Erratic Temp Warning.

[newsh]

Just nearly home from MRC last night and I had some beeps and a temp warning come up on the autocheck sytem. Don't think I've ever seen this one before even when I've had water leaks and been boiling up, its the thermometer in waves icon meaning either water level low or high temp alert I guess. Anyway the gauge was reading normal or even a bit low so I nursed the car for the last couple of miles back and popped the bonnet. All looked normal and there was very little pressure in the system and water level was normal so I think it must have been a faulty sender. Is this the MFTS? This was replaced not long ago.. Anyway an hour later I started the car and it was still flashing, drove for a while and suddenly it stopped.

[pastures16]

isnt that a safety device to stop you wrecking the engine

[newsh]

isnt that a safety device to stop you wrecking the engine

Yeah, very funny, thing is it wasn't overheating and it wasn't low on water.. Just did the same thing this morning just after I started it for a few minutes.

I don't think there is a water level sensor anyway. It would be in the bottom of the expanion tank.

[s2dude]

Theres a level sensor in the bottom of the tank as far as Im aware Newsh??
Either way....I had exactly the same warning as you coming on and off....
Topped the water up to slightly OVER the marker in the tank and bingo
It seems to be very very sensitive.

otherwise check and clean sensor contacts??

[terrybullwon]

My old 80 had the same problem, it was worse when i drove it hard even though the tank was full.
i took the expanion tank off cleaned it out with a good dose of fairy and topped it back up

[newsh]

Topped it up, did take a litre or so which is a major worry, but even with the gauge reading cool the light will still blink, leave it to tick over and the gauge comes up to 90, fan cuts in, take it for a drive, gauge falls to 70ish, stop and remove cap water spurts out.. so if I believe the warning it seems to be running hot when the gauge is reading low, maybe the thermostat is sticking. If I've got a leak I cant see it. If its the head gasket again I'm going to go bonkers.

[LHD_Kid]

I am not a mechanic, as you well know John, but my old supra turbo did very strange things when there was any air (however small a quantity) in the system...
Maybe, just maybe there is a small pocket of air there somewhere will come out eventually...
Hope so, good luck.
Chris

[newsh]

This is what I'm hoping, air in the system, but why was it alright till yesterday?
Looked with a mirror, there's a level switch in the bottom of the header tank but no wires to it, pretty sure there never has been.

[volcano rs]

sounds like air lock to me too .

[aelred]

Was the head pressure tested when the head gasket was replaced?

[newsh]

Was the head pressure tested when the head gasket was replaced?

Not sure, will check tomorrow but the head is a different one and known good one I believe.

With the header tank out of the way I found the wiring for the water level switch under the power steering fluid reservoir, been there for some time by the looks of it.. Thought I'd fixed it but no, a look at the handbook reveals that the warning is the thermometer in "moving water" and so is the "over temperature" warning not the low level, I'm pretty sure the warning lights up when the engine is not hot so could be the Multi Function Temp Sender is faulty. Disconnecting the MFTS gets rid of the warning.

[newsh]

Just tried with the car stone cold, the warning flashes about 10secs after turning on the ignition and cancelling the brake warning, seems like its deff the MFTS.

[LHD_Kid]

Thats good news, sounds like you found the culprit... at leats lets hope so, mine also went up the swanny, just manifesting as temperamental water temp display....
Not at all the same symptoms, but it seems it does have alot to do with everything...!
Nice one...!

[dan_b]

The MTFS is a shonky piece of kit. Glad to hear it's that though and not a major leakage... Get it replaced pronto!

[newsh]

Yes, mine has been doing the temp gauge display dance, a slow dance and not very rythmic.. Just spoke to Pete and he says he had a box of about 15 of these under the bench removed from cars, they're always going wrong, sometimes you can tap the unit with a long socket extn or similar and it will work ok again for a while, kind of proves the point. Theres apparently all kinds of stuff inside the unit, circuit boards and mechanical contacts etc