773 not warming up

[MT428]

My 773 has always been slow to warm up and after draining the coolant to replace a valve I can only get it to take about half the coolant that came out. I assume the thermostat isn't opening. I don't work it very hard but I think it should warm up completely. The gauge barely gets to the normal range. Is this normal? Bad thermostat? If I just start it and let it run at around 1/4 throttle, how long should it take for the temp gauge to reach the middle of the normal range?

 

[Jyuma]

Sounds like an air-lock behind the thermostat. Look around for a bleeder valve. If there is none then you might try to loosen the thermostat housing just enough to let the air escape. Loosening the hose won't do it... the air must be bled from the block side of the thermostat.
Also... check the lower radiator hose... make sure it isn't collapsing from the suction created by the water pump.

 

[jerry]

Sounds like an air-lock behind the thermostat. Look around for a bleeder valve. If there is none then you might try to loosen the thermostat housing just enough to let the air escape. Loosening the hose won't do it... the air must be bled from the block side of the thermostat.
Also... check the lower radiator hose... make sure it isn't collapsing from the suction created by the water pump.

a non contact or infrared temp sensor is a big help in telling whether or not the thermostat is working , after it has run a few minutes if the temp is the same on both sides of the thermostat it is stuck open. It really should not have a air lock but could happen. I think most thermostats have a weep hole for air but who knows.

 

[Ironmule]

a non contact or infrared temp sensor is a big help in telling whether or not the thermostat is working , after it has run a few minutes if the temp is the same on both sides of the thermostat it is stuck open. It really should not have a air lock but could happen. I think most thermostats have a weep hole for air but who knows.

When I used to race, we had air lock problems with a gas engine and we drilled an 1/8th inch hole in the plate of the thermostat. This will not affect the flow but will allow it to bleed the air out.

 

[skidsteer.ca]

When I used to race, we had air lock problems with a gas engine and we drilled an 1/8th inch hole in the plate of the thermostat. This will not affect the flow but will allow it to bleed the air out.

If your in a cold climate like Ontario a 1/8" hole is far too big for the winter. I suggest the thermometer and checking it. My 93 753 with "boss" always showed cold. Only the first bar would light in the summer unless it as real hot out and working hard then the second wuld come one. The engine temp was fine it was just the guage.
What year is the 773, G or F or older?
Ken

 

[MT428]

If your in a cold climate like Ontario a 1/8" hole is far too big for the winter. I suggest the thermometer and checking it. My 93 753 with "boss" always showed cold. Only the first bar would light in the summer unless it as real hot out and working hard then the second wuld come one. The engine temp was fine it was just the guage.
What year is the 773, G or F or older?
Ken

It is an F model. Thank you