Overheating under extreme conditions?

[blueiraq]

I have a 2005 Lincoln LS V8 with 18000 km, just back from 15k km service, in UAE.

I was driving on a highway at 200-210kph (basically right at the fuel cutoff), for about 20 minutes. Outside temperature was 45-50C. The car dropped power, and I could keep it around 120kph, but not accelerate to pass anyone. I noticed the temperature was high, but not in the red, but there was no "engine temperature warning" in status.

I drove with minimum acceleration in 100-140kph for a while, and the engine cooled down. I could then drive comfortably in 160-180kph, but I kept an eye on the engine temp to try to keep it at nominal. I also kept the AC off, which was a bit unpleasant.

Later in the day/at night, I could drive 210kph or so fairly comfortably without increase in engine temp.

I opened the engine and checked the radiator (clean), no other obvious damage, although I didn't check fluid levels.

Is it normal for the car to overheat in high ambient temperatures at high speed? I always assumed cars could only overheat in low gears, towing, etc., and not with airflow from high speed. I've driven plenty of german and japanese cars in similarly hot/dusty/etc. conditions, and the only overheating was when I took it offroad in low gear.

(I also saw a Bugatti Veyron on the highway going the other direction!)

 

[lseguy]

Should not be overheating at all.

You need to check the coolant level. Also, check underneath your car just behind the front drivers side tire. Any fluid on the ground or leaking from the wheelwell liner? If so, that usually indicates a leak from the coolant reservoir when the engine is fully warmed up, and the tank is under pressure.

 

[Jim Henderson]

Depends on the car design. We don't have many stretches of road here in the US where we can cruise at that speed for that long so it is hard to say from experience.

MY old 79 TA cruised at 120mph for about 1.5 hours in the heat of summer thru the Arizona/California desert with AC on and me enjoing myself immensely. The car ran totally normal . It was not maxed out so maybe that is why the car did so well.

I have read other stories about other brand cars, like Impala SS that run just fine at 100-120 all day long but as you get up towards max speed, 140-150, the car exceeds the ability of the cooling system, especially the transmission cooler. Most American cars are designed to run at less than 100mph all day long. They usually are not designed to run at full throttle for much more than a few minutes. So, I have read and my opinion. The reading is from old Impala SS web postings and comments about common failure modes in the Silverstate race, which is a race in the Nevada desert at whatever speed you can get your car up to. Typical failures were transmission failure due to overheat due to inadequate pumping and cooling of the ATF at speeds above 120 or so. This was for many cars, not just Impalas. So the conclusion is that most cars were not designed to run at full speed for very long. The Impala SS and Lincoln LS are pretty heavy cars, 4000# and up so that is probably a factor too.

Since you are running at max throttle for longer than a few minutes and you live in a sun blasted desert wasteland ;^) , I am GUESSING, that your car is exceeding the cooling system design limits and is running a bit hotter than usual. Your car cutting out after an extended run at full speed and then running fine after a cool off of more normal speeds seems to fit my guess.

My 2004 LS V8 runs a bit higher than the "normal" reading whenever we drive thru the desert to Las Vegas at a steady 85mph and 100+ temps. For my car, "Normal" is right at half scale. To vegas it is maybe 2/3 scale. SO speed and air temps will affect your guage reading and at maximum throttle I would guess it may heat enough to put the engine into lower power mode until it cools.

Good Luck,

Jim Henderson.