NEED HELP Trailblazer Overheating / Coolant

Discussion in 'Engine & Drivetrain' started by Hoop1101, Nov 21, 2016.

  1. Hoop1101

    Hoop1101 Member

    Messages:
    6
    Likes Received:
    2
    Hi guys. Long time lurker, first time poster here. This site is great! I have found other similar threads to this but they have either gone unsolved, or they were fixed by something I have already tried. I'm looking for help on where to go from here. Here is the story:

    This spring, I replaced the water pump on my 04' Trailblazer 4.2L due to worn bearings. Part # Gates 41122. I also "flushed" the radiator with a DIY fluid from Prestone. Then filled with 50/50 distilled water and DEXCOOL. A couple of months later I had the first overheat while pulling my boat on a hot summer day on the highway. Coolant was bubbling in the reservoir. I had the car towed home and I replaced the thermostat. Part # AC Delco 15-11006. The new and old thermostat were tested with boiling water and both seemed to operate properly, which made me think that was not my actual problem. I also replaced the radiator cap, but did not use AC Delco brand. Filled again with 50/50 DEXCOOL. The truck seemed to run fine, but would still occasionally overheat when pulling the boat or running the A/C on a hot day. I lived with the problem until about a month ago when the truck overheated badly and unexpectedly on a long highway drive at 70mph not towing anything on an 85 degree day. Engine had to be shut off to prevent damage and towed home again. Coolant had been pushed out of the radiator and into the reservoir, creating loud bubbling sounds again after the engine was shut off. I filled up the radiator again and drove it a few days short distances without a problem. Then the vehicle started overheating slightly almost every day driving around the city. So the last part I tried was a genuine AC Delco radiator cap AC 85. I am still having the same problem. If I fill up the radiator while the engine is cold, the car will not overheat for 2-3 days until it has time for the coolant to be pushed out of the radiator into the reservoir. There is no coolant smell in the exhaust. No visible coolant in oil. I have used a block tester with fluid and no exhaust gasses were detected. The fan clutch is engaging, which I have verified by sound, (seeing overheated dash gauge = jet engine sound) and by hand (trying to stop the fan at idle while the car is overheating. I also tried my best to get the air out of the system with the rad cap off.

    To recap things that were replaced this year (in order):
    Water Pump - Gates 41122
    Thermostat - AC Delco 15-11006
    Radiator Cap - AC Delco

    Any other ideas guys? My only idea right now is to have a radiator shop look at the radiator. I am not sure if/how they can test for blockages. Thank you!!!
     
    Last edited: Nov 21, 2016
  2. Wooluf1952

    Wooluf1952 Well-Known Member

    Messages:
    2,496
    Likes Received:
    298
    [​IMG][​IMG] Welcome [​IMG]

    In case you haven't heard:
    http://gmtnation.com...eres-the-story/

    How many miles on the truck?
    Is the serpentine belt original?
    Have you checked for blockage between the AC condenser and the radiator?
    Others will jump in, but that's all i can think of for now.
     
    littleblazer likes this.
  3. Hoop1101

    Hoop1101 Member

    Messages:
    6
    Likes Received:
    2
    Thank you!! I forgot that important info, I apologize. 190K miles currently. I replaced the serpentine with the water pump this spring. I have not checked for a blockage. How would one go about checking for a blockage between the ac condensor and radiator?
     
  4. Wooluf1952

    Wooluf1952 Well-Known Member

    Messages:
    2,496
    Likes Received:
    298
    I don't think you can see looking down from the top. You'll probably have to remove the grille.
     
    littleblazer likes this.
  5. AtlWrk

    AtlWrk Well-Known Member

    Messages:
    632
    Likes Received:
    210
    Have you cleaned the outside of the radiator? Preferably by spraying with a hose and nozzle from the fan-side forward. You'd be surprised how much gunk can accumulate over the years and compromise the airflow of an already undersized radiator. When I had my fan and shroud off to replace a clutch I took the opportunity to clean the radiator and it took probably 20 minutes of constant spraying before I stopped seeing sediment running off.

    Do see any signs of contamination, corrosion, gunk build up, etc. in the radiator on the portion you can see when you remove the cap? Not going to be conclusive (blockages may exist in other areas) but it could give us an indication of the overall health of the radiator.

    Air isn't particularly troublesome on the 4.2L as long as you don't leave a ridiculous amount in the system when you refill. The system can pretty effectively purge itself assuming the radiator cap is functioning correctly. That being said...
    Do your radiator hoses get stiff (under pressure) when the engine is hot? It's unlikely that both your new and old radiator caps are bad but it is possible. Without the normal operating pressure the boiling point of the coolant is significantly lower and once you start boiling your engine is going to overheat real quick.

    The other possibility is a bad (inefficient) pump that's only doing a marginal job circulating coolant. I've only heard anecdotal evidence about this happening but might be possible considering your problems started after a pump replacement.


    EDIT: Just re-read your post and it sounds like a radiator cap is definitely not your problem.

    EDIT 2: Next time it happens crank the heat (with the windows down so you don't kill yourself)...if it isn't all that hot or starts off hot and tapers off you may have a blocked heater core. If part of the coolant's circulation path is blocked in the engine it may boil locally in that spot and start the whole process of overheating the entire engine.
     
    Last edited: Nov 21, 2016
    littleblazer likes this.
  6. MRRSM

    MRRSM Gold Supporter

    Messages:
    1,287
    Likes Received:
    543
    And as per @Wooluf1952 ...

    Something as simple as a Small Plastic Bag from Convenience Store...once ingested by the partial vacuum of the Electro-Vicous Fan into the cavity under the Front Grill and covering either the front of the Condenser Coils or wedged in between it and the Radiator...can prevent enough of a Heat Exchange to allow a Thermal Runaway of the Coolant Flow.

    Another place worth investigating is an excessively blocked Catalytic Converter. The Back Pressure there can cause a severe Heat Soak that remains in the Exhaust Manifold and add to the Heat Signature of the Engine Head... which in the case of the GM 4.2L LL8 Engine... receives Coolant first in the Flow Path because of the Higher Compression Ratio.

    And @AtlWrk has it precisely right about the Water Pump... There really are only two kinds to observe: AC-Delco or Delphi... and the REST that WILL FAIL. This link leads to a parallel post on that subject and will be worth a good review for more data on the value of using only the OEM Pump, Part Numbers, etc:

    https://www.amazon.com/ACDelco-252-822-Professional-Water-Pump/dp/B000IYXKBO/ref=au_as_r?_encoding=UTF8&Make=Chevrolet|47&Model=Trailblazer|489&Year=2002|2002&ie=UTF8&n=15684181&newVehicle=1&s=automotive&vehicleId=1&vehicleType=automotive

    [​IMG]



    http://gmtnation.com/forums/threads...ay-out-after-just-6-months.15365/#post-502412

    ... and even MORE Props to @AtlWrk for suggesting the Clogged Heater Core... THIS link covers that topic quite well for "How -To-Flush" Data:

    http://gmtnation.com/forums/threads/2003-tb-ext-4-2-overheating.15558/#post-503514
     
    Last edited: Nov 21, 2016
    AtlWrk likes this.
  7. Mooseman

    Mooseman Moderator

    Messages:
    7,944
    Likes Received:
    3,380
    Since it seems to overheat only when towing and/or with the A/C on, I would suspect the fan clutch. Check out this thread on how to test it: How to test the electro-viscous fan clutch

    Other suggestions above are also good.
     
    littleblazer likes this.
  8. littleblazer

    littleblazer Gold Supporter

    Messages:
    5,794
    Likes Received:
    2,863
    You could take an ir temp gun and look at the radiator, temp should change consistently across it, if you see any hot spots it could be junk in the fins blocking air flow or its plugged internally. Both were mentioned above. One of those thermal imaging scopes would work best but I doubt you would have access to one. If that checks out let it cool and drain a small amount of coolant from the radiator, enough that it is below the cap neck. Start the truck and let it run a bit and leave the cap off, you should eventually see it start circulating. You're looking for relatively turbulent flow, if it seems questionable it probably is. That last bit is the wrong way to do it, and doesn't really show much... but if you start with it off and remove enough it won't boil over or splash or anything like that in such a short period of time. Only use as a last resort, sometimes it will show a sludge in circulation too.
     
  9. Hoop1101

    Hoop1101 Member

    Messages:
    6
    Likes Received:
    2
    Thanks for the suggestions guys. I have compiled a list of things I will try very soon based on your posts:
    1. Clean/inspect fins and passages near radiator etc.
    2. Check for buildup inside top of radiator
    3. Check for stiff radiator hoses to indicate pressure in system
    4. Temp gun radiator/check for flow

    I am interested specifically in the comment MRRSM made about a plugged cat. Around the same time I changed the water pump this spring, I had to have the valve cover gasket replaced because oil was leaking and causing a cylinder to misfire. This went on for a few months before getting resolved, which I believe could have resulted in un-burned fuel to be going though the exhaust.

    As far as the heater core goes, I have tried turning the heat on when the engine is overheating and I do get a steady flow of continuous very hot air for minutes at a time. It usually helps the engine cool down a bit too by adding another means of radiation for the heated coolant. Thanks for the link, I will consider flushing the heater core if the testing I do does not lead me to the answer.

    For the fan, I have tested the fan and it is functioning properly as far as I can tell. I hear the jet engine sound when accelerating the vehicle, and I cannot stop the fan with a glove when idling overheated.

    Looks like I'll do the free tests I can do listed above and call a muffler shop tomorrow to see about testing the cat. It might be in my head, but I may have been noticing a decrease in engine performance this past year too...
     
  10. littleblazer

    littleblazer Gold Supporter

    Messages:
    5,794
    Likes Received:
    2,863
    If you have the means to remove the upstream o2 sensor, do that and take it for a quick drive and see if it has more power. If the cat is plugged that will release some of the back pressure
     
  11. freddyboy61

    freddyboy61 Well-Known Member

    Messages:
    180
    Likes Received:
    42
    If the cat testing doesn't show anything, maybe a test for exhaust gases in the coolant is in order to rule out a cracked or leaking block.
     
  12. Hoop1101

    Hoop1101 Member

    Messages:
    6
    Likes Received:
    2
    If I remove the O2 sensor, can I leave the wiring harness unplugged while testing/running?
    Freddy, I tried using the "Block Tester" with fluid, and had no results with that method. I'm not sure if there is another test.
     
  13. AtlWrk

    AtlWrk Well-Known Member

    Messages:
    632
    Likes Received:
    210
    Yes, just unplug the O2 sensor altogether. You'll get a check engine light either way but at least you won't have to worry about securing it somewhere in the engine bay where it wont touch anything or come loose. Also, just a heads up, it's going to sound like you hacked off your muffler while the O2 sensor is out.
     
  14. Hoop1101

    Hoop1101 Member

    Messages:
    6
    Likes Received:
    2
    Called a muffler shop today who would pressure test the cat for free. They just completed the test, and said that I have less than 2 PSI on the entire exhaust system at high RPM. So he said it is not the cat. I am on to my list of 4 items I listed above, hopefully tonight.
     
    Matt and Mooseman like this.
  15. TollKeeper

    TollKeeper Well-Known Member

    Messages:
    2,473
    Likes Received:
    34
    I'm wondering if his impeller on his water pump is still connected to the shaft. That's how after market water pumps always fail on me.
     
  16. Mooseman

    Mooseman Moderator

    Messages:
    7,944
    Likes Received:
    3,380
    In that case, it would overheat constantly and fairly quickly with absolutely no coolant circulating.
     
    littleblazer likes this.
  17. NJTB

    NJTB Well-Known Member

    Messages:
    203
    Likes Received:
    17
    Hoop;
    Another suggestion if the ones above don't work-take the radiator to a shop and have it cleaned professionally.
     
  18. Hoop1101

    Hoop1101 Member

    Messages:
    6
    Likes Received:
    2
    Thanks again for the help. Sorry for the long delay in giving an update. I have tested a few of the things I listed in a previous post, but I'd like to skip that stuff and focus on what I found yesterday. Milky oil. AND I did the block test again and the result was positive. So unless you guys tell me otherwise, it does indeed look like a bad head gasket. So should I just sell this vehicle, buy a different motor, or try to replace the head gasket myself? I have seen videos on replacing the head gasket and it does not look fun. That's why I thought a motor swap might be just as easy if not easier. I have never personally done either though. Thanks. 20161210_123846_resized_1.jpg 20161210_123846_resized_1.jpg 20161210_180215_resized.jpg
     
  19. Mooseman

    Mooseman Moderator

    Messages:
    7,944
    Likes Received:
    3,380
    It's a bitch of a job, just ask @MRRSM . Head bolts ALWAYS break and the head would need to be shaved/rebuilt. Timing chain is another thing to deal with. It all depends on what the truck is worth, age, how attached you are to it, money, etc...
     
  20. MRRSM

    MRRSM Gold Supporter

    Messages:
    1,287
    Likes Received:
    543
    Amen @Mooseman … This is The One Real Heartbreak of owning a vehicle that is otherwise in every respect… Our Favorite One to have and drive when it is running well… and when it is NOT... it will take you on a repair journey that has a fast arrival at The Gates of Mechanical Hell when serious engine problems crop up. Your most immediate problem is not having to be concerned with the R&R of the Engine Head… but rather with what has been going on chemically inside of your engine; Post Overheating-Head Gasket Failure: The Chocolate Milky Oil you describe is proof that your Engine Oil has been contaminated with a sufficient amount of of Coolant that has been cycled and mixed with Oil enough having passed through the Gerotor Oil Pump many times to have contaminated every part of the Oil Galleys and Bearing Surfaces.

    And unfortunately....cleansing all of the interior spaces of this block of all that Pudding Crap with the engine still inside the vehicle would be well nigh impossible and still become a useful deterrent to further damage that has probably already begun. It would never be cost effective for you to Remove and Repair this engine ... as from here forward... the climb gets very steep indeed. Unless you have a Few Thousand Dollars of Mad Money to burn through to rebuild this entire engine on your own...and the Mechanical Skills to Match the Weight of your Wallet... Please... Think twice before you continue to either drive or conduct further repairs on this motor without serious consideration of what follows.

    Even as I write about this problem… the Highly Acidic Poly-Ethylene-Glycol within the Dark Milky Oil is acting to dissolve and corrode the surfaces of all of the Babbitt Bearing Material surfaces in contact with the Crankshaft Main Journals and the Big Ends of the Connecting Rods... eating its way into those Bearings. Some of these Bearings will eventually seize to Crankshaft as though they were welded in place… and can wallow out their seats in the engine block and inside of the connecting rods ruining both.

    That problem is compounded by the fact that the Lubricity of all Engine Motor Oil is diminished to the point of being Essentially Useless. And when the Coolant boils off and out of the Oil ...it will turn that sickeningly sweet smelling Anti-Freeze into a congealed thickened mass that has the consistency of Brown Pudding. Neither will that stuff lubricate… nor will it be able to get sucked up via the Oil Pick Up Tube from the bottom of the crankcase. Without enough Oil Pressure ...Oil Pump Cavitation can follow and soon after… Engine Seizure would destroy what is left of the insides of this Motor.

    I am attaching a video that directly demonstrates what happened when Anti-Freeze was accidentally poured into the Crankcase along with Motor Oil… to demonstrate what invariably happens if your engine is allowed to run from now on while the interior spaces have this stuff inside. Listen to the dilemma facing the Mechanic as far as whether he will be able to clean this stuff out of the engine block well enough for it to matter. The video does not reflect upon your own special circumstances of suffering from a Head Gasket Failure...but nonetheless… the outcomes will be the same:



    And for a whole panoply of symptoms and outcomes... Jesus Wept… Look what happened to this Poor Kid:



    I am adding this last video for demonstration purposes only as a similar outcome happens here… but at much faster rate when an awful Mixture of Sodium Silicate “Liquid Sand” and Water is used for the deliberate purpose of destroying this engine. Listen to how quickly the Engine self destructs once the Babbitt Bearings go bad and begin to seize tightly onto the Crankshaft:



    I have two major posts here at GMT Nation that will take you through my sad devotion to my my son’s 2002 Trailblazer… beginning with the work I started for the R&R of the GM Atlas LL8 4.2L Engine Head… and which eventually morphed into my present project of conducting an Engine Swap with a 2004 Engine that is in excellent shape. In my humble opinion… since pulling your engine will be necessary if you decide to rebuild it… I would consider saving a great deal of time, money and effort and ponder replacing the engine with the Latest Model, Lowest Mileage...and Recently Wrecked Trailblazer Envoy or Ranier that you can obtain for around $1,000.00 after you verify that it was in great shape… and running well… right up until it was stopped by the accident that felled it.

    The Story of my “$85,000.00 GM Atlas 4.2L Engine Repair” is a Lengthy Tome that will spare you none of the agonies, difficulties, details or imagery in all that is required to accomplish this task and can be found here.. .and THIS one is exclusively dedicated to only the R&R of the Aluminum Engine Head. And I would like to add a small Caveat to what @Mooseman has already forewarned:

    There are Only Two Types of TTY Engine Head Bolts in the GM Atlas LL8 4.2L Engine:

    (1) Those that HAVE Broken when being Removed.
    (...and in some cases it can happen even when New Bolts are being Installed Too...)
    (2) ...And Those that are GOING to Break when being Removed..

    http://gmtnation.com/forums/threads/the-85-000-00-gm-4-2l-engine-repair.14423/

    The Second Project is a contemporary post involving the R&R of a 2004 GM Atlas 4.2L Engine and is also a lengthy read that will be as equally “Detailed to Death”. I am actively preparing my ‘04 Donor Engine for this purpose even now… as we speak:

    http://gmtnation.com/forums/threads/engine-swap-2004-for-2002-gm-atlas-4-2l-motor.15786/

    In a 20-20 Reflection... I really just wish that I had just gone ahead with getting the Replacement Engine as a First Choice to solve the dilemma.
     
    Last edited: Dec 12, 2016

Share This Page