Thread: Engine overtemp alarm

Originally Posted by B92 8NW

Watchdog TM2 measures the block temp. But I think ideally you'd need one of those and the low coolant alarm.
TM2 Engine Watchdog - Digital Temp Gauge with Alarm - Full Wave Marine

I fitted a TM2 to my V8. Simple to install and a well made product. The manufacturer was good to deal with too.
ENGINE WATCHDOG TM2, Engine Coolant Temperature Alarm, Gauge & Sensor

Originally Posted by njz

I fitted a TM2 to my V8. Simple to install and a well made product. The manufacturer was good to deal with too.

What an excellently timed thread. I was looking into one of these the other day but didn't know just how easy the device would be to fit.

The manafacturer says it is an "easy fit" but I'm not really inclined to believe that "easy" to them is "easy" to me

Something that is relatively simple, cheap and effective that I have on my Defender, two tractors and a header is temperature sensitive switches on the heads. 105 degree on 300 Tdi. (95 degree ones open too soon.) Power feed to fuel solenoid on injector pump goes through it. Have push button bypass so motor can still be run with it held down but operator should be very well aware motor is overheating.

An important advantage of this type of setup over some others is being relatively fail safe. Most things that can go wrong with the protection system itself will result in the motor stopping. Malfunction of some other types results in no protection or warning of overheating.

Have previously put up posts with more details of this. Maybe someone who knows how to put links to them here could do it.

Originally Posted by PAT303

It's a 96 D1 3.9.It didn't loose a drop of coolant so a low alarm would be useless. Pat

In this scenario, water loss is not your issue. Overheating relies on the manufacturers warning mechanism - the temp guage/warning light to alert you.

If the vehicle was driven and excessive boiling ocurred, you would lose water and the low coolant alarm would alert you as designed. This alert works well for both slow leaks and sudden catastrophy. If there's no water in the cooling system, the manufacturers warning mechanism cannot work as designed.

I believe a low coolant alarm is mandatory and any other after-market warning mechanism is optional. This is especially so on older vehicles.

I have been caught out over the years with cooked engines....

hmm..... this over temp alarm looks good. I think it is is a definite purchase in the next week or so.

Thanks for the thread.

The cap will release at about 1 bar(g), or 130C, while hoses will start to go at 2-3 bar(g) or 140C. Both of these are corrected for coolant compared to steam (increased by 10C). While this is not a safe long term operating temp, it won't do immediate catastrophic damage would (like losing all fluid would). It will also ping, lose power, etc for a while, giving you plenty of feedback that something is not right (and prompting you to check the gauge). The absolute worst would probably be a blown head gasket.

/Damien

I tried a search to get an answer, but the issue has been discussed so often that finding the details of the answer would take more time than I have available at the moment.

My question is:

Will an overheating engine which starts off full of coolant boil off enough coolant to trigger a low coolant alarm before any damage is done?

My guess is that it would. In which case why do you need anything more than a low coolant alarm?

Edit. damienb seems to be suggesting that I am right. Have I read him correctly?

Originally Posted by damienb

The cap will release at about 1 bar(g), or 130C, while hoses will start to go at 2-3 bar(g) or 140C. Both of these are corrected for coolant compared to steam (increased by 10C). While this is not a safe long term operating temp, it won't do immediate catastrophic damage would (like losing all fluid would). It will also ping, lose power, etc for a while, giving you plenty of feedback that something is not right (and prompting you to check the gauge). The absolute worst would probably be a blown head gasket.

/Damien

This man is dot on, that's what your temp gauge is for, it won't kill your engine until you loose your coolant/water, then imminent death is heading your way

You CAN'T overheat an engine full of water, its that simple, it must expel-turn to steam before it will damage the motor