OT: I'm getting hot warning

[whiskychaser]

Reading Gene's post about radiator puking coolant and BigKriss's post about headgasket blowing has got me thinking. Yes I know its dangerous. We have got 4 sensors on the car and none are bright enough to tell us BEFORE the engine gets too hot and does some damage:
The engine temp sensor must tell the ECU but it keeps it to itself
The low coolant only works when the engine is stopped - bit late then
The aux fan wont cut in if the coolant is low because the sensor isnt in contact with hot coolant. So that wont save the day
The temp sensor may tell the gauge but thats not very accurate and you might not notice it till its too late anyway
So I'm thinking why not link into a temp sensor circuit that will bring on the 'low coolant' warning and the accompanying 'bong' while the engine is running? Wouldnt want to meddle with the ECU circuitry but the gauge sender is a likely candidate. The E34s suffer from overheating and the E39s even worse. Any thoughts or should I go find a good book....?

[DaveVoorhis]

It's already there! At least, it is on the E39 with the high OBC and I vaguely recall it's on the E34 with the OBC. If the temperature gets too high (for some unspecified value of "too high") it bongs and puts COOLANTTEMPERATURE on the instrument cluster display.

Unfortunately, I suspect the message only appears at a temperature hotter than that required to turn an aluminium head into a puddle of dripping molten metal. I'm not about to test it.

[philbyil]

Never trust idiot lights!
Just one of the reasons I installed oil pressure, oil temperature and voltmeter gauges!

[whiskychaser]

It's already there! At least, it is on the E39 with the high OBC and I vaguely recall it's on the E34 with the OBC. If the temperature gets too high (for some unspecified value of "too high") it bongs and puts COOLANTTEMPERATURE on the instrument cluster display.

Unfortunately, I somewhat suspect the message only appears at a temperature somewhat hotter than that required to turn an aluminium head into a puddle of dripping molten metal. I'm not about to test it.

You see a lot of E39s advertised with 'just' a blown head gasket. I read that as it got too hot and probably pulled the bolts out of the block so the engine is totally fkd. It doesnt have the high coolant temp warning on mine. But you have posed a very good question- how hot should the engine be when you get the warning?

[tim eh?]

If the temperature gets too high (for some unspecified value of "too high") it bongs and puts COOLANTTEMPERATURE on the instrument cluster display.



I got that message just about exactly when my headgasket blew I think.

[whiskychaser]

I got that message just about exactly when my headgasket blew I think.
That unfortunately proves the point. You get a light that tells you the fuel is getting low but nothing to say that your engine is about to blow up

[DaveVoorhis]

You see a lot of E39s advertised with 'just' a blown head gasket. I read that as it got too hot and probably pulled the bolts out of the block so the engine is totally fkd.
Yeah, that's what happens. I'm half tempted to get one of those and see if I can fix it with a bucket of helicoil inserts.

[tim eh?]

That unfortunately proves the point. You get a light that tells you the fuel is getting low but nothing to say that your engine is about to blow up

Actually I was already well aware of the situation as I had heard a pop (water pump it turns out) and was watching things closely. Unfortunately it heated up really fast and I was really badly stuck in traffic and couldn't even pull over so the bong (the noise I'm talkin' yo) just made me panic more. Not sure actually when it started bonging but I was already swearing pretty loud.

[whiskychaser]

Yeah, that's what happens. I'm half tempted to get one of those and see if I can fix it with a bucket of helicoil inserts.
Me too. I have a sneaky feeling the best solution would be an old M50 block under the E39 head. Dont even know if it fits:D After hours of research (ok, a few beers) my colleague in the stage lighting business tells me we need a thermocouple. I only know them as the safety device to turn your boiler off if the pilot light goes out. He tells me they use them in stage amps to ditch power if they get too hot. Some have a pot so you can adjust them. So we just need the critical temp at which the switch should throw. I intend to patent this device so dont tell anybody;)

[whiskychaser]

Actually I was already well aware of the situation as I had heard a pop (water pump it turns out) and was watching things closely. Unfortunately it heated up really fast and I was really badly stuck in traffic and couldn't even pull over so the bong (the noise I'm talkin' yo) just made me panic more. Not sure actually when it started bonging but I was already swearing pretty loud.

Some silly arse is going to ask why you didnt just turn off the engine. There was probably enough residual heat there to fry it anyway. I'd like the system to go back a few miles (before you got in traffic) and gently but firmly advise you that all is not well in the coolant department

[tim eh?]

heh well i had zero options man i would have been skinned alive if i had 'just turned the engine off'. but whatever... the bong works.

[whiskychaser]

heh well i had zero options man i would have been skinned alive if i had 'just turned the engine off'. but whatever... the bong works.
The fact the bong works is good. But its a bit late if you had zero options:D Would be better if it said ' er.. excuse me.. I'm getting a bit hot.. pull over when you are ready'. I'm after a simple solution that warns we are about to wreck an engine. I guess the question is how hot is too hot?

[tim eh?]

The fact the bong works is good. But its a bit late if you had zero options:D Would be better if it said ' er.. excuse me.. I'm getting a bit hot.. pull over when you are ready'. I'm after a simple solution that warns we are about to wreck an engine. I guess the question is how hot is too hot?

yes I would have preferred that myself, it wouldn't even need to be so polite :).

[DaveVoorhis]

One of these http://www.maplin.co.uk/Module.aspx?ModuleNo=220003 or equivalent, suitable (or modified) for a switch-on temperature up to about 130C, combined with a 12 volt buzzer (I wouldn't trust the bonger -- the speaker in them is prone to failure), would make a good early-warning system.

I'm not sure where to mount the temperature sensor (thermistor), though. It would need to be a location that is suitably reflective of the head's core temperature, that closely tracks any rise in combustion chamber temperature, and is independent of whether there's coolant in the system or not.

Calibration would be straightforward: On a hot day, drive the car hard with the A/C full on and tune the warning to just on the silent side of buzzing. Any rise in temp from that baseline, even slightly, should set it off.

[whiskychaser]

One of these http://www.maplin.co.uk/Module.aspx?ModuleNo=220003 or equivalent, suitable (or modified) for a switch-on temperature up to about 130C, combined with a 12 volt buzzer (I wouldn't trust the bonger -- the speaker in them is prone to failure), would make a good early-warning system.

I'm not sure where to mount the temperature sensor (thermistor), though. It would need to be a location that is suitably reflective of the head's core temperature, that closely tracks any rise in combustion chamber temperature, and is independent of whether there's coolant in the system or not.

Calibration would be straightforward: On a hot day, drive the car hard with the A/C full on and tune the warning to just go off. Any rise in temp from that baseline, even slightly, should set it off.

Thats exactly what-and where from-my colleague recommended. I dont see mounting a board on the side of the engine but you could split it up. Think you have it though-run your motor on a hot day and set the pot to that. Anything above triggers a warning via the 'low coolant' route. Trouble is I think we need to be a bit more precise about what is a hot day:D But I think we are on to something here. If we can come up with an easy mod that warns of imminent engine destruction its got to be worth a look

[DaveVoorhis]

If I get a chance, I'll pop into Maplin tomorrow and buy the relevant bits, assuming the sensor kit will (or can be modified to) switch on above 120C or so. I think I'll mount the board and buzzer in the interior somewhere -- probably on the removable dash panel above the pedals -- with leads to a thermistor mounted (epoxied, maybe?) on the head. I'll try it on my E30 first, as I don't mind experimenting with it and the temp gauge has a tendency to sneak just above 12 o'clock on hot days.

[whiskychaser]

If I get a chance, I'll pop into Maplin tomorrow and buy the relevant bits, assuming the sensor kit will (or can be modified to) switch on above 120C or so. I think I'll mount the board and buzzer in the interior somewhere -- probably on the removable dash panel above the pedals -- with leads to a thermistor mounted (epoxied, maybe?) on the head. I'll try it on my E30 first, as I don't mind experimenting with it and the temp gauge has a tendency to sneak just above 12 o'clock on hot days.
Hero! If you can sort it and the manufacturers cant its got to be worth a patent.

[genphreak]

Hero! If you can sort it and the manufacturers cant its got to be worth a patent.Too right. terrific idea this. I've often thought the same thing- what's cool is that it applies to practically all Bimmers.

The thing that wil make (or break) it will be location (and variance). A spare bolt hole on the head would be good, but I expect that even a bolt hole on the head may not provide a consistent, indicative temperature that is reliable enough to trigger above a threshold (without many false positives)

I'd expect that it may need a circuit to smooth the readings so the alert can trigger only based on a set of averages over the shortest period of time that is practical.

For that, a $20 programmable USB board like this would be perfect... www.teensy.com (http://www.teensy.com). It'll also do a lot of other things too ;) but this could read the input from the thermistor and allow the levels and times to be easily adjusted programmatically. It can even do the logic to calculate mean, average and be programmed for other scenarios such as certain prolonged (above threshold) readings.

[whiskychaser]

I'm not sure where to mount the temperature sensor (thermistor), though. It would need to be a location that is suitably reflective of the head's core temperature, that closely tracks any rise in combustion chamber temperature, and is independent of whether there's coolant in the system or not.

This is a very good point. If coolant is low you might not get a reading as is the case for the fan switch. This isnt cheap but might be an alternative:
http://tscsensors.com/chtws0722p0kssnchts.html
Apparantly it fits between the spark plug and head so would be easy to install. A feed off that to a Maplin type board and a buzzer could do the trick?

[DaveVoorhis]

This is a very good point. If coolant is low you might not get a reading as is the case for the fan switch. This isnt cheap but might be an alternative:
http://tscsensors.com/chtws0722p0kssnchts.html
Apparantly it fits between the spark plug and head so would be easy to install. A feed off that to a Maplin type board and a buzzer could do the trick?
Unfortunately, that is a thermocouple (voltage-generating temperature sensor) which isn't compatible with the thermistor (varying-resistance temperature sensor) used by the Maplin board, but a circuit to work with it would be relatively trivial. I think I'll start with the Maplin board and try poking the thermistor down a sparkplug well.

I didn't make it to Maplin today. Hopefully I will tomorrow.

[Mordan]

back then i fried my M40 engine as well due to lack of coolant. the lack of a timely warning really sucks.. but it is all good for car manufacturers anyways.. mother ****ers.

[DaveVoorhis]

I've bought the necessary bits:
http://shark.armchair.mb.ca/~dave/BMW/EarlyWarningSensor.jpg
Development commences.

[whiskychaser]

I've bought the necessary bits:
Development commences.
Nice one! Is there a pot on the board so you can adjust the temp or is that what the spares are for? Was wondering what type of wire to use from the thermistor and if it will go under the coil pack without getting crushed.
Actually, instead of asking questions I will get down to Maplins...:D

[DaveVoorhis]

Nice one! Is there a pot on the board so you can adjust the temp or is that what the spares are for? Was wondering what type of wire to use from the thermistor and if it will go under the coil pack without getting crushed.
Actually, instead of asking questions I will get down to Maplins...:D
There's a pot on the board to adjust the switch point but I suspect the range of temperatures within which the board will switch is limited. So, I got the bag of miscellaneous pots to put in parallel or series with the thermistor (depending on the type of thermistor) to put the active range of the device roughly around boiling point. I was planning to try thin speaker wire, at least initially, to wire up the thermistor.

[e34.535i.sport]

There's a pot on the board to adjust the switch point but I suspect the range of temperatures within which the board will switch is limited. So, I got the bag of miscellaneous pots to put in parallel or series with the thermistor (depending on the type of thermistor) to put the active range of the device roughly around boiling point. I was planning to try thin speaker wire, at least initially, to wire up the thermistor.

This is fascinating... I just wish it was available in english.

:D

[Mordan]

to get reliable temp readings woudn't the best thing to do is resuse the slot for the temp sensor and fit yours in it?drill a hole fit the your custom sensor and solder back?

i might be wrong since i have never seen a temp sensor

[whiskychaser]

There's a pot on the board to adjust the switch point but I suspect the range of temperatures within which the board will switch is limited. So, I got the bag of miscellaneous pots to put in parallel or series with the thermistor (depending on the type of thermistor) to put the active range of the device roughly around boiling point. I was planning to try thin speaker wire, at least initially, to wire up the thermistor.
Should have looked at the spec before I asked if it had a pot on the board:D I noticed in the FAQ section they say it is good to 50 deg C. I think that must refer to the board and even that is going a bit! The thermistor should take the heat and if not I bet one can be substituted. Sounds promising!

[DaveVoorhis]

This is fascinating... I just wish it was available in english.
Sorry, it isn't. :p