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[BazaJT]

The recent overheating issue on my Elite has set me thinking[not something I do well ]On the coolant bridge there is a sender unit with a single wire which I understand is for the temp gauge on the instrument panel.Then there is a sensor with a plug,what does this control/send a signal to?Surely if it's sending a signal somewhere then when the temp gets to or near critical it should then do something to "protect"itself/the engine?Reason I ask is that although temp gauge needle on mine was banging off the stop at top of red zone the engine was still running smoothly with no issues other than the temp being way over the top.

[Nick W]

The single wire one is for the gauge. The other is for the engine ECU and is more sensitive/accurate. And yes, you could drive the gauge from the ECU, but German engineers don't think like that

[Andy B]

..... And yes, you could drive the gauge from the ECU, but German engineers don't think like that

There's only one sender for both gauge & engine on my Smart 

[05omegav6]

The other sensor is the ecu coolant temp sensor the ecu then manages the fans, which as a backup have their own thermoswitch in the radiator. This too can fail, but the ecu should still trigger the fans if the block starts to cook...

Any doubts about either then replace both sensors. You can also follow the fan test guide to be sure that they are working as they should.

In your example I would start with the fan test, then replace the gauge sensor if the fans check out fine. Any further issues then change the ecu sensor

Obviously for ease of access vs cost,  you might as well replace both. And unlike crank and cam sensors, pattern sensors from reputable local motorfactors are usually reliable. Not sure how much genuine gm sensors are, but when it failed on mine, the genuine ecu coolant temp sensor was in stock and about £12 iirc

Generally speaking, if the coolant has been changed regularly from new with the correct mix then the sensors should be pretty bombproof

[05omegav6]

..... And yes, you could drive the gauge from the ECU, but German engineers don't think like that

There's only one sender for both gauge & engine on my Smart 

Which was designed by the Swiss

[BazaJT]

I thought the sensor would send to the ecu but wasn't sure.So if the ecu gets the signal that the temp is way out of range i.e.overheating shouldn't it take steps to protect the engine,shut it down or something?

[BazaJT]

Must learn to type faster

[BazaJT]

Where would I find instruction on doing fan test? I've had a look but being a full on numpty with computers I can't find one.

[Webby the Bear]

I thought the sensor would send to the ecu but wasn't sure.So if the ecu gets the signal that the temp is way out of range i.e.overheating shouldn't it take steps to protect the engine,shut it down or something?

That's why there's a head gasket  designed to be the first thing to let go before engine damage.

[05omegav6]

I thought the sensor would send to the ecu but wasn't sure.So if the ecu gets the signal that the temp is way out of range i.e.overheating shouldn't it take steps to protect the engine,shut it down or something?

That's why there's a head gasket  designed to be the first thing to let go before engine damage.

The the ecu input is the back up... fans are independently switched by the thermoswitch on the radiator, as is the radiator coolant pump (v6 only iirc). The ecu can also switch the fans on according to engine (rather than radiator) temp and also if the aircon is on...

Similar issue to the one you describe, yours being a late 3.0... http://www.omegaowners.com/forum/index.php?topic=133058.msg1704776#msg1704776

Fan test here... http://oldsite.omegaowners.com//forum/YaBB.pl?num=1295795115

Hth

[Webby the Bear]

I thought the sensor would send to the ecu but wasn't sure.So if the ecu gets the signal that the temp is way out of range i.e.overheating shouldn't it take steps to protect the engine,shut it down or something?

That's why there's a head gasket  designed to be the first thing to let go before engine damage.

S'what I was told in college 

[Andy B]

..

[Webby the Bear]

Could be wrong and sorry to op if I am 

[BazaJT]

Thanks for those links HKT.The rear fan does seem to operate as it should since I replaced fuse in fuse box below steering wheel,but don't know about front fans.Still don't know how it stood mot without the fuse and without overheating.However weather permitting I'll do the fan test over Xmas and go from there.

[Nick W]

I thought the sensor would send to the ecu but wasn't sure.So if the ecu gets the signal that the temp is way out of range i.e.overheating shouldn't it take steps to protect the engine,shut it down or something?

That's why there's a head gasket  designed to be the first thing to let go before engine damage.

Surely it's more of a necessity to keep the oil and water in their respective jackets when the head and block are separate? After all, with an aircooled two-stroke engine you can lap the head and cylinder block together and eliminate the head gasket.