confused about over heating devices

[The Great Pretender]

I'm biased toward the TM-2 for 2 reasons:

1 - That is what I fitted to my Bongo and I am thoroughly chuffed with it
2 - it gives a readout in actual degrees C, not 'o-clocks'
There is another reason to do with dumbing a dumb gauge and getting a double dumb answer (measured in o'clocks)

Whichever unit you choose, NONE of them will prevent problems happening, but you will get an early warning so that you can deal with it before it starts to get into the cost zone.

I think my thoughts on measuring degrees C are well known by the techie's. You can read temperature from anywhere on an engine. The result that you get needs to be understood in relation to where it is fitted.
The reason water temp is monitored is because it reacts first to power fluctuations (heat produced), if you wish to measure heat in the metal of the engine you need to measure it from the part that gets hottest first. This is and will always be around an exhaust valve.
If I was fitting a TM 2 I would strap it to the underside of the outlet pipe from the head reading as close as possible water temp.

[lindeelu]

"I think my thoughts on measuring degrees C are well known by the techie's. You can read temperature from anywhere on an engine. The result that you get needs to be understood in relation to where it is fitted.
The reason water temp is monitored is because it reacts first to power fluctuations (heat produced), if you wish to measure heat in the metal of the engine you need to measure it from the part that gets hottest first. This is and will always be around an exhaust valve.
If I was fitting a TM 2 I would strap it to the underside of the outlet pipe from the head reading as close as possible water temp."

With the greatest respect, if the sensor is fitted in that position, in the event of a sudden coolant loss, the indicated reading will drop.
Once the designed coolant volume is reduced, so does it's ability to transfer heat to external pipes & galleries, giving no chance for the alarm function to operate.

The temperature monitoring should be applied to the component you are most trying to protect i.e. the cylinder head it'self
The temperature of the water pump outlet pipe is irrelevant as it cannot be hotter than the cylinder head where the heat is produced.

The cycle is: Combustion heats pistons, liners, valves, head. These components heat the coolant. Most of the heating is done in the head on the exhaust side as you say.
The water pump circulates the coolant through the engine and radiators, cool it and return it.

The coolant gives an average temperature reading of the whole engine.
It is better if possible to attach a Block Sensor type gauge to an external point on the head that responds very quickly
to rises in temperature, but not close to the exhaust manifolds where you merely turn it into an EGT monitor and not a cylinder head monitor.

The coolant does react very quickly to temperature changes, but by the time it reaches the outlet pipe, it has given up
quite a lot of heat to the air surrounding the thin pipe, the hose attached to it and indeed to the cooler parts of the cylinder head it passed through on it's way to the pipe.

I believe Haydn has done much practical research into the specific location for these gauges and has the right location for the sensor, well away from cold air cooling from the fans and wind rush.

[mikexgough]

I'm biased toward the TM-2 for 2 reasons:

1 - That is what I fitted to my Bongo and I am thoroughly chuffed with it
2 - it gives a readout in actual degrees C, not 'o-clocks'
There is another reason to do with dumbing a dumb gauge and getting a double dumb answer (measured in o'clocks)

Whichever unit you choose, NONE of them will prevent problems happening, but you will get an early warning so that you can deal with it before it starts to get into the cost zone.

I think my thoughts on measuring degrees C are well known by the techie's. You can read temperature from anywhere on an engine. The result that you get needs to be understood in relation to where it is fitted.

Exactly.......But you also have to have a degree of understanding of how the cooling system works too.
I personally like the idea of owners making informed choices if they want to fit a gizmo/monitor to their Bongo.... with information as to what is on the market and what it does in relation to the cooling system.....not so they fit everything through fear.....and not understand what the add ons are really doing.
The Bleeding of a Bongo system as well as "how hot does your TM2 read" are all subjects that are raised & chewed over at many Bongo meets, for me......read the information there is on the cooling system & add ons, check out all that is on offer to keep an eye on your cooling system, choose what suits you for cost/degree of complexity, Know your cooling system and lift the bonnet and check your coolant level..... more than once in a while

[mikeonb4c]

The only thing I know is that if we coud decide on that best place, and get everyone to stick to it, we might then try and get some useful comparative data with with to suggest figures that tell an owner whether there is possible cause for concern over the effectiveness of their cooling system

I'd always imagined the coolant loss thing didn't matter safety wise as the low coolant alarm would have informed you well before that happened. So the debate should focus on whether measuring coolant temp is better than measuring engine block themp?

[widdowson2008]

The only thing I know is that if we coud decide on that best place, and get everyone to stick to it, we might then try and get some useful comparative data with with to suggest figures that tell an owner whether there is possible cause for concern over the effectiveness of their cooling system

I'd always imagined the coolant loss thing didn't matter safety wise as the low coolant alarm would have informed you well before that happened. So the debate should focus on whether measuring coolant temp is better than measuring engine block themp?

Couldn't agree more Mike.
As lindeelu pointed out, (and I tend to agree) the purpose of the coolant is to PROTECT the engine components by maintaining a consistant temperature, the cylinder head being the most vulnerable as it probably gets hotter than any other.
I have tried the TM-2 in several positions but have come back to the original spot on the hottest part of the head (above the exhaust). My reasoning (and it may be flawed) is that the TM-2, by nature, measures the surface temperature of whatever it is bolted to and NOT the coolant temperature which may be a few centimeters away.
Unless the sensor is positioned within the actual flow of the coolant, you are never going to get an accurate coolant temperature. Never ever.
There already exists a tapping on the thermostat housing which would place the sensor very close to the return flow form the cylinder head (vulnerable bit) and is quite easily accessed. Why can't this be used Haydn? Is there some reason?

[mikexgough]

Steve & Mike......your thoughts on a "correct" or Uniform location for the TM2 is precisely what is needed....an absolute location plus what range of temperatures it should read, for me and call me stupid, old fashioned or whatever.......coolant temp is most important so if a TM2 type device was reading coolant temperature, then I would probably consider one in addition to what I already have......although I have some ideas.... ...


Steve....sorry about delay with the write up.. .....you will have a concise and an Idiots one this week........

[2sticks]

I have my TM2 sensor fitted to the cylinder head on the passenger side of the
engine bolted to the spare bolt holes in front of the exhaust. This does not
inconvenience me because I am quite used to the temperature going up to at
least 127 C when I pull my caravan up a long steep hill with full throttle.
There is nothing wrong and is simply what I would expect under those extreme
conditions. Driving sedately without the caravan, the TM2 temperature almost
exactly reflects the Coolant and cylinder head temperature at a point close
to the standard temperature gauge sensor position.

Given the initiative to do so, I would prefer to bolt the TM2 Sensor as close
as possible to the standard gauge coolant sensor as this would avoid me having
to raise the TM2 alarm point while towing the caravan. I would certainly not
fit it to the rear of the engine block for the following reasons.

1:
The Block temperature is much closer to the return temperature than the head
temperature would be and does not accurately reflect the cylinder head
temperature or the head coolant temperature.

2:
The cylinder block would be far slower to react to temperature change if there
was sudden coolant loss. The cylinder head could be full of air whereas the
cylinder block may still be full of water.

As a point of interest, the standard gauge coolant sensor does not drop below
the temperature of the cylinder head itself when the cylinder head is full of
air. In fact it can still be very close to the head temperature due to thermal
conduction - the sensor is brass and the head aluminium - don't ask why but I
have tested this on several occasions and I have all the necessary instruments
to do so.

Ben.

[widdowson2008]

Steve & Mike......your thoughts on a "correct" or Uniform location for the TM2 is precisely what is needed....an absolute location plus what range of temperatures it should read, for me and call me stupid, old fashioned or whatever.......coolant temp is most important so if a TM2 type device was reading coolant temperature, then I would probably consider one in addition to what I already have......although I have some ideas.... ...


Steve....sorry about delay with the write up.. .....you will have a concise and an Idiots one this week........

Is that a promise Mike? I would like to put that topic to rest (so to speak)
With regard to the TM-2 - Folk have differing opinions on where the sensor should be fixed but for consistency an absolute location is ideal. However, I don't see why the readings at different points should create problems providing folk specify where theirs is fitted, do you? Getting readings from different locations could actually be very informative providing you know where the locations are. What it needs is a consensus similar to the one Ian set up in 'Bongo Fury Survey' (but I don't know how he did it

Ian ..................HELP!!

[lindeelu]

"Quote"
I have my TM2 sensor fitted to the cylinder head on the passenger side of the
engine bolted to the spare bolt holes in front of the exhaust. This does not
inconvenience me because I am quite used to the temperature going up to at
least 127 C when I pull my caravan up a long steep hill with full throttle.
There is nothing wrong and is simply what I would expect under those extreme
conditions. Driving sedately without the caravan, the TM2 temperature almost
exactly reflects the Coolant and cylinder head temperature at a point close
to the standard temperature gauge sensor position.

I found an interesting table from a coolant manufacturer.
They refer to Ethylene Glycol based antifreeze 33% and 55% concentrations and give the boiling points for each.

RADIATOR CAP PRESSURE 33% ANTIFREEZE 55% ANTIFREEZE
25Kpa (3.7lb) 110.5 degrees C 114.0 degrees C
50kPA (7.4LB) 116.5 degrees C 119.5 degrees C
75Kpa (11lb) 120.0 degrees C 125.0 degrees C
100Kpa (14.7lb) 125.0 degrees C 129.0 degrees C

So I suspect if you are regularly recording 127 degrees C you are either flirting with disaster
or your sensor (most probably) is mounted too close to the exhaust.
Another thing to be aware of is the Tm-2 max reading is 127 degrees.
So If you regularly record 127 degrees C how do you set the alarm at a temperature above that?
This is another reason Haydn moved the recommended sensor position to a cooler spot in the interests of the average
customer.

Haydn also doesn't sugest mounting the sensor on the rear of the block, but on the rear of the cylinder head.

There already exists a tapping on the thermostat housing which would place the sensor very close to the return flow form the cylinder head (vulnerable bit) and is quite easily accessed. Why can't this be used Haydn? Is there some reason?

Why insist on monitoring coolant temperature when what is really important is cylinder head temperature.

I believe Haydn has spent considerable time on selecting his prefered location for the
Tm-2/Enginesaver sensors and has arrived at a position that will work in most vehicles
with uniform and reliable results.

Regarding actual temperature monitoring by external devices, the readings are relative & simply provide a normal datum point for reference and will always vary a bit engine to engine.
The measuring devices are also made to a tolerance of about plus or minus 2 degrees,
so trying to be too precise is futile.
So the requirement is to install a device with the sensor in the most reliable/sensitive position,
record the normal maximum running temperature for that engine and then set the alarm at a level above that setting which will not be subject to false alarms due to
post shutdown heat soak, peak hot day uphill towing loads and will generally not give Bongo owners wives heart attacks..

[The Great Pretender]

lindeelu your not contributing to this thread, your confusing it. Your response to my post said The coolant gives an average temperature reading of the whole engine. Then you state

I found an interesting table from a coolant manufacturer.
They refer to Ethylene Glycol based antifreeze 33% and 55% concentrations and give the boiling points for each.

RADIATOR CAP PRESSURE 33% ANTIFREEZE 55% ANTIFREEZE
25Kpa (3.7lb) 110.5 degrees C 114.0 degrees C
50kPA (7.4LB) 116.5 degrees C 119.5 degrees C
75Kpa (11lb) 120.0 degrees C 125.0 degrees C
100Kpa (14.7lb) 125.0 degrees C 129.0 degrees C

This has nothing to do with what is happening in the engine.
The head gets hot, coolant passing through the head picks up some of this heat keeping the head down to a stable temperature. The heat in the head is what is left after the coolant has done its job.
If there is a problem (other than an immediate total loss) of coolant, taking a reading from the bottom of the exit from the head will show a rise in temperature if there is air in the head. Less coolant = a rise in temp

[lindeelu]

lindeelu your not contributing to this thread, your confusing it.

Don't see why you are confused.
My response was to 2sticks who has his sensor reading 127 degrees C
Hence the table of temperatures.

[mikeonb4c]

But surely, temperature of the metal can vary considerably. To take the extreme case, if you measure next to the exhaust it will be very high. So 127c means little as an absolute figure. it seems to me there are a few key points:

1) Acurate monitoring of the engine core temp (head/block adjacent to combustion chamber etc.) is the ideal

2) Coolant that has just left this area is the best chance of doing this. The principle is compromised though because there is an active cooling system attempting to lower coolant temp if it detects a rise above a certain safe level. Concerns over loss of sensor data due to loss of coolant can be put aside if a low coolant alarm is fitted (cos we are stopping engines then anyway if it goes off!)

3) Whatever is done, two things stand out as being the 'must dos' and they are:

a) Mount sensor where compromising influences are minimal. So avoid hot spots, minimise chances of cooling by ambient air flowing past, or where the cooling system itself may have an influence.

b) Make a decision on what that best measuring point is and try and get everyone fitting their sensors in that position. Because comparative data can then be gathered, and that is the only thing that is of real value as no-one (probably not even the Mazda/Ford engineers!) can give you definitive data on what temps are suposed to be all over the place. They would probably only tell you what the designed temp (range), for the engine core is. But with carefully categorised comparative data, it should become possible to advise an owner if their engine is behaving abnormally).

I'll fetch me coat......

PS - the one Haydn is currently recommending doesn't sound bad to me but that's just a personal view.

PPS- the above are just thoughts. Please challenge them.

[mikexgough]

good thoughts Mike........... My other thought is, after visiting many Japanese Bongo owners groups and sites...........Why don't they fit any devices?.......

They do fit HID lights,Zorsts,Boost gauage,Seats,Wheels,Air suspension,Webasto type heaters and camping bits etc.........but nothing to do with overheating nor undamping the temp gauge......

crouches down awaiting the flack and fall out........of such a suggestion....

Is it because they have a better car maintenance regime than we do?........or perhaps not as lazy as us and check levels more often?......or maybe don't use their Bongos as much.......(but this guy puts the latter theory to bed....... http://kurumatabi.net/) - he even write books/magazines/runs camp weekends and has website.....

[widdowson2008]

I have my TM2 sensor fitted to the cylinder head ............... This does not
inconvenience me because I am quite used to the temperature going up to at
least 127 C when I pull ................sensor position.
Ben.

Hi Ben
You say you are used to getting readings up to at least 127. Are you aware that the TM-2 will not show temperatures above 127?
quote from an earlier post from Haydn........
...the TM-2, it's just that it only goes up to 127C and then it will be quite happy to sit there
edit: Just noticed others have made this point before me

and Mikes recent contribution makes a lot of sense

[mikeonb4c]

good thoughts Mike........... My other thought is, after visiting many Japanese Bongo owners groups and sites...........Why don't they fit any devices?.......

They do fit HID lights,Zorsts,Boost gauage,Seats,Wheels,Air suspension,Webasto type heaters and camping bits etc.........but nothing to do with overheating nor undamping the temp gauge......

crouches down awaiting the flack and fall out........of such a suggestion....

Is it because they have a better car maintenance regime than we do?........or perhaps not as lazy as us and check levels more often?......or maybe don't use their Bongos as much.......(but this guy puts the latter theory to bed....... http://kurumatabi.net/) - he even write books/magazines/runs camp weekends and has website.....

Did I read (on here?) that (some) modern cars do now have a low cooling warning fitted as standard?

Probably only Lexus and makes like that though