injection Pump thermostat

[Paul Robinson]

Having possible troubles with a thermostat from a two-plunger injection pump (M127 engine).  If placed in a pot of boiling water, how far should the pin extend?  I am trying to determine if a defective thermostat is the cause of my fluctuating idle.  My mechanic tried the boiling technique, but did not get the pin to move at all.  I would not think that it would move too much, but am curious if anyone has any experience in this regard (new thermostats from the dealer as you would expect, are horribly expensive).  Thanks for your time,  Paul

[Paul Robinson]

One more photo...

[IXLR8]

Hi--

I don't have the dimension, but the pin doesn't move very much--maybe an eighth to a quarter of an inch at most.

If the pin doesn't move, I would suggest taking the valve apart and cleaning and de-gumming it.

The other Joe

[Paul Robinson]

Thank you, Joe.  I see now on the Starting Aid Tour that the thermostat pin extends .5mm per every 10 C increase in coolant temperature.  So if it's 0 degrees centigrade outside, I would not expect it to extend more than 4 millimeters or so, about an eight of an inch as you say.
I'll boil some water and see if I get some movement.

Have you ever taken one apart?  I'm sure that it's filled with an expanding gas, so I'm not sure that's possible...

Paul

[George Des]

This thermostat does not come apart. I believe it is wax filled.

[Paul Robinson]

Yeah I agree, this baby is sealed.

 I did the boil test and got some movement of the pin, but there is crud around the newly exposed portion.  Is there a cleaning solution that I could soak the thermostat in that would be beneficial in dissolving some of this unwanted material?

[Paul Robinson]

Thermostat just out of the hot water with pin extended and crud visible.  Extension is about 3.5 mm.  This may well be normal, and the crud is not affecting the pin extension at all
-I just don't have enough experience at this point to know one way or the other...