Overheating with AC on Max


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Old 06-05-21, 10:02 AM
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Overheating with AC on Max

So I'm driving home from work, AC on high cuz its so hot, and noticed the air suddenly get hot. It must be a safety switch because I checked my gauges and sure enough, the temp gauge was on Hot. So I shut off the air and the gauge immediately began to drop. No harm done, I hope.

So I get home and open the hood to see whats wrong. The coolant level seems fine. So I look at the radiator and notice its got a LOT of bugs on it, and quite a few of the fins seem to be flattened from bug impacts. So I assume this is the problem.

I've been carefully straightening fins, poking with thin wire and lightly scrubbing, hosing the radiator out and it seems to be doing some good... I can really feel the fans pulling air through the parts I have cleaned and straightened as opposed to the areas I have not.

I just wondered how common this is, and do people often replace radiators for this reason? Seems like they should be bug proof but guess that after 269,000 miles the effect is cumulative. I think I will keep cleaning and straightening rather than replace if this helps solve the problem.

 
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Old 06-05-21, 10:24 AM
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How big are the bugs where you are (or maybe how fast do you drive ). I haven't had your issue, I'm able to spray them off when I wash my car. My veh have 208,000 and 234,00 and still look pretty good.

https://www.amazon.com/HonsCreat-Conditioner-Radiator-Condenser-Straightener/dp/B077K2KCJ2/

Example of a cheap tool to assist you.
 
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Old 06-05-21, 10:31 AM
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Thanks for the link. Yeah I think a lot of it might be June bugs, flying beetles, there is just tons of stuff in the air at night, not just moths. And 70-75 mph is typical on divided highways here. Living in a river valley this must be like bug heaven.

 
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Old 06-05-21, 10:46 AM
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It's automatic for me to put a bug screen or a piece of window screen across the front of all of my vehicles from the day I buy them. Never had an overheating problem in 40+ years doing that and the radiators are as clean as when they were new. You might consider trying that after you get done cleaning yours. You also might want to back flush the fins with a fairly strong pressure from a garden hose from the engine side outward toward the front of the vehicle, it will help get rid of the last of the debris between the fins.
 
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Old 06-05-21, 11:03 AM
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not uncommon for radiators to clog up enough were just a little extra load like having the ac on could cause over heating , would just monitor it see if the problem is resolved or not.
on most vehicles usually the condenser is in front of the radiator so it would be the most impacted may be able to find a bug screen to protect it.
 
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Old 06-06-21, 05:36 AM
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Are you able to get the radiator and anything else in front of it / behind it clean? Suggest using a (typically 3/32") wood barbecue stick.

Even if you don't get it completely clean, you can try driving and seeing how high the engine thermometer on the dashboard reads and then decide whether you cleaned it "good enough."

Another (and common) cause of engine overheating is a stuck or weak in line coolant thermostat.
 
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Old 06-06-21, 07:46 AM
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You likely could straighten bent fins.
If you do a reasonable job of it what the rad looks like would be mostly a cosmetic defect.

Another thing you could try is to spray the radiator surface with a cleaner labelled for bug removal.
Bugs tend to be greasy and are hard to remove with water alone.
Just be careful to direct the water stream straight on as some fins are easily bent if forcing them to the side with a misaligned spray.
 
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Old 06-07-21, 07:46 PM
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Thanks guys. Kept a careful eye on it today, and it seems a little better but still wants to get hot, especially if I exceed 65 mph for very long. Slowing down seems to make the temperature come down to normal operating temperature the fastest. Transmission temperature is normal at all times. Coolant level is not low. No leaks. Fans are working normally and each fan clutch has good resistance.

So with the way it fluctuates at different speeds, I'm leaning toward thermostat. Plus the fins still obviously need more straightening and cleaning... even if that's not the root of the problem. Will post back if I have time to get it changed this weekend.
 
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Old 06-10-21, 03:28 PM
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Changed the thermostat and it didn't help. The coolant I drained was clean as a whistle so I doubt it needs a flush. I read that a possibility is a small exhaust/head gasket leak that is superheating the coolant. If it's not the bent radiator fins.

It's odd that it only overheats on LONG drives... Only on very hot days... And only at 65-70 mph or above with the AC on max. The gauge just slowly creeps up to H.
 
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Old 06-10-21, 10:07 PM
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radiator passages may be clogged internally enough that you may have to replace it, as cores do clog up you reduce your cooling capacity and most manufacturers do not install large radiators to begin with so its not uncommon to have to replace radiators that otherwise may not have no external damage.
 
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Old 06-12-21, 03:51 PM
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Hopefully it's not a head gasket. Just curious, what brand and year is your vehicle? Great you've brought it to 269,000 miles.

Also - couldn't find where to ask this but how does one quote a post? I think I've seen a few replies with quotes here.
 
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Old 06-12-21, 03:54 PM
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It's a 2013 F150 with 3.7L V6. I had a tune up done a while back and I'm pretty sure he put a new head gasket on, but maybe thats what screwed it up and I'm just now seeing the problem now that its summer again.

Since shutting the AC off and running the heater oneaterseems to cool it down really quick, you guys are probably right that its related to the radiator ability failing.

Quoting is done by pushing the quote icon and then copying and pasting the text you wish to quote.
 
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Old 06-13-21, 09:28 AM
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Wow, a lot of miles for a 2013! Ford trucks have been known to be one of the highest mileage achievers.

Quoting is done by pushing the quote icon and then copying and pasting the text you wish to quote.
I was looking for the quote icon on your message, I then saw it only after I hit reply. Didn't think Ford engines would typically have a head gasket failure.
 
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Old 06-15-21, 06:16 AM
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I'd replace the radiator, they do tend to clog up internally over time which reduces it's ability to dissipate heat correctly. Also make sure you don't use straight coolant as it also does not dissipate heat well either. Use a good premixed solution.
 
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Old 06-15-21, 07:50 AM
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If you go down the route of cleaning your cooling system I've had acceptable results on my F150 with

https://www.amazon.com/Liqui-Moly-20.../dp/B00CPL99N6.

Pretty amazing what comes dribbling out with this stuff. I still have the original radiator on my '99.

A head gasket leak would show itself in a variety of way, the most obvious would be your coolant level slowly decreasing.
 
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Old 06-15-21, 04:05 PM
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Alright, you've convinced me to give flushing a try. Might get to it this weekend. Will let you know how it goes.

If I can't run my AC on maximum high I might just melt.
 
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Old 07-04-21, 09:40 AM
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I'd replace the radiator, they do tend to clog up internally...


My son recently bought a 84 Merc Grand Marquis with 40k miles and it did the exact same thing.
Hour each way to work at 55 and it was fine. Get on the freeway and it'd get hot.

After changing the water pump,?. thermostat and radiator cap, nothing helped.
Couple decades ago I bought a new radiator for my 85 Grand Marquis, junked it shortly after
but kept the radiator in my shed.

With my radiator in it he just drove from south of Green Bay, WI to Northern MN, temps ~90
and AC on the whole way - no problems.

No idea if this matters but Rockauto has 9 radiators for your truck, 5 out of stock.



 
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Old 07-04-21, 10:28 AM
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Yeah I'm thinking that's it too. Flushing really hasn't solved it.
 
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Old 07-05-21, 07:22 AM
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What type of fan clutch do you have?
If it is an electric fan clutch it may be cutting out at higher speeds.

A type of fan clutch I am familiar with has the water temp sensor close to ground to enable the relay.
On this type you can temporarily connect the sensor wire to ground to operate the fan continuously as a test.
Do not leave it connected after testing because the fan may run when the engine is turned off.
 
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Old 07-06-21, 06:03 PM
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It must be an electric fan clutch, I don't know what other type it would be. I will have to look into jumping it as you suggested Greg. That may take some doing, I'm not a whiz when it comes to electrical. But it makes sense to rule that out as a possibility. And it seems like a safer way to test it than to have me riding on the front bumper watching the fan while the wife is driving the truck 70 MPH down the freeway. LOL.


But it seems like if it was the fan clutch, it would do it all the time at 70+ mph... not just when its over 90F and I'm going 70+. When it's in the upper 80s it barely goes past normal. When it's in the 90s I have to watch it, as it will approach the H. And when it hits 100, it will peg it out unless I shut the AC off and turn the heater on. All of this only at 70 mph+. If I keep it at 60 mph it won't overheat much more than normal.
 
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Old 07-06-21, 07:00 PM
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I'm pretty sure the fan affects are negligible at speed. The fan is only there to pull air through at low speed.

I don't know what other type it would be
My F150 fan clutch is hydraulic (older F150). You can easily tell, is the fan connected to the engine, if yes then its hydraulic. I'm pretty sure the 3.7s had an internal water pump. I assume when you did the flush you would notice if there was anything like oil in the fluid. Take quick look at your oil and make sure there are no signs of fluid (milkshake) in it. If you have a scan tool, take a look at your fuel trim to see if you're running lean at high speed (though I would think you'd set a MIL). You can also check the temp of the engine to see if you gauge is reading correctly. If you have an infrared thermo you can use it to check the temp of the engine and see if it matches the thermostat.
 
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Old 07-06-21, 07:51 PM
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Its an electric fan then... not connected to the engine. Dual electric fans. Coolant is clean, no coolant leaks, it's never been low and there is no coolant in the oil. There are no codes and the check engine light has never come on.
 
 

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