NEED HELP 02 Trailblazer LT Over heating

Fmechanic

Original poster
Member
Aug 9, 2021
1
Downey
About 3 months ago we(me and my baby JB) got hot. I was about to park and she(Just Blaze) turned off. We got pushed into a car wash parking. I lifted the hood and the coolant was everywhere. I started her up and moved into a stall and to let her cool off & washed her up. The overflow and radiator were empty filled them with water and started her again. She made it home and still had water. Been checking her oil periodically and no bad signs. I put my scanner on her and it didn't want to read. WTF. The next day I start her and she was good was omy way to Autozone to use their scanner and saw steam coming from the engine and the gauge quickly rising. Went to the gas station and let her cool off again. Got to Autozone and their scanner didn't work either. So I looked online for suggestions.
I set out to fix my baby radiator looks good.
1.Changed the water pump(didn't help)
The next day she didn't want to start so looked and found I had a wire under the steerng wheel that had burned fixed that with some electrical tape she stared up.WTH.
2.Changed the thermostat(didn't help)
10 miles later she starts over heating. Flushed the radiator and let her run then I hear water hitting the ground. It was coming from the catalytic converter. WTF. I patched that up. Now I find her oil is milky. So I'm taking her apart to check the head gasket. What a job.
My questions are
1. I had one head bolt break how do I get it out?
2.) What else could be her problem?
 

Mike534x

Member
Apr 9, 2012
894
There could have been a blockage during the first overheating event, somewhere in the coolant hose/water pump or block. It sounds like you blew the head gasket on the 2nd or 3rd attempt going off your "milky oil". Head bolts are notorious to break when removing the head from this engine, its highly recommended getting the correct replacements. They are also not easy to remove, and can be pretty time consuming and the use of some special/expensive tools to extract them safely (going off comments/threads from those who have done it).
 
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Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
So difficult to do this we usually recommend replacing the whole engine. Head bolts ALWAYS break and 90% of the time, it's the rear ones that are difficult to get at. You usually need a special Time-Sert tool to remove the broken bolts (@MRRSM is our SME on it). And then there's the cams and timing chain to contend with. And for the cost of reconditioning the head, you could find a whole engine cheaper. And if the head is cracked, you have to find another one at even more added expense.

It's up to you if you still want to pursue this course of action.
 
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mrrsm

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Oct 22, 2015
7,639
Tampa Bay Area
:iagree:

A Few More Issues to contend with...

Even if you were to remove the Aluminum Engine Head... you would very likely need to replace it rather than attempt to have it re-built. The symptom of having Coolant Mixed with Motor Oil making that "Brown Gravy" in the Oil Pan can only have two sources (and a third unfortunate possible outcome):

(1) The VERY LONG Aluminum Engine Head has either Warped, Twisted or Cracked enough to allow the Coolant to get around the almost indestructible Multi-Layer Stainless Steel Head Gasket and go where it should not be.

(2) One or More Cast Iron Cylinders and Engine Block areas have Cracked due to High Temperatures and Liquid Coolant has leaked into the Crankcase-Oil Pan.

(3) In-compressible Liquid Coolant may have leaked into the Combustion Chamber(s) while the Engine was operating and Hydro-Locked one or more Pistons... bending the involved Connecting Rod(s) and totally FUBARing the Motor.

(4) The Engine Coolant circulating through the Oil Galleries means that the Main and Connecting Rod Bearings have already been exposed to this Caustic Stuff and will become damaged from this chemical exposure, causing them to suffer from electrolytic corrosion if the Motor is not completely flushed clean soon after such any events occur.

(5) You are looking at $1,500.00 in Basic Repair Costs for PARTS alone... at a minimum. So performing an Cheaper Engine Swap is "The Lesser of Two Weevils".

I concur with @Mooseman. If you Love your SUV as much as your 'affectionate naming convention' implies, then seek out similar Year-Make-Model Trailblazers-Envoys-Raniers with the 4.2L Engines and perform a Motor Swap. Focus only a candidate(s) that were actually RUNNING and got involved in disabling accidents rather than on getting any that are "Tow-Aways" formerly sitting out in Vacant Lots somewhere.
 

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TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,045
Brighton, CO
I will also agree with the above. Dont fix it, just replace it. If you put the head gasket in it, and there ends up being a bent rod, or wiped bearings, your back to square one, of replacing the engine. Its just not worth it. And from the stories that I have read here on the forum, its faster to swap the engine! And here is the kicker.. It will also be cheaper! (given you get a known good runner).

Not sure where you are in the world, or the specific details of the truck, so we cant really suggest swap candidates, as they are year specific.

I have had real good luck finding cheaper running 4.2s. So if I can help, let me know.

Dont be afraid of buying a complete truck either, from an accident, or? As long as its a good runner, and its one of the year specific trucks, and its cheap, then you will come out ahead.
 
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TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,045
Brighton, CO
Also, for the codes not reading. The cigarette lighter must be in working condition. Its usually easier to just replace the fuse under the hood if you dont have a way of testing the cigarette lighter socket.
 
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JayArr

Member
Sep 24, 2018
504
Mission BC Canada
I broke a few of my head bolts too but found that giving the remaining part in the thread a light tap with a long drift punch freed them right up and then a reverse drill spun them right out nice and easy.

YMMV.

I agree with the above, if the oil is milky get a new engine, it's a Looong head and easily warped beyond repair. The trouble is that when you warp the head you misalign all the bosses that hold the cam shafts so it's not just a matter of milling it flat again like old V8 heads, now you have cams that won't spin properly.

It's not that hard to change the engine and while it's out you get some great opportunities to repair common faults like rusting steering lines and seals and front end bushings, ball joints and tie rods etc.

I would also pay close attention to your radiator or replace it. They work great when they work but it doesn't take much of a clog in the rad to create an engine that overheats. I used stop-leak on a trip last year and clogged about 20% of the rad with it and could barely drive the car without overheating. New rad and suddenly I can pull a trailer up a mountain without the temp going over 200!

JayArr
 

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