Cool Off Period After Driving

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pop the hood release lever but leave hood latch still in place? yeah, kinda rednecky and i wouldn’t do it on highway but around town the half inch venting may offer some relief and still be safe.

Please do not. Pretty bad idea not just for safety reasons. With additional air forced into the engine bay not flowing through the radiator you'll reduce air flow going trough the radiator for obviuous reasons thus actually affecting cooling as a result. For optimum cooling efficiency you want maximum delta P in and out of the radiator, say high pressure before and lowest possible pressure behind it aka in the engine bay. As a consequence, if you think you acutally need additional vents on the hood you want them to suck out hot air, not forcing air in. That's how race cars are built btw..

In general I think with complicated and/or expensive suggestions you're not doing the OP any favour. I don't think he should be overly concerned, but if he'd sleep better when doing something, then I'd suggest doing the easiest and cheapest thing first - change coolant to 35/65 ratio.
 

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On my 17 Regal GS with a 2.O T after long drives in triple digit heat i'll pop the hood to let all that HOT air out, just a feel good thing. ;)
 
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I have a pre-luber installed in my E-150. During hot summer days if I get stuck in a lot of traffic I flip the switch after I shut the engine off and it allows oil to continue to flow. I let it run a few minutes and turn it off. In reality it serves two purposes, getting oil flow before starting a cold engine, and oil flow after shutting off a hot engine. It might be worth looking into for the OP as well.
 
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Easiest do deal with it: ignore and drive on. Second easiest: Change coolant concentration to 65 % distilled water and 35 % Dex-Cool. Don't overdo as you'd affect the coolant's anti-corrosion properties, however more frequent coolant changes would help to counteract any adverse effects. With 65/35 you're still safe I'd say.


There's a coolant section on this forum btw.:


Good thing I read a bit further for once.. The idea is to lower the coolant concentration, lower the nucleus boiling point (where the heat transfer is at it's maximum) and increase the heat capacity of the coolant mix. a 205F 65/35 water coolant mix contains more energy than a 50/50 or 40/60 at the same concentration.

To see what nucleus boiling is, put a pot of water on the stove, before the whole pot boils you will see bubbles forming on the bottom. It's the water at the bottom boiling and dissipating it's heat in the bulk fluid. The heat transfer rate is around 6 times higher when you are in this mode. The surface of the head/engine will only be slightly higher than the boiling point of the fluid, and reduced from what you get at higher concentrations. Don't forget that pressurising the system increases the boiling point further.

You can go quite a bit further than 65/35 but you will have reduced coolant change intervals. Audi recommends 90/10 for it's R8 for maximum coolant performance while maintaining corrosion protection, but then you don't have frost protection anymore, and 5 times less coolant life.
 
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Manufacturers heat test their cars to 120F so while you might go over that occasionally, your coolant temps are fine. You could help by looking at the oil side of it. Additional capacity and an external oil cooler would help lower coolant temps more than anything. Also, I be more worried of the transmission fluid temperatures.
 

Nick1994

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Is your thermostat OEM? My grandparents Trailblazer, we put in a Stant thermostat and it ran warmer. Then bought an OEM one and measured with a micrometer. If I remember correctly it was like a 30% larger opening on the OEM.

That helped it, but what made a world of difference, like life changing difference, was a new OEM fan clutch. Engine cooled back down and the A/C was awesome afterwards. 115+ is a normal day here too and we were dying at stop lights without air flow.
 
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I've found the worst part of engine heat in high temps is what it does to my garage. It's been around 100 here the last 3 days for a high and pulling a car in at full temp as made it hard to keep the garage under 85. For the OP, as long as your cooing system is maintained well, which it sounds like it is, you'll be fine.
I always leave my vehicles to cool outside then bring them in.
 
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How do you figure?
I’m just going by maximum power efficiency. Anything over 185 is costing maximum power from my research. This research being in superbike racing. So I assume a vehicle maximum efficiency couldn’t be much higher if any.and he is way over that.
 
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JHZR2

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228-234 isn’t particularly concerning. I had thought it was, but folks like @SteveSRT8 had a lot of detail on GM vehicles routinely running that hot. I’ll be honest, such temperatures bothered me when I started seeing them in my BMW N55 engine, they’re hotter than I’m used to seeing in other vehicles. Time at temperature always has the ability to degrade stuff faster (see Arrhenius), but you live in the desert, that is the nature of the beast.

You have less delta T. Your only option is to add supplemental cooling and lower thermostats and be to active with swapping ratings between hot and cool season. Or move someplace more temperate. I suppose you could explore less coolant, more water, which gives less protection but better heat transfer. The worst that can happen is more pressure. The question then is what is worse for the system, more temperature or more pressure?
 
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I have a pre-luber installed in my E-150. During hot summer days if I get stuck in a lot of traffic I flip the switch after I shut the engine off and it allows oil to continue to flow. I let it run a few minutes and turn it off. In reality it serves two purposes, getting oil flow before starting a cold engine, and oil flow after shutting off a hot engine. It might be worth looking into for the OP as well.
Wow awesome, I’ve not heard of this. But I do know this is done with some cooling systems. My 00 Vw GTI had a secondary electric water pump that continued to go after the VR6 engine was shut down. I’d say doing both oil and coolant to eliminate hot spots would be best.
 
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Manufacturers heat test their cars to 120F so while you might go over that occasionally, your coolant temps are fine. You could help by looking at the oil side of it. Additional capacity and an external oil cooler would help lower coolant temps more than anything. Also, I be more worried of the transmission fluid temperatures.
Obviously you meant 220 and yes this is about as high as they like them to get. Corvettes will go beyond this on occasion.
 
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I commented quiet a bit in this thread because heat is one thing that I always obsess over. My 2002 Yamaha R1 always ran 162/175 no matter how hard you beat the bike. Now at a stop light they climb fast and the fans kick on at 220 bringing them to 210 and kick off. We have tuners get in our ecu and switch the fan start to 200/205 and off at 190-195. With that said, my newer model R1 if I’m giving it a good beating on a super curvy slow road like the dragon, (AKA deals gap) it will hit 200-210 max. My older R1 maxed out at 175 on that same road. It drove me crazy until I finally installed a secondary radiator. My other vehicles tend to always run pretty cool. We just picked the wife up a 15 Toyota Yaris my parents were selling and it doesn’t even have a temp gauge. Now I’ll definitely be looking for a way to know my temps in that car. Isn’t there some type of gadget I can plug in to get that info? I’d love info on that.
Lastly my response to the OP, unless you don’t mind spending some cash on engine ice, which is what I use in my performance vehicles I would try the coolant mixtures already mentioned as your cheapest option. But it’s not going to do enough that would satisfy me. I would find the largest radiator that can be installed and get it. And make sure your fan/clutch fan is up to par as well. My lord where are you that it’s this hot??
 
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My trailblazer (pretty much identical vehicle) saw the same temps, I sold it to a friend around 170k with no issues and its still going fine
 

Falcon_LS

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So you have completely misconstrued the comment by RooflessVW.

Keep your cooling system clean (reasonable drain and fill maintenance interval) and just go worry about other things.
That was supposed to be humorous, but never mind. Although I reckon he probably got it.

My cooling system is immaculately clean and well maintained; it's all shiny aluminum on the inside, and everything still looks factory. I'm not worried about it, and it operates as intended by the manufacturer.

The only thing I'm "worried" about with the cooling system is the plastic radiator tank. It is extremely common for them to crack right at the filler neck, which is exactly what happened to the factory unit after 11 years and 111,300 miles of service. The replacement was identical, both manufactured by Modine. A custom-made all-aluminum unit with additional rows may be a future consideration.

Having said that, my main (and biggest) concern are the seals, which was what I intended to focus on in this thread.

Unfortunately, going with a lower thermostat won't accomplish anything. There will only be a small delay and then you will get back up to those temperatures you have now.Stronger coolant mixes and pressure will not help with temperatures but will slightly raise the boiling point of your coolant. You are still a long way from that. Highway speeds you are doing fine. You could improve your city driving temps by increasing airflow. Fan and radiator upgrades would be worth investigating, otherwise there's not much else you can do with it.

Considering the blistering heat you are encountering in Kuwait, I think your engine is coping with it pretty good.
Absolutely, a lower temperature thermostat wouldn't do much at all, unless the PCM is reconfigured to command the fan on at lower temperatures to match. I did this with my Grand Marquis; the factory programming would command the fan on full blast at 212°F and now it comes on at 206°F. However, that vehicle is modified, and even runs spark plugs that are two ranges colder, so it's not exactly a fair comparison.

The electro-viscous fan actually pulls enormous amounts of air. When I let it idle with the hood up, you can feel just how much hot air is being pulled by the fan, but with the hood shut, that hot air has nowhere to "rise" and the heat stays in the engine compartment. Hood vents would probably do good for this application.

Ab, the extremes you experience are very hard on gaskets and seals, that's why when you and I get into a project build for use there we use a lot of teflon and kalrez seals.
There are a few things you can do, as Lubener said increase the size of the heat sink which in this case is the radiator and increase the amount of air flowing over it.
Increasing the size by adding more rows is the easiest way although you may need to make some slight mounting modifications.
Adding a large electric fan is another possibility.

All that being said you may be dealing with another phenomenon that Land Rover did a lot of research into because their vehicles were often operated in extreme conditions called heat soaking. I have experienced this twice over the years in hot summer driving at Autobahn speeds for a long period, you turn the engine off and a hose or gasket blows, letting it idle for a few min is one of the tricks in preventing this.

I have also noticed the thermostat being lower rated than on the same car with the same engine sold in the USA. Combined with improved cooling it does help control heat soak. I will try to find the original paper from Land Rover and email it to you.
Today, some manufacturers are using an auxiliary electric water pump that kicks on after shut down. Lots and lots of papers about this, a very interesting topic indeed.






Trav; I certainly remember all the lengths we went with a lot of those seals - especially for the transmissions! Those have actually been doing very well, and a lot of them are still just as pliable as they were brand new.

After 16 years of extreme service, and not knowing how much longer those factory seals will last, I reckon a refresh wouldn't be a bad idea when we beef up the transmission!

I’m not sure if this would help, but I suppose you could reduce the amount of coolant in your mixture and go with more water...water absorbs the heat from the engine better than coolant, but then you’d have to worry about boil over (and then maybe add a higher pressure rated cap)? Couldn’t hurt I guess, then just make sure you adjust it for winter.

I’d go on the forums for vehicles in the Middle East and see if they have some tricks that are working efficiently without causing damage.

Honestly I don’t think you’re damaging much of anything anyway...lots of taxis in the Caribbean are running 12 hours a day in blistering heat with their air conditioning on...car loaded with people and luggage...driving like maniacs...stuck in traffic...sun heat and pavement just pounding on these high mileage vehicles. But then again, I shouldn’t say...not damaging much of anything...when I talk to these guys half of them tell me they just put their third engine into it...and I’m like, man, you have 300,000 miles on this thing, time for a new one. Lol.
To be frank, forums for vehicles in the Middle East are about as useless as a one legged man in a butt kicking contest. A lot of "suggestions" are to install cold air intakes, at the expense of filtration, because "cool air cools down the engine". Not much knowledge to be shared in this part of the world, it's rare.

Having said that, the majority of vehicles that have had any type of cooling system service run straight tap water here. It's nothing but rust and the consequences that follow.

Back in the day, Jeep Cherokee (the XJ's) guys would add louvers to their hood to lower the underhood temp and improve flow.
It seemed to work for a friends XJ who drove and wheeled his XJ in Moab.

BTW, after driving home from Boston, I'm the one who needs a cool off period. LOL
I've actually got a set sitting on my desk for the Pajero/Montero that will be going on next month. I'm looking forward to any differences, if any.

I was mostly inspired by K-9 units I've seen with vented hoods, and it turns out this has quite a following in the off-road community!

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.
I've tried Red Line Water Wetter about a decade ago as a coolant substitute for the Grand Marquis. The issue with that was, about six months, the system needed to be thoroughly flushed and refilled. It looked almost as if oil was floating on top of the coolant reservoir at that point, and I never went back to it. Others I know who've tried it reported the same issues with murky looking reservoirs. It is certainly an option, just not too sure I'd want to use it again.

Does the fan on the Envoy stay on when the engine is very hot after the key has been removed?

If it's a real concern, I would do as Trav recommended and upgrade the Rad and Fan components. What you are doing by letting it cool off is good preventative practices. Are those parts easy to get in Kuwait or do you need to order online and ship them to you?
Although the fan clutch is electronically controlled, the fan is still belt driven and stops when the engine is turned off.

Parts are usually available, but I always order them and have them shipped.

If it's anything like my old Trailblazer, the 4.2 has an electric fan clutch that is isn't know for it's longevity. Might look into that too.
They did away with it in 2008, probably because it was a year before the end of production and they wanted to cheapen production as much as possible. It's a Hella Behr design, and I've only replaced it once. I guess it's been good to me.

I would think you are using synthetic oils for the transmission and engine to stand these higher temperatures, right?

Also, in my experience idling before shutdown is a great idea. Turbo cars do this to prevent coking on the bearings and while you have no turbo, it certainly seems like a good idea. We had to do this with our military vehicles - five minute "cool down" after reaching destination.
I go with the "heavy duty" alternatives or just go plain overboard for everything; 15W-40 HDEO for engine oil that gets drained for every 25% decrease in oil life, TES-295 in the transmission, 75W-140 ester based lubricant for the rear axle, CHF-11S in the power and DOT 5.1 for brake fluid. I stuck with Dex-Cool for coolant, although I have considered something like Caterpillar ELC as well.

Popping the hood is very common practice with motorcades as well, the fan clutches on 3/4 ton GMT900 Suburban 2500s were quite an issue at one point.

I wouldn't worry about it as that's what the block can take and I don't believe GM used 195f thermostats. It's actually good to have a hotter block for efficiency until it gets too hot. Didn't that car have a 210f one from the factory? And If you try to go to a lower one which I don't know if they even exist it'll just delay the amount of time it'll take. I think the cooling system in my 05 Yukon is overbuilt because the temp never goes beyond 210f in city driving. Only went to 220 after over a half hour of idling in stalled traffic but went down quickly once I went going. To be honest I'd just put the scan tool down and perhaps use a bit more coolant like 60/40 and I think you'll be good.
Factory rating is 195°F; I replaced it with a GM Original Equipment part just 2 months ago and that was the temperature rating on it as well. The OE supplier is Hella Behr, who I believe may have done a lot of work on the cooling system for this application. Almost every component is supplied by them.

The Tahoe/Yukons from that era used 188°F thermostats, at least that's what we got over here for them. I still remember the ACDelco part number for those, it was 13-11-56.

Manufacturers heat test their cars to 120F so while you might go over that occasionally, your coolant temps are fine. You could help by looking at the oil side of it. Additional capacity and an external oil cooler would help lower coolant temps more than anything. Also, I be more worried of the transmission fluid temperatures.
For this part of the world, they get tested at temperatures over 120°F, artificially if so required. 120°F is only 48.8°C, the reading on my outside thermometer in the shade right now is 52°C (125.6°F) at 15:57 hrs.

I have a stacked air-to-oil cooling for my transmission, it rarely sees a hair over 200°F.

Is your thermostat OEM? My grandparents Trailblazer, we put in a Stant thermostat and it ran warmer. Then bought an OEM one and measured with a micrometer. If I remember correctly it was like a 30% larger opening on the OEM.

That helped it, but what made a world of difference, like life changing difference, was a new OEM fan clutch. Engine cooled back down and the A/C was awesome afterwards. 115+ is a normal day here too and we were dying at stop lights without air flow.
Thermostat is OE, so is the fan clutch - both supplied to GM by Hella Behr as mentioned previously.

The fan is definitely working, even at 8% commanded by the PCM, it is moving MASSIVE amounts of air you can feel with the hood up! Usually when the clutch goes bad, it'll be stuck and sound like an airplane taking off! LOL

228-234 isn’t particularly concerning. I had thought it was, but folks like @SteveSRT8 had a lot of detail on GM vehicles routinely running that hot. I’ll be honest, such temperatures bothered me when I started seeing them in my BMW N55 engine, they’re hotter than I’m used to seeing in other vehicles. Time at temperature always has the ability to degrade stuff faster (see Arrhenius), but you live in the desert, that is the nature of the beast.

You have less delta T. Your only option is to add supplemental cooling and lower thermostats and be to active with swapping ratings between hot and cool season. Or move someplace more temperate. I suppose you could explore less coolant, more water, which gives less protection but better heat transfer. The worst that can happen is more pressure. The question then is what is worse for the system, more temperature or more pressure?
Both high temperatures and high pressures won't do the system any good, and while initially I was a bit concerned with this being an all-aluminum unit, I started getting more concerned about seals, particularly the likes of valve seals, etc. on the inside that are on the inside that are a pain to replace. With this being a reverse flow cooling system, the heads get cooled before the block, I guess that somewhat helps, but these are still higher than I feel comfortable with! LOL
 
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People with a turbo may benefit the most from a 5 minute cool down period after high speed highway driving. The high heat in a turbo can cook the oil if there is no cooling water flowing.
 
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I would only worry about doing this cool-down if my vehicle model was known for having head gasket issues. Otherwise just keep up on the maintenance and drive it normally.
There was a comment about the boiling point of dex-cool and water... keep in mind that the system pressure will drive up that number, unless you already factored in the rad cap pressure on the system.
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.
 
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