pickup overheating while towing spare car?

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Old 07-19-20, 04:55 AM
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pickup overheating while towing spare car?

Pickup: 2000 Chevy Silverado, ext. cab,, 6' bed, 4.8L, 250,000 miles, engine rebuilt at 200,00.

Towing: Uhaul auto transport trailer with 2015 Subaru Forester on it.

Truck has been running fine when not towing and no issues of overheating at all.

As part of a move I was towing this car from NC to WV where I am moving too. About 1 1/2 hrs into trip as I started up the mountain on I-77 N in VA near Fancy Gap, the truck overheated. I pulled off and VADOT stopped to help me.

There was no visible sign of where a leak was, hoses were all good and no sign of rupture. Coolant level was low though and we added about 1 1/2 gallons of coolant to it. Started back on trip.

Was able to complete the 400 mile trip but did have to add a little coolant 2 times during trip when stopped for gas.

Problem: When I would have to climb fairly steep hills the temp on the truck would increase but never to the danger point. And once the road would level back out the temp would come back down to a closer to normal level.

Now that I am not towing anything the truck is running fine with no overheating issue.

My question is this: What are your opinions of what the underlying issue is? Could I have a small leak such as if the water pump on this truck has a weep hole? Could it be related to transmission? Or more likely something else?

Thanks for your help.
 
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07-19-20, 06:46 AM
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No, it is not normal. I had 99 Silverado, I sort of know what I am talking about.
First, do you have electric fans or central clutch fan?
Next, knowing Chevy engines, I'd be suspicious that you have puncture in head gasket. It's tiny so, under normal load, it does not produce noticeable effect on operation. but, when towing, load increases, pressure goes up, and it manifests itself.
Coolant should stay dead smack at certain level, towing or not. If it goes down, you have loss somewhere.
You need to do system pressure test and combustion gas test in coolant.
 
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Old 07-19-20, 05:04 AM
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That's to be expected when pulling a heavy load uphill for an extended period of time (up a mountain) even if you were not exceeding the towing capacity of the vehicle.

I remember once as a kid we never made it to Pikes Peak, Colorado because the car overheated. (Due to the constant uphill climb) And we werent towing ANYTHING.

Watch your coolant level carefully over the next few weeks and months. You could have just been cooking off the water (steam) which is part of your coolant solution. But if you continue to lose coolant in the weeks ahead it could be a head gasket or worse.

You could check transmission fluid, it could be low, dirty or cooked if it's never been serviced.
 
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Old 07-19-20, 05:23 AM
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If I back-up the 100 yards steep hill at my cabin with my Chevy Travisty, after turning it off the fan will continue to run for at least five minutes to cool the transmission. Typical running temp will be 210, but as soon as I try to climb the near 45 degree hill it will rise significantly. But I do not haver the problem even when towing on regular roads.
I think X is correct that it's typical.
 
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Old 07-19-20, 06:09 AM
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I would want to double check the fan's operation along with the shroud. I agree it's typical to run hotter when under a heavy load.
 
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Old 07-19-20, 06:22 AM
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I also agree that since under normal use, everything is fine, but under your circumstances runs hot, its normal. That V6 might have a smaller radiator that is fine under normal use but pulling hills/mountains in tow may be a little small. Radiator might need servicing/cleaned/flushed, but I think your fine for normal use.
Its apparent that this is something you're not likely to do very often if at all again, so as mentioned in another post, just keep an eye on your water level & if you continue to have issues that concern you, we can offer advice later with a little more info on your concerns at that point.

good luck.....
 
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Old 07-19-20, 06:46 AM
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No, it is not normal. I had 99 Silverado, I sort of know what I am talking about.
First, do you have electric fans or central clutch fan?
Next, knowing Chevy engines, I'd be suspicious that you have puncture in head gasket. It's tiny so, under normal load, it does not produce noticeable effect on operation. but, when towing, load increases, pressure goes up, and it manifests itself.
Coolant should stay dead smack at certain level, towing or not. If it goes down, you have loss somewhere.
You need to do system pressure test and combustion gas test in coolant.
 
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Old 07-19-20, 07:16 AM
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Does your truck have a towing package installed? Additional transmission cooling is necessary when doing your described towing.
 
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Old 07-19-20, 08:10 AM
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That truck, as is is rated to 8700lb towing capacity.Forester is half the weight at 3500 lb. Even with trailer, it's maybe 4500lb, depends on trailer and, that is curb weight, not actual rolling weight when towing.
Also, we do not know, what OP means by "overheating". Slight needle upward movement that stopped at a bit higher mark? Sure, no problem.
Red lining? Not so good.
I towed heavier loads, than that Subie, with mine, up 12% grade, and it didn't even notice it.
OP, will you clarify, what exactly you mean by overheating, please?
 
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Old 07-19-20, 08:52 AM
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sounds like you have a leak some where would also do a pressure test on system just to make sure, radiator cores could also be getting plugged over time, would not bother flushing as there not that expensive to replace and a flush is very unlikely to clean the plugged cores in the radiator.
 
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Old 07-19-20, 08:57 AM
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we added about 1 1/2 gallons of coolant to it.
You already identified the problem now you need to find out where the leak is occurring!

Never normal to need to add that much coolant under any circumstance!
 
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Old 07-19-20, 10:38 AM
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You should of been towing with overdrive locked out.. 3rd gear. And put tow haul mode of if you have it. That changes shift points and locks the converter sooner. IMO overheating is trans related. Those 4l60 transmissions heat up while towing. Aside from a leak you may or may not have. the coolant could of simply boiled out of the overflow during that condition.

I installed a second trans cooler on mine to combat heat during towing of my camper.

see here. I added a second cooler and lowered the factory one as it was right in front of the bowtie on the grill.

https://www.rv.net/forum/index.cfm/f...print/true.cfm
 
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Old 07-19-20, 10:42 AM
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I would change that trans fluid ASAP. All of it and filter change. Dont just drain and fill as its only about 4 quarts
 
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Old 07-19-20, 04:17 PM
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After reading all of this I now have several things to have looked at. One of which is to change the transmission filter. I am hesitant to have a complete drain, filter change and refill done as it has 250, 000 miles on it and has never been service. I know, I know, but my wife became disabled about 10 yrs ago and a lot of things have had to let slide. I have read a lot of articles that say if a transmission has gone that long without service, better to just change the filter and leave it alone. Your thoughts on taht?
 
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Old 07-19-20, 06:05 PM
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I'll let some of the other guys answer that, that maybe a little more knowledgeable on that specific question, but if it were me, I think I'd service it. Oil & filter. I understand your financial situation but just me & my experience, I'd change oil & filter.

Its just a decision you'll have to make on your own situation.

Good luck.......
 
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Old 07-20-20, 05:00 AM
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Overheating under conditions that never overheated before can be due to a stuck thermostat.In a vehicle, the thermostat is an in-line valve that stops the flow of coolant through thenormal radiator to engine loop until the engine reaches a certain temperature. If it sticks closed then of course you get overheating. Going up steep hills with a heavy load, set the shift manually to a lower gear. You can stay in second gear going no more than 30 MPH.


 
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Old 07-21-20, 04:45 AM
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Additional transmission cooling
Been touched on a couple of times, but I think in addition to the other items you are doing, I would add an external transmission cooler, i.e. take it out of the engine cooling system equation.

Also, I may have missed it if someone else said it, but the last time I had an overheating problem it was a defective fan clutch (5.7L Chevy on the wrecker). It was pretty hard to diagnose but when i replaced, problem disappeared.
 

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Old 07-21-20, 08:02 AM
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Agree with checking fan clutch. Also, if you have been lax with engine maintenance that would exacerbate overheating. An out of tune engine runs hotter, especially under load. A neglected trans and cooling system are suspect. Coolant not flushed regularly can result in clogged radiator. That is a lot miles on an original radiator. If you were running the air conditioner while towing and climbing and the AC was low on Freon it would run longer, etc.

Accept that a vehicle that age with those miles that was not in a well maintained state would be expected to problematic when pushed hard.
 
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Old 07-22-20, 10:33 AM
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The engine has been maintained and oil regularly changed. Transmission service is only place that I have let slide. Question about just changing trasmission filter instead of full flush is because of age of transmission and not because I don't have the money to do it. It is more of an issue of what I have read about transmissions that have gone 200,000 miles w/o service.

Thanks
 
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Old 07-22-20, 11:02 AM
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would change the fluid and filter if your not having any issues with slipping and it is shifting ok many shops have a fluid exchange machine that can be installed at the cooler lines to change out most all of the fluid in the transmission the machine does not really flush anything it uses the normal pressure created by your transmission, if they was advertising a flush its probably just an additive they add prior and I am sure they could leave that out if you wanted.
 
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Old 07-22-20, 11:07 AM
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You dont "just" change the filter. You change the fluid too. Dirty fluid gets hot and does not dissipate heat as well.

So your choice should be either change filter AND oil, or flush AND change filter and oil. Whether you should flush or not is the risky part depending on whether your existing oil is clean and in good shape or not, and whether or not your vehicle service manual recommends flushing or not.
 
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Old 07-22-20, 11:27 AM
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The thing I am kinda missing is why people (the stuff your reading on line) are saying not to change it if it hasnt been done with your mileage. I'm not saying its not valid, I'm just saying, I dont see the issue. I'm not a certified, everyday mechanic & I am more of an old school mechanic but I dont see the issue in changing the fluid & filter regardless if its never been changed in over 200,000 miles.
Again, if it were me, I'd get the transmission serviced. Fluid & filter replaced.

It needs to be done regardless of the reason/issue you originally posted about.

I do know that some manufacturers say that filters not are not supposed to be "changed". Your supposed to "flush". Maybe so. They have the engineers, but ........

Good luck to you either way. Whatever you decide.
 
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Old 07-22-20, 12:40 PM
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The school of thought there is that there may be some places in the tranny where a little sludge and dirt is helping keep things sealed up and when you replace the fluid the new fluid (because ATF is a pretty good solvent) it will loosen things up. That may not be the precise argument, but you get the idea. It's been debated in threads here in the past.
 
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Old 07-22-20, 12:44 PM
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Couple of points here.
1) Thermostats are designed to fail in the open position, they cause a cold engine condition. By design, they open in the direction of flow so as the spring gets weak, it opens sooner.
2) Your radiator over the years most likely has some build up in it which will cause a slight decrease in it's ability to dissipate heat. A good acid flush can restore it's performance.
3) Straight coolant isn't good at thermally absorbing and releasing energy. You must have the correct blend of coolant and water, or a pre-mixed solution. A water wetter helps too!!
4) Your transmission could be running hot due to the lack of maintenance and causing an additional load on your cooling system. Have it serviced as well.

Combine a little of all of the above and you have a cooling system issue when the vehicle is under heavy load.
 
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