anyone using Engine Watchdog or similar for temperature check

Thanks Rosco for taking the time to reply, you may be interested in the replies from others who show that what happens practically is sometimes quite different to therory.

Certainly interesting Cruiser. The whole point in having a pressurised system is to raise the boiling point above 100 deg.
From the postings it would appear this to be unnecessary which I find surprising, given that philosophy is applied across the board.

Hi Rosco
Yes I am finding all the replies very interesting and appreciate the feedback.

I believe with a 15 psi radiator cap and 50/50 mixture of Ethylene Glycol the boiling point is raised to 130deg, so we all have a lot in reserve.

Engine Watchdog or similar is a great way to monitor our cooling system however I find I become a little bit obsessed and worry uneccessarily sometimes while on a trip when I see a rise in temp.
This post is an attempt to learn more from others and find reassurance that all is well with my system.

Ideally if manufactures could design a cooling system that maintained a constant temperature motors would last even longer than they do but I think this is impossible

The actual block temperature of most vehicles in good health should vary very little once warmed up, until it gets to the point where the cooling system is not keeping up then the temperature will rise.

Our cooling systems DO self regulate by a couple of means.

The use or presurisation and addition of glycol does most definitely increase the boiling point of the coolant......many modern cars will boil their little heads off with very little provocation if the correct amount of coolant is not used.....Most modern cooling systems run fairly hot..normally.....many cars especially toyotas run a pretty stiff concentration of glycol in the coolant.

The first self regulation mechanism is the increased boiling temperature.....it allows the radiator to run a a much higher temperature in comparison to the surrounding air.
As the temperature of the radiator increases, the temperature gradient to the surrounding air increases making the cooling system more efficient.......thus a tendancy to stabilise the temperature.


Even the heat variance within the radiator effects the cooling efficiency......the radiator is not always all hot......there are times when the bottom of the radiator may be quite cool while the top can be at operating temperature...thus the radiator varies in efficiency...the top will be transfering heat very much more effectivly than the bottom.

The second mechanism for temperature regulation is the thermostat...many people are under the misconception that the thermostat is either open or closed and once it opens it stays open.
This is not true, the thermostst is constsntly opening & closing and varying its opening regulating coolant flow from the radiator to the block.

The third mechanism is the fan...most modern cars have some sort of temperature variant fan, be it an electrick fan with a temperature switch or a viscous hub mechanical fan the varies its drive coupling with temperature.

Without exception pasenger car radiators have limitations and are not capable of dealing with full engine output for extended peroiods.

Once the temperature has risen above normal, that is a sign the the cooling system is not keeping up...if the engine continues to produce the same amount of power under the same curcumstances it will eventually overheat.

A clasic example of this is burn out competitions........vehicles put in a situation where they are constantly producing maximum power, with poor airflow......If the engine and transmission hold there are two limitation...how ling the rubber lasts and how long till the radiator boils.....neither are very long.


Cheers

Yep .... what Bantam says so eloquently is more or less what I said in a couple of lines.

Hi Bantam and Rosco
You describe the function of a cooling system very well.
But do these mechanisms that regulate water temp maintain a constant temperature?
I think if a vehicle was working at a constant speed and load then yes the engine temp would be constant.
But when variables like changing speed and load and in particular reducing air flow through radiator are introduced then I don't think the system can respond quick enough to maintain exact engine temp.
An extreme example is when travelling at highway speed, the thermostat is probably only partly open and maximum airflow is going through radiator with an engine temp probably 85deg. Then come to a sudden stop and idle at roadworks for 5 minutes.
Now there is very little air flow through radiatot because viscous fan varies with engine speed and the water pump is pumping a lot less water, the thermostat must open immediately to compensate. Would this not cause a variance in temperature while the cooling system "catches up"
For your consideration

If you think any part of the engine is at a constant temperature, you are dreaming.....it never will be.

But considering the operating range of the coolant is well below zero to well abover 120C....10 or 20 degrees is neither here nor there.

The cooling system efficiency will continue to increase right up to the boiling point of the coolant or the venting pressure of the radiator , due to the increased temperature gradient to the oustide world.

As soon as the cooling system boils or vents, system efficiency drops considerably.

What we need to know is.....is the coolant temperature increasing above normal...if so the cooling system is not keeping up.

If the coolant temperature continues to increase you have a problem......and not soon........have had for a while.

most vehicles will sustain coolant temperatures moderatly above "normal" and below venting indefinitely as long as heat in is less than heat out.
But that comes down to knowing your vehicle and how far you can push it.


As for setting an alarm for a particular coolant temp.........BEEP BEEP BEEP.........mate you had a problem 5 or 10 minutes ago......now you have a real problem.
Set it too low and it will be nothing but a neusance, set it too high and well its pretty pointless...above all remember coolant temperature lags heat generated and heat disipated by quite a bit.

I can see a role for coolant temperature allarms on engines that are not actively operated or attended.

But in a car or truck....you should have known you had an issue long before the allarm tells you.

cheers

That's exactly my point, temperatures do vary. I guess that is proved by the thermostat spec being; starts to open at 82 fully open at 95 showing that engine temp should be controlled within that range
Anyway I am happy that my engine and cooling system is working fine but these replies have been very informative,
Thanks

Being informative is what these forums should be all about.

A far exchange of information & ideas.

I think the reasonable range is a bit outside the thermostst range...but by the time all the regulating factors come into operation the normal window of a cooling system is pretty damn narrow and well regulated considering.

And remember all these regulating mechanisms are good old 40's & 50's phsyics & mechanics.

We have seen a few new fangled things like electric thermo fans & electric water pumps...but the majority of cars & trucks run cooling systems pretty much as you could have seen them in the post war period.

cheers

Thanks Erad, exactly the sort of information I was looking for.

best regards

Another example of that philosophy (not showing the driver the actual coolant temperature) went further for us with my wife's new Mazda CX5 - no temperature gauge at all ! - one is simply advised that the coolant is cold, or too hot.

Hi Athol
I bet you were glad that you had scan gauge as well otherwise seeing 125 on the watchdod would have been worrying.

Cruiser 3
Yes, each system serves its own purpose. I also closely watch the auto trans temp with the scangauge, and keep the temp down as much as possible by prudent use of the gears.
Regards
Athol

Thanks for your reply Darian.
Like you I travelled the Nullabor towing a van and was told by the attendant at Balladonia servo that it was mid 40's. That was before Engine Watchdog was fitted but all was well.

it seems that a 10 deg varience is quite normal under conditions from normal to heavy loads.

My observations show some situations such as idling after highway running cause further increased temps (see my reply below)

These systems do not monitor water temp but the metal temp of the engine and water temp and metal temp may not have any correlation with each other.

I appreciate many instructions say mount the sensor on a thermostat bolt but I would advise not to do that as the metal in that area will be primarily influenced by water temp rather than engine block/head temps. Afterall you have the vehicle water temp gauge to advise water temp.

My advise is to have the sensor mounted to a bolt in the head or top of the block.Mine is mounted to a spare bolt on the lower head.

The temp from the Watchdog is not absolute temp but a reference temp to measure changes. For example my engine in normal operation has a water temp of 85-100 degrees. My watchdog has a temp of 72 degrees when the engine is operating normally and water temp is around 85-90. I have set my alarm at about 85 degrees. In normal driving the watchdog temp only moves from about 70 to 75 degrees while water temp can be all over the place. When stopped at traffic lights the watchdog temp can go up to about 80 as the head soak from the engine increases as there is less airflow over the engine when stopped.

On a hot day after I have parked and come back to the vehicle the the Watchdog temp alarm can go off because when stopped there is no removal of heat from the engine via the coolant or airflow over the engine so the heat soak builds up - shows how an engine seize when switched off when it has been overheated.

To set the watchdog up I get my engine to operating temp and then note the watchdog temp - then set the alarm at about 15 degrees hotter. Make sure then low coolant alarm works when the actual radiator get low and not just the overflow bottle. In some vehicles the main coolant system can drain if there is a hose failure but the remote filler bottle can still have coolant in it so if the low coolant sensor is there it may not set the alarm off.

Cheers

Garry

Thanks Bantam for your very informative replies.
I agree that my method of trying to monitor engine temp to avoid any problems is certainly not perfect but it is the best I can do.

I would like to fit a Scan gauge but I believe they are not compatible on a 1996 petrol Landcruiser, the diagnostic connector is rectangular and has irregular positioned pins.

I keep comming back to "what are you measuring and is that actually usefull"

The majority of pasenger car "temperature guages" are not marked with actual figures and are not calibrated with any sort of accuracy.

Generally the method of "measurement" is crude & fundamentally inaccurate in many ways....we realy have to ask ourselves is that realy a bad thing.

Consider that many of the modern vehicles retain the same old crude and inaccurate temperature guage system for driver viewing, but have several far more accurate temperature sensors for the purpose of engine managment.....we have to ask ourselves why.

The "temerature guage" realy should be called the "driver temperature indicator"....its role is to show that the general operating temperature of the engine is..."normal" or not.

Still most drivers do not know how to read a factory temperature guage..

These ..suposedly accurate temperature guages are sold on the basis of fear, uncertainty and doubt.

They tell us that we need to accurately know what the engine temperature is and that these guages can do that.

I believe wrong on both counts.

The major selling point is prevention of engine failure, due to critical coolant loss.

Realy if coolant loss is the issue, perhaps a coolant loss allarm would be more appropriate....but those can not be constructed cheaply & easily from pretty well off the shelf electronic parts and quickly bolted to the outside of the motor..


As can be found in heavy transport, earthmoving, high performance marine, critical task stationary engines and motorsport, if you want meaningfull temperature measurements...you will not get them by mounting a sensor on the surface of the motor.

A coolant temperature sensor needs to be mounted where it is immersed in the coolant and in a meaningfull place....some high performance engines will have multiple coolant temperature sensors in well chosen places.

As for measuring block or head temperature....serioulsy..how usefull is that.

What will save your bacon is......knowing how the cooling system behaves and learning to read a crude old temperature indicator.

Afterall, engine temperature is a slow changing variable, whatever temperature you are reading will significntly lag, in the order of minutes or at least tens of seconds the temperature where it matters.

If the temperature begins to rise above normal....the cooling system is already not keeping up.

As has been mentioned eralier...it is very common for coolant temperatures to continue to rise after the load has been removed and the engine turned off....have seen in the past several times vehicles reading near normal temperatures pull up turn off and boil by the side of the road, minutes after pulling up.

Because the heat is still comming out of the block and the coling system is no longer working well.

If you realy want an accurate and meaningfull temperature guage, yoi want to be bolting INto the block and getting it into the water jacket..somewhere meaningfull.

cheers