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2004 chevy trailblazer_lt
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Discussion Starter #1
I'm trying to figure out this crazy situation. My 04' TB just started overheating when towing our new boat. It doesn't seem to have much of a problem when not towing, but when I tow it can quickly reach 235F once it is on the road for a min.

I turn off the A/C and turn on the cabin heat and the temps move back down to normal quickly. It will also cool down to normal when I stop and let it idle.

I just replaced the thermostat and it seemed like it helped for a few minutes and then the temps started to creep up again until it was near 235F again!

It seems like an airflow problem on the road, but I'm just not sure. It is about to drive me crazy! :duh:
 

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2005 gmc envoy_sle_xl
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I'm trying to figure out this crazy situation. My 04' TB just started overheating when towing our new boat. It doesn't seem to have much of a problem when not towing, but when I tow it can quickly reach 235F once it is on the road for a min.

I turn off the A/C and turn on the cabin heat and the temps move back down to normal quickly. It will also cool down to normal when I stop and let it idle.

I just replaced the thermostat and it seemed like it helped for a few minutes and then the temps started to creep up again until it was near 235F again!

It seems like an airflow problem on the road, but I'm just not sure. It is about to drive me crazy! :duh:
Did this just start happening or has it always been like this when towing?

Mine does the same thing when towing a 5000lb trailer. Either way, I would be interested in knowing if it's normal or not. Sounds like the fan clutch is going.
 

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Above 30 MPH or so, the fan clutch is out of the picture and road speed induced airflow predominates. I think the fan clutch is OK, especially if it cools down at idle, where the fan clutch is the source of airflow.

So there's too much heat being generated in the engine when towing. When was the last time the air cleaner was changed? How many miles? Coolant changed at 100K along with all the other servicing that's required?

Very important: add a transmission cooler (run a search for the phrase) and get the tranny some assistance, and get much of its heat out of the radiator.

Depending on the mileage, a cat problem might also cause excessive heat. Do you notice bogging down at higher RPMS or a loss of power? When it's running hot, can you pull over and see if the cat is glowing red?
 

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2002 gmc envoy_slt
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I'd start by taking a hose and washing out the radiator core, spray from inside the engine compartment outward. You should see light easily pass through both the radiator and a/c condensor.

Also check the hoses to make sure they're not soft and the suction side is compressing with increased engine speed. You'd replaced the thermostat, so you should be good, however I noticed decreased flow and a lazy openning with the Motorad thermostats from Autozone. (That's the brand they happen to sell). Switched to a genuine AC-Delco, problem went away...they have a larger valve btw, so most likely flow better.

One inexpensive thing to check is the pressure cap on the radiator, my Envoy was running warm with the a/c on until I replaced it. You need to hold pressure to prevent formation of steam and/or premature flow of the coolant into the recovery tank.

After that I'd check the coolant flow through the radiator and if there are any issues causing the engine to run hot. I think that somebody already mentioned the converter, which will cause a hot condition under load....but this is also accompanied by a loss of power, you'd know it, the engine would be gutless.
 

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please let me know what you find, I have an 02 and I just had a tranny cooler installed so I can tow my boat but the temps are still getting a bit high for my comfort while I'm towing
 

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Check the protection level with a coolant tester, either the ball type or plastic float type. How old is the coolant mix? If it's past it's due date or looks kinda funky, a flush and fill is in order. Maybe get the rad cleaned/rotted out by a rad shop. Add a bottle of Water Wetter. If mixing the coolant yourself, use distilled water with the Dexcool 50/50.

If all fails to lower the temps, do what another forum member did; add a switch supplying +12V to the white wire on the fan clutch. This will engage the fan 100% when needed. You'll sound like a low flying F16 but at least it'll be cool.
 

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Discussion Starter #7
Thanks for all the suggestions guys! Here are some answers to your questions.

For starters, it just started happening, but I also just got this boat and it is the heaviest thing I've towed before...The boat is an 18ft inboard 1997 Mariah, but I'm not sure what it weighs.

Fan clutch is good...thermostat is good and I just cleaned the radiator to the best of my ability last night. At least without completely removing it from the TB. Sprayed it down with foaming condensor cleaner and washed from front side several times. I know it is best to wash from engine side, but I haven't decided yet to remove the fan, shroud and the whole mess.

The TB is an 04' model with 152,000 on it, BUT the engine is an 05' oem motor with about 20,000 miles on it now. I put it in the car with about 800miles on it. That being said, there is some potential for the CAT to be bad...it does seem a bit sluggish to me but I am used to driving a 5.3L V8 so I don't really know how to compare

Intake filter is a K&N with about a year or 20000 miles on it. Coolant is new with the engine...orange stuff. I also flushed the system before putting the new coolant in.

I did put a tranny cooler on the TB first thing, so it has a Hayden cooler(one of the bigger coolers).

One thing I have thought about is the fact that I put a new tranny cooler out front, and it does probably help the trans temps...but it may actually make the engine temps go up. It is removing more heat from the tranny and restricting airflow thru the condensor and then through the radiator.

One last major consideration is that it continues to be 110F during the day, so ambient temps are thru the roof. Sad thing is I pulled the boat the same day with 2000 explorer 5.0 V8...cool as could be.

Trying to decide whether to pull the radiator this weekend for a thorough cleaning. Still runs perfectly cool at any time without towing anything.
 

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My bro-in-law borrowed mine to tow his tractor. Total about 6000 Lbs. It did apparently get warmer, close to 112C (233f), which is about halfway to an overheat, and he had trouble with the load balance. He removed the backhoe (~1000 Lbs) and all was good, including the temps. It did move north of 100C during a hill climb but that's it. I also have the biggest Hayden tranny cooler available but I doubt that this would impede air flow that much.

It could just be that these trucks can't take that much weight, especially if equipped with the higher geared (lower numerically) differential. I have the 3.42 axle.

BTW, you do tow in 3rd gear right?
 

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It could just be that these trucks can't take that much weight, especially if equipped with the higher geared (lower numerically) differential. I have the 3.42 axle.
That's what I am thinking as well. I also have the 3.42
 

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You need to find out how much that boat & trailer weighs before you go much further with this! If you can't get specs on it, take it to a CAT scale.
 

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Towing overheats 5.3 engine

i had the same problem. TB 5.3EXT with a double axle trailer and 22ft 1991 boat.

the simple obvious things i checked seemed to have fixed the problem:

1. it overheated when AC was on. so i replaced the AC belt tensioner.
2. ensure you drive in 3rd gear and not Overdrive
3. added Waterwetter to the radiator (probably not helpful, but what the heck)
4. ensure the radiator is burped sufficiently. air in system or pressure leak (ie radiator cap) will increase temperature on fluid system. PV=nRT
5. check trailer brakes/axles to ensure they float smoothly. i plan on drilling hubs and add zerk for inner bearing so i won't have to repack them as frequently.
6. serpentine belt tension
7. engine belted accessories may have tired bearings. remove belts and wiggle all the belt connection points and check AC/serpentine tensioners.
 

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Discussion Starter #12
So what is an overheat temp on these trucks? 235F worries me because that is very hot on most cars...when should I be worried on the TB.
 

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So what is an overheat temp on these trucks? 235F worries me because that is very hot on most cars...when should I be worried on the TB.
As a previous poster noted engines can take much more heat that 235F. I have stuck my finger in boiling water before and took it right out and my skin did not fall off. My general recommendation would be to check the mixture of he dexcool and water 50/50. Plus check the pressure cap which is rated in PSI. I believe 15 PSI is the right one. If that checks out you may have gotten a defective or cheaper thermostat. Is the thermostat an AC Delco brand? Perhaps you got a 210 stat and not a 195 stat.

As roadie said, if your on the highway your fan will not help in any fasion becasue the air forced into the grill will cool the engine. Fans are just used when your going slower speed and an idle. If the overheating happens on the highway you can rule that out. Another positbility is to check the flow of coolant in the radiator. Take the cap of and run the engine until it starts to warmup. You will see a bunch of flow inide. If that turns out ok then the water pump is ok.

The differnce in temperature between a fully warmed up engine and normal ambient temperature out side is actuall a much larger drop then you putting ice cubes in a glass full of warm cola. So think about that in reference to how engines cool. Thin kof the radiator as like a giant icebox.
 

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Discussion Starter #14
Thanks for the help Ralph! I do understand the principles behind forced convective heat transfer within a closed loop system, but thanks for the analogy.

I guess my question was in regards to the temperature that I can expect to start having problems with things like a blown head gasket, ect...

That does make me feel better if the engines are truly able to handle temps up to the 260F mark like the gauge indicates.

Has anyone experienced serious problems below the 260F temp?
 

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Discussion Starter #15
By the way, I did take the advice and double check the coolant mixture. It is prestone Dex-cool and it tested good down to around-40F..5 balls floating.

The radiator cap is an oem 15 psi cap that is probably original, but I don't see anything that indicates a problem with it.
 

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With all things aluminum, I would try and play it safe and not let it go any higher than the halfway to overheat.

Just for comparison's sake, I have an efan setup in my '00 Jimmy. I was too cheap to buy an actual fan controller so I used a setup basically from a pre-computer '80's Citation that used a temperature switch screwed into the head of the old Iron Duke to actuate the relay for the fan. I used two of those switches, one in a head and the other on the intake manifold. Since these are mechanical switches they aren't that precise and actually found that one actuates before the other, which worked out well for me to not have both fans come on at the same time. The first fan comes on just under the halfway mark (112C/233F) and the other just over, which rarely comes on. So to me, these are "normal" operating temps for the old Iron Duke and 2.8L engines of that era. But they didn't have aluminum components neither.

One last thing. In another thread about a possible failing fan, the possibility exists that the impeller in the pump may have rotted out and may not be pumping right. It may be worth it to pull it to check it out.
 

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The radiator cap is an oem 15 psi cap that is probably original, but I don't see anything that indicates a problem with it.
I would get a new one because it's cheap insurance anyway. I see these go out all the time around 100,000 miles and should be part of preventative maintenance when changing the coolant. You should change the coolant hoses as well when changing coolant. Mine are rock hard and brittle for a 2005. I know I need to change them.

I would also check the water pump.
 

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Discussion Starter #18
Changed the radiator cap today. Hoping for good results on a test run tomorrow.

I filled the overflow reservoir the other day and I am noticing it is not up to the fill mark anymore. May be loosing a little coolant somewhere. Radiator doesn't seem to be leaking at all, but time will tell.

I am seriously thinking about relocating the tranny cooler off the radiator and mounting a small fan on it, but there sure isn't much of a place for it...not to mention what a hassle it would be!
 

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5.3L Cooling Issues for Trailblazer 2004 EXT LS

PLEASE RE-POST IF NEEDED:

Dear Friends:

Last year while driving from Connecticut back to New York. My water pump was showing a leak in the weep hole, Thus indicating a defective water pump. Because the water pumps on the 5.3L contain an auxiliary impeller I was able to make it home.

Knowing I had to replace the pump. Since I already had 130k on the TB may as well do a total change out. The following was replaced:

WATER PUMP

ALL BELTS Changed

UPPER & LOWER HOSES

NEW CLAMPS* Note: Always use new hose clamps BEWARE of the Chinese one at Autozone they suck & will leak on you.

New Belt Tensioner

New AC belt tensioner

For water pump installed Fel-Pro gaskets much better than AC Delco.

OEM Thermostat & Housing

New Fan Clutch

Flushed Coolant replaced with new DEX COOL

All parts from www.rockauto.com

So far so good no cooling or heating problems. Now at 155K looking to do an engine rebuild as part of on going maintenance. Looking to get ONE MILLION MILES out of my TB.

Hope this helps.
 

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2004 gmc envoy_slt_xuv
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Today my scanguage showed my 04 4.2l xuv was pushing 225,, outside temp was 90, we were on the freeway, with NO trailer just two people. The trans temp also kept hitting 225, then would simmer back to 218.. NOT comfortable with these temps.

Tomorrow the trans with get a exchange,, dont know what else to do... my rig has 108000, and I dont know if or when the fluid has ever been changed.. In addition there was a ever so slight surge and there has been even at side road speeds... super very slight,, almost not noticiable,,, so im really hoping new fluid cures it
 
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