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modain
Dodge Dakota
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6/06/2005
17:23:54
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 Subject: Towing and Coolant Temperature
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I have potential overheating situation when towing I need to resolve shortly. (Maybe Kowalski has tackled this already with his heavy towing loads?) My apologies for a long post. Here is the situation...
I have a 2002 4x2 QC SLT+, 4.7, NV3500, 3.92 LSD, all stock with the exception of the Superchips Towing/Performance program (with the requisite 91 octane), 55K miles, the original coolant and thermostat. The truck came with the heavy duty engine cooling package. I guess that means a larger radiator than the non-heavy duty? Air filter is clean, plugs are about 12K miles old, no problems at all.
I was towing my 20' (24' tongue to bumper) toy hauler trailer (Carson Trailer FC-202) this past Memorial Day weekend. The trailer weight was close to 5500#, my tow rating is 6050#, with a GCWR of 10,500#. There were four occupants for a combined weight of around 675#, 20ish gallons of gas. The trailer has a large sail area, so it’s pushing a lot of air. (I refer to it as my 5000# parachute.)
I live in Los Angeles, so anywhere you go out of town requires climbing steep hills going north. Going up the 14 freeway approaching the Escondido Summit (~4,400K feet) the temperature gauge got to just below the top mark of the normal operating range. Any more and it would have been into the hot zone. I am not too keen on overheating, so to save a little heat I made the last 5 miles of this leg without the A/C. The ambient temperature according to the overhead display was 77F. Certainly not a scorcher. The engine speed was about 3800RPM, third gear, 60(ish)MPH. Because of the Superchips program the engine wasn’t working nearly as hard (I didn’t have the throttle buried in the floorboard) as before pulling the same load up the same hill using the stock program and 89 gas.
I will be making this same trip for Labor Day weekend and I’m sure the temperature will be closer to 100F than 77F. I’m pretty sure if nothing is changed it’ll head for a meltdown. I want to avoid that.
I checking into a larger radiator at a local shop to find that the replacement radiator cores are also two rows, as is the stock one. That’s no relief. If I wanted to go with three rows I would have to have one custom made. The radiator guy suggested that the coolant and/or thermostat may be suspect. I’m not sure the thermostat is malfunctioning, because the temp is always a little below halfway at all other times and temperatures. But he said that contaminated coolant could be the problem and he could easily test for this.
Now, I read in my owner’s manual that the coolant should be changed after 5 years regardless of the mileage. Could my problem be this simple? Is/has anyone else facing/faced a heat problem under heavy loads and found suitable solutions?
I suspect the engine is putting out more heat as a result of the power increase brought on by the Superchips tuner. And it's not being bled off sufficiently. I can’t buy into the increased power being “the problem”, because this same truck equipped with the 5.9 engine uses the same radiator *and* less coolant. Besides, the radiator is not doing any transmission cooling on my truck, as it would be with an automatic.
Thanks for any meaningful responses you can offer.
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Kowalski
GenIII
6/06/2005
18:19:21
|  RE: Towing and Coolant Temperature
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I think impact of superchips program on heat would be minimal at best. I've pulled about that weight but not with that sail area or as much weight in my truck but it was in July heat with AC on, many large hills and lengthy wait in line to get parked at the races with no problem with cooling. Still on original coolant here too, I have to change that and the hoses this year. I'd try a new thermostat for the hell of it with a flush and fluid change.
Lead, follow, or get out of the way
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bykerdude59
Dodge Dakota
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6/06/2005
18:26:04
| RE: Towing and Coolant Temperature
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I would say make sure you have fresh oil, if your truck isn't having overheating problems during normal driving it probably isn't your thermostat. If it was your temp would climb up above the half way point then probably kick on and cool down the motor. A sticky thermostat will do that. But like I said, if it is fine while not towing or whatnot it's probably not that. Is your coolant green colored? or is nasty looking?
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modain
Dodge Dakota
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6/06/2005
18:48:33
| RE: Towing and Coolant Temperature
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Thanks for the ideas. The next oil change is due at 57.5K miles, so what is in there was still plenty fresh at the time. I haven't checked the coolant color. I'll do that tonight. I'm guessing I should check it at the overflow bottle, and not crack it open at the fill cap?
I didn't mention this origianly, but when towing on level ground the needle headed back to the usual spot on the gauge, and going downhill it went down to about 1/4 way on the gauge. Duh, the engine's not doing much work in that case.
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bykerdude59
Dodge Dakota
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6/06/2005
19:07:15
| RE: Towing and Coolant Temperature
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It won't hurt to open at the radiator cap (unless the engine is not cooled down) Many times coolant in the resevoir is nasty because it rarely gets used. Make sure you have coolant in there..not water! If you have the truck running and you don't see coolant at the top of the radiator fill it up.
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modain
Dodge Dakota
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6/07/2005
04:01:16
| RE: Towing and Coolant Temperature
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I checked the coolant. It appears that the overflow is at the normal level. I checked under the radiator cap and the hose is full.
Funny thing is the coolant is that HOAT stuff. It's brown, and not green. Not knowing anything about how it should look or feel I can't tell from a visual inspection what is up with it.
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Bob Lincoln
Dodge Dakota
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6/07/2005
09:44:59
| RE: Towing and Coolant Temperature
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I've never seen BROWN coolant, except when it's expended sludge. It should be bright green, orange, or red. Sounds like it's really old crap that should be flushed and replaced.
You can also install a 2nd electric fan if you can find room to mount it, and use it to bring the rad temperature down.
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DCRobert
Dodge Dakota
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6/07/2005
10:19:14
| RE: Towing and Coolant Temperature
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Perhaps I overlooked it in your post, but is this the first time you've overheated while towing this same load uphill with the A/C on or did it just start happening?
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bykerdude59
Dodge Dakota
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6/07/2005
11:04:26
| RE: Towing and Coolant Temperature
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I don't know what the HOAT stuff is...but you should change it. Like stated above it should be bright green.
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DCRobert
Dodge Dakota
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6/07/2005
11:32:10
| RE: Towing and Coolant Temperature
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modain didn't say what brand of coolant he was using, but a quick search brought up Zerox: "...an ethylene glycol based coolant with an HOAT (Hybrid Organic Acid Technology) inhibitor package. It is phosphate free, fully formulated (contains nitrite) and protects against hard water deposits and corrosion. As a testament to the quality, Mercedes has been using this formula for over 20 years."
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modain
Dodge Dakota
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6/07/2005
12:06:04
| RE: Towing and Coolant Temperature
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The coolant in my truck is the factory fill. It's been in the truck since it was built in April of 2002. According to the owner's manual and the service manual it says that the coolant should be HOAT because it has the proper corrosion inhibitors for the vehicle. It says *not* to mix HOAT with non-HOAT antifreeze. My 2001 Durango's information says the same thing.
I didn't overheat the engine. It got almost to the normal range's upper limit on the analog gauge. (Boy, wouldn't it be nice to have numbers on it?) What concerns me is that it was only 77 degrees F outside and the engine wasn't cooling. I know it will cool even worse in August when the outside temp is closer to 100.
On previous trips up this route I didn't run the A/C. Mostly because I needed the power, as I was running the stock PCM. Now that the Superchips has arrived I thought I could let my wife enjoy some comfort in the cab with the A/C on this trip up until the temp started climbing to the top. She's gotta have her cold air or nobody is happy. If the answer turns out to be as simple as no A/C, I'll have to get earplugs. :-)
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JimmyD
Dodge Dakota
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6/07/2005
14:24:03
| RE: Towing and Coolant Temperature
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I don't know what the NV3500 transmission is, but if it's a manual, use a lower gear and keep the engine about 2500-3000 RPMs.
If it's an automatic, turn off overdrive, and keep the engine in the same 2500-3000RPM range. That will allow the torque converter to lock up so your tranny won't be generating a lot of heat from converter slippage while you're climbing those hills, and passing it to your coolant.
Gas consumption may actually decrease, because your engine will be running closer to its "sweet spot".
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bykerdude59
Dodge Dakota
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6/07/2005
17:23:33
| RE: Towing and Coolant Temperature
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Yes his NV3500 is a 5 speed manual
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.boB
Dodge Dakota
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6/07/2005
19:17:09
| RE: Towing and Coolant Temperature
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Fortunatly, the cooling system is pretty simple. Water/coolantr flows through the engine and picks up heat, then flows through the radiator and gives off heat. It really is that simple. In theory
In actual operation, things can get a little more complicated. My first step would be to flush the coolant system with something like Prestone Flush. You put it in the radiator and run it for a little while, and that helps to clean the junk out. You don't have that many miles on it, so you shouldn't have to worry about knocking loose big chunks of scale and blocking the system. Remove the thermostat, and re-assemble the neck with the a simple gasket, which will probably leak.
Drain the entire cooling system, including the block. Use a flush kit and hot water to make sure you get it all out. Then drain the entire system again.
Replace the thermostat with a 180* high flow unit from Mr. Gasket or similar. Be sure and drill a small hole in the plate to facilitate purging. Now is the time tou use a little of your favorite silicone sealant to ensure it doesn't leak. Be sure and let it sit for a few hours before adding water. And then let it sit 24 hours before getting the engine hot.
Now refill the system with whatever coolant you like, at whatever mixture you feel is appropriate. Distilled water cools better than any mixture. But you need some anti-freeze to protect from freezing, corrosion, and to lube the water pump. If it were my truck, I would use a 25:75 mixture of Zerex and distilled water. That will provide excellent cooling and freeze protection down to about 10* or so. Be sure to add a bottle of Water Wetter or similar.
By doing all that, you can make sure that your cooling system is at tip-top shape, and functioning as well as it can.
Adding another electric fan will do nothing, since the problem you have occurs at >45mph.
I would also back off the Hyperchip program to the mid grade setting. You won't lose any low end torque. But the less agressive timing curve and shorter injection pulse works better for towing and higher altitudes. Kind of like a carb, too rich or too lean may cause overheating.
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DSW
Dodge Dakota
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6/07/2005
22:50:09
| RE: Towing and Coolant Temperature
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Check your fan clutch, even if it "seems" to be OK I bet it's your problem. My 00 CC would keep cool while towing 3500# then one day the temp started to go 210^. Nothing changed and it was even pretty cool out, but the temp would rise quickly going up grades and cool down slowly on the down grade.
The first hot spell (120+) we had in Las Vegas the truck started overheating on the freeway if I pushed it 75-80. When I replaced the fan clutch it solved the overheating on the freeway and also while towing.
What I didn't notice is that when the fan clutch was working properly, it will ROAR the first thing in the morning and then quiet down in 50-100 yards. When I had the overheating problem the fan clutch didn't roar in the morning.
I got a replacement fan clutch from Auto Zone for $55 which lasted 40K, then it started acting up, no roaring and engine getting hot. Replaced it under AZ warranty and replacing the fan clutch resolved the problem for the second time.
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modain
Dodge Dakota
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6/08/2005
11:53:11
|  RE: Towing and Coolant Temperature
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Thanks to everyone for their insight and suggestions. It looks like I have quite a list of viable cuplrits for my cooling issue which I'll be addressing Saturday. I'll let you know how it turns out.
A quick question for .boB (or anyone else that wants to chime in) regarding the 180 thermostat. Will this adversely affect the emissions, MPG, or any drivability concerns in the sort and long terms?
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bykerdude59
Dodge Dakota
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6/08/2005
13:14:14
| RE: Towing and Coolant Temperature
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I have a 5.2 v8 with the 180 t-stat. Just got it smogged and it passed with no problem. Drivability is not an issue at all. It just keeps the motor a bit cooler. The factory (195 degree I think) T-stat is better for emissions, but you should have no problem at all. I have about 130,000 miles on my truck and it passed. MPG I didn't notice any change.
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Kowalski
GenIII
6/08/2005
15:47:34
| RE: Towing and Coolant Temperature
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The main reason I haven't gone to a 180 thermostat is that I want the extra heat to put on the windshield in an ice storm - a consideration if you do that kind of bad weather driving.
Lead, follow, or get out of the way
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bykerdude59
Dodge Dakota
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6/08/2005
19:20:07
| RE: Towing and Coolant Temperature
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I was going to mention that to him also but I noticed he lives in LA area. I live in Orange County and that isn't far away. We won't be seeing any ice storms..or hale...or snow, any time soon...I hope. I get cold when it hits 70 degrees.
Wayne
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.boB
Dodge Dakota
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6/08/2005
22:33:16
| RE: Towing and Coolant Temperature
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I tried a 180* thermostat a few years ago. But the truck ran like crap, and worse fuel mileage. So I put the stock 195* part back in, and it ran great again
A year or so ago I used the hypertech programmer. Just last month I got around to trying it again. Truck runs better, because the heads are cooler, so less pre-ignition.
The thermostat only specifis the lowest temp the truck will run at. It won't really help with overheating issues. But once the real problem is fixed, it will run better.
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Darryl
Dodge Dakota
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6/09/2005
18:51:45
| RE: Towing and Coolant Temperature
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modain:
I live in the Lancaster area and commute to the San Fernando Valley daily, so I know a thing or 2 about the 14fwy!
I would go with the 180* stat and 1 bottle of water wetter in a mix of 60% distilled water and 40% Zerex G-06.
This is what I run on my modified '99 and if you spend much time here in August, than you know just how flippin' hot it gets. I've never been anywhere close to overheating with my truck on the 180* 60/40/water wetter mix.
You will still have plenty of protection with the 40% coolant mix, and the 60% water will help keep the coolant temp from spiking as water cools much better than coolant.
We don't live back east so 40% G-06 is MORE than enough, some of my buddies run 75% water 25% coolant but that's a little too aggressive for me.
Darryl
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