Kevin Parkes

Towing a 6500 pound boat work a 2015 GL 550. I'm in So Cal. Going up pretty much any hill, the engine temp increases. Towed across I40 recently. Outside temp around 100F. Engine temp went up to just under 120C on every hill. Just below the red zone. Only myself and 2 kids in the vehicle. Not heavily loaded. In the shop now. So far, no answers. They are saying "it's not a truck" "the radiator is smaller" With a towing capacity of 7500 pounds, I would think there wouldn't be an issue. None of the other vehicles towing on the same trip had overheating problems. Not good answers, as far as I'm concerned. Anyone have issues with overheating while towing? Thoughts? Thanks.

silkysmooth_96

Get the Diesel model. sure it's dead slow in comparison but is fantastic at towing! Fuel economy is a major bonus as well with over 600mi to the tank! Is it an issue though if the temperature rises, but isn't in the red?

BlownV8

Are you taking it to the MB dealer? "Not a truck" is a BS response and equals we don't really know what the problems is with your GL. I'd bet the radiator fans are not running properly or you have an intercooler pump issue or a combination of both. As for the diesel, before you go that route, do some research on the diesel issues. No free lunch there.

RostamDastan

What was your speed going up the hills?
We have a GL 350 Bluetec and tow a camper weighing ~6000# and have not had any overheating issues. We are in northeast though, so I guess it does not get as hot as LA. I agree that GL should tow a 6500# boat without overheating (boat has much less air drag than a camper). It is also true that trucks have superior cooling systems and are better equipped to tow heavy. Regardless, your GL should not overheat. Maybe you go to another dealer to get a second opinion?

fabbrisd1

Running close - but under - Red Zone is not overheating... good to get your system checked out.... if it was me - I would get check aircon pressure level - add Water Wetter to the system - and call it a day..

Gl550designo

Hi Kevin,

I know this is an incredibly old post but wondering if you ever found an issue or solution? I am having the exact same problem in a 2013 550. Towing a 6200lbs travel trailer and every hill it jumps up to 120c pretty quickly. We have also had very warm temps, 100+ in some places with a pretty good head wind so I understand the “it’s not a truck” comment but…. It wasn’t doing this before and now seems to be getting worse. It overheated going up a slight incline in 80 degrees. I believe I have isolated the issue as the turbos. It only seems to overheat when the turbos really spool up, appears that the revs are irrelevant. I can be clicking down the highway below 2000 revs, hit a slight incline and without kick down or coming out of lockup it will still overheat. Brand new radiator, new fluid 4 months ago. Checked the inter cooler reservoir under center cover and full as well as good movement when engine running (seems inter cooler pump is fine). Any suggestions or data you ultimately discovered would be very helpful. Thanks.

Ben

RostamDastan

I think the photo clearly illustrates your problem. Your trailer is MUCH bigger than your tow vehicle. I would assume the naturally aspirated V8 engines in first generation GL would not overheat like the turbo engines in the second generation, but that is besides the point. You need a truck, and I'd say an HD truck, to have a worry free and relaxed towing experience. I suggest you rent a 3/4 ton pickup once to notice the night and day difference in towing. Also, have you weighed your trailer? I suspect travel ready it will weigh much more than 6000#. Best of luck.

chassis

This is borderline relative to the vehicle's capability. What was your actual trailer weight on a scale?

Weight near max + 100deg ambient temp + what appears to be mountainous terrain = borderline vehicle performance, overheating not out of the question.

oldmangrimes

I think there is an important distinction between "running hotter than normal on the temp gauge" and "overheating". The word "overheating" implies a failure, damage to the engine, etc. I've had many vehicles, including my 2013 GL450, that will "run hotter than normal" when towing a heavy load up a mountain on a hot day. I just turn off the AC for a few minutes, maybe even turn on the heater, etc. and the engine temp will go down. I've never "overheated" an engine. Seeing the temp needle move up from the stable (and electronically filtered) "normal" temp is a little scary, and should be a warning sign that you might need to make an adjustment to what you're doing, but it is not "overheating". The X166 is a great tow vehicle, and that travel trailer might be ok but you should take it across trucking scales while loaded. I tow a 30-foot travel trailer with my GL450, but it's ultra light (5500 dry). I am careful to keep it under 7500 loaded and I don't load up the GL450 with people and gear when I'm towing heavy to keep the total weight in the limits. But I've towed my trailer for thousands of miles, including over the Rocky Mountains, and it ran hotter than normal on the steepest grade but didn't break anything or "overheat". You don't need a 3/4 ton truck to tow a travel trailer. But you do need to be smart, keep your loaded trailer under the weight limits, keep the weight balanced so you don't overload your rear air suspension by exceeding the tongue weight, use a weight-distribution hitch with anti-sway, drive at reasonable speeds, air up your tires, use tow mirror extensions so you can see better, use a brake controller, etc etc.

RostamDastan

Tow vehicles discussions, IMO, are similar to discussions about religion/politics. With that caveat, I'll just say one thing and bow out. Statements like 'You don't need a 3/4 ton truck to tow a travel trailer' do not say anything about the desirability/comfort/operating cost/utility of a tow vehicle. Sure, you CAN tow a 32 foot, 7000# trailer with a GLS up and down the Rockies. However, a (HD) pickup truck will do it significantly more effortlessly. With GLS, you have to fine tune a lot of things and still have to be super alert. This translates to driver fatigue. With an HD truck, you get to your destination much more refreshed. Also, the operating cost of a GLS is significantly higher than a pickup (rear shock absorbers run at $1800 a piece for GLS). I've towed a 6000# camper with GL 350 for 5 years. Now I have a Tundra and towing wise it's a serious step up. Longer wheelbase means better stability, specially going downhill. Trucks generally have better cooling system, integrated tow mirrors, integrated brake controller, class IV hitch, rear solid axle for carrying a heavy load, larger fuel tanks, tow/haul button, better engine/exhaust braking, and a bed for dirty items like gasoline, grill, firewood, lawn chairs, etc. My experience proved that 'it can be done' but the consensus seems to be that there are many better alternatives. Thats why you see very few SUVs towing large trailers in campgrounds. Its mostly trucks, and among trucks, mostly HD trucks. HD trucks, while not ideal as a daily driver, are, IMO, the ideal towing machine.

arsupisemnet

The only problem here is a driver's skills, i can boil 18 wheeler going uphil in high gear, not a problem, but normally you downshift your gears and have no worries... Last comment about upgrade from diesel to sheaty Tundra is comical...