Prepping for a long trip with high coolant temps.

[phattyduck]

EDIT: Also, the jiggle valve allows for a small amount of coolant to flow through the thermostat so that coolant can still flow through the engine and allows the hot coolant to reach the thermostat and open the thermostat. Without the slow coolant flow from the jiggle valve opening you would be depending on heat transfer to warm up the coolant by the thermostat enough for the thermostat to open which would likely mean that the coolant in some spots of the engine would be way too hot by the time that happened.

No, there is a bypass hose that always pumps water past the 'active' size of the thermostat.

The jiggle valve is traditionally for bubbles, as has been stated. There is something about the 5VZ design where the orientation of the thermostat matters that is different than most engines... I have not seen a good explanation, but I have seen lots of engines that run a bit too hot fixed by rotating the thermostat though.

-Charlie

 

[Bad Luck]

No, there is a bypass hose that always pumps water past the 'active' size of the thermostat.

The jiggle valve is traditionally for bubbles, as has been stated. There is something about the 5VZ design where the orientation of the thermostat matters that is different than most engines... I have not seen a good explanation, but I have seen lots of engines that run a bit too hot fixed by rotating the thermostat though.

-Charlie

There is a bypass hose, but without the flow through the jiggle valve it would be difficult for hot coolant to reach the thermostat and open it.

 

[Romeo1]

My 99 is literally hot within two minutes of running up to the point where the thermostat opens, especially this time of year.

My Cummins on the other hand sometimes can take a half hour to open depending on how cold it is that day.

Time to open the thermostat 5VZ is kinda relative.

I love getting lost in the weeds in these things, but the point of this entire discussion is that they need to get diagnosed out completely to rule out what is and isn’t going on.