over heats going around the block.

[oldbeater1]

when it is idling it take forever to warm up. once you put it in gear and go around the block it over heats real quick. they, the owner has put a new radiator in, a new ecm, three new thermostates the latest is 180, new fan, shaved the heads, moved the coolant temp sensor from the driver side cylinder head to the upper radiator hose they found out the fitting they use is a 32 mm female thread and the senser is a std thread so it leaks. that will be my first project. i have heard of moving the sensor but i thought itvwas over to the passenger side. so far i don't even have a book on it. the guy has spent a lot of money shooting the parts cannon at it with no change except when it over heats it looses power. he is a few miles away so i would like to bring it closer to me but i will tough it out. he is thinking of scrapping it. i will see if he wants tio give it to me if i can talk my wife into it.

 

[mrrsm]

Welcome to GMT Nation...

This reads like your Coolant System might be -=Air Bound=-. Investigate On-Line and over at YouTube for the Methods and Means to Jack (Tilt) the Vehicle (While Supported on Jack Stands) and find, bleed and relieve those areas where the Air may have become Trapped enough to form compressed pockets as the Water-Coolant nears the Boiling Point that can prevent the Coolant from Circulating through the Engine Block, the Radiator, the Coolant Reservoir and the Heater Core.

On some of the Full Size Trucks with the 5.3L Engines... the Coolant line leading from the Reservoir was preventing the purging of Trapped Air due to a clogged port in the fitting (Port) where it attached to the upper right side of the Radiator as the Small Internal Hole was becoming clogged and blocked. Also, If the V8 equipped Trailblazers sport a Heater Valve like the ones on the Full Size Trucks...THAT could also be part of this issue if it has become inoperative.

 

[gmcman]

Might just have a large air pocket in the cooling system somewhere, or.....

moved the coolant temp sensor from the driver side cylinder head to the upper radiator hose

This could be the problem.

If I had to guess the coolant temperature sensor is mounted vertically from the top and it's not touching the coolant but when you rev it up it does touch it.

I have no idea why someone would move it from the original location in the head to the upper hose.

Is this a factory head or aftermarket?

Worst case would be a blown head gasket which would cause air bubbles in the system.

 

[budwich]

get an obd data reader hooked up and check codes and data like ECT at idle and going around the block. Who did the work on the "changes"? Maybe the thermostat was put in backwards. Moving an ENGINE COOLANT Sensor to a hose isn't likely going to get an accurate read because little or no coolant circulates until the thermostat opens... maybe.... so your "warm up" if you are looking at ECT might no happen or take longer.

When you say the vehicle "overheats", how did you determine that... code, check engine light, coolant blowing into the overflow, "steam out the engine"... what? IF coolant blows into the overflow and there is "air leak" in some fittings, then the system on cool down will not "retrieve" the overflow and instead the system will likely be "air locked" which then likely has to be "burped" to get it functioning as designed again.

Again, as suggested get a data reader going.... your loss of power will likely show a code... go from there.

 

[Mooseman]

As mentioned, it's likely an air pocket probably at the thermostat. I had the same problem on the Saab with the 5.3. Make sure when installing the thermostat, you install the little hole part at the 12 o'clock position so that it can let air through.

I'd move the sensor back to its original location and install a new one as they can fail. The way I resolved it was to drive it until the thermostat eventually opened and bled the system of the air. I know it sounds scary but it doesn't actually go into the red. Or try idling it at a higher RPM until the thermostat opens.

 

[TJBaker57]

so far i don't even have a book on it.

Free Service Manual for the 2004 Chevy Truck TrailBlazer 4WD V8-5.3L VIN P | Operation CHARM

Detailed repair manual for the 2004 Chevy Truck TrailBlazer 4WD V8-5.3L VIN P, including electrical diagrams, recommended bolt torques, and estimated labor times.

charm.li

 

[Mooseman]

IIRC, manual says that while filling to remove the cap on the crossover tube (the one between the two heads in front of the engine). I would also keep it off while idling until it flows coolant out of it. Also the use of a radiator filling funnel helps while it's idling to keep filling as the air comes out.

https://www.amazon.com/dp/B01A2CQSU6/?tag=gmtnation-20

 

[christo829]

Amongst that list of replaced items, I saw fan, and I'm assuming that included a properly working clutch, but I may have missed whether the water pump was checked/replaced?
Cheers-
Chris

 

[Mooseman]

Here's something you might want to consider is to get a vacuum coolant refill kit.

 

[mrrsm]

Here is that same Snap-On Kit "In Action" on a Trailblazer 4.2L LL8:

One of many (either Simple or Complete Solutions Kits... like this one) available over on Amazon:

 

[oldbeater1]

The heads are original but they have been shaved. The previous owner was trying to solve the overheating problem and bought an adapter and cut the upper radiator hose the problem was one thread was metric and one standard and when it overheats it sprays steam out the adaptor .

 

[oldbeater1]

i finally have the vehicle in my name. The sensor has been moved back to the cylinder head. now it gets up to 210 or just under that and stays there. The only thing i cannot get to work is the a/c it is out of freon, so i added some and it filled right up and leaked right out. i am thinking a leak to the rear. and the compressor never did kick in. I was thinking of a block-off plate and eliminating the two lines to the rear. for now. However, I don't know where the connections are located to the rear of the vehicle.

 

[oldbeater1]

it is a 2004 ext lt