How hot is considered overheating?

[CyFi6]

Ive been doing some research on the cars normal operating temperatures and from what i have found it looks like 176-210 degrees farenheight are about the regular ecu operating ranges, anything outside of this the ecu will adjust timing, from what i read. Well ive been driving my car today quite a longer distance than i normally do and through los angelas. THe temperatures ehre seem to have been between 85 and 95-98F throughout the trip, and im experiencing some issues. normal freeway driving ~60mph ac on the car seems to run around 200-205 degrees, i thought this was a little hot so i was a bit concerned. In slow or stop and go traffic with ac on, the temp will vary between 200 and 210 about. Im a little concerned with overheating in warmer weather around Arizona in the next day. The car has had a complete cooling system flush, new thermostat, fairly new radiator (less than 2 years), new radiator cap, and filled 50/50 with genuine toyota red. I also replaced the head gasket just a couple months ago. Everything seems to be working good but my operating temperatures seem to be on the high side. When i approached and climbed a grade ( im not sure the percentage, but fairly steep) the temperature also rose to about 210 degrees. I must add the car is full with stuff including a lot of tools so it is a bit heavier than normal. Im wondering if i should be worried about this or not, and at what temperature should i begin to worry and stop running the car? If the temperature were to climb beyond 210 degrees F should i immediately shut off the car and pull over to avoid damage to the engine? Thanks.

 

[RazoE]

you need to also make sure you have a fan guard and intact under tray, both still available brand new from Toyota...

in order to run optimally, all OEM cooling parts need to be in working order...

 

[GotTurbos?]

yeah, make sure you have the turbo 10 blade fan, and a fan shroud. I can not emphasize the importance of a fan shroud enough, I saw over a 10 degree drop in temps when I got one put on my car. The undertray will also help you out.

 

[Wills7MGTE]

I have electric fans and an undertray makes it run very nicely, the original shroud broke and some blades were borken too so I went ahead and went electric and replaced the old undertray that was in dire need of replacement anyways.

 

[CyFi6]

both the engine under-cover/skiplate and the fan shroud is in place and working fine, neither are broken. Im really not quite sure why its getting as hot as it is, the only thing i can think is because the radiator is from here and i dont know how reputable this place is.

http://radiatorbarn.com/search.php?product=radiator

Basically i am wondering, what temperature is it safe to drive up to.

 

[Poodles]

Technicly speaking going over the T-stat temperature setting is "overheating."

Are you probably safe? Sure, but it means that if you DO have a really hot day and you're stuck in traffic, up a hill... you don't have any extra compacity to get rid of that heat.

 

[CyFi6]

so if my thermostat is rated at 190 degrees F and my engine runs at 200 degrees it means ive overheated and am at risk of blowing a head gasket/ warping the head?

 

[Poodles]

Not at that temp, but it's not the ideal setup.

 

[Doward]

Poodles is right - anything over the thermostat rating means you have no extra cooling capacity. Fix that.

 

[SupraClaou]

Poodles is right - anything over the thermostat rating means you have no extra cooling capacity. Fix that.

No...I think it is not true. Anything down under the T-stat rate is not
good for the optimum operation of the engine! For MA70 7M has an 88 C'
T-stat,so anything under 88 is not good.

Any engine in the world is working (after it's warm up) above the T-stat rating.
Normal temps for MA70's T-stat is 88'-98' Celcious....ok if it goes
sometimes above 98'C like 102 C' or 104 C' it is not the end of the
world :nono:. And yes the ECU adjusts timing cause of the high temps.
It is a hot operational temparature for the engine but not
overheating. Overheating is above 110'C (220'F)....Then you must stop
your car,open the heating valve to get rid some part of the heat,and after
the Temps have dropped a little you can shut down the engine and check
the cooling system for leaks!

Ohh..and the stock needle on the oem Temp.gauge will start rising above
105'C / 220'F ...this is double checked by me with new water temp.sensor!

One thing is for sure... The coolant temps will rise if :
# Driving uphill
# Have a heavy load
# During very hot days (about 36'C / 95'F)
# Running a 'thick' oil
# Bigger HP than oem/racing
# Big front mount intercooler
# Bad condition of the cooling components or missing parts
(like...water pump,fan,coupling,fan shroud,udercover,old/cracked radiator)

AND one fault from the Toyota factory is the weak ability of the angine
bay / hood to discharge the heat! Times have changed and global warming
is nearby...so the factory T-stats of 88'C (190'F) are no good,except if
you live in Alaska :biglaugh:
For example the newer engines series JZ (1jz/2jz) run a 82'C / 179'C T-stat,
so..I think they did their math this time.

 

[Orion ZyGarian]

No...I think it is not true. Anything down under the T-stat rate is not
good for the optimum operation of the engine! For MA70 7M has an 88 C'
T-stat,so anything under 88 is not good.

Any engine in the world is working (after it's warm up) above the T-stat rating.
Normal temps for MA70's T-stat is 88'-98' Celcious....ok if it goes
sometimes above 98'C like 102 C' or 104 C' it is not the end of the
world :nono:. And yes the ECU adjusts timing cause of the high temps.
It is a hot operational temparature for the engine but not
overheating. Overheating is above 110'C (220'F)....Then you must stop
your car,open the heating valve to get rid some part of the heat,and after
the Temps have dropped a little you can shut down the engine and check
the cooling system for leaks!

Ohh..and the stock needle on the oem Temp.gauge will start rising above
105'C / 220'F ...this is double checked by me with new water temp.sensor!

One thing is for sure... The coolant temps will rise if :
# Driving uphill
# Have a heavy load
# During very hot days (about 36'C / 95'F)
# Running a 'thick' oil
# Bigger HP than oem/racing
# Big front mount intercooler
# Bad condition of the cooling components or missing parts
(like...water pump,fan,coupling,fan shroud,udercover,old/cracked radiator)

AND one fault from the Toyota factory is the weak ability of the angine
bay / hood to discharge the heat! Times have changed and global warming
is nearby...so the factory T-stats of 88'C (190'F) are no good,except if
you live in Alaska :biglaugh:
For example the newer engines series JZ (1jz/2jz) run a 82'C / 179'C T-stat,
so..I think they did their math this time.

I think the factory thermostat is still good regardless of where you live. Why would you want to run a cooler one? The only reason I can think of is that its a crappy way to make the ECU always run richer to compensate for not ever getting up to temp. Its one thing if the t-stat needs to be replaced, another if it isnt the right temp to begin with.

The 7M block doesnt have the most efficient cooling in the world. Even with a JZ thermostat, if other parts arent operating correctly, then they need attention.

 

[CyFi6]

Just thought I would bring this back. My Supra has always had this problem in the dead of summer (110 degree+ ambient temps). When cruising on the freeway for long periods of time (roughly 65 to 70mph, 3000 to 3500rpm) with the AC on the stock gauge starts to creep up. Never seems to go past the halfway to 3/4 area. Driving around town it is usually fine, but prolonged low speeds with AC it starts to creep up. If I am on the freeway, it may stay steady at about the 4oclock to 3 oclcok position, but then creeps up even higher if I approach an uphill area.

The cooling system is all up to specs with mostly new components (all under 2 years old) with fresh 50/50 GO5. Has an aftermarket aluminum dual core Koyo radiator. All shrouds etc in place, only concern I have is that the aftermarket intercooler could be causing airflow issues.

Just want to make sure that I don't need to worry until it hits RED like it says in the owners manual. The car runs perfectly cool in the reasonable months (there aren't many of those in Phoenix), but when temps outside skyrocket it struggles to keep up.

Is there anything aftermarket I could do to raise my cooling system capacity? It really sucks having to watch that gauge like a hawk.

 

[IJ.]

I ran an EWP as a booster in my 7M, it helped a lot.

 

[Orion ZyGarian]

As a booster, meaning both? I always wondered if there would be an easy way to have coolant go in at the head around cylinders 1 and 6, and down through the block. 2 entries and reverse flow. Just one of those "in a perfect world" ideas

 

[IJ.]

The Electric pump is plumbed in series with the mechanical pump as both can flow through, I ran the EWP with the MoTeC and had it run at low road speeds, idle and high engine speeds covering the lack of pump flow at idle and cavitation above 7500 rpm.

 

[stevenr816]

How old is your clutch fan? Or are you e fan?
Also does your car have the helper AC e fan?


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[Hotwheelsjr]

Here's my 2 cents...basically worth 1/10 of a cent in this day and age, so take it for what it's worth. I had my fair share of cooling issues when I first converted my NA car to a 7M-GTE with a T67 and big ass 31.5x12x4 FMIC. When I did the "conversion", I also installed a new 3 row aluminum radiator with ebay electric fans...BIG mistake. The electric fans didn't pull crap for air. I pulled them out and dropped in a pair of large electric fans from some other type of OEM car...they flow VERY well. Driving around town (I'm in Phoenix, also) the temps weren't bad, hovering around 90*c. At sustained highway speeds (70-75) temps would creep to as high as 106-107*c...a little too high for my liking. I did not have an underbelly cover, so my search began and I found one local for $50 and installed it. I drive from Surprise to Mesa for work (45 miles one way, mostly freeway) and my temps now rarely rise above 95* c. My around town temps stick between 87-90*c...when I pull up to a red light, my temps actually drop 1-2*c...that's how well my elec fans are flowing! I have my fan controller set to turn on/off at 86*c and often times around town, they turn off because my temps drop to 84-85*c. My lessons learned? Good flow is a must! The underbelly cover is a must!

 

[stevenr816]

Have you guys experimented with pulling the seal off the back of the hood?


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[IJ.]

Have you guys experimented with pulling the seal off the back of the hood?


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Ran slightly cooler at low speeds and hotter at highway speeds.

 

[destrux]

A few well placed naca ducts should let some air out if you place them right. I'd put them on the front fenders as close to the door as possible and run ducting from the rear of the engine bay to the ducts. I don't know how that would look, but it should be effective. The back half of the front fenders are a low pressure area. A proper hood vent would work too, but I don't like the way they break the look of our cars, and designing a proper one with that tall engine in the way is tough.

Also, cars with electric fans don't kick the fans on till the engine reaches 220-225 degrees on most models (unless the A/C is on, then they run constantly). I've never seen a car that kicked the fan on below 210 degrees. They do this to keep the engine hot to minimize emissions at low operating speeds/loads. If your cooling system is up to task there's no reason that this should make the car overheat (above 230 degrees), as the coolant temperature should drop toward thermostat temp as soon as you start moving and the fans aren't the primary source of airflow (above 35 mph or so). Above that speed the car should stay at thermostat temp or a few degrees (about 5 or 10) above, if it keeps creeping up toward 230 degrees you have a problem. The cooling system isn't able to keep up with the thermal load the engine is placing on it, and you need to figure out why or beat on the car less.

This is why you hear people who have been daily driving or drag racing an engine reliably for years with a stock cooling system suddenly blow it up at a track day or on a top speed run, because the engine had been living with it's inadequate cooling system fine for years because it never got the chance to fully heat soak till it was asked for full power for longer than 15 seconds.

This also applies to the oil cooling system.