As the title indicates the water temp reading on my S1 is fluctuating quite a bit. During town driving and open road up to about 60mph its sitting around the high 70's to very low 80's. However when pushing on around or slightly over the legal limit the temperature read out moves about from 60 to 65 to 80C. When stationary the fan is cutting in at an indicated 85C
Checked water level and its OK, I was thinking possible Temp sender replacement required.
Any other suggestion's/advice would be appreciated.
Cheers
Flucuating water temp reading on S1
Re: Flucuating water temp reading on S1
Weak stat spring or pinhole leak in hoses?
http://www.rathmhor.com | Coaching, training, consultancy
Re: Flucuating water temp reading on S1
The ecu and stack each have their own temperature sensor, sounds like a low temperature for the fan to be kicking in, but the stack might not be getting the same info as the ecu. Mine certainly doesn't fluctuate that much, usually fairly consistently between 80 to 85. I would be tempted to try new temperature sensors. I am far from expert though!
Re: Flucuating water temp reading on S1
To me it sounds like a combination of two common-ish faults.
As Dom says, indicated 85 is too low for fan to be cutting in for hot & stationary - so chances are one or other of the temperature senders is reading bollocks - either the ECU one is over reading or the stack one is under reading.
I would correct this fault first. It's possible to test both sensors if you know the target resistance at a range of temperatures - or you have a way of measuring the actual coolant temperature (e.g. a pointy laser thermometer thing pointed at the coolant elbow) - but it's perhaps easier to replace them both and be done with it (though a bit of a PITA to do). What you should get is a car that when hot & stationary indicates approx 100C when the fan kicks in (it will never be the same on all cars due to tolerance variations between the two sensors). Note you should always do the tests with the same electrical load - so that's lights and blower motor all off - the electrical load creates an earth voltage offset such that the indicated temperature can change by +/- 4 degrees IIRC as you turn sh*t on/off.
At that point you have reliable (in Elise terms) temperature indication. Now here's what I would expect to happen. Cruising at motorway speeds and loads the temperature should hover around the stat control temperature of 85 degrees +/- 4 degrees to allow for variations in stat and sensor. If you then drop it from 5th to 3rd and maintain road speed more or less constant, indicated temperature should first drop sharply, then rise back to the stat control temperature. This is because when you double engine speed you increase coolant flow rate and thus cooling (lots of air over radiator at 70mph) - the stat will react to this drop in engine input temperature and close; now the reduced coolant flow rate will see less cooling and indicated temp should return to normal. If you now pop it back into 5th you'll see the reverse effect; temporary rise in temp until the stat reacts and opens up a bit. In each case you might see over/under shoot depending on ambient conditions and actual road/engine speeds.
If the stat is weak what you may see is that when you drop from 5th to 3rd the increased water pressure might overwhelm the stat return spring and force coolant past the stat into the engine; at that point the system will run open loop, more or less, and you'll see a drop in running temperature - it could go off the bottom of the scale quite happily on a cold day at 6,000 RPM in 3rd - and the temperature will level out at some lower value rather than returning to the stat operating temperature. If you see this, you need to replace the stat.
If the stat is just broken (e.g. low operating temperature) then I would expect the cruise temperature (5th gear motorway) to be lower than the expected 85 degrees.
Changing the stat is an utter barsteward of a job and were it me, I would remove and discard the stat and replace it with a PRT if only to not have to ever replace the stat again
Cheers,
Robin
As Dom says, indicated 85 is too low for fan to be cutting in for hot & stationary - so chances are one or other of the temperature senders is reading bollocks - either the ECU one is over reading or the stack one is under reading.
I would correct this fault first. It's possible to test both sensors if you know the target resistance at a range of temperatures - or you have a way of measuring the actual coolant temperature (e.g. a pointy laser thermometer thing pointed at the coolant elbow) - but it's perhaps easier to replace them both and be done with it (though a bit of a PITA to do). What you should get is a car that when hot & stationary indicates approx 100C when the fan kicks in (it will never be the same on all cars due to tolerance variations between the two sensors). Note you should always do the tests with the same electrical load - so that's lights and blower motor all off - the electrical load creates an earth voltage offset such that the indicated temperature can change by +/- 4 degrees IIRC as you turn sh*t on/off.
At that point you have reliable (in Elise terms) temperature indication. Now here's what I would expect to happen. Cruising at motorway speeds and loads the temperature should hover around the stat control temperature of 85 degrees +/- 4 degrees to allow for variations in stat and sensor. If you then drop it from 5th to 3rd and maintain road speed more or less constant, indicated temperature should first drop sharply, then rise back to the stat control temperature. This is because when you double engine speed you increase coolant flow rate and thus cooling (lots of air over radiator at 70mph) - the stat will react to this drop in engine input temperature and close; now the reduced coolant flow rate will see less cooling and indicated temp should return to normal. If you now pop it back into 5th you'll see the reverse effect; temporary rise in temp until the stat reacts and opens up a bit. In each case you might see over/under shoot depending on ambient conditions and actual road/engine speeds.
If the stat is weak what you may see is that when you drop from 5th to 3rd the increased water pressure might overwhelm the stat return spring and force coolant past the stat into the engine; at that point the system will run open loop, more or less, and you'll see a drop in running temperature - it could go off the bottom of the scale quite happily on a cold day at 6,000 RPM in 3rd - and the temperature will level out at some lower value rather than returning to the stat operating temperature. If you see this, you need to replace the stat.
If the stat is just broken (e.g. low operating temperature) then I would expect the cruise temperature (5th gear motorway) to be lower than the expected 85 degrees.
Changing the stat is an utter barsteward of a job and were it me, I would remove and discard the stat and replace it with a PRT if only to not have to ever replace the stat again
Cheers,
Robin
I is in your loomz nibblin ur wirez
#bemoretut
#bemoretut
Re: Flucuating water temp reading on S1
Thanks for the advice guy's. Got two new sensors on the way from EP.
I'll see what effect they have and take it from there.
Cheers
I'll see what effect they have and take it from there.
Cheers
Re: Flucuating water temp reading on S1
I had the same problem due to a dodgy engine earth cable.
Check that too. It could be a cheap fix
Check that too. It could be a cheap fix
If you're not living on the edge you're wasting too much space!