Coolant Temperature Sensors

[colecruzer]

Hi,
I have a 79 MC-5C with a 6V-71 engine.  I am in the process of replacing all my gauges with VDO Vision type.  I'm starting with the coolant gauges first and planning to have two (one for each bank).  Also, I want to replace my hot engine sensors while I'm at it.  First question:  What is the thread size for the senders and sensors on the thermonstat housing (one connection on the left bank, two connections on the right bank)?  Second question:  I noticed the engine compartment temp gauge sensing line is not connected to anything.  Where should this be connected?  Third question:  What temperature would you recommend for the temp. sensors?
Thanks for your help.
Rich

[Tim Strommen]

First Question: Can't help you
Second Question: Sounds like a fire detector - depending on the type it can go many ways...
Third Question: Typical water temp is around 180-195F...  a gauge/sender that has a range from 120-240 should have all bases covered.  If you have a thermostat that is 190, the water should heat up to that temperature as the engine warms up, but as the thermostat starts to open (a bit before the set-point) the radiator/fan should keep the temperature within a few degrees.

A high-temp shutdown should be at around 20 deg of the thermostat set-point - this way, if you forget to watch the temp gauge and it starts to run away, it can shut down the engine before it melts...  Assuming a NO (normally open - not conducting) overtemp switch, you can use that for a low-side switched alert and time-delay trigger.  In this way, if your engine hits critical temperature you get a bright light and buzzer at your dash, then after a delay the engine gets killed (this should give you time to pull safely off the road).

-Tim

[JackConrad]

All the alarmstats I have seen on DDs are either 210 or 220 degree. we use 210 degree on our 8V71.  I would have to go look, but I think the threaded openings in the thermostat housings a 1/2" pipe thread. There are more than the 3 you mentioned, look close and you should see a couple plugs that can be removed for additional sensors.  We have 2 sensors in each thermostat housing (1 gauge and 1 alarmstat) plus a mechanical gauge bulb in the passenger side housing.  Jack

[Tim Strommen]

What Jack said...   

Also, if you have an extra port, you can put in a lower temp alarmstat, that can turn on a relay activating a radiator misting system pump (I know, I know - it's not optimal to do this, and has been gone over many times - but it sure beats a burned up engine ).

I'm a fan of "automagical"...

-Tim