How hot is too hot?

[shadow88]

Person experience with hot running engines needed. I'm wondering at what temperature do you pull over and let it cool off? 220? 230? 240? Where do you draw the line and why?

[Vigo]

I actually draw the line at 'what's causing it'. If it's running hotter than normal because i'm in Death Valley, I won't pull over until i think it's going to boil over. If it's running hotter than normal and there's no obvious reason why it should, i'll pretty much immediately try to figure out why.

[cordes]

It depends on what I'm doing with the car. I would let my Shadow run really hot to get better gas mileage. I would cruise at close to 230 in it.

[sdac guy]

These engines will take a lot of heat with no obvious ill effects. While I don't recommend the following, here is my experience. In 2006 I was on my way to SDAC-16 in Topeka in my 90 Daytona VNT. I was cruising at between 75-80 mph with the A/C on full. We were in western Missouri and I knew it was hot outside. I kept an eye on my temp gauge as it was well over the halfway point.

It must have been getting hotter outside as the temp gauge kept creeping toward the 3/4 mark. Not too long after that it got to about 1/8 before it would have pegged, I turned off the A/C to help bring it back down and the gauge retreated to below 3/4. I drove along till it got so hot in the car that I couldn't take it and then turned the A/C back on. I had gone maybe 50 miles since I turned it off. I drove again till the gauge was about 1/8 before being pegged and turned the A/C off again. I had gone about another 50 miles. But the car had cooled considerably inside.

I repeated that process until we arrived in Topeka, where I then learned it was 106 degrees outside. Now the kicker was this. After the car cooled in the motel parking lot, I checked the coolant level, it was low. The overflow bottle was empty. I found an empty gallon water bottle in the nearby construction area, and topped off the coolant. It took well over a gallon, almost 2 gallons, to top it off.

I was shocked that it took so much water and the thought of the drive I just finished with all the overheating really scared me that I had damaged the engine. The car ran fine the rest of the trip, and runs fine to this day (10 years later). It doesn't use oil, has had no head gasket problems, or other engine troubles. So from my experience, I would say that these are tough engines we got.


Barry

[Vigo]

I had an intrepid i overheated to the point of seizing MULTIPLE times and put 20k miles on it before it ever showed signs of damage (headgasket leak). But turbo cars are more sensitive. Ive broken a piston at 12psi in an overheated engine. I have a friend who broke pistons in his turbo caravan while it was running hot even though he was trying to baby it. So its not just coolant temp you have to worry about as your throttle position and boost level have a huge effect on actual temps that the engine parts are having to deal with. Seeing as how ive broken pistons at stock boost on two occasions, the question is probably not 'what coolant temp til engine damage under no load' but more like 'how comfortable am i with the thought that one absent minded right foot movement will break my engine'.

So unless youre talking about intentionally running hotter for mpg in which case you might as well convert to a more reliable non turbo exhaust manifold, then if your engine is running any hotter than normal i would diagnose and correct it immediately.

[thedon809]

The fans on new pentastar 3.6's don't hit high speed until 230.

[shadow88]

Some great info here. The cause is simply poor airflow across the radiator. I saw a high reading of 221F with no signs of boiling over or detonation, and that's just cruising, not into the throttle much at all. Last summer, I saw 238F but as soon as it cooled down, it was fine. It seems as long as the coolant is staying in the system, it's not much problem...

[A.J.]

The fans on new pentastar 3.6's don't hit high speed until 230.

GMs have been like that for years. At least the past 15. Only their fans don't come on at ALL until 230*.

[Ondonti]

I had an intrepid i overheated to the point of seizing MULTIPLE times and put 20k miles on it before it ever showed signs of damage (headgasket leak). But turbo cars are more sensitive. Ive broken a piston at 12psi in an overheated engine. I have a friend who broke pistons in his turbo caravan while it was running hot even though he was trying to baby it. So its not just coolant temp you have to worry about as your throttle position and boost level have a huge effect on actual temps that the engine parts are having to deal with. Seeing as how ive broken pistons at stock boost on two occasions, the question is probably not 'what coolant temp til engine damage under no load' but more like 'how comfortable am i with the thought that one absent minded right foot movement will break my engine'.

So unless youre talking about intentionally running hotter for mpg in which case you might as well convert to a more reliable non turbo exhaust manifold, then if your engine is running any hotter than normal i would diagnose and correct it immediately.

Well, the pistons will scuff the first seize and just get worse each time from there.
I would say that the larger piston to cylinder wall clearances allow you to get hotter on the same material cast piston. Its nothing about the engine being stout, it just turbo style factory clearances.

In racing situations then its more about how that heat is or isn't contributing to knock or preignition.

[fixit]

Al expands more than cast iron, as it over heats the piston grows 5x the block

Al 2618 3.6 x 10-5in.3/in.3 -°F (forged-product-2618.pdf)


Cast Iron Gray 6.0 x 10-6 in/(in R) http://www.engineeringtoolbox.com/li...ents-d_95.html

[tryingbe]

With a front mount intercooler, TII radiator, and a/c, my GLH ran HOT. I once saw 238F and the dash overheat light to come on while cruising steadily on the freeway during AZ 110F summer.

I upgraded my radiator and the issue ran away.

http://www.turbo-mopar.com/forums/sh...l=1#post934940

[black86glhs]

GMs have been like that for years. At least the past 15. Only their fans don't come on at ALL until 230*.

221-227*F was the range on the GM cars in the late 80's into the lates 90's. These are N/A engines and can take it no problem. On our engines, I would want the fan coming on around 210* at the latest due to the heat buildup in the block/head on a turbo car. Poor air flow and plugged/inefficient radiators make driving these suck balls. My .02.

[shadow88]

Alright, a bit of an update. I went out the other morning and kinda beat on the shadow a little on a warmer day about 90F

For those not aware of what I'm up against, I have made an additional rear engine and cooling system driving the rear wheels. Both engines must be running at once, and the overheating issue is related to the rear engine.

The rad is a used mishimoto unit specified for a 95-99 neon. I have added 2 10 inch fans and made a shroud for it and still, on the hyway, it's running 232 max, but cools off once the speeds are reduced.

The rad lies flat, it's bled properly, and uses 50/50 mix and water wetter added.

The question I have related to the size of the radiator required. Anybody seen any calculators online to help with this? I've ran across a couple and it seems I'm in the right ball park, but still have an overheat issue.

The links I found are:
http://www.super7thheaven.co.uk/blog...ator-need-car/
and
http://www.clubhotrod.com/shop-talk/...ator-size.html

Anyone have any other info to share?

I'm seriously considering a motorcycle radiator with fan run in series along the upper rad hose.

[tryingbe]

Pics of setup?

[shadow88]

https://www.facebook.com/photo.php?f...type=3&theater

Not exactly this, 2 different fans with a different shroud,

[tryingbe]

I think we need to see your exact setup to help you figure out your car.

[crusty shadow]

i think the radiator laying flat has a lot to do with your heat issues. even with fans you're not going to get anywhere near the same airflow through the radiator fins as you would if it were mounted straight up. the fact that the engine gets hot on the highway but cools off when you slow down tells me its an airflow problem.

[Vigo]

I have a stock neon radiator in my SRT4 van and it doesn't overheat in south texas.

[thedon809]

Probably need some kind of ducting to the radiator.

[cordes]

Probably need some kind of ducting to the radiator.

I think there needs to be a way to get air into and out of the cabin where the engine is too.