03 5.3 Running Warm While Towing

Hello all! Newbie here. I've had my 2003 Avalanche since 2007, bought it with 77k got it about 133,000 now. I've used to tow small trailers and such locally and never have had any issues. Last year I purchased a 2001 Bayliner 215 with a tandem trailer (I'm assuming can't weight more than 4,000lbs). This past years out here in Southern California I took it out to the river around June, Air temp about 105, going up hill around 30mph it ran right in the middle of 1/2 and 3/4 temp. Noticing that, I brought it down to about 20mph. I assumed it was because it was so hot out. Made it to my destination, 4 days later on the drive home, the entire drive it ran the same thing, dead center between 1/2 and 3/4. I took it easy because I was nervous it was going to overheat. So when I got home i changed out the thermostat, and a supposed "heavy duty" Murray fan clutch from O'reilly as well as new upper and lower hoses. made the same trip in october this past summer and this time I went at light. Randomly while towing in the evening when the air temp was all of 80 degrees F. it did the same thing, it would move mid between 1/2 and 3/4, and thats not even uphill or anything.

I guess my question is, is this normal? I've considered adding a trans oil cooler, and also seeing if someone makes a heavy duty aluminum radiator. I've been wanting to get a travel trailer but I'm concurred, if it can't even handle this light boat how can I  handle anything close to the 7200k tow rating? Any help is appreciated! Thanks!

Without a doubt, installing a transmission cooler is a good idea.

With the miles you now have on your truck, if you haven't already done it, you are in the prime mileage for typical transmission failure.

Mine crapped out at 116K, even with a factory cooler installed.

And without having a transmission cooler installed all of this time, you are probably pressing your luck and getting close to a break down and rebuild.

No way I would consider towing that travel trailer until I had a cooler installed.

Your engine temp should remain fairly consistent at right below the 1/2 mark on the engine temp gauge during normal driving most of the time, unless maybe, if the outside air temp is extremely high.

Even when it was a little over 100 degrees here a few summers ago, my engine temp ran ever so slightly above it's regular temp and usually only when driving slow or stopped.

When towing, your engine temp can rise somewhat, but mine has never been as high as the 3/4 mark while towing, even with the a/c on in the middle of the summer heat.

I tow a 25' party barge that weights in right at 5000 lbs. fully loaded for the lake.

Since you have already replaced the thermostat and clutch fan, I would first make sure the area between the radiator and a/c condenser is totally clear of debris.

I have had a couple of trucks where this area was nearly completely blocked with bugs and debris while the outside areas of both the radiator and a/c condenser were perfectly clean.

This caused a huge blockage of air flow and did nothing to aid in engine cooling.

If all of that is clean and clear, I would suspect that there may be a good sized air pocket that is moving around in the engine block.

An after market radiator might help, but I would be inclined to make sure you have all of the basics covered before I went to that expense.

The factory set up should suit you just fine, if everything is working properly.

Good luck.

So lets look at this a little more. With no assumptions...

I assume you don't have a trans temp sensor and just using your engine temp sensor.

I am assuming you towed in "tow" mode? (Button pushed in on gear shift)

If not towing in tow mode you will overheat. You did not mention this. I have found if I am only towing 2,000 lbs in the bed or behind the truck I see no issues but if I forget to put in tow mode above that weight either in the bed or behind me the temps go up.

If you ENGINE temp is going up you really need to consider doing a coolant flush and insure your water pump is not leaking. You may have some blockages in your radiator if your water pump is doing well. Common with the original coolant since they put in clay tablets. The first think anyone should do is flush the heck out of their system and get rid of those clay tablets. The issue with them is they are to seal your system in case of a minor leak but if your coolant system is ever exposed to oxygen (such as replacing a thermostat) those clay tablets can settle out and plug up stuff...

The other thing to consider. 2500 trucks came with a trans temp gauge. You CAN retro fit your truck with this but MAY require reprogramming. I STRONGLY suggest contacting dashdr.com to discuss having a trans temp gauge added to your cluster. He will also rebuild your cluster and give a lifetime warranty so you never have to worry about having issues with it. As far as I understand he is also able to program for the trans sensor. Worth asking him. No better setup to watch your trans temp while staying factory. The trans temp is already read by the computer so the cluster can show it just fine.

As already mentioned a trans cooler is never a bad thing. Wish they added large ones on our trucks from the factory.

I would first replace the coolant temp sensor to verify that the readings you are seeing are correct.  It is pretty easy to get to - above (if I remember correctly) spark plug #1, which is the frontmost on driver side.  Pretty much behind alternator.

If you see the same readings with the new sensor then I'd assume they are real.  I'd next replace the radiator - it's 14 years old after all and there's a good chance of internal scale buildup.  They can be had from most parts stores for under $300.  I've changed my 03's radiator - it's not too difficult of a job but a bit messy because you probably are not going to catch anywhere close to all of the coolant.

If after doing the above you've still got a problem I'd then replace the water pump.  You may want to try this before the radiator as a water pump is cheaper than a radiator but unless you've been real good about flushing the coolant every 5 years or so I'd say the radiator is ready to be replaced.

And I agree with the others regarding installing an aux tranny cooler.  Replacing a transmission will generally set you back 2-3 grand so it's a relatively cheap way to put that expense further down the road.

Also when you refill your radiator never use tap water or "spring" water. Only use distilled water. Other types of water have minerals and other additives added to them that will coat the inside of your engine and radiator.

This of course with your anti-freeze to make a good 50/50 mixture.

Rodney

Wow! I can't believe how quickly you all replied you guys are absolutely awesome!

In 2011 at about 110,000 I replaced the thermostat along with belts, ac delco plugs and MSD ignition wires. Along with flushing the system and replacing with GM DEXCOOL 50/50 Orange coolant. around the same time I was having issues with the truck not idling properly in the morning, someone had mentioned it may be the coolant temp sensor, therefore I had replaced it with a Duralast. So that is not OEM. (Ended up being the Intake manifold gaskets, haven't had an issue with that since!)

After this issue this past June, I decided it was possible the Motorad thermostat was not opening all the way, so figured may as well replace it again, flush the coolant and replace the fan clutch for a "heavy duty."

EXT4ME: I clean the condenser in the front regularly and make sure there is no debris. So unfortunately that is not the case. I will definitely adding a TOC based on everyones reviews. Do you guys have any recommendations on a TOC? I was considering just getting a universal from UHAUL or Napa. But I've heard there are AC DELCO coolers out there with OEM lines that plug right in. So i'll have to look into that and decide whats best.

READHEADROD: Unfortunately I do not have a trans temp gauge, which is also why I chose to take it easy towing uphill. When I saw my temp gauge start crawling the first thing I thought was man, I wonder about the trans fluid temp. I have considered getting a new clustered, and having it programmed with the correct odometer and what not. However, I was considering buying one of those OBDII plugs that sync up to your phone for $30 that display the trans temp and syncing it to my phone to use while towing.

I was not using Tow Mode, I assumed since it held the trans in gear longer and got to higher RPMS, that it would make it run even hotter due to the fact that it taking longer to shift so I avoided that at all costs, but now that bring it up, I am wondering if the fact that its revving higher it may make the fan clutch spin faster and cool quicker? Something I'll have to test out!

ENONIAM: Like I mention in the beginning, I had replaced it. It does have a lifetime warranty so I may just replace it again to be safe. I am most likely going to replace the radiator before summer, I've just been holding off, trying to find a HEAVY DUTY or I was really hoping for an aluminum radiator as I've heard those cool off better.

The ONLY thing, thats stopped me from replacing the water pump, is I've seen people replace there water pumps with aftermarket such as murray, or duralast, and then they fail a year or two later time and time again. So I almost am unsure of whether to stay with the one I have now or replace it. I'll probably end up replacing it with an AC DELCO though because I'd hate to be stranded in the desert on the way to or from the river and have to wait 6 hours for a tow truck and say man I should've just replaced it! 

Once again, I really appreciate you all taking the time to help me out with this and give me your opinions!

Tow mode is there for a reason...

You will burn up your transmission if you tow without that on... With or without a cooler.

It changes how the transmission shifts and also may affect how the torque convertor locks up. (Was informed that without it on the torque convertor locks and unlocks at cruise speeds. With it the torque convertor stays locked up but may stay in lower gear. And yes will affect your mileage but is intended that way.)

As I mentioned, I didn't notice a difference when towing/hauling less than about 2,000 lbs with my truck but most certainly do when towing more.

DO NOT TOW WITHOUT TOW MODE ON OR YOU WILL BURN UP YOUR TRANSMISSION!!!

You may have already caused the lifespan of your already weak transmission to be weakened if you have towed without being in tow mode for any length of time.

I will hope that if I have any error in this information that it will be corrected but if you look in your manual it should state you have to have tow mode on when towing above a certain weight. I know I certainly feel a different in my truck...

Rodney

redheadedrod said:

Tow mode is there for a reason...

You will burn up your transmission if you tow without that on... With or without a cooler.

It changes how the transmission shifts and also may affect how the torque convertor locks up. (Was informed that without it on the torque convertor locks and unlocks at cruise speeds. With it the torque convertor stays locked up but may stay in lower gear. And yes will affect your mileage but is intended that way.)

As I mentioned, I didn't notice a difference when towing/hauling less than about 2,000 lbs with my truck but most certainly do when towing more.

DO NOT TOW WITHOUT TOW MODE ON OR YOU WILL BURN UP YOUR TRANSMISSION!!!

You may have already caused the lifespan of your already weak transmission to be weakened if you have towed without being in tow mode for any length of time.

I will hope that if I have any error in this information that it will be corrected but if you look in your manual it should state you have to have tow mode on when towing above a certain weight. I know I certainly feel a different in my truck...

Rodney

Click to expand...

I don't agree that towing without being in tow/haul mode is as dire as indicated in this quote (assuming use of a stock torque converter).  If this were indeed the case there would be strong language in the owner's manual regarding to always use tow/haul mode when towing, but it isn't there.  There would be too many cases of GM having to replace transmissions due to owners not using tow/haul mode for GM to release the trucks under warranty that needed to have it on to prevent damage.

Tow/haul basically does 2 things - holds gears longer and firms up shifting.  Yes, torque converter lockup is adjusted in the stock tune but mainly just because the gears that it locks up in (3 & 4) aren't run in as low rpm conditions as what they'll normally lock up in.

I'm not saying that the trucks won't run a bit cooler when towing with tow/haul mode.  The higher rpms will run the coolant through the engine/radiator faster and drive the mechanical fan faster.  Will also keep the rpms in 3rd and 4th suitably above the stock torque converter's stall speed.

Edit - main reason for tow/haul is to limit transmission shifts and to keep the engine in higher torque range.

Thanks for the responses guys. I didn't often use it because I didn't feel the transmission was "searching" for gears as some would say. If I felt it was searching I would just downshift to 3 or so. Before summer I am probably going to replace the radiator with an AC DELCO radiator, and at the same time install the Trans oil cooler. I've read somewhere on here that many people install this kit. GM part #12497071. I'm gonna talk to the dealership and see if this kit will fit my av. I am considering also replacing the water pump with an Ac Delco. If it still runs warm then I guess its time to trade up to a 2500  thanks again for all the input

Here's my 2 cents, I tow way more than you do and I never use tow mod.

Granted I have a 2500, it makes a serious hard shift. If you like your sungear in the tranny don't use it

All I can tell you is we tow all the time with 3/4 ton trucks at work and no matter if GM, Dodge, or Ford we are told to always use tow mode or we will break the trucks. And with the GM trucks having weak transmissions to begin with I wouldn't push it but that's me...

They believe in it enough to threaten discipline if we are found to drive without it on consistently.

So do what you want, I will continue to use tow mode on any truck I drive with protecting the transmission in mind. If it didn't do anything why would they put it on all trucks? Prior to the tow mode we had to downshift out of the top Drive (Over drive?) gear when towing...

Our 1 ton fords (Diesel) have the same issue and it is common for us to pull over 10,000 lbs with those trucks and same thing. Not sure how tow mode affects those trucks since I am unfamiliar with Diesels.



Rodney

So, after 3 months I finally made it out to the river. Before this trip I decided to thoroughly wash out the condenser and radiator and I was really surprised how many small rocks were lodged in there. I also added a Hayden 678 transmission cooler. This time towing up the 10 freeway on the way to parker I ran that thing 55-60mph the entire time and the temp gauge did not move at all from that center where it always sits. At certain parts climbing uphill I even ran the A/C because it was so hot out! I purchased an obd scanner that connects to my phone to display the trans temp, so I was keeping tabs on that as well, which thanks to the trans coolers stayed nice and cool. Driving there ambient temp was about 90 degrees and driving back the outside temp was 112. I also decided that I would take everyones advice on here and use the tow mode. So I'm not sure if it was cleaning out the radiator, adding the trans cooler, or using tow mode but whatever it was it worked! I finally tow up there without having to stress about my truck overheating. Thanks everyone for the input!

Enjoy your summer.