Temp alarm V low coolant alarm

THEORY - "Because the TM2 is so accurate and most people set the
alarm at only a few degrees above the maximum normal running temperature,
you will find you get plenty of early warning whether your coolant is
blocked or completely absent. "

REALITY - "I cooked my 3L pajero engine about 8 years ago (hose failure) and temp guage didn't move. "

Duhhhh ... temps for the TM2 are not provided from the computer ... thats the OBD2 scanner ....

.... and

Benefits of either unit will depend on expectations of the purchaser I think.


In regard to your question .... I tend to agree with the ... Wont instantly explode " line of thought .... but in fairness to the "engine saver", the escort vehicle situation posted by DougT shows "prior warning" is much better than .... finding out later.

I have fitted mine down near the ash tray

at least I can find where my small change is while I am driving at night now :-)

I checked the alarm this morning I seriously doubt ( even though I am pretty deaf ) I will miss hearing that go off if it ever does !

I agree about the escort vehicle scenario.

G'day ChipPunk
OK once again you impress the Mooose with your knowledge of things electrical on vehicles. Mind you the Moose is easy to impress on this subject!
Would you mind providing me with a bit more information on the actual sensors you use (name, source) and how they are attached to the bit whose temp is being measured (glued?). I Googled temp sensors but confusion set in regarding contact sensors, non-contact sensors, thermocouples, RTDs, and others. Too much info for me. I need simplicity and you indicate that what you have is simple. If you prefer to do this offline please drop me an email at esantin at whba dot com dot au.

Thank you Moose, though I should put you in touch with my masters...

Klixons - as from Jaycar here albeit a limited range.
Dick Smith also had them.
Oddly enough 80C is difficult to find, but that may be a bit low for typical systems anyhow (82C being a common low-temp thermostat).
90C is usually fine as a warning, but it depends where & what for.

For temps closer to coolant boiling points (eg 130C), audio suppliers may be a better source (typically 100C - 150C being used for speakers and amplifiers).


For fail-safe applications I use Normally Closed, but as extra or non-critical applications, the N.O.s are fine.

As per RACV and similar publications (Age Motoring section, old car mags etc), they are merely connected to buzzers whatever. (They are rated for 5A at 125V AC etc.) (
IE - just a normal fused +12V source like IGN etc; the switch is non-polar and isolated form chassis to switch earth or +12V to the indicator.)

Attachment is up to the individual - screw or rivet to plates, or glue.
I recently merely tied and taped to things like radiator hoses.

hi every one
when i purchased my engine watchdog i was as usuall wary of claims made by sales pitch
so after fitting it to the rear of the head i went for a drive to establish the average running temps and found 79-84 deg was the ball park so then set the alarm at 89deg chosen as what i thought would be a reasonely cautious setting after it kept going off with heat rises when pulling up suddenly and leaving it idling mode i re-adjusted it to 92deg which has proved ok for my mazda bravo diesel that done

i got to thinking out side the circle
i decided to do a trial

i drained the header tank and also removed 1.5 litres out of the top of radiator so that i had a low water situation as with loss of fluid overnight etc
this was done when the engine was cold i then started the engine and went for a short local drive within a very short time the temp went up and the engine watchdog alarm sounded
so i was happy with the trial results and am quiet confident that it will warn me in a low water situation as dicussed in this thread
hope this is of some use

ps. i am not connected with or trying to sell the product
this just my own experiences
cheers

I understand both would be possibly better but if I can only choose and fit one ( as I can ) I am going to go for the temp gauge.

I had a look at the cheaper options on ebay and I have reservations about trusting a $10 gauge to monitor a $10,000 engine.

I really cannot see how you can cook an engine while the temp remains in the normal operating range.

Nor can I imagine driving more than a fey yards with THAT alarm blaring :-)

hi d200dug
i also went to a beach the other weekend it was a warm day
and while the going was easy on hard sand the temp remained in the normal range 79-84
but as soon as i entered a very soft section/ down a gear and up the revs the engine watchdog temp rose to 90deg and then dropped back as the beach got hard again
i have found it responded very quickly to changes in engine temp and feel confident enough to trust it
i am also wary of the cheaper options
cheers

Thanks ;-)

I preferred the simple option of the TM2. I didn't want to break into the cooling system to install a sensor. May daughter's 80series went over 100degrees going up a hill once and her TM2 alarmed loudly! We were watching it rise and her dash temp gauge disn't move until it got to 97 degrees. The factory temp gauge is deliberately flattened so it sits in the same spot between 50 and about 97 degrees. So all you Landcruiser owners who say your vehicle never overheats because the gauge never moves - be warned! A rising temp gauge is a late sign of overheating.
Her cooling system has since been fixed and now sits between 76 and 80 degrees.

The problem with toyota temp senders as well as being slow to rise as pointed out by Phil, is that they must have coolant actually touching them to work.
I've had two cruisers suffer total coolant loss and both times the temp gauge was slow to respond, quickly flicked up into the red and then dropped back to the cool position once the coolant had all gone despite the poor old 2H diesel nearly glowing red hot at the time.
Ever since I've had both a low water alarm and a digital temp sensor fitted to all my vehicles.

a far more reliable way to tell if your tojo is getting warm is the aircon turning off
- thats always the first youll know of a blocked radiator with seeds etc rather than the gauge moving which comes later

Strange that I have had the temp up to just under a 100deg and the air kept on going.

I think its only the 1HZ that does that and the 1HDFTE certainly doesnt seem to.

You can't always rely on no aircon as a sign of Tojo Wagon 4.2 non turbo overheating.

We came from WA border to Alice on 42C day,,, at 120KPH temp guage went straight up to high 1/2 way through the day ,,, slowed to 110KPH guage went to normal slowly,,ALL this time aircon worked fine

this has occurred to me with different 4.2 s,,, one size doesn't fit all with Tojo guages,,,

so please don't rely on aircon to indicate a temp problem OR the Tojo guage (which can be slow to react but when it reacts it goes from normal to high very quickly),,, fit a temp sender somewhere independant of the fluid level is my preferred.

The temp gauge only registeres whilst its immersed in water.

If the coolant drops out the gauge doesnt move at all usually

Thereby rendering it useless.


I have both a low water and a temp gauge attached to the head. (of the car)

This is the Ford sensor, it is fitted to a 1/8" NPT threaded hole that normally has a vent fitting in it on the 4.2 GU TDI . It is basically a piece of stainless steel with glass filled nylon moulded around it as the body. Image Could Not Be Found Phil G mentioned about breaking into the cooling system, I think there are similar spots on some of the Toyota motors also..

I do like coolant (level) alarms - they should be considered standard design on modern vehicles.

Overheating with "normal" temperature indications is very dependent on the vehicle and may be less prevalent these days (they keep the temp sensor well under else above the thermostat and in places unlikely to have air (pockets)), but it is certainly not uncommon.
The problem is, if the coolant drops below the temp sender's position, the gauge etc often stays as is until the "superheated" (LOL!) steam forces past.
And way before then, it is likely to have had various hot-spots that do damage.

PS - I checked out the TM2.
It's a temp sensor which feeds a digital display (with memory) and the alarm triggers on a gradient - ie, how fast the temp changes - which is settable by the user.

It should be bolted to a "solid" bit of engine - preferably the head. (Solid meaning not fins or head covers etc.)

That is a GOOD technique. As the blurb says, a sudden change in temperature can be a good indicator of coolant loss or faults. (I didn't check if it has a "max allowable temp" setting for the slow overheats.)

Not sure why they confuse the issue with air-cooled engines though.... They have solid cores - hence not the same problems with non-coolant-filled cavities around blocks & heads - that being the reason for many hot-spots and damage to typical engines.

Similar circuits can be added existing temp sensors, but if they do not register heat changes (as from low coolant) then that's pointless.
The klixons still work, but they switch when a particular temperature is reached - hence a bit delayed from the TM2 as well as being ambient relative (ie, though engines should maintain a certain temperature, some do run colder in cold ambients).

The klixon is a nice cheap & simple backup tough - especially if the TM2 does not have a "max temp" alarm point.


But IMO the TM2 is a good & reasonably price unit. Being "change" sensitive, it is not "crap" as I have seen with other (overpriced!) units.
And at the price, I doubt that any electronics hobbyist would bother building their own. (Unless they could merely add a temp sensor to their programmable onboard in-car system & display(s)....)
I hereby withdraw and apologise for my earlier comment about bullsh overpriced eBay systems in regards to the TM2! (If that isn't obvious.)


Which is better - a coolant level sensor or TM2? IMO only specific vehicle differences might decide that - they are both worthwhile.
However, the TM2 should alarm what is ultimately important - a fast temperature change. After all, a coolant level sensor will not detect a weak water pump or blockage or slipping or broke drive belt.
And I believe I have just answered my question.... The TM2 is better....
(And I like it's "bolt-on" fitting - no need to get into existing plumbing; no warranty issues; etc.)

ChipPunk, How did you "checkout" the TM2 alarm?

I can find no reference on the manufacturer's websites that indicates or even suggests that the device operates with respect to "rate of change" of the engine temperature. In fact the several expressions re operation make clear reference to actual temperature setting and detection.

As for maximum range, the specifications quoted are 1 to 125C for both indication and alarm point setting in 1C increments.

A temperature alarm system incorporating a derivative function (rate of change) may have some advantage but could also introduce false alarms at times where engine load rapidly increases due to say heavy sand. The real criteria is the absolute engine temperature.

If what you say is true, then I'll stick to Klixons. $6 per measuring point, a buzzer or light etc... Why spend extra?


But from ebay-ENGINE-WATCHDOG-TM2-TEMPERATURE-SENSOR-GAUGE-ALARM-item130394207139:

To Wit:
"The sensor detects changes so quickly, drivers can see their engine temperature rise and fall degree by degree as they drive in varying traffic and road conditions.

- You can program the TM2’s alarm sensitivity to suit your engine

With a TM2 you don't even need to know your engines temperature specifications to set the overheating alarm."


But now I see the following....
"You simply note the highest temperature your engine reaches during normal driving, then set the audible alarm to go off at a few degrees higher by pressing the button on the front."

Hence I think you are correct.
Hence I argue misleading blurb where "your engines temperature specifications" means "specified" temps as opposed to "actual" temp, and references to CHANGING temperatures like "the slightest engine temperature change as it occurs" are confustigations - deliberate or otherwise.
etc
etc

If so, I withdraw my previous withdrawal and apology.
And I apologise for my overestimation of the product.
And I wish I could post-edit the above (by inserting "Ignore all that follows")

And I thank you Allan for showing that I too can get sucked in by the advertising blurb that is so effective on others. LOL!
(I'm readjusting to the new-Australia - I'm used to the more ACCC compliant days, not the current infomercial-style of cross-promotion, misinformation and garbage.)

Allan - THANKS!
Me - D'oh!! And coolant sensors and Klixons.

No worries Chip (can I call you that? lol) Many marketing blurbs use rhetoric to impress but are not necessarily accurate. I thought I knew the TM2 product and decided to recheck. (Got nuthin better to do waiting for Cape York departure!)

When Engine Watchdog say "sensitivity" etc they are really referring resolution but by design the product resolution can be no better than one digit i.e. 1 degree C.
I still think it is quite a good product and easier for some to install than Clixons.

I have used a Clixon or similar thermostat on an earlier vehicle after I blew up the motor due to sudden water loss. The only concerns that I have about Clixons is that 1. They are an electromechanical device. 2. They have open-circuit contacts with the possibility of dirty contact. 3. If installed in a draft, heat cam be lost from the body and thus the sensing element is cooled and reads low. This is particularly so if clamped to a hose with inherent low thermal conductivity. It should be shielded or thermally shrouded for accurate results. But yes they are cheap.

Chip, when I display mud on my chin, please be gentle in correcting me too hey?

LOL - Chip is fine, though I'd forgotten the old adage about how well balanced we Aussies are (we have a chip on both shoulders!). Unfortunately too I had forgotten about our tall poppy syndrome - but that may simply be the new commercialism at work. (I've been away for too many years. I've been taken aback by a few responses on this site...)


And yes, the blurb is obvious. I won't bother discussing resolution versus accuracy versus repeatability, nor sensor versus detection circuitry versus display.... But damn - I thought the rate-of-change methodology was excellent. And so easy... What a pity it doesn't (yet) exist...(?)


As to Klixons, they are electro-mag devices, but probably more reliable than analog temp sensors.
But if critical, I'lll use 2, but I usually distribute a few - eg, front, centre & rear of head(s) etc.
It's similar to fitting a second single-wire earthing oil-pressure switch - I merely connect the switch outputs together - either will trigger the light or alarm. (Redundancy is almost pointless without notification, but testing & alarming is another issue.)

But as I hinted earlier - Normally Open for non-failsafe applications.
If dirty contacts are a concern or issue, I'd use Normally Closed instead, but that needs (say) a changeover relay to invert the alarm signal unless a "green is ok" display is sought.
This seems to be overkill for most. Normally Open oil-pressure switches (ie, closed with oil pressure present) only became standard with the advent of EFI. (Excluding those that used to used them for fuel pump control in carby vehicles LOL!)


As to air cooling etc - I agree, but this case was specifically for a good mounting to a solid spot. The metal-metal (or metal-glue-metal) conduction should well exceed air cooling.
But my experimentation with Klixon on rubber radiator hose proved your point - too slow & too "remote" from the heat-conducting coolant etc.


There are other temp switches too - whether small poly-fuses (or whatever they call those capacitor-like thermal fuses) or even Curie-effect switches.

But I'm happy with my existing temp sender - unlike the temp meter, it does NOT have a flat spot (now where did I read that... lol) and a voltage switch cheaper than......
And if I had EFI, I'd probably have an existing second temp sensor as a backup....


And Allan, please let me know if I am vicious - my expression can be bad.
Idiots and errors do not provoke me, only those that (should) know better that repeatedly push the same one sided accusations without answering questions or trying to express differently or seeking clarification...
But I am one of those that often has the last entry in a topic/thread - and that will usually be a question (which the alleged "more knowlegeable" never seem to answer...).
I often say "attitude is everything". However it's only in recent months I've realised that has a negative outcome as well....

125 degrees Celsius (255 F) is the operating range for the TM2

I have not been up in the top end for decades but I know it can get mind numbingly hot up there.

If your local mechanic thinks everything is OK then local knowledge would be the best option.

I am guessing the ambient air temperature would be around 50 to 60 oC I am not sure about the engine running at double that figure.

Hi Reg,

I thought that the upper range of 125C was a bit low for engines operating under severe conditions in Australia and you have confirmed that.

An engine does not operate at some absolute temperature. The heat energy of a loaded engine elevates its temperature to some point above ambient so for the same load it will obviously run hotter in a high ambient than in a cold one and for higher loads it will also run hotter. Of course, in a very cold ambient the engine temperature is maintained at a suitably elevated temperature by reduced cooling air and thermostat throttling.

For this reason of differing operating temperatures, it is better to have an adjustable temperature alarm than one with a fixed setpoint such as the Clixons that ChipPunk describes although they may be satisfactory where the engine operates in a reasonably constant ambient.

I find my alarm, adjustable from the dashboard, ideal for the wide-ranging ambients and engine loads that my vehicle experiences.

Remind me NOT to visit the top end in the build up season !


I would love to spend a wet season up there and photograph a big wet.

Geez, if only someone could come up with a "rate of change" device....

You'd think technology would be advanced enough....

Then again, what sort of a nerd would think up a solution like that?

Wise action.
Without an inspection method, you have little choice.

"Oh, but they are sealed!"
- Yeah, and heater and other cores never leak; clamps never loosen; hoses never craze. And of course if coolant leaks out, it will never suck air back in will it?.

I occasionally give my (cold) top hose a few quick squeezes to ensure coolant and pressure/resistance is present.
But having a regular radiator cap (with overflow bottle), it's easy enough to check. (The cap seal is bypasssing - I'm expanding out but sucking air back in.)

Just a pity I was wrong about the TM2's operation, otherwise that would have been a winner.