Need help! Gas engine overheating. Cannot resolve.

Partial from
4th-Generation Toyota Prius Teardown (Part 1) - MarkLines Automotive Industry Portal

Stronger airflow in combustion chambers

The re-designed intake port shape (Source: Toyota)
The first improvement was changing the shape of the intake port based on an analysis of the "tumble flow," which is the vertical swirl of air-fuel mixture entering the combustion chamber. As illustrated in the image on the right, (1) the airflow was made straight and, (2) the inverse tumble component that blocks the tumble flow was reduced. As a result, the tumble ratio was improved from 0.8 to 2.8, the combustion velocity increased, and induction of a large volume of EGR (exhaust gas recirculation) gas became possible.

The shapes of the combustion chamber and the piston-top surfaces account for the tumble flow described above.

Large-volume cooled EGR
The EGR distribution passage in the intake manifold has been restructured to a tournament design. This allows a larger amount of EGR gas to enter evenly into each cylinder.


The intake manifold cross-section (Source: Toyota)
The aluminum pipe at the left connects to the EGR passage



An external view of the intake manifold

The throttle valve (center)
The intake manifold that directs air into the intake port is shaped so that it branches into two passages from the throttle valve, and supplies intake air into the respective ports after converging once at the collector located immediately before the cylinder head. This design ensures a smooth flow of intake air by increasing the cross-sectional area that the incoming air passes through, which minimizes air resistance and interference between cylinders.




The EGR cooler configured at the back of the engine
The EGR cooler unit


A newly-designed water jacket spacer optimizes cylinder bore wall temperature


The structure of the water jacket spacer (Source: Toyota)
In order to achieve optimized cooling by means of the cylinder bore region, a water jacket spacer consisting of stainless steel and foam rubber has been adopted. This involves a foam rubber with a brand name of EXPAD being placed in the coolant passage at the bottom of the cylinder bore. This allows a large amount of coolant to flow over the upper part of the cylinder bore, which becomes very hot, and ameliorates knocking by raising the cooling effect. At the same time, allowing a smaller amount of coolant to flow to the lower half portion of the bore to maintain a high temperature. With these techniques, fuel efficiency is achieved by making the expansion factors of the upper and lower cylinder bore even, and piston action friction is standardized at a low level.

Plus new inverter and hv battery design.

 

I think the “tournament flow” of EGR gasses through intake was adopted in a (2012 model year) revision, at least the concept: 1>2>4 passages, instead of previous 1>4.

that was touted as a cure for the EGR blues for a while, then not so much.

there are other improvements in 4th gen Exhaust Gas Recirculation though, intake location and increased volume.

 

I know this is quite an old thread, but it could simply be a stuck thermostat, have you tried removing the old one and replacing it with a new one?

 

Update: So I've been driving around the last few days with the thermostat taken out of the thermostat housing, running about 150-160 degrees Fahrenheit. I ordered a Dorman thermostat to see if I had any better luck with that than the Toyota thermostat. Replaced it today, gave it a test run and it was back to running at 220 degrees and higher... so I do think there is a separate issue causing the heating, apart from the thermostat. Perhaps it is the 3rd gen computer not being compatible with the 4th gen engine, as has been suggested.

Anywho.. I removed the Dorman thermostat and put the Toyota thermostat back in. This time, I cut the jiggle pin with wire cutters and drilled the hole out to 3/16". Then I drilled two new holes about 1/8". Test drove it and it stayed around 175-185 degrees on the highway (upwards of 195 degrees when accelerating). I'm hoping to take it on the interstate in a few days to test it. It's slightly cool, but I'm not going to worry too much about it at this point. If I were to do it over again I'd probably just drill one additional hole.

Note: not sure how I commandeered this thread. ... I'm thinking I moved to this one because I thought the problem was the water pump, which had been an ongoing conversation here. It's also entirely possible I'm a little a.d.h.d.

 

HI SERGEY DID YOU EVER FIND OUT WHAT WAS THE CAUSE OF YOU OVER HEATING IN THE CAR ? I HAVE SAME SENERIO I ALSO TOOK APART THE EGR SYSTEM AND CLEANED EVERYTHING THIS OUT NO CODES JUST STILL OVERHEATS SAME AS YOURS . IF IF FOUND ANYTHING ELSE OR RESOLVED IT COULD YOU PLEASE LET ME KNOW ? THANK YOU MIKE

 

Please check post 35

Posted via the PriusChat mobile app.

 

My 2012 Prius V (Wagon) runs 197.5f and above all time. Is that normal or I have air pocket? I don't have any warning, I recently changed pump and have been watching since then. 197f and up , is that normal?

 

Are you running pretty steady, all day, Uber, deliveries, something like that?

 

I have never seen reading below 197 any time of the day unless engine is Off at lights. In Hwy at 70mph, consistently I see 197.5 to 200, since I am watching it after changing my WP, I become worried at 200 and remove my feet from gas pedal. Yes it's always above 197.5f if engine on.

 

The thermostat is fully open at 204F and the temp should never pass that.

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Under a heavy load I will see 203f for a short time. Either a serious incline at 25 mph or a serious tollway at 80 mph. Depending on the conditions the engine's "typical" coolant temp (warmed up) is between 170f-203f. Quite a range due to the inherent thermal cycling of this engine, a clear issue that contributes to certain problems like oil leaks and head gaskets.

I continuously monitor the CAN bus for accurate speed and realtime temp.

 

Sounds normal

 

I don't think that is the cause of oil leaks and head gasket issues, the Toyota Aqua [Prius C] works in a similar way and does not suffers from these issues.

 

I did cut the Jiggle pin, now my engine stays at 195f at hwy and goes till 199 when doing high acceleration. I live in Texas and hence Jiggle pin fix is advisable. If anyone living in up north, i wouldn't recommend it since warm up will be really long. Mine takes about 25mins in cold morning. Adding additional hole to thermostat is Big now since constant flow of coolant will make engine run cold and warm up time will be more. I am happy with cutting Jiggle pin since i live it hotter climate - no need for heating about 10months a year.

 

I have same problem like Sergey With load (Mountain + AC + summer heat) engine overheating, i already blown head gasket because didn't see engine overheat, now after headgasket fix i have engine temp gauge installed + new water pump.

I have Prius plus+ (EU version) with about 600.000km on clock. I think my cooling system have air, but interesting is that - i dont have any temp sensor or air ventil on this hose.. why? i try just push that hose, maybe that's how the air will go away.

Question, please see pic, why no any temp sensor or air ventil????? hose i think is original

what i don't like it to - that my water cooling reservoir is the same level like this hose.. i think i will try slightly raise the reservoir (2-3 cm)

 

Toyota discontinued the vent, in model year 2012 I think. You can pull one of the EGR hoses off (the one in your picture) and try filling coolant some more. You might get air out. Pour coolant till it starts coming out of disconnected hose, then quickly reconnect hose.

 

Thanks, i will try, but i dont have temp sensor to.. its in another place? maybe engine block?

And i have one more question, what is this? some sensor, but i cant find any cable to connect (prity same place like that hose)

 

Same area on my 2010:



the centre of picture is the temp sensor and coolant vent bolt (vent bolt missing since 2012 model year).

coming off lower/front (of black plastic piece) you can just see hose, which goes to pipe on EGR cooler.

 

I just did the egr system cleaning, and replaced the impeller for the water pump.
I filled up the coolant, s l o w l y, and had not problem. This is the 3rd time I've done it.
Never opened the valve. I've done several different models of coolant changes and never
had a problem. But I always fill slowly, and a little at a time.

Maybe you are filling to quickly?