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Truck overheats in reverse while backing boat


kayakwv

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This has happened twice in the last week. My 2004 Suburban pulls my 2005 VLX with no problem and the temp of the truck stays at 210. However, in backing the boat up a slight incline into my garage, the truck temp jumps to 260 and then the warning light comes on.

Any suggestions as to the problem?

-kayakwv

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It doesn't seem to be a surge brake issue, because it backs up fine. I do have to give it some gas, because the first part is steeper, but it is only like 50ft of backing. After that, its another 70ft or so of just a slight incline.

It stays in gear fine. I do think that both times it happened I used the 4wd auto button, to avoid any tires slipping. That is what I usually use, and it's never been a problem until now.

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I don't know what temp your thermostat is, but 210 sounds pretty warm, like it's already on the verge of overheating. Then, with the engine already just about to over heat, you start backing the trailer with little air flow through the radiator. It might not have anything to do with backing up, maybe there's another problem.

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I don't know what temp your thermostat is, but 210 sounds pretty warm, like it's already on the verge of overheating. Then, with the engine already just about to over heat, you start backing the trailer with little air flow through the radiator. It might not have anything to do with backing up, maybe there's another problem.

That's what I was thinking. My fan kicks on any time my temp exceeds 195 on my Titan.

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I don't know what temp your thermostat is, but 210 sounds pretty warm, like it's already on the verge of overheating. Then, with the engine already just about to over heat, you start backing the trailer with little air flow through the radiator. It might not have anything to do with backing up, maybe there's another problem.

My Avalanche runs 200 all the time, and will reach 210 at a light or in stop & go traffic on a hot day. My brother's Tahoe is the same way. Both are 5.3s. Pretty typical.

To the OP, maybe something to do with the trans cooler? I think I'd be checking all the fluids, fan sensor, thermostat, & anything else you can think of related to the cooling system.

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I'm going to check it again this weekend. The Temperature being at 210 is the normal range on my gauge, and always has been with that truck.

I'm going to take another look at the Surge brakes being a possible cause. The way my driveway is situated, I pass it going down a slight hill; slow to a stop, and then back up into the driveway. It sounds possible that I didn't get the surge brakes fully released before backing up. But I didn't have a real problem backing up, and they weren't locking up or anything.

A couple years ago, I had a surge brake lock up problem. Turned out I had a light fuse blown that was causing the problem. So I went back and looked over the truck now, and just noticed I have a front running light out, and both times I had the overheating were at night with lights on.

Edited by kayakwv
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I'm going to check it again this weekend. The Temperature being at 210 is the normal range on my gauge, and always has been with that truck.

I'm going to take another look at the Surge brakes being a possible cause. The way my driveway is situated, I pass it going down a slight hill; slow to a stop, and then back up into the driveway. It sounds possible that I didn't get the surge brakes fully released before backing up. But I didn't have a real problem backing up, and they weren't locking up or anything.

A couple years ago, I had a surge brake lock up problem. Turned out I had a light fuse blown that was causing the problem. So I went back and looked over the truck now, and just noticed I have a front running light out, and both times I had the overheating were at night with lights on.

Along with 75% of the GM trucks/SUVs I see on the road. (Not bashing GM, as we are on our 3rd Suburban/Tahoe.)

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Along with 75% of the GM trucks/SUVs I see on the road. (Not bashing GM, as we are on our 3rd Suburban/Tahoe.)

Funny you say this. I don't know what it is with GM and their parking/marker lights. Complete trash. Perfect example of year after year failed QAQC and supply chain management of parts. Drive the road for 5 mins and you'll see a Tahoe or a Silverado with aster light out.

$1 replacement. But an indication as to how GM approaches QAQC and the rest.

I grew up playing punch bug. My boys play GM marker light punch out when we are on the road.

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It's the ideal gas law. Not sure what it would have to do with a truck overheating in reverse....

Nothing . The point was GMs run a hotter tune at 210degs vs most other brands at 195.

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No truck should over heat idling in gear.

Initial thoughts would be to ensure the radiator is clean... All the bugs removed... How many fins are bent?.... And pop for the $150 or whatever it is for a tranny flush service and new AF.

Edited by nyryan2001
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I just want to make sure of the OPs comments. The temperature you are saying hits 260 is it the engine coolant temperature? Are you sure it's a warning light for engine coolant temperature or could it be for the transmission?

Backing up in reverse with a trailer is hard on the transmission. Depending on the trailer weight and how steep the grade is, it can make the transmission fluid heat to the point of burning if driven under those conditions. 50 feet was the distance your ruined but how long did it take to do that 50 feet?

For the senario you explained we actually test this for OEM transmission development. You have a few things working against you for heat rejection. First it's at low speed and it's in reverse, so the only air flow you are getting across the radiator is what the engine driven or electric fan is moving. Next is the actual driving maneuver. You have a "heavy" load applied to the vehicle. The load is the combination of both the boat and trailer plus the grade is adding to that load because the vehicle has to "work harder" to go uphill.

In this situation the torque converter will be near a full stall condition but could be seeing a moderate to high torque input from the engine (even though the engine speed is low the engine can still generate a decent amount of torque). When the torque converter is at full stall it generates a lot of heat from the transmission fluid sheer (essentially the friction of the oil molecules slipping past each other under high pressure induced by the impeller in the torque converter).

GM did some funky thermal management back then, in some cases they would run the powertrain (engine and transmission) as hard as they could until a critical temperature then just cut power significantly to save parts from self destruction and the driver just had to pull over to let things cool down.

So how long does it take to go that 50 feet? Also what RPM is the engine at while backing up when your foot is on the gas pedal? How steep is the grade? A VLX with trailer is probably 5k pounds or close to it with all the gear we all carry.

If you back up relatively quickly and traverse that 50 feet in less than a minute it's not a big deal. If it's taking you 10 minutes to back your VLX up, that is a lot of time to generate heat and not be in a condition to reject it.

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It only takes 30seconds to back up that distance, maybe 1 min or more if I have to make any corrections. I'll be trying it again this weekend, and will pay more attention to the rpm's, temp., and other things mentioned in the comments herein. I'm also going to be careful that the surge brakes have released fully before backing up.

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Kayak- also verify that while in your overheat situation... Your fan clutch has kicked the fan up into high gear even at idle.

Generally they have 3 gears: off/barely spinning, low and high.

That loud rev of the fan when you first start the truck from a cold start is your fan clutch in high gear just for a few seconds. Anything over 215ish your thermostat should sense the rise in temps and lock out the fan clutch in high gear.

I speak from experience here. I chased an over heat situation on my 5.3L GM a few years back, wasted a ton of money and never could get it right and got rid of it.

There was an issue between the computer code, thermostat and the fan clutch that would not lock the fan up into high gear when it should have.

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