A friend of mine is a diesel mech, and suggested a thing called a 'murphy switch'.
it apparently is a temp sender that measures the block temp directly (?) and when it reaches a set temp it simply shuts the engine down, not allowing it to get to criticle temp.
Anyone know anything about them?

Dave.

- (#8737) DaveW, 22 Feb 04 17:48

Ok if you are in the Outback, but in the outside lane of the M25 London ring main, not a good idea to shut the engine down.
I've understand these were fitted to generators for use in tropical climates by the UK armed forces.

- (#8737) Clive (Bristol UK), 23 Feb 04 01:07

This sort of protection crops up in all sorts of industrial electromechanical systems but, as Clive says, the car is an exception where we are very fussy to compromise safety and reliability to a point for the sake of convenience and cost.

Toyota's sender in the 2CT is fine for sensing the block temperature - well at the point it's attached anyway.

My modification (see Ace Answers Handbook) does two things. First, stop the gauge from "sticking" around the middle - making you think, wrongly, that the temperature is nice and steady. Second, attract your attention with an audible alarm once the temperature exceeds what you've decided is a "normal" limit - allowing you to do what DaveW wants, "when it reaches a set temp it simply shuts the engine down" - but allowing Clive to pull over to a safe location first!
- (#8737) Dave Mason (Sussex), 23 Feb 04 04:34

As a proud user of said "Mason Alarm", I can say it does what it says on the box, well leaflet, but you get the idea. The best modification you can make to your Ace in my opinion!
If you are still not sure then come and see one at an Ace Jam.

- (#8737) Clive (Bristol), 23 Feb 04 04:48

That will be an awfully long drive from Australia Clive!

- (#8737) dave Bright, 23 Feb 04 05:13

Let me just point out that even an auto will freewheel if the motor dies.
And further to that if your motor overheats drastically like ours did, due to a catastophic failure of the radiator and subsequent total loss of fluid the standard sender unit WILL NOT WORK - either to activate the alarm, or work the gauge.
And if that happens to you, then your motor will stop just as surely.
Isn't it better to have it stop before the damage occurs?

Please note: I am not suggesting this as an alternative to the Mason alarm mod - only as an extra safeguard.
I have checked out several sources, and spoken to more than mechanic - both amature and professional, and a diesel specialist, and have been assured that the standard sender unit will not register accurately without water in the system. I also know that to be the case in several vehicles I have owned in the past (from experience - the warning in my old Fiat 128 was when the temp gauge went down - that indicated no water in the system!).

- (#8737) DaveW, 23 Feb 04 21:34

Dave, even on those vehicles where the gauge sender DOES respond incorrectly when the water goes (my wife's Citroen ZX springs to mind), the gauge will spike up before going down. The Mason mod (or Durite gauge, or whatever) ensures that the spike is more noticeable, so that anyone with an ounce of wit will realise...

Now, whenever I fitted my electric fan system, I had three stages, each with an LED on the dash. A sensor on the rad itself (55c thermal switch) that signalled the low speed fan (ran continuously then), an intermediate (103c on the outlet neck) which brought the fans on full, and an overtemp (can't remember, 107 maybe?) that brought on the horizontal rad's fans too.
The upshot of this was that the LEDs would light sequentially. Green, plus amber, plus red. But if the water was going short, the green light would go out. No green, not good...

- (#8737) david miller, 24 Feb 04 00:15

Dave,
"And if that happens to you, then your motor will stop just as surely.
Isn't it better to have it stop before the damage occurs?"
That sounds good but, have you ever been at the wheel of a Townace when the motor dies? It becomes almost unstoppable because of the loss of servo vacuum and, also, it becomes virtually unsteerable because of the loss of pressure from the power steering pump.
Of course, any improvement on the "middle of the road" Toyota temperature gauge, is welcomed and Dave Mason's device overcomes this deficiency. I use an accurate Durite gauge and this is a great improvement on the standard Toyota gauge but, that catastrophic and rapid loss of water, due, possibly to a hose/head/radiator failure, has had expensive consequences for many owners. Is there a case for experimenting with a pressure sensing device, say, on a main hose which, I should think, could activate an alarm if air/steam starts to replace solid water?

- (#8737) John Davis, 24 Feb 04 01:45

I still have the wire temp probe stuffed into the side of the coolant temp sensor, held on with cable clip. This does measure block temperature as its on the side of the block. If I start to worry I just put the plug (stuffed under the seat) on the multimeter for a temp reading.
Readers of my last years posts will know calibration of the multimeter is critical to prevent false alarms and uneeded worry/panic.
You could always hook up a sensor on the block/head surface and link to a seperate guage with a modified DM alarm!
Perhaps the murphy switch could just sound some bells and whistles (strong heart needed) rather than cutting the engine?

- (#8737) chris turner, 24 Feb 04 05:24

This reminds me that I was looking in to the possibility of fitting a pressure gauge to the cooling system. There is a digital gauge that is a combined oil pressure/coolant temperature, that is accurate enough to sense pressure much lower than 13 psi. I'm going to have to fit the pressure sensor to the cooling system somewhere, and I am planning on fitting it to the thermostat bypass circuit or drill and tap the coolant outlet from the engine. Then I will have one gauge that will tell me the actual engine temperature and coolant pressure, so any coolant leaks small or big will be quickly noticed.

- (#8737) dave Bright (Bournemouth), 24 Feb 04 06:17

Dave. That sounds a good idea. I have spare outlet pipe/casting and would like to experiment. If you do go ahead, perhaps you would be good enough to advise the outcome, details of the digital gauge etc

- (#8737) John Davis, 24 Feb 04 06:22

Hi John
The only drawback is the cost. Digital gauges aren't cheap and as this is two in one so it's a double whammy on cost, but I think the result will be worth it so I will be going ahead. I will keep you informed of the progress, and where to buy and how to fit it etc.
Now all I have to do is decide which one of my fleet to fit it to.

- (#8737) dave Bright (Bournemouth), 24 Feb 04 06:38

Dave. Yes, digital gauges are not cheap but, my thoughts are towards a pressure switch, range, say 0-20 psi, switching a lamp ON at start up, off at, say 10/11 psi, and on again should the pressure fall below a pre-set figure. I am presently awaiting details of such a pressure switch from a well known manufacturer.

- (#8737) John Davis, 24 Feb 04 08:38

The gauge I have ordered has two readouts, one for pressure and the other for temperature. Both have internal programmable warning lights, and additional Programmable outputs for driving external LED's or relays. Send me an email and I will tell you what I have so far.

- (#8737) dave Bright (Bournemouth), 24 Feb 04 08:53

Sounds suspiciously like a SPA gauge...
Oooh, nice, but way too dear!

- (#8737) david miller, 24 Feb 04 09:49

Hi david,
Oooh yes, it is an SPA gauge. Oooh yes, it is nice, and errr yes it is a bit pricey.

- (#8737) dave Bright, 24 Feb 04 10:17

David,
My wife was driving when ours went, and she is aware of the reputation of these, and was also subjet to my old Fiats - so she keeps a solid eye on the gauge - and I trust her enough to believe her!
Our problem was the side of the radiator blowing out, and by the size of the hole/s down the side, the water was probably all ejected BEFORE the temp went up - ie, in less than 60 seconds.
Again I say that I have spoken to several people and they assure me that the standard Toyota type sender unit will not register properly without water, and the likelyhood is that this particular kind of problem gave no temp warning. The water went so quickly that it was all gone before the temp could rise.
(Add to this that my oldest Son is a worry wart, and also looks on from the middle seat, and He didn't notice anything either!)

John, if you heat the engine to lock up then you will have no power in any case - isn't it better to shut down the engine before you damage it, rather than cease it and still have no power for the steering and brakes while you panic as to why it has blown up?

What is the big problem with another alternative.

I guess you could also attach a warning buzzer to this unit instead of a kill switch - the advantage being that it measures an accurate block temp, regardless of water temp and/or water in the system.

I had been told of this unit and was wanting to know if anyone knew more abot it - that's all.

- (#8737) DaveW, 24 Feb 04 14:23

Having driven mine to the point of catastrophic head failure a couple of times, I'm happy (?) to confirm that the gauge in fact DOES do really odd things before all the coolant goes. It rises and falls quite sharply as coolant surges through the system. But any addition block- mounted senso will do the same. It needs the water to transfer the heat wherever it is...

- (#8737) david miller, 25 Feb 04 00:40

If I could add...
The best indication of an impending cooling disaster is the front heater going cold. It's easy for us in the UK to keep an eye on, 'cause we have the hearer on most of the year.
Maybe for you chaps from warmer climes disconnecting the heater matrix and pitting a loop of hose to about the same height w/ a sensor at it's top would be a good way of confirming flow?

- (#8737) david miller, 25 Feb 04 00:49

The temperature sender does act sporadically as any remaining coolant circulates. I’ve just blown a gasket (or worse) and my temp stayed exactly in the place it always does, when I saw smoke (I hope steam) in my rear view mirror I checked the Temp as I pulled over, it was showing normal.

I filled up with water (which I always carry) and the Temp. shoot up the moment I started up.

So I can confirm without water the temp. gauge is useless. Having said that I’ve just purchased an audible alarm in the hope that in the early stages of coolant loss I get enough warning.

I will investigate monitoring the head temperature by another method to provide an audible alarm and let you know how I get on.

Chris Harding
- (#8737) Chris, 25 Feb 04 03:16

I hear (read) what you say, and feel it all comes down to reaction time unless you have a shutdown Murphy Switch. My own experience of Alpine hill climbs, with a lorry so close behind you could read the makers name of off the screws on the number plate, does not inspire me to fit an engine killing switch.
The Mason Alarm works well, easy to fit and adjust.
Without the Mason Alarm I would have just had the Toyota guage to go by, but would I be looking at a guage or blinking lights when these events occur? A bleep alerts me, look at the guage, check for steam, pull over or whatever.
I accept the water sender may not be the best, and alternative/expensive options are available, a pressure audio alarm would be my choice.
Unless a cheap audio water pressure alarm becomes available I stand by the Mason Alarm, with the knowledge that if the temp rises slightly above normal it will go off! I'm then alerted and can react.

- (#8737) Clive (Bristol), 25 Feb 04 04:43

Yes, I admit that I wasn't (above) considering this rapid coolant loss situation and the distinction between block temperature, head temperature and sensor temperature.

To say "without water the temp. gauge is useless" is justified by the behaviour of the Toyota indicator - it's a sluggish meter in its own right, as well as not budging beyond its "sticking point" soon enough - but is unfair to the Toyota sensor.

Owners who have an audible overheating alarm will know the impact caused by it's first tentative bleep which will occur with the slightest and briefest overheating of the sensor whether or not the indicator needle has time to move.

It seems to me consistent with all that has been said that a sensor in the Toyota position, in the head, and any audible alarm connected to it, will probably briefly detect the overheating during total coolant loss just as well as a temperature sensor placed anywhere else. Without the coolant big, and damaging, temperature differences presumably build up between different parts of the head and block.

A pressure switch will be more reliable but you'll have to deal, reliably, with the fact that it'll always register "fault" prior to, and for a minute or so after, starting.

Isn't this all about risk management? You have a reliable engine despite which we, with all the horror stories on this forum, can easily get gloomy about. You could invest a lot in reducing this area of risk and then hole the sump on a rock or something else. And as was explained in a recent long posting about disastrous electric fans on a trip to Chester - any improvement you try to make should be better-engineered than what Toyota provided in the first place.
- (#8737) Dave Mason (Sussex), 25 Feb 04 07:50

Well said Dave, most informative. I come back to my often quoted(by me)theory that the Townace is, as it's name implies, a town vehicle. Can anyone say if they have had serious overheat/coolant loss/head cracking etc, when motoring sedately, even on motorways? By sedately I mean not over 60mph. I have seen postings where drivers mention 90 mph motorway journeys and, in my opinion, the vehicle is just not built for that kind of travel and it's shape and engine/radiator location, does not allow for the margin needed to prevent an overheating situation from developing. I did go right through my 2CT Masterace engine three years and 45,000 miles ago,ie new head gasket, bolts, head skim, careful attention to the cooling system by regular and thorough flushing, slightly modified thermostat flange with 3 mm drillings, latest type Toyota rad cap, Durite gauge etc and particular attention to the discharge and suction hose to the expansion tank. Also, I do check the levels very regularly, at least every week and, always, before any longish journey. Subsequently,I have never had any problem and I put that down to fairly careful motoring.
Of course, sods law might give me a rude awakening and I promise to post the gory details if it does happen.

- (#8737) John Davis, 25 Feb 04 14:29

So, John, you've brought us back to sod's, or Murphy's, law which I assume is where the switch that started this thread got its name. I recall a corollary of Murphy's Law ("if anything can go wrong it will" - for anyone uninitiated) is that it doesn't apply to any situation where you try to use it, which is why we've come a long way from the Murphy switch which "simply shuts the engine down ...".

- (#8737) Dave (Sussex), 26 Feb 04 02:18

As Dave Mason has pointed out the sender is actually quite good. The problem is that it's on the outer wall of the head, not the inner bit where the walls are thinner and the head is at its hottest. Now this is not a problem in a working system because the metal of the head will transfer heat through itself and the coolant, which allows the heat to be more evenly distributed throughout the head. If all the coolant has exited the system though, the rate of heat transfer will be slowed dramatically because it will have been reduced to the metalwork of the head only. This will allow the temperature of the inner metalwork to reach much higher temperatures, to the point where the thinner walls will overheat enough to allow the combustion pressure to cause cracks, before any significant rise in temperature is found on the outer walls of the head.

I suspect therefore that the Murphy switch is intended to protect unmanned and unobserved generators from general overheating, because the sensor is mounted on the outside wall of the head. In order for it to protect from sudden and total loss of coolant, as in DaveW's case, it's going to have to sense the inner temperature of the head, if it is going work well enough to protect the 2CT engine.

Pressure gauge.
The gauge I have gone for is a duel programmable gauge. A brief look at the program manual last night shows that two alarm settings can be applied to both temperature and pressure.

It would seem that I can program one Temperature point to say 60° C and use the output to switch a relay. If I then set the low pressure point to 10PSI, I can run the Pressure alarm output signal through the Temperature relay. This way the low pressure alarm would be disabled below 60° C, by which time the pressure should be above 10Psi.

Then I can program a second higher temperature point to sound an alarm, if the temperature goes over 105° C or thereabouts.

The end result should be that the low pressure alarm can only sound once the engine has reached 60° C, by which time the cooling system pressure should be above 10Psi. If not, then the low pressure alarm will sound. If pressure is suddenly lost at any other time, the residual temperature in the outer walls of the head will keep the temperature sender above the 60° C low setting, which will sound the alarm.

This would result in an overheating alarm and a low pressure alarm in one.

- (#8737) dave Bright, 26 Feb 04 09:30

The cooling system, in good order, is always brim full of liquid coolant - no steam, no air - whatever the temperature, unless something goes wrong.

So when you stop the engine with the coolant at, say, 95degC within a minute or so everything starts to cool gently and coolant starts to suck back from the expansion tank, in other words the pressure at the top of the cooling system is less than atmospheric and near the bottom it will be a fraction of a psi.

Doesn't this mean, DaveB, that every time you come to restart your warm engine, and for a minute or so after it starts you will have your fault condition - 60+degC and low pressure? Annoying if it sounds an alarm all that time, until pressure has built up again.


- (#8737) Dave (Sussex), 26 Feb 04 09:57

I have to admit that this is something of an unknown area.
I have no idea of the time between stopping the engine and the pressure dropping to allow the drawback mechanism to work. I have presumed that the volume of expansion is linked to the temperature, so as it takes a while for the temperature to cool, I had thought it would take some time for the pressure to reduce also. It takes about two hours for there to be any noticeable change in the expansion tank level, by which time the temperature is way down.

Without a pressure gauge I just don’t know, but I am trying to figure out a way to use a non latching switch to trip a relay to inhibit the alarm, that will itself be reset when the default low pressure warning would stop.

If that fails, then I might have to resort to a very bright light on the dashboard in stead.

- (#8737) dave Bright, 26 Feb 04 11:16

Or an audio warning " red alert, red alert, coolant breach in 5 seconds!"

Sorry, Star Trek withdrawal symptoms - I'll get my coat.

- (#8737) Ian Dunse (Derbs), 27 Feb 04 00:53

A Townie and a Trekie Ian?
And you recently call ME a sad man.

Regards
dave

- (#8737) dave Bright, 27 Feb 04 02:17

Hey don't you go slagging off Star Trek. Some of the best minds on the planet are Star Trek fans - Isaac Asimov, Arther C. Clarke, me ....

No scrub the last one.

Wonder what bhp I could get if I swapped the 2C for a matter/anti-matter engine? Where would I fit the dilithium crystal chamber? Answers on a postcard please to Toyota TRD, Warpdrive Development Section, Rigel 7

- (#8737) Ian Dunse (Derbs), 27 Feb 04 02:38

Ian, the first two of those are not trekies anymore - they're both dead - I hope that's not a trend????????

I think an 'infinite improbability' drive would be more compatible with the basic architecture of the Townies - the pre 1992 ones anyway!!!!!!!

Dave.

- (#8737) DaveW, 1 Mar 04 18:37

nice touch. brain the size of a planet and i missed the improbability drive ........

- (#8737) idunse, 2 Mar 04 03:53

don't forget you would have to make room for orac in the back & as for zen, he's a super computer, he'd have to take up the roof rack.

still, you could fit a new fog lamp switch that lights up black on a black background!!!!!!!!!!

regards rob.

by the way............the answer's 42, now what's the question?????????????

- (#8737) Rob Drinkwater, 2 Mar 04 13:55

ian you would be better poring some di-lithium crystals in the tank,just bear in mind that the engines won't take it (cptn) now that is really old

- (#8737) john collier, 4 Mar 04 01:16