Coolant Pressure vs Oil Temp

[DavidInWilmNC]

Back in the summer, I blew a hose in rural SC on the interstate.  Luckily, it was one of the smaller hoses that leads to the 'Y' that has the shut-off valve for the heater lines.  A couple of hours of drivers passing me with wipers on with no rain should have told me that something was leaking, but, hey, this was  SC!     I realized that I was out of coolant when the shutdown system did what it was supposed to do.  The cooling system still had a lot of water, but couldn't build up pressure and overheated.  If this had been a larger lower hose, things could have been a lot worse.  If the water level had dropped below the sending units, the gauge and shutdown system wouldn't have known anything was up. 

All this makes me think that there should be another way of knowing about the loss of coolant.  I'm wondering if a pressure sender in the cooling system would work or if I'd be better off monitoring oil temperature.  The coolant sender would be much easier to install, but I wonder if this would be a very effective method of accomplishing what I'm trying to do. 

What are some pros / cons of these ideas or entirely new options for what I'm trying to do?  Thanks for any input.

David

[Frank @ TX]

Hi David,
Mine seems to have a float in the surge tank which lights an indicator "Low Coolant".
Your's may have the same , look at your indicator lights , maybe just a bulb is out.
Frank

[DavidInWilmNC]

Frank,
I'll have to check.  I know it does have a sensor in it, but it never lit (maybe it didn't get too low but did lose pressure).  I hate to rely on an on / off light, although it would certainly be helpful and better than nothing. 
David

[tomhamrick]

The low coolant indicator on my Eagle is part of the shutdown system. It senses the water level in the expansion tank and activates the shutdown if there is no water touching the sensor.
Tom Hamrick

[DavidInWilmNC]

The low coolant indicator on my Eagle is part of the shutdown system. It senses the water level in the expansion tank and activates the shutdown if there is no water touching the sensor.
Tom Hamrick

Perhaps that's what shut my system down.  All I know is that when the engine stopped, I looked down at the warning lights and most were on... like when a car's ignition switch is 'on' but the engine's not running.  I'll check it for continuity before and after draining the system this weekend.

David

[Sammy]

David, a "Low Coolant" indicator will definitely let you know if you're losing coolant, before the engine will shut down,before most major problems will occur.
I'm looking at a electrical diagram dated April of 1977 of an MC-8 that has a "Low Coolant Level" circuit.
It shows a "Water Level" telltale light and it's wired into the engine stop relay.
It has no "float", just a sensor that needs to be in coolant to complete a circuit, similar to an Eagle.
Let me know if you'd like a copy.
Sammy 

[Tony LEE]

My MC8 has two level probes in the top tank - one via the test switch to check the water level and one a couple of inches below the sight glass that trips the engine protection system.

This trip switch seems to operate for a second or so when the level first gets that low so the engine just cuts out momentarily and the warning lights flash on for a second. If you are quick and see the lights you can work out that it is the coolant level, but otherwise the engine just comes back on and you haven't a clue what caused it.  If it just cut out permanently it could result in a very dangerous system, particularly if the driver panicked (thinking it was oil failure) and took it out of gear. Then the engine wouldn't turn and the power steering would fail. Leaving it in gear and or pressing and holding the starter button to override the shutdown would solve that problem but it is not that easy to think that rationally with the engine stopped and alarms buzzing away and red lights everywhere at 60mph in heavy traffic.