Grand Cherokee Running Warm Towing

[JHZR2]

Load increases by the cubic (3rd power) with speed. You probably doubled frontal area, so imagine 2x load to the 3rd power as you pick up speed. Of course you’ll be burning more fuel, making more power, shedding more heat.

I’d be more concerned why your cooling system needed such repairs in 2018 given a pretty high use tempo (~30k miles per year). That thing should have been like new inside.

 

[Nick1994]

Load increases by the cubic (3rd power) with speed. You probably doubled frontal area, so imagine 2x load to the 3rd power as you pick up speed. Of course you’ll be burning more fuel, making more power, shedding more heat.

I’d be more concerned why your cooling system needed such repairs in 2018 given a pretty high use tempo (~30k miles per year). That thing should have been like new inside.

1/2018 at 102k miles we bought it from an Acura dealership and 2 days after buying it the radiator was leaking from the seam, so the dealer put in a new OEM radiator. A couple months later one of the radiator hoses had a slight leak, probably from one of the hose clamps being reused so I just had my mechanic do the thermostat(s) and radiator hoses with new clamps. For some reason I seem to remember it having 2 thermostats from what my mechanic said.

 

[wwillson]

are you trying to hold the posted speed limits on the climbs? Get out of that mindset if you are, it’s not neccessary.

That is sage advice! When I pull our 5th wheel up a grade, I will get behind a semi in the slow lane and match their speed, usually between 30 and 40 MPH. I'm not a diesel bro and don't have to prove to anyone how fast I can tow a 20,000lb trailer up a grade. It takes no skill to tow fast uphill and my EGTs don't exceed 1200°F, if you race up the hill, you'll exceed 1500°F all the way up. No thanks. The same applies down slope, I get behind a slow truck and follow them all the way down, usually 25 MPH. At that speed the exhaust brake will maintain the speed all the way down and I never touch the brakes. You can't believe how many diesel bros race down the grade and end up with smoking hot brakes or worse. We see it almost every time we pull passes. It really makes you wonder if they have ever seen an occupied runaway truck ramp or a crumpled mess at the bottom of a ravine or if they just believe it can't happen to them.

 

[mt23]

It may be worth checking radiator cap is holding proper pressure as well

 

[Nick1994]

Well I took it for a test run up the mountains with my OBD2 reader to watch the coolant temps, was between 102-110 degrees outside. Also hosed out the condenser and transmission cooler ahead of time. On flat ground it runs about 235 degrees, if there's any incline it gets to 240. On the biggest mountain climb I made it most of the way up before I had to pull over. It hit 253 degrees and went into some sort of a limp mode, it cut engine power a lot.

I think I'm going to flush the radiator, install a new thermostat and radiator cap and try again.

It does pull great though. Just the right amount of power and it handles and stops great. Vehicle speed doesn't seem to make a difference on temperature for the most part. I didn't drive it hard either.

 

[meep]

Nick, it may be the picture, but your camper looks a bit taller than mine did. It appears nearly 2x the height of the vehicle. will your code reader display the percentage output power commanded during that climb?

I recall with my 3.7, a 5x8 uhaul trailer would present a pretty big load when on steep inclines, and it doesn’t have nearly the frontal area.

ambient temps are high, too.

engine speed seems way too low for climbing speed. If it’s steep and you’re working it, it needs to be 3500-4500 rpm.

if it’s in its natural gear and you’re overheating at a low enough load for the vehcile to select a 2500rpm ascent rpm, I agree, the cooling system may be weak.

the rpm is low to my liking for ascending a hill will towing.

 

[Kira]

Wrap your radiators!

Is there a particular type of screen? There must be established products.
I'm thinking about temperature (fiberglass screen?) and gauge (size of holes).

 

[wwillson]

Is there a particular type of screen? There must be established products.
I'm thinking about temperature (fiberglass screen?) and gauge (size of holes).

I use standard nylon window screen. You'll see something similar over most class 8 truck radiators, but their bug screens appear to be made for the truck.

 

[andrew_j]

Looks normal to me given outside temperature and stress of the load(mostly wind) .

 

[LouC]

I’ve towed approx 5,000 lbs with my 2007 WK Grand Cherokee 5.7 V8 but only local no Highway or high speeds. Steep hills but around town speeds. I use tow/haul on the Chrysler 545RFE and it never shows elevated temps even with AC on when towing. Maybe the hydraulic cooling fan cools better who knows. Anyway I’d use the manual shift option to keep rpm between 3,000 and 4,000 rpm climbing hills at Highway speed. That circulates coolant & oil faster & may moderate temps some. The 3.6 does have a factory engine oil cooler built into the oil filter housing. I’d also use full syn oil. I wonder if they bled all the air out of the cooling sys when the rad was replaced. On some vehicles it can be difficult. I use a Lisle radiator funnel for that.

 

[wlk]

Yeah, something is off on your cooling system, temps should not climb that high. Definitely change the thermostat and make sure fans are both coming on and a sensor is not bad.

 

[spasm3]

I think you dont' have enough power to pull up inclines. A sub 4 liter non turbo engine pulling 3200lbs on a 100f day. Besides weight, the trailer is a good bit taller that the tow vehicle. Yes the trailer is pretty aero, but think about how the air comes off the jeep and probably hits the trailer just above the tongue mounted tool box. Plus the air over the top dragging on the roof.

The long tear drop shape probably has a lot of down force on the rest of the trailer past the roof peak.


BTW your tow chains look a bit close to the pavement, but it could be an optical illusion.

 

[wwillson]

I'm sure it's dirty though. It's just so hard to get in there.

Is there any way you can shine a flashlight from the engine compartment forward through the radiator/condenser and see how much light comes through? When I do this, I see all the air channels are completely open and clear of any debris. As I said before, I'll bet you the problem with your overheating is blockage in the air channels either in the condenser or the radiator or both.

 

[wwillson]

BTW your tow chains look a bit close to the pavement, but it could be an optical illusion.

This is a good point. If a law enforcement officer sees your chains even come close to touching the pavement, you'll likely get one heck of a ticket, especially in the Western US where brush/forest fires are a large threat.

 

[meep]

This is a good point. If a law enforcement officer sees your chains even come close to touching the pavement, you'll likely get one heck of a ticket, especially in the Western US where brush/forest fires are a large threat.

I had zero idea that was a thing! Is that a thing?

 

[ctechbob]

I had zero idea that was a thing! Is that a thing?

Probably location dependant.

Certainly not a thing anywhere around me, but I could see it being a thing in states with big open dry grass fields and the like.

 

[Chris142]

1/2018 at 102k miles we bought it from an Acura dealership and 2 days after buying it the radiator was leaking from the seam, so the dealer put in a new OEM radiator. A couple months later one of the radiator hoses had a slight leak, probably from one of the hose clamps being reused so I just had my mechanic do the thermostat(s) and radiator hoses with new clamps. For some reason I seem to remember it having 2 thermostats from what my mechanic said.

Are you sure they used an OEM radiator? I had a customer insist that I buy a radiator from the dealer for his Chevy truck. The radiator we got came from 1800 radiator

 

[Nick1994]

Are you sure they used an OEM radiator? I had a customer insist that I buy a radiator from the dealer for his Chevy truck. The radiator we got came from 1800 radiator

I remember the invoice showing a free $600+ radiator that said it was OEM. I believe they bought it from a Jeep dealer and didn't fake it.

 

[Chris142]

I had zero idea that was a thing! Is that a thing?

It's a major thing. The chains have to cross too.

 

[Falcon_LS]

When your coolant temperature starts to rise like that, turn off the AC and see if it starts making a difference over the course of the next 3-5 minutes of driving. If you notice a change, and this vehicle is used regularly for towing in the summer, you may wish to consider looking into an electric water pump that runs full flow regardless of engine speed. They will be expensive, but in my own personal experience, they have been worth every penny.

Case in point, after modifications, my Grand Marquis was undriveable during the summer when ambient temperatures routinely range between 105°F-125+°F. Regular driving on the freeway at speeds to 55 - 75 MPH would result in coolant temperatures ranging from 215°F-230°F, sometimes higher, even with a 180°F thermostat and a tune that configured the electric fan to come on full blast at 206°F. It also has a custom, all-aluminum radiator and a high flow OE water pump from a Lincoln Navigator. I also looked into a Stewart EMP mechanical water pump, but a lot of folks had similar results with this compared to the Navigator water pump. Turning off the AC would drop coolant temperatures back down to the 209°F-220°F range, but that is still hot considering the temperature range this engine is supposed to be operating in. WOT was completely out of the question, because detonation would start to become an issue even under light throttle.

What really helped my situation was switching over to a Meziere electric water pump that constantly flows at a rate of 55 GPM. Coolant temperatures now range from 200°F-204°F at highway speeds. I realize a lot of folks will be turned off by the "electric" part and the initial cost; that certainly was the case with me, but then again, fuel pumps are electric as well and generally tend to last a reasonably long time. This particularly unit has a lifespan of "3,000+ hours" according to the manufacturer, although the 3-4 year mark is what I'll consider as its service life to prevent unexpected failure at the worst possible moment.