Help, Lexus GS450h engine overheating?
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Joined: Dec 2016
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From: Romania
Help, Lexus GS450h engine overheating?
Hello guys, i need some help with my car... again 
) So the story goes something like this. Today i was on the highway cruising at about 80 mph. In my country today was extremly hot. On the highway the outside temperature was about 40C (104F). As i was driving, behind me a Volvo was tailgating me so i wanted to have some fun and i floored it from 80 to 120 mph for a couple of times(it was some traffic in front of me). At about the fourth time when i was flooring it from 80 i noticed a hesitation of the engine and the power was going down and car did not accelerate, i saw that i drained the battery completely and i thought that's why i do not have power, but when i looked at the engine temperature gauge it was almost near the H sign. Instantly i let the accelerator off, the speed dropped to 80 again and in a couple of seconds the needle dropped at the middle between C and H where it sits normally.Then i drove it a couple of miles at 80, floored it again to 120 to see if the temperature rises again and the needle moved very very little up to the H (one square). After many miles, i was curious to see again if the engine temp rises if i floor it so this time i flored it from 40 mph to 120mph, everything was perfect the temperature did not rise at all.
So my question is... what is rong with my engine? No check engine or anything on the dash, it is the first time i encounter such a problem with the car. The coolant is at top level and it is perfectly clean. Oil same... (i thought of the worst, head gasket ex.)Is this relatively normal because of the extreme heat outside? It was my fault for pushing the car hard or my engine has problems? I don't really know what to say, i thought this cars can live with such extreme temperatures, i don't think it is normal. I am a little worried.Please help and thank you for your answers.
) So the story goes something like this. Today i was on the highway cruising at about 80 mph. In my country today was extremly hot. On the highway the outside temperature was about 40C (104F). As i was driving, behind me a Volvo was tailgating me so i wanted to have some fun and i floored it from 80 to 120 mph for a couple of times(it was some traffic in front of me). At about the fourth time when i was flooring it from 80 i noticed a hesitation of the engine and the power was going down and car did not accelerate, i saw that i drained the battery completely and i thought that's why i do not have power, but when i looked at the engine temperature gauge it was almost near the H sign. Instantly i let the accelerator off, the speed dropped to 80 again and in a couple of seconds the needle dropped at the middle between C and H where it sits normally.Then i drove it a couple of miles at 80, floored it again to 120 to see if the temperature rises again and the needle moved very very little up to the H (one square). After many miles, i was curious to see again if the engine temp rises if i floor it so this time i flored it from 40 mph to 120mph, everything was perfect the temperature did not rise at all.So my question is... what is rong with my engine? No check engine or anything on the dash, it is the first time i encounter such a problem with the car. The coolant is at top level and it is perfectly clean. Oil same... (i thought of the worst, head gasket ex.)Is this relatively normal because of the extreme heat outside? It was my fault for pushing the car hard or my engine has problems? I don't really know what to say, i thought this cars can live with such extreme temperatures, i don't think it is normal. I am a little worried.Please help and thank you for your answers.
Last edited by alexchris1; Jun 29, 2017 at 12:48 PM.
Lead Lap
Joined: Apr 2016
Posts: 476
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From: California
Maybe your coolant temp. sensor is going bad, or had some kind of mini-stroke? The radiator can't dump enough heat to drop the coolant temp from almost in the red to normal in only a few seconds. And the power loss could be some kind of failsafe that puts the engine into a low power mode when the coolant reaches x°C and the computer thinks an overheat is imminent.
It's the first time something like this has happened, right?
It's the first time something like this has happened, right?
Thread Starter
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Joined: Dec 2016
Posts: 53
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From: Romania
First of all, thank you all for all your answers. After the heating problem i added some distilled water to dilute the antifreze. Coming back home i pushed the car pretty hard to see if it happens again. This time the temperature gauge did not move an inch but the temperature outside was 70f (21c).
Strange thing was... after the heating problem i did have a p0430 code but it was in pending. After i started the car to come back home after about 10 minutes the CEL light up and the code p0430 was permanent. This was the first time i got this code, could it be somehow this was related to the heating issue?
Strange thing was... after the heating problem i did have a p0430 code but it was in pending. After i started the car to come back home after about 10 minutes the CEL light up and the code p0430 was permanent. This was the first time i got this code, could it be somehow this was related to the heating issue?
Lead Lap
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From: California
If cylinder bank 2 was running lean, the engine would've been running hotter and the exhaust stream would also be hotter, which could damage the bank 2 catalytic converter (which is what P0430 indicates). Of course, plenty of other things could trigger a P0430 – bad coolant temp sensor, bad air/fuel sensor, bad O2 sensor, vacuum leaks, leaky exhaust gaskets, bad injectors or ignition components, etc.
Catalytic converters don't go bad on their own, but they can be damaged by a performance issue in the engine. A bad O2 sensor can also trip a P0430 even if the cat is working perfectly
Also, was the antifreeze you had in there at the time of the overheat already diluted (like 50/50 water/glycol) and you just diluted it a bit more?
Catalytic converters don't go bad on their own, but they can be damaged by a performance issue in the engine. A bad O2 sensor can also trip a P0430 even if the cat is working perfectly
Also, was the antifreeze you had in there at the time of the overheat already diluted (like 50/50 water/glycol) and you just diluted it a bit more?
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Thread Starter
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From: Romania
Honestly i do not know what was with the antifreeze because from what i know it has never been changed (car has 105.000 miles). Anyway. i suspect that all this problems where related to bad fuel. Sincer then i did not have anymore problems with the overheat or the cat. I'l keep you guys posted.
As usual thank you very much for all your answers.
As usual thank you very much for all your answers.
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I had something like this happen recently. I was running some errands and I let the car idle for upwards of 5-10 minutes in 99f heat, with the A/C on as my teenage son was napping in the car. Car was running fine, but I had noticed earlier in the day that the power seemed a little short. After the 3rd stop I noticed that the gage was at the top end of the temp, so I coasted down a hill to get some air moving over the radiator. It rapidly went down, so I went back to driving, within 2 minutes the temp gage shot back up. I parked, let the car sit for 45 minutes, checked the reservoir, and it was empty. 
Fortunately NAPA was one building over, so I bought a gallon of pink Asian coolant filled the reservoir and let the car idle. Within 2-3 minutes, the temp shot up again. So I figured the thermostat wasn't opening. Limped it home (2 miles) let it cool completely down, bought the thermostat. Went to install it, and hardly any fluid came out. So I added 1.5 gallons and it stopped taking coolant. Been driving for a few days, and the level hasn't changed, it seems full, and the temp has been 100% stable. Look there first maybe?
Fortunately NAPA was one building over, so I bought a gallon of pink Asian coolant filled the reservoir and let the car idle. Within 2-3 minutes, the temp shot up again. So I figured the thermostat wasn't opening. Limped it home (2 miles) let it cool completely down, bought the thermostat. Went to install it, and hardly any fluid came out. So I added 1.5 gallons and it stopped taking coolant. Been driving for a few days, and the level hasn't changed, it seems full, and the temp has been 100% stable. Look there first maybe?
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From: Romania
OK, after some time the problem with the overheating did not come back, i suspected bad fuel was the problem and the enginer was runing poor but now there is a new problem. The p0430 keeps coming, not permanent to light the check engine up but in pending. Funny thing is that i started to see that my idle is pretty rough. When i put the car in N the car shakes and underneath i can hear some strange knocks... What the hell is going on with my car, should i prepare for the worst? A lambda sensor or my cats ar starting to fail )
Also is it normal, first morning start (after the car was sitting by night for about 20 hours) the engine starts, runs for about 1 minute then shuts off and it goes into EV mode? This thing started happening when the summer and hot days came (95F/35C).
110.000 miles on the clock
Thank you all for the help.
)Also is it normal, first morning start (after the car was sitting by night for about 20 hours) the engine starts, runs for about 1 minute then shuts off and it goes into EV mode? This thing started happening when the summer and hot days came (95F/35C).
110.000 miles on the clock
Thank you all for the help.
Last edited by alexchris1; Jul 10, 2017 at 07:18 PM.
Lead Lap
Joined: Apr 2016
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From: California
Jesus, you just can't catch a break!
Well bad fuel could probably foul the cats and A/F sensors, and a fouled A/F sensor could cause idle to be rough. If you have techstream, you can check the output of the A/F and O2 sensors.
Well bad fuel could probably foul the cats and A/F sensors, and a fouled A/F sensor could cause idle to be rough. If you have techstream, you can check the output of the A/F and O2 sensors.
Thread Starter
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Joined: Dec 2016
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From: Romania
)))) Hey Sodium, wassup. I know, one problem does not come alone ) Today the car ran pretty good, the shakes where barely noticeable. Thank you all for the help! I will keeup you posted with the evolution of the problem.
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