4.2L running hot under load

[mrwhipper]

Hello.

I have read all the threads related to my problem here and on another forum but I am still stumped with my 2003 Trailblazer 4.2L. At idle and normal cruse with air on engine temps are fine but when I climb a hill or tow the coolant temps will creep up. They have got to 210F not towing and 225ish when towing and still creeping up. I have replaced radiator, radiator cap, thermostat and pump. The old rad is clean inside and so is the pump and pump cavity. I power washed the condenser. I have maliciously maintained this car with all fluids change way before they were required. I have done an emission gas test in the antifreeze with no gas detected and I have pulled the plugs after an over night cool down and scoped the cylinders with no coolant found in any of them. I am 100% stumped on what to do next. What am I missing here? Both of my mechanic friends are stumped. Pics of everything are attached.

I know when I pulled the old thermostat off it did not have the rubber seal around the plunger. (not talking about the O ring for the housing) Did GM make some of them with out the seal? If not, if that fell off and went into the system could that cause the issue?

 

[TJBaker57]

They have got to 210F not towing and 225ish when towing

FWIW, my own 2002 4.2 runs at 206° F normally. This figure is from the J1850 data that drives the temp gauge so there is no possibility of an incorrectly installed gauge needle.

Mine generally heats to this temperature within 10 minutes. I would not consider 210 out of the range of normal.

I do not expect to see fan clutch engagement until about 230° F or around 300 psi A/C High pressure.

 

[mrwhipper]

FWIW, my own 2002 4.2 runs at 206° F normally. This figure is from the J1850 data that drives the temp gauge so there is no possibility of an incorrectly installed gauge needle.

Mine generally heats to this temperature within 10 minutes. I would not consider 210 out of the range of normal.

I do not expect to see fan clutch engagement until about 230° F or around 300 psi A/C High pressure.

View attachment 114291

Thank you. What are you thinking with the very warm temps of 225+ for towing?

 

[TJBaker57]

I would want to confirm (with OBD2 data monitoring) that the fan clutch does indeed begin to see activation from the PCM at these warmer temperatures. I have not towed with my TrailBlazer for like maybe ten years now. I had installed a transmission fluid cooler for towing and that helped the transmission fluid temps but of course does nothing for the engine coolant temperatures.

I will say I would be a bit concerned at seeing greater than 225° F for long. The last time I towed anything was 2018 in my Yukon and that has a poor gear ratio for towing, 3.42. I was going up over the Rocky Mountains in south central Colorado and when I hit 230°, maybe 235° I pulled over to allow the temps to cool a bit.

 

[mrwhipper]

I would want to confirm (with OBD2 data monitoring) that the fan clutch does indeed begin to see activation from the PCM at these warmer temperatures. I have not towed with my TrailBlazer for like maybe ten years now. I had installed a transmission fluid cooler for towing and that helped the transmission fluid temps but of course does nothing for the engine coolant temperatures.

I will say I would be a bit concerned at seeing greater than 225° F for long. The last time I towed anything was 2018 in my Yukon and that has a poor gear ratio for towing, 3.42. I was going up over the Rocky Mountains in south central Colorado and when I hit 230°, maybe 235° I pulled over to allow the temps to cool a bit.

I agree with the temp during towing. I use to have an Envoy with the same 4.2 and it never went above 200.

 

[mrrsm]

The Last Device in the "Loop" for Thermal Sensing would be a possible errant Thermister Temp Sensor Pick-Up point for sending Temperature Data to the PCM... Located in the Engine Head-Block (Driver's Side, Front, Lower Area). All Thermostats respond to the Physical "HOT or COLD "Changes inside the moving 50/50 Mixed Water & Coolant Column...BUT... it is the Thermister that alerts the PCM to the conditions necessary to Turn On the Electro-Viscous Fan.

Available at RockAuto HERE:

2004 CHEVROLET TRAILBLAZER 4.2L L6 Temperature Sender / Sensor | Shop Now at RockAuto

Cooling System Parts and More for Your 2004 CHEVROLET TRAILBLAZER at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

The other issue is that there are TWO Choices for OEM Thermostats for the GM 4.2L LL8 Atlas Vortec 4200 Engines: ACDelco (GM) or STANT. These Images show all of the OEM Components when Brand New for your visual comparison and Part Number Cross Checking:



Since the Serpentine Belt drives the Water Pump... having one of the Correct LENGTH may also factor in How FAST the WP Impeller Blades can push against the Coolant Water Column... First up THROUGH The Engine Head...and then down through the Water Jackets inside the "Lost Foam" Block casting.

NOTE:

On VERY Rare Occasions...Blue Paper Shop Towels and Shop Rags HAVE been found STILL stuck up inside of the Hoses ...left their accidentally in order to prevent Coolant Drips and Seepage during Radiator Repairs... and THAT mistake would definitely obstruct the Flow of Coolant through the system.

 

[Mooseman]

The EV fan clutch does start to engage at 211f however really cranks up at 228-232. This chart shows the engagement temps and %.

225f is not super hot but the fan would start pulling quite a bit. If you don't have a bi-directional scan tool to perform functional tests, you could use this method to make sure it does work:

How to test the electro-viscous fan clutch

If it doesn't work, it would be especially evident with the A/C on high, just idling, it would not be very cold or even warm but would cool down while moving.

 

[mrwhipper]

The Last Device in the "Loop" for Thermal Sensing would be a possible errant Thermister Temp Sensor Pick-Up point for sending Temperature Data to the PCM... Located in the Engine Head-Block (Driver's Side, Front, Lower Area). All Thermostats respond to the Physical Changes inside the water Column...BUT... it is the Thermister that alerts the PCM to the conditions necessary to Turn On the Electro-Viscous Fan.

Available at RockAuto HERE:

View attachment 114312

2004 CHEVROLET TRAILBLAZER 4.2L L6 Temperature Sender / Sensor | Shop Now at RockAuto

Cooling System Parts and More for Your 2004 CHEVROLET TRAILBLAZER at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

The other issue is that there are TWO Choices for OEM Thermostats for the GM 4.2L LL8 Atlas Vortec 4200 Engines: ACDelco (GM) or STANT. These Images show all of the OEM Components when Brand New for your visual comparison and Part Number Cross Checking:

View attachment 114292View attachment 114295View attachment 114296View attachment 114297View attachment 114298View attachment 114299View attachment 114301View attachment 114302View attachment 114303View attachment 114304View attachment 114305View attachment 114306View attachment 114307View attachment 114308View attachment 114309View attachment 114310View attachment 114311

Since the Serpentine Belt drives the Water Pump... having one of the Correct LENGTH may also factor in How FAST the WP Impeller Blades can push against the Coolant Water Column... First up THROUGH The Engine Head...and then down through the Water Jackets inside the "Lost Foam" Block casting.

NOTE:

On VERY Rare Occasions...Blue Paper Shop Towels and Shop Rags HAVE been found STILL stuck up inside of the Hoses ...left their accidentally in order to prevent Coolant Drips and Seepage during Radiator Repairs... and THAT mistake would definitely obstruct the Flow of Coolant through the system.

Thank you for the time you spent with the pics!!!! Well I definitely pulled the OEM thermostat out. The Stant is the one that has the rubber around the plunger and looks very different then the OEM one I pulled out. One less thing it can be. I did have all the hoses off when I did all the work I mentioned and did not see any obstructions unless they moved to the head?

 

[mrwhipper]

I would like to add one thing. This maybe nothing but It seems when the trans is out of lockup the temps can creep up.

 

[TJBaker57]

I would like to add one thing. This maybe nothing but It seems when the trans is out of lockup the temps can creep up.

Without lockup the torque converter will generate more heat. Heat from the transmission is passed to the engine coolant, unless you have an aftermarket auxillary transmission fluid cooler added.

 

[Mooseman]

An auxiliary tranny cooler is a must, especially for towing. The bigger the better. The one in the radiator can actually add heat to the tranny fluid when it's running hot and vice-versa.

Transmission Coolers..

Ok, so here I am trying to search through the forums on this subject. And I keep getting lost in threads, I swear I could read these for hours, lol! Anyways, does anyone have a suggestion on an aux transmission cooler (to go along with the stock one from the factory tow package, I think) that...

gmtnation.com

 

[budwich]

Tough to say from your first description... what speeds up the hill are you talking about? What speed when towing? What weight are you towing. I don't think your 210 when "flying" up a hill is much out of line and neither is the 225 if you are pushing 65-70 in tow.... and all of that with AC on.

 

[mrwhipper]

Tough to say from your first description... what speeds up the hill are you talking about? What speed when towing? What weight are you towing. I don't think your 210 when "flying" up a hill is much outline and neither is the 225 if you are pushing 65-70 in tow.... and all of that with AC on.

Great questions. Let's start with that this is south central PA, so not talking about mountains. Lets do this in order 1. Towing up a hill at 55ish at 2700 RPM with 85F ish ambient temp reaching water temps past 225F towing around 4000lbs. NO AC on. 2. Climbing up a hill 50ish, 2200 rpm with air on 85ish ambient temp, just me in the car and water temps between 210 and 215. Now please keep in mind my 2004 Envoy with the exact drive train never got above 195ish doing the exact tasks in much warmer ambient temps.

 

[budwich]

ok... thanks for the further info. Tough to "argue" against the "my envoy never had an issue doing the same thing" type scenario. I have never owned an envoy... but know there are some differences, like "ext" and such.

What other history for the TB? Has it always reacted this way? How many miles on it? maybe look at the fuel trims to see how they are running, at idle and at constant road speed. Maybe a slightly clogged cat causing issue. Other suggestions to look at fan speeds are a good place to look.

I pull close to the 10K lbs GCW and see 210 regularly at highway speed. Up grades (depending on grade and length), it will head towards 215-220 along with 190-200 tranny temps especially with AC. Shutting AC may give me 5 degrees less.

 

[Mooseman]

You have not mentioned the EV fan clutch at all. Did you check it? It is a high failure rate part.

 

[mrwhipper]

ok... thanks for the further info. Tough to "argue" against the "my envoy never had an issue doing the same thing" type scenario. I have never owned an envoy... but know there are some differences, like "ext" and such.

What other history for the TB? Has it always reacted this way? How many miles on it? maybe look at the fuel trims to see how they are running, at idle and at constant road speed. Maybe a slightly clogged cat causing issue. Other suggestions to look at fan speeds are a good place to look.

I pull close to the 10K lbs GCW and see 210 regularly at highway speed. Up grades (depending on grade and length), it will head towards 215-220 along with 190-200 tranny temps especially with AC. Shutting AC may give me 5 degrees less.

More great questions! Thank you for the time you are spending with me! My 2004 Envoy was not an EXT, it had the same 4.2L and drive line as the 2003 Trailblazer. We are the second owner of the Trailblazer. It was maintained VERY well by the first owner. We got it at 70,000 miles. I am a maintenance maniac. Trans fluid, transfer case every 40,000, Dexcool antifreeze every three years (about 30,000), engine oil every 3,000 to 3,500. and so on.

As far as "has it always acted this way", It was my wife's car until we got her the Canyon and I took the Trailblazer over. I am not sure how much she monitored the gauges and I know she does not use the air as much as I do. There is 159,000 miles on it.

 

[mrwhipper]

You have not mentioned the EV fan clutch at all. Did you check it? It is a high failure rate part.

Thank you! I do know the fan is working but I have not had a chance to monitor it using a scan tool though. I am taking a long trip tomorrow so I may plug the scanner in during the trip.

 

[Mooseman]

Now please keep in mind my 2004 Envoy with the exact drive train never got above 195ish doing the exact tasks in much warmer ambient temps.

One factor that may change between the two is the gearing. If the TB has steeper gears (3.42) than what the Envoy might of had (possibly 3.73), that could affect the engine load a bit.

Often times the fan may look like it's working but often times, it's just freewheeling from residual friction and is not really pulling a lot of air. This would be evident if the A/C becomes warm while stopped in traffic. Do monitor the fan speeds and if it gets warm and the fan is not appreciably increasing in RPM, I'll bet it's dead.

 

[mrwhipper]

One factor that may change between the two is the gearing. If the TB has steeper gears (3.42) than what the Envoy might of had (possibly 3.73), that could affect the engine load a bit.

Often times the fan may look like it's working but often times, it's just freewheeling from residual friction and is not really pulling a lot of air. This would be evident if the A/C becomes warm while stopped in traffic. Do monitor the fan speeds and if it gets warm and the fan is not appreciably increasing in RPM, I'll bet it's dead.

Gotcha. I know I can sit at a red light in 90F ambient with the air on and the water temp will not go above 201. When the light turns green I can hear the fan a bit then when I get the RPM up the fan will release. (It is not a full engagement sound like a bus but you can hear it)

 

[budwich]

You have not mentioned the EV fan clutch at all. Did you check it? It is a high failure rate part.

I guess I don't quite understand how the fan operation becomes involved at highway speeds. Surely, the air flow past everything is greater than what the fan could pull even if it was totally "engaged". I think I asked about this a long while ago while looking at the thermal type clutching.

 

[mrwhipper]

I guess I don't quite understand how the fan operation becomes involved at highway speeds. Surely, the air flow past everything is greater than what the fan could pull even if it was totally "engaged". I think I asked about this a long while ago while looking at the thermal type clutching.

I have noticed after continuing my research that is situation in not the norm but there a people out there with the same or similar issue. I have seen more than one comment about putting in a full aluminum dual core radiator with electric fans and it solved the problem. What do you all think about that? Here is a link to the rad that was recommended: https://www.amazon.com/dp/B0D1XKP3ZX/?tag=gmtnation-20

 

[Mooseman]

Wow. In the old days, some guys were fitting other rads from Dodges that required modifications to work and now we have actual ones for our platform despite having been out of production for over 15 years. This was sought after for those wanting to use electric fans because the original was marginal at best. That's why the engineers used a mechanical clutch fan to compensate for the poor cooling characteristics of the original radiator.

Yes, it should help a lot however I would still confirm everything else is working correctly before plunking down that much coin for it. I'd give the stink eye to the thermostat. Never had good luck with aftermarket. I currently have a Mahle, which is the manufacturer of the ACDelco. No issues. I don't see why Stant had to add a rubber seal.

For the fan, if the clutch was ever replaced with an aftermarket one, a member did some tests of different clutches and the aftermarket ones just don't work as designed.

EV Fan Clutch Recommendations for proper operation

 

[mrwhipper]

Hello again. An update with the fan clutch. I followed the video from the provided link using a rag testing the clutch. I did it cold and other then feeling a small timed grab it was free. I then got it to temp and checked it again with the air on and it definitely had more grab. So I feel very confident the clutch is working. I ordered the radiator in the above link. I will keep you all posted.

 

[mrwhipper]

OK... So.... That radiator was a piece of doo doo..... Somebody was sleeping while trying to put it together. Brackets that are supposed to hold the bottom of the condenser were welded on 90 degrees inward on both sides, the bracket that is supposed to hold the center upper shroud was welded way too high up and could not get the shroud down off of the fan, the brackets that hold the speed nuts for the upper condenser bolts are WAY too close to the tank. the bolt hit the tank and it wasn't close to being tight. The best one is I could not use the hood latch bracket because the radiator kept it up about 1" too high to get the bottom bold in. Wasted vacation day.... Here are some pics. A few pics are from an OEM Rad for comparison.

 

[Mooseman]

Are you still going to try and use it? If dimensions and hose outlets are correct, maybe the rest can be made to fit?

 

[mrwhipper]

Are you still going to try and use it? If dimensions and hose outlets are correct, maybe the rest can be made to fit?

No, I sent I back. I figured if they cannot get that basic stuff right how bad is the rest.

 

[Mooseman]

If you can, try to leave a review to prevent others from doing the same. The one review that's there doesn't look legit. If you already returned it, you might not be able to. Amazon has prevented me from leaving reviews of stuff I've returned so I leave the review before I return it.

So how are you going to tackle this issue now? It's too bad there aren't any upgraded radiators available. I'd still be looking at that Stant thermostat and the fan clutch. IIRC, @TJBaker57 does have a way to increase fan speed using an OBD adapter and Torque.

 

[budwich]

Do you still have the original thermostat / housing? You could try pulling off the thermostat and running without one for a "test" to see if things change. I know its work to "change out" that area but its basically your time. I am not sure that the thermostat portion can be removed from the housing but I assume it is some sort of "press in" deal.

 

[mrwhipper]

If you can, try to leave a review to prevent others from doing the same. The one review that's there doesn't look legit. If you already returned it, you might not be able to. Amazon has prevented me from leaving reviews of stuff I've returned so I leave the review before I return it.

So how are you going to tackle this issue now? It's too bad there aren't any upgraded radiators available. I'd still be looking at that Stant thermostat and the fan clutch. IIRC, @TJBaker57 does have a way to increase fan speed using an OBD adapter and Torque.

Thank you. I have not left a review yet but I have returned the rad. I wanted to get my money refunded before I left a review.

 

[mrwhipper]

Do you still have the original thermostat / housing? You could try pulling off the thermostat and running without one for a "test" to see if things change. I know its work to "change out" that area but it’s basically your time. I am not sure that the thermostat portion can be removed from the housing but I assume it is some sort of "press in" deal.

I do still have the OEM thermostat and was thinking about doing this but there are two problems…. 1. It sucks pulling the thermostat out of it…. 2. The weather is changing and I am not having any issues now.