) the gauge will suddenly read very hot after driving 1st-2nd gear med-high reving. The gauge will sometimes display erratic readings
I've tired replacing the temperature sensor in the engine and the temperature gauge itself but the problem still persists.

Any suggestions??

Thanks!

zuutroy

Off the top of my head, thermostat could be stuck closed or low coolant, or some more serious engine problem.

crosstownk

Sounds like a short circuit. You may have a problem with the wiring whereby it short circuiting to earth causing the gauge to read hot. It's also possible that there is a fault with the gauge, but I'd get the wiring checked first.

ctc_celtic

or the head gasket could be fecked. check if there is a mayo like substance in the oil cap, or oil in the water expansion tank.

crosstownk

Read the first post - the gauge displays hot when the engine is physically cold. It's obviously an electrical fault.

ctc_celtic

when the head gasket goes, the temp display will read hot very quickly, even after seconds of driving. the top of the engine may not be warm.
if its only an electric fault, turn the ignition on but don't start the car, what does the gauge do then?

slash2000

When i turn the ignition on nothing happens the gauge. If i repeat this when the engine is warm it will read very hot.
As far as i can tell theres no sign of the head gasket gone!

MercMad

But you have checked that there is sufficient water in the system ??

To do this correcty you should set the temperature to hot before you park up for the night, then check the level tyhe next morningwhen its cold !!

Avns1s

Either a short circuit or a problem with the sender unit.

Wouldn't appear to have anything to do with the coolant level or head gasket.

MercMad

Wouldn't appear to have anything to do with the coolant level or head gasket

........except if the level is low, it sometimes doesn't make contact with the sender unit !

crosstownk

From reading the original post, it would appear that this problem has been present for more than a short while as the OP has replaced both the gauge and the sender unit. Add the erratic gauge reading into the mix and I'll put my money on an electrical fault.

OP, maybe you could let us know how long this fault has been present?

slash2000

Its been doing this for about 2weeks nows. Theres plenty of coolant in it, changed the sensor and the gauge but problem still persists! I'll get the electrics looked at first, hopefully its not the head gasket!!!