Cool Off Period After Driving

Joined
Jun 5, 2020
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Oz with Dorothy and Toto
The only time we saw the temps rise with our Suburbans in Baghdad was when we idled them in the 115*+ heat for hours on end. We'd open the hoods and the gauge would go back down and that was with the 8.1l Vortec engines. Never had any issues mechanically. You're good.
 

Falcon_LS

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Joined
Oct 3, 2008
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4,644
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Kuwait
Also, people talk about their engines getting hot in stop/go traffic which is mostly idling, but they idle it at home and now it cools down? Please explain.
Stop and go traffic in extreme heat, you got your AC compressor engaged, the transmission is in gear and you've got your hood closed. You're surrounded by other vehicles, all generating the same level of heat, plus ambient temperature. Not much airflow going in through the condenser and radiator, your AC is not blowing much cold air like it does at highway speeds. Much of the air being pulled in by the fan is also hot. Plus, the engine rpms rise slightly every other minute to move forward 30 feet, and you're stopped again for minutes at a time.

Idling at home, you've got your hood up and you're not surrounded by other sources of heat, particularly up front. Now the fan is pulling in cooler air; hot air rises, now it has somewhere to go past the fan instead of being contained in the engine bay. There's no load on the engine either; it's not in gear and the AC compressor is not engaged. You'll quickly see coolant temperatures (and cylinder head temperature) drop.

Not only that, but after extended idling in traffic during the hotter months, there is a noticeable change in alternator output voltage. When heat soaked, alternator output drops to 13.0-13.2 volts at time. If it's really hot, you'll even see 12.8-12.9 volts momentarily. Once the alternator has had a chance to cool down, it goes back up to the 13.6-13.8. While it's always 14.2-14.3 volts on cold start, during cooler months of the year, you rarely see it drop below 13.8 volts.
 
Joined
Jan 2, 2021
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244
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Central FL
You beat me to it-a lot of racers run a product called Water Wetter to prevent corrosion with NO coolant, the OP in Kuwait likely never sees subfreezing temperatures-even a reduced percentage of Dexcool in the coolant, say 30%, would increase heat transfer. That would be an easier experiment than a bigger radiator, a big electric fan, etc. The thermostat only really serves to keep UP the coolant temperature, at 250F both a 195F & 165F are both as open as they’re going to get.
They run that combination in racing so that the track won't become slick with coolant in the event of an overheat or hose/rad blowout.

If you never see near freezing temperatures, go with a 40:60% ratio of coolant: water. Pure water cools the best, but offers no corrosion protection, overboil protection, pump lubrication or mineral neutralization. If I were you:

Whenever you need to change a battery (every 3 to 5 years) just dump the radiator contents out too. That or flush the entire coolant system to keep it tip-top. Refill at the 40:60 ratio. Electro- mechanical clutches are a wear item, swap it out for new too. Inspect and replace as needed: water pump &/or thermostat for same temperature as stock and a pressure cap. (If memory is right, every PSI = 2°F in boiling point rise. I.e. a 15 psi pressure cap can keep plain water from boiling over up to 230°F...by itself. Coolant adds additional boiling resistance but lowers speed of heat transfer from liquid <-> air)

As others above said, extra duty cooling may work very well. A radiator with just one more row of tubes can quickly calm and dump temps especially in high demand situations or stop and go traffic. Many fit without further modification, they'll slip into the same footprint as the factory stock radiator.

TL;DR

Ultimately, just maintain your cooling system with regular spill-n-fills or plain water flushes. Refill to 40:60 ratio of coolant. Check and replace reservoir cap/rad cap. Check pump for visible leaks or squealing sounds, replace as needed. Check/ replace fan clutches and thermostats as needed. Aftermarket, extra or super duty cooling radiator can help, but not necessary. Just keep your coolant system serviced regularly and you'll be fine.

As other great minds above stated, going full synthetic on your oil and transmission fluids will go together great in extreme situations. Keep them fresh and topped up. They will count greatly in your favor and resist temperature extremes vastly better.
 
Joined
Dec 17, 2009
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Wash, DC
I do a 1 minute or so idle cool down if I pull off a highway right to a rest stop or gas station.
Done this for decades with my non-turbo cars.
Back in the day my 1988 Accord radiator cap stopped holding pressure.
The way I found out was I pulled off the highway after cruising 70 mph, let idle for a minute, shut off, and after another minute it boiled over.
 
Joined
Jan 2, 2021
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Central FL
The way I found out was I pulled off the highway after cruising 70 mph, let idle for a minute, shut off, and after another minute it boiled over.
Dear goodness, me too. I had an '84 Olds Delta 88 way in the day. If I didn't idle her for 5 minutes after an interstate run, she'd first boil up into the recovery bottle after shut down. A few minutes after listening to the gurgling, steam would just explode from the front wheel wells. I mean, train wreck grade *poof*! 🗯 🚆

It was a shared family car. Pop never fixed a hose leak and just topped it up with hose water. The radiator was severely blocked up with calcium deposits. A flush, refill, new hoses, clamps and a new radiator tippity-topped with the correct fluid made her hum for a decade later until traded.
 
Joined
Jul 12, 2012
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Caldwell Idaho
As Trav said, opening your hood after a drive to reduce heat soak is a good idea IMO. At the ambient temps you mentioned, reducing heat soak would help extend the life of all underwood components (including the battery).
For the climate your driving in, the higher operating temps you mentioned sound normal to me.
It won't be not popping the hood after driving the vehicle that will make you sell it and get another vehicle.
 
Joined
Jul 12, 2012
Messages
3,504
Location
Caldwell Idaho
I do a 1 minute or so idle cool down if I pull off a highway right to a rest stop or gas station.
Done this for decades with my non-turbo cars.
Back in the day my 1988 Accord radiator cap stopped holding pressure.
The way I found out was I pulled off the highway after cruising 70 mph, let idle for a minute, shut off, and after another minute it boiled over.
the boil over is because all of a sudden the water pump has stopped and the heat is not transferred out of the radiator. Back in the 1970 I built a boat and installed mechanical temperature gauges that screwed into the cylinder heads . 1 bank ran hotter than the other and when you turned off the engine the temps would raise quite a bit. I sold the boat but I still have the gauges.
 
Joined
Dec 10, 2013
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Kuala Lumpur ,Malaysia
I just completed my little project on heat soak and will be editing the video and sharing soon on this forum. Its a combination of a 12V remote control relay that powers a 12V temp controller with a probe. I designed my own casing and safely pulled a 16ga wire from the temp control relay to the engine bay. The temp probe measures the head temp. I set the temp controller to turn the fans off at 55C and below. There is a 4 pin relay in the engine bay which is connected to three 80mmx38mm thick ball bearing brushless fans, mounted at 3 locations with custom Stainless steel brackets. The lowest fan is under the turbo and pulls cool air from below , to upwards blowing hot air from turbo up towards the hood. Another fan is mounted on the power steering pump bracket and blows under the distributor and blows the front turbo to the firewall. On the left fender where there is quite some empty space and temps are lower, I mount one fan to extract all this hot air and blow it out the left fender/hood gap as well as the front grille.
 
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