Coolant Temp: How Hot is Too Hot?

[RH77]

My winter rad block is simply an unfolded cardboard box. Ironically, it covers the radiator entirely without modification.

So, on sub 20F days, the system doesn't struggle to cool and life is good. The additional heat works to improve FE: both with accelerated warm-up, but also with ideal IATs. With our heat wave today, the ambient temps were up to 40F -- and the coolant system? Really working at it...

The SG showed a max of 240F and the fans were at full-tilt. But the upside: much better FE and aggressive TC lockup around town. So how hot is too hot?

The temp gauge (somewhat unreliable, I know) moved a bit from the norm, but not much. At what point does heat = damage?

To avoid rapid cooling, I generally run the heat and blower at maximum to reduce the coolant temps to below 200F before parking.

I run premium fuel and haven't noticed any pinging/detonation with the hotter temps. So far the 50/50 coolant mix has held-up, and the replacement radiator hasn't complained. On cold days like this morning (at 11F, the heat felt good and didn't require intervention). Restart after EOC is pretty rapid and the transmission performance is improved (synth fluid used).

So, what's the take on temp?

-RH77

[cfg83]

RH77 -

I have heard that 250F is the danger zone, but I'm not a car dude. I don't like my coolant to be over 210F when I am stuck in traffic. The ECU/PCM always turns on the fan at 220F. Would the detail that I have an aluminum block lower the temperature of the "danger zone" for damage?

I drive up a hill when I go home, so I use my manual fan radiator switch to cool things off as needed.

CarloSW2

[RH77]

Originally Posted by cfg83

RH77 -

I have heard that 250F is the danger zone, but I'm not a car dude. I don't like my coolant to be over 210F when I am stuck in traffic. The ECU/PCM always turns on the fan at 220F. Would the detail that I have an aluminum block lower the temperature of the "danger zone" for damage?

I drive up a hill when I go home, so I use my manual fan radiator switch to cool things off as needed.

CarloSW2

I've considered a fan lockout switch, but with the wide swing in temps here, the fail-safe has been to let the fans engage and blow-back the heat into the intake, or to do the job in the summer. I can really feel an electro-mechanical burden when they kick-on at cruise -- the trade-off seems to be of positive FE. The rad-block is very efficient: highway speeds at 2500-3000 RPM really heat up the coolant temps, despite cold air flowing around entire system (neither a sealed grille-block, nor undertray is installed). It seems to act in the sense of a "delayed EBH" without one inherently available.

The coolant temp can easily be controlled using the heater core and blower.

I also have an aluminum alloy engine block with cast iron cylinder liners (the head is also aluminum alloy), so I worry about the expansion/contraction near the head gasket and the result of metal fatigue. The SG temp readouts are likely on the high-side. I haven't come close to the "overheat" warning in the OBD system -- actuality and reported perception may be different, so I don't want to run added risk if the payoff is negligible.

I have to say, when the TC kicks-in using a mild TPS input, it results in a strong-pull at a lower RPMs with reduced fuel consumption due to the hotter temps -- this seems highly beneficial.

I'm working in town more these days, using my own vehicle -- the route is a suburban and urban commute of roughly 50 miles r/t. I've given-up on the highway, since FE and consumption plummets during the hours in which I am requested to commute. As you may know, winds, temps, and precip widely vary from day-to-day (indluding traffic density). "If you don't like the Weather, wait a day". What seems to be relentless is the wind; year-round. On an aside, I feel the breeze and dream of a small wind generator on the house That's another thread

-Rick

[blueflame]

I was running my engine so hot, after big hill climbs, it would start to pink and the rubber top breather hose started to perish and crack...I never turned on the heater though as its the height of summer, and the radiator fan never cut in, so I guessed the heat was isolated to the combustion chamber.

Normally I just slowed a little and chose a lower gear at a higher rev on the hill to mitigate the pinking.

I have no temperature gauge fitted...

Its a non ECU carby ICE, so auto ignition retarding never happens.

After noticing the breaking down of breather hose, I redirected intake air away from 100% exhaust manifold to 100% ambient air, and no more hill climb pinking occured.

However, my FE has now dropped maybe 5-8%.

Superheated ICE economy testing does work, but you've got to question longevity.

[Formula413]

I wouldn't want to see my engine running higher than fan activation temp for any extended period (which is 220*F in my car also). However, I am not basing that on anything except the wisdom of Ford engineers.

[Ryland]

If your radiator cap can keep the pressure at 14psi then a coolant mix of 50/50 ethylene glycol will boil at 263F, at that point you will rapidly start to loose coolant as the coolant escapes in to the over flow it will boil at 226F, so you will get ALOT of steam and your coolant will be gone.

[RH77]

In the summer (without a grille block), the A/C and city driving pushes the envelope to 220F under normal circumstances. The fans kick-on at a varying degree of temps -- from 206 to 218.

But, in the essence of longevity, I'm trying to stay below 230F anymore. Parked in the garage after a 240 run, it just smells hot. At her age, Teggy doesn't need any more stress than she's under already

Pulling-down 3 MPG may not be worth the heat...

[Formula413]

I would be worried about things like head gaskets and all the vacuum hoses in the engine bay. Like you said, better safe than sorry.