[TheOtherLeft]

I was just thinking about the best way to measure temperatures, either water or oil.

As most traditional temp probes are in contact with the medium it is measuring it means you have to modify the system, eg tap a thread in the transmission to put a sender in, or use a oil sandwich plate between the oil filter and block, or put a wire in the radiator hose.

What about the sensors that bolt onto the engine block, such as Engine temp sensor? Do these work just as effectively? I suppose it could be used on the transmission as well.

Cheers

[shandy92]

i have been thinking about something like this as well, so ill be watching this thread for responses.
just had a look at that watchdog device, looks like an awesome piece of kit, and not majorly overly priced.

Mitch

[fordem]

One of the potential issues you'll have with a contact sensor of that nature is that it will indicate the temperature where it is mounted, so you have to find a way to mount it where you want the temperature measured.

The engine temperature is not a constant number across the entire engine - cylinder head temperatures are higher than the cylinder block, exhaust valve temperatures are higher than intake valve temperatures etc.

An interesting experiment - if you have access to a digital thermometer either one with a contact thermocouple or an infrared, non-contact unit, is to start with a cold engine and take readings off of a few different points - perhaps the exhaust manifold, the oil pan, the oil filter, the radiator inlet & outlet, etc., and then start the engine and let it idle and take more readings as the engine warms, and after maybe 10 mins or so, switch off and continue to take readings for another 10 mins or so - you'll probably find that certain parts of the engine continue to show a temperature rise after the engine is switched off, whilst others show a drop.

By the way - this will also happen if the engine is allowed to reach full operating temperature before it is switched off, if you have a mechanical temperature gauge that works with the ignition off, you should see the coolant temp increase immediately after the engine is switched off. In fact, I know of a few vehicles that I can depend on to "burp" into the coolant overflow bottle a minute or two after the engine is switched off.

On most liquid cooled vehicles the engine temperature is considered to be the coolant temperature as it leaves the head, and for this reason the temperature sensor is located near the water outlet elbow.

The contact sensors work, but how well they work will depend on how carefully you locate & install them.

[mnemonix]

Great post fordem.

I use a watchdog style temp sensor on my zook. A great backup with alarm should I fail to notice a sudden rise of temp from lost coolant etc.
I have it mounted to the thermostat housing.
It shows a pretty consistant temp during running and a temporary rise of ~10 degrees when the car is switched off from running temp.

Accurate enough for my needs.

I can't say that I'd trust one for oil though, in the belief that the radiant heat being measured would not be an accurate indication of the actually temp.

[PJ.zook]

I would just use gauges as they are easy enough to fit with a little bit of work. Just dont use Speco, im on my 2nd coolant temp sender and gauge and its farked now too.