Prius intermittent temp light when driving uphill

So the valve moved freely but the actuator was seized?

Did the valve move easy enough that exhaust pressure would have opened it per the manual?

Was the coolant hot when you tried to move the actuator?

I wonder if there is room for a screw coming up similar to this?

 

Jam the exhaust valve open, to see if your problem goes away. You can fix it at your leisure or just leave it that way - but your winter warm-up times will increase.

Good Luck....

 

That is what he did in post #39.

 

The valve/gate seemed to be a bit seized at first, but I was able to get it moving freely by rotating the spring loaded plate several/many times.

The spring that holds the valve in the default closed position seems to be pretty robust, I can't imagine exhaust pressure overcoming it. Unless the gate/valve is still somewhat seized beyond normal resistance to rotation, I don't know what a "normal valve" should feel like.

Here in Hawaii it rarely gets down into the 60s in the winter, it's mostly in the 70s.

I will continue to monitor the temps with the Carscanner app and track fuel economy on Fuely. I have a feeling that I was losing efficiency when the ICE was running, due to the fact that I definitely hear the engine revving more freely now under throttle. The engine revs into the Powerband easily now, whereas before, I really had to push down on the accelerator to get it into the Powerband. I guess I will lose a bit of efficiency from the ICE running more/longer while the engine/coolant gets up to operating temperature from cold starts.

I do have parts coming in (actuator, stopper, and a gasket), but I'm not sure if I want to bother with draining the coolant again, I just replaced the thermostat housing/thermostat, and coolant pump rotor (the old pump rotor looked fine), tearing everything down and rebuilding the EGHRS actuator if the valve/gate is sticky and the rebuilt actuator can't operate the valve within spec. I would know, I guess, if the coolant temps responded to normal operation and throttle under different conditions easily enough. Seems like a lot of work for a possible underwhelming outcome.

 

Why would you want to operate the car with an airlock in the cooling system?

 

The valve seemed stuck at first, it took a bit of effort to get it to move. Then it did loosen up after working it back and forth many times.

The coolant was cold at the time I worked on it. It's been hot and humid here, I didn't want to work in tight quarters underneath a hot exhaust system as well.

No, I don't believe that exhaust pressure would be able to overcome the resistance of that heavy spring holding the valve in the default closed position.

I don't think a screw or bolt through that hole you indicated would be able to hold the valve open, even if I put a rivet nut in the hole to bolster it, I don't think there's enough clearance for a rivet nut anyway.

I have the valve jammed open quite well I think. That spring creates a lot of tension against the piece I jammed in there.

 

Due to your environment, and if the replacement parts don't fix it - I'd probably cut the spring and wire it open; permanently.

Good Luck.....

 

I seriously doubt you will see more than two or three minutes difference in warm up time. In theory the biggest advantage to the exhaust heat recirc is heated coolant flows through the throttle-body before it returns to the colder engine during warmup. Maybe a factor if the car had been left out in freezing temperatures all night.

Better than the Rube Goldberg* -thermos bottle, pump and valving used in gen2.

The manual clearly indicates exhaust pressure should be able to open the normal exhaust path.

 

Don’t leave those pliers dangling under the car though. It would make a dangerous projectile.

 

You can try to lube them. You can probably tell if either the valve with the spring or the actuator case with the shaft is seized. If the thermostatic actuator itself inside the case is not extending when hot, then replacing it will solve your problem. I would lube the case shaft with moly grease and the valve with WD-40.