Block coolant drain plug?

[dhanger]

Does the 4.2L have a drain plug for the coolant in the block? According to the manual it does, it's mentioned after step 8 of the draining procedure:

Cooling System Draining and Filling (Static Fill) — 2008 Chevrolet TrailBlazer 2WD L6-4.2L Service Manual ~ LEMON Manuals

Repair manual for the 2008 Chevrolet TrailBlazer 2WD L6-4.2L, including electrical diagrams, bolt torques, and labor times.

lemon-manuals.la

I can't see any plug that might be for coolant and Google gives me nothing about it. I'd like to completely drain the coolant for a flush--just using the lower radiator hose drains about 6.5 quarts and the spec is for 9.7 quarts so there's still about 3 quarts remaining.

 

[movietvet]

Typically a "drain plug" on the block, will have either a square head or a 6 point head and will be located on either side of the block and may even be hidden behind a motor mount. Should have a pipe thread too. May even have a sunken allen head hole.

 

[dhanger]

Yeah I looked for all the signs and I just recently changed motor mounts so I've been all over the lower block area on both sides. I'm beginning to think the manual is wrong, especially since I can't find any info about it anywhere.

 

[movietvet]

I would bet there is a block plug somewhere. It may be at the back or front, too. Just a guess.

 

[budwich]

I suspect there is no drain plug. I believe there are frost plugs (which could be punched out and replaced there after) but most people doing a "complete flush" just do multiple water flushes and then follow up with a "calculated concentrate fill" there after.

 

[Mooseman]

I have to agree. I have never seen a coolant drain plug on these. Google AI seems to agree:

The 4.2L GM Atlas engine (LL8) does not have a dedicated, accessible engine block coolant drain plug. To drain the cooling system, you have to use the drain valve (petcock) on the bottom corner of the radiator or detach the lower radiator hose. [1, 2, 3, 4, 5]


The lack of an engine block drain plug means a standard radiator drain won't empty the entire system. Because a significant amount of coolant stays trapped inside the block, DIYers and mechanics often use specific techniques to ensure a complete flush. [6]
Best Practices for Draining the System

• Use the Radiator Petcock: Locate the drain valve at the bottom of the radiator to let out most of the fluid.
• Remove the Lower Radiator Hose: For a faster or more complete drain of the radiator, squeeze the hose clamp and pull the lower hose off.
• Flush the Block: If you are changing coolant types (e.g., from an unknown fluid back to manufacturer-recommended Dex-Cool), disconnect the heater core hoses and flush the block with a garden hose to push out the trapped old coolant. [6, 9, 10, 11]

If you are doing a coolant flush, let me know:Is your Atlas engine currently overheating?Are you switching to a different coolant type?I can provide step-by-step instructions for a full system flush and refill without trapping air in the engine.
AI can make mistakes, so double-check responses
[1] https://www.trailvoy.com/threads/4-2-i6-envoy-cooling-system-flush.53430/
[2] https://www.trailvoy.com/threads/4-2-i6-envoy-cooling-system-flush.53430/
[3] https://www.carcarekiosk.com/video/2008_Chevrolet_Trailblazer_4.2L_6_Cyl./coolant_antifreeze/flush_coolant
[4] https://www.youtube.com/watch?v=kSlwU-RVWmU
[5]

[6] https://www.youtube.com/watch?v=Hy6DB71Ab90
[7] https://www.youtube.com/shorts/myZiEo5-9ZE
[8] https://www.youtube.com/watch?v=k2Uk8fqadM0
[9] https://www.youtube.com/watch?v=TVifd5BzTgs
[10] https://www.youtube.com/watch?v=Hy6DB71Ab90
[11] https://www.youtube.com/shorts/VpRF5GsBpCI