Engine overheating with AC on while off-roading

Hey guys, with summer now here in SoCal it's going to be impossible to wheel without using the AC (well, very uncomfortable anyhow).

Last weekend, I was doing the Miller Jeep trail and was creeping up the narrow, steep switchbacks in 4lo. It was getting really dusty out (truck in front of me) so I rolled my windows up and turned on my AC. Within 10 minutes I noticed my temp gauge had gone up and was slowly rising. I turned the AC off and it went back to normal.

This doesn't happen when I'm driving around town with my AC on, only when I'm in 4x4. I searched the forum on the issue but most people suggested that it's the stock fan clutch. I have dual electric cooling fans and they run fine (as far as I can tell) so I don't think it's a fan issue. In fact, these fans are supposed to do a better job of keeping the truck cool than the stock clutch fan.

Any ideas? Truck is a 2004 5 speed, supercharged with 28k miles on it (very low). I wonder if maybe I need to flush my cooling system as it's probably the same fluid from '04?

 

Your fans are not moving enough air.
Most modern vehicles with electric fans typically have 3 speeds. Low, Medium and High. With each temp increase the fans move more air. All this is done buy the ECM monitoring the Engine Coolant Temp (ECT) and A/C System.

You need to find a fan controller that will increase airflow as the engine temps go up.

Something like this:https://www.flex-a-lite.com/accesso...rs/flex-a-lite-variable-speed-controller.html

I am not saying that is the one to get, but one that fits your truck would be sufficient.

 

Maybe change thermostat along with changing coolant. I also have a '04 v-6 5 speed with stock fan and live out in the desert where it's 110 out sometimes and can lug around in lo range with ac on all day and never even think about getting hot so I'll say fans too.

 

Yeah, definitely something's not right. Engines actually are supposed to run cooler with A/C on because of the additional fans running. People seem to think the opposite but that's not the case. I'd check to make sure all the fans are working, replace t-stat and do a radiator flush, something could be clogged up in the radiator tanks.

 

Thanks guys. I'll start with a coolant flush since it probably needs one, but I'll definitely look into the fan.

Weird thing about my fan is that the previous owner installed it so that it's manually activated via a switch in my cab, I leave it 'on' all the time obviously as I wouldn't want to forget about it and have my engine overheat, but it makes me wonder how well it was installed in the first place...

 

not really, with the AC on you are adding additional load to the engine and more heat right in front of the radiator. however with whats happening to the OP, i would check fans. i am also i socal and i have my AC cranked when wheeling with no issues wheeling lol

 

I would do a radiator flush to start off.
And for some reason i lose a good amount of coolant from overflow and when its low or dry i overheat slightly.

 

Had it happen with my 04' out in Moab. Was same deal, up and down in 4lo with a/c. It was on hells revenge. Never saw it on any other trail. Shrugs??

It never got to the red, so I shrugged it off. I figured it was due to the extreme low speed and not enough air movement across the radiator to dissipate the heat so I never pursued the issue.

 

Yeah mine never got to red, it sorta just hung there between halfway (normal temp) and the red marker, took about 10 minutes to get to that point before I just turned off the AC and it went back down. It may have just stayed in that spot for all I know, but I didn't want to risk anything.

 

Might be a dumb question but I gotta ask, is there a shroud for the fans? Or are they just two circular fans mounted on there?

In other words, is it a kit designed for the truck or a universal/custom setup? Any pics?

 

and i wonder if getting your AC serviced would help at all. the condenser in front of your radiator is increasing the temperature of the air that is supposed to be "cooling" your radiator.

 

I saw your video of Miller jeep trail . Next time you go hit me up , I'll be down to go .

 

It's designed to sit right up against the radiator, not back from it like the stock clutch fan.

That's actually an interesting point, my AC works but it makes a weird sound from inside the cab whenever it's on. Like it's got a leak in a hose or something, it's hard to explain. Sounds like it's sucking in air and then letting it out. I haven't gotten around to getting it looked at because other than the annoying noise, it works fine. I might have to go have it looked at now that you mention it though, they may be connected.

 

Definitely! Have you checked out our meetup thread? It's titled for the next Rowher Flats meet in a couple weeks, but that's the thread where we organize little side trips like the Miller Jeep trail we did last weekend. You should subscribe to it if you haven't, anytime any of us in that group wants to wheel we post up in there and see who else wants to come

https://www.tacomaworld.com/threads/rowher-flats-bbq-fiesta-trail-rides-bs-6-25-16.425646/page-98

 

Ok so it does have a shroud. Could be that your radiator And/or your condenser may be filthy/clogged a bit too. You said it was really dusty out. Do you wheel often in these conditions? Of so, I would go ahead and take compressed air to the radiator as well as the condenser. The best way, would be to remove the fans, and blow out from the inside, out towards the front. Instead of from the front towards the engine. Even better would be to unbolt the radiator and push it back a bit, and do the condenser and radiator separately. Instead of trying to blow out both together possibly blowing crap back into the condenser or vice versa. Of you wanna test it just to see if it is clogged, just spray it once or twice from the inside, spraying out towards front of truck and see if a bunch of dust spews out. If so I would go all the way and disassamble those and give them a good cleaning with compressed air..
But this may not be it and may just be the controller. Or something else. Just figured I'd throw that out there.

 

That's the noise the expansion valve makes when refrigerant is not properly passing through. you could either be low on refrigerant, or have a defective valve. get a full service and ask for a new valve and drier while youre at it. should only cost like 90 bucks extra, but will make sure the new system is that much colder.

this next bit is inaccurate. please see following explanation 2 posts down.

• little bit of how the system works. compressor increases pressure of freon, i think turning it into a hot liquid, so it can pass through the valve/tube. the valve/tube expands the liquid and this expansion causes the gas to become extremely cold. that cold air is then immediately passed through the evaporator where the temperatures are exchanged and the returning heated freon is cooled when passing through the condenser, only to return to the compressor and cycle again.

if the system isn't pressurized properly (low on freon) the liquid may never properly expand and return hotter than it should, causing the condenser to be a little warmer than it should, and thereby the air passing through it is heated up a little more than IT should.

im hoping that's your issue, if not one of them.

 

I do wheel quite a bit in dusty conditions, I try and go out at least a couple times a month and out here the trails are always dusty. The last one especially. Granted I've only had the truck for a few months now, but I think you're right in that I should be sure to keep the fans clean and operating at their best. Thanks for the tips, I'll make a project out of it next weekend

Awesome thank you! It's great to know what it is exactly, I hate going into the service department asking them to try and figure out what's wrong when I don't know myself. That sounds exactly like what the issue is, and it could very well explain the overheating when the AC is on. The temp gauge climbed real slow over 10-15 minutes or so, and immediately went back to normal when the AC was turned off so I wouldn't be surprised if this is the main problem. At the very least, it would be great to get the AC working the way it should again.


Thanks for the help guys!!

 

Only thing to add, the freon flow starts at the suction side coming from AFTER the evaporator core, to the compressor where it becomes MUCH hotter due to the extreme pressure from the compressor, then through the condenser to phase change the hot gas to a hot liquid, then to the Tx valve which sprays refrigerant through the evap core to pick up heat, then back out to the suction side to repeat. Main problem with your explanation is that it goes through the compressor first, which greatly raises the pressure, and therefore the temp, so that the temp differential between the hot, high-pressure gas and the air is maximized. As the gas cools, the pressure causes it to condense to a liquid to re-start the cycle...

As far as overheating goes, if you compare the pitch / diameter of the stock fan to those two small electric fans, I bet the stock fan will move 4x the air. At 4low vehicle speeds, the air flow is pretty minimal (flow caused by vehicle speed) so the fan is pretty much it. With the A/C on AND the engine working at moving the truck, it needs a LOT of air to keep the coolant temperature down where it can keep the engine in the proper temp range.

Just because a fan makes noise, doesn't mean it moves much air.

 

I'm going to start with recharging the AC system and replacing the expansion valve, if that doesn't take care of the slight overheating I'm experiencing then I'll know I'm dealing with the fans exclusively. I'll do a full radiator flush too just to make sure that's not the issue. I wish the PO had just kept the stock clutch fan on there, I know the electric ones are supposed to do the job well but the way these were installed doesn't give me much faith in them.

 

why not just put it back on? 65 bucks for the clutch, couple bucks for new bolts and washers, a im sure you can find a fan blade on ebay or from someone parting out their 3.4