Prius intermittent temp light when driving uphill

Here's some screenshots of the two readings I got after climbing a hill.
Look at the Max temps on the upper left side of the gauges.

The exhaust heat coolant temp is higher after the ICE has been running, especially when the engine is in the Power Band of the meter on the dashboard.

 

It is major and you need to find out what it is and fix it.

 

Either air is in the system, and since you're hearing the coolant, it is very likely.
Or thermostat is sticking, or the coolant pump is failing, a hose is collapsing, or is clogged.
Or the radiator is clogged/blocked, or the coolant fans are failing or have failed....

Or any combination of the above.

 

People are sometimes kind of bad describing noises which sometimes are normal.

 

But in addition to the abnormal noises he is hearing, his car is overheating under load and/or high temperatures, which is also abnormal.

 

You have to measure both temperatures sensors at the same time. No codes and the first engine temp of 206f won't make the light come on.

You might be seeing a light other than the engine temperature such as the inverter temp which has a much lower trip point of 149f. This one will code and requires a reset to clear.

The two engine temps feed into the same light and won't code. It requires 248f at one of the two.

But I would guess you and Xliderider have stuck Exhaust Heat Recirc valves which in your case is causing a quick engine temp flash. There is not enough heat added by the Recirc valve to raise the overall engine temp high. But it can and will flash the engine temp light from the second sensor as described on page 1.

Otherwise the prognosis is not so good including another head gasket leak. But to overheat with a hg means combustion gasses replacing the coolant which would be burning off. Coolant would be slowly going down; cold start rattles would occasionally be happening. Borescope inspection.

 

This is the EGR valve on the EGR cooler you are referring to? I never thought of a problem with that, as it doesn't seem to have any drivability issues, other than a possible loss of a few mpg.

 

No. The Exhaust Heat Recirculation System and its control valve are on the exhaust pipe, under the car.

The temperature sensor for the EHRS coolant return is sort of near the EGR cooler, though, in an upside-down-U bend of hose. That's as close as it gets to having anything to do with EGR.

 

Exhaust Heat Recirculation System

It has the second engine-coolant-temperature sensor which can flash the engine temperature warning light

Link

 

TY rjparker, do you have the part number of this exhaust heat recovery thermostat that controls the valve? I only see the main thermostat when I try to search for the assembly.

 

Exhaust-pipe gas-control actuator #17495-24010 | autoparts.toyota.com

 

Can I bypass the actuator and somehow fix the rod in the forward, open position?

I'm not worried about getting the coolant and engine up to temp rapidly, as I drive in a warm climate that doesn't get below 60 degrees.

 

I think I would check for free movement of the "exhaust flow control valve" first. It is designed to open with increased exhaust flow even if the coolant temperature is not high enough to move the actuator.

"After the engine-coolant-temperature rises and the engine has warmed up, the heat of the coolant expands the thermostat and the exhaust pipe gas control actuator rod extends. This opens the exhaust flow control valve to switch to the normal exhaust gas path. The exhaust flow control valve can also be opened by exhaust gas pressure to prevent insufficient acceleration..."

But I would force it open with something like this if an actuator repair was unsuccessful.

 

I have a replacement actuator on order, but have to wait for it to be shipped out.

Till then, I will try to see if the rod/valve is stuck or if it moves freely. I will put a clamp on the rod to keep it in the open position, or at least in a partially open position.

Thanks for the picture.

 

You might need the following parts, too. You will certainly need the gasket.

Exhaust-pipe gas-control actuator #17495-24010 | autoparts.toyota.com
Exhaust-pipe gas-control actuator case #17498-47010 | autoparts.toyota.com
Exhaust-pipe gas-control actuator stopper #17496-47010 | autoparts.toyota.com
Exhaust-pipe gas-control actuator gasket #17499-47010 | autoparts.toyota.com

 

TY, I am trying to add the stopper and the gasket to my original order for the actuator to combine the shipping. I don't want to pay an additional $15 for shipping parts that are about $6.

I am hoping I can reuse the original housing.

 

You can certainly bypass the heat exchanger. I was able to reroute the hoses coming from firewall/EGR cooler. You'll get some major smoke from heat exchanger burning all the left over coolant. Ive done it before. I had a clogged exchanger due to head gasket sealer. I tried replacing that actuator before. Did not help. Once I removed heat exchanger out of the loop. It ran perfect. Side note on my prius V highest coolant temp I seen was 207 going uphill behind a big truck on a very hot day.

 

Today I addressed the exhaust heat recovery valve that is apparently stuck closed.

I couldn't get the actuator rod to move out of the housing to open the valve/gate.

I ended up clamping the plate with a pair of needle nose locking pliers and wedging in a piece of 3/4 x 1/16 inch aluminum stock to keep the valve/gate open while holding it with the pliers.

As you can see in the picture, there is a significant distance between the end of the actuator rod and the plate it pushes against.

Went for a short test drive, which included some uphill inclines. The ICE seems to have more power, and it even sounds different due to the freer flowing exhaust.

Now the EGHRS coolant sensor reads below the engine block/head coolant temperature sensor at all times.

TY to all who posted helpful responses to this thread.

 

I don’t miss fixing old cars!

It looks like the shaft on the actuator case might have seized. If you get a new case, perhaps apply moly grease on the shaft.