C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Engine Block Drain Plugs??

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Old Oct 31, 2024 | 08:03 PM
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Default Engine Block Drain Plugs??

TLDR: Where is the passenger-side engine block coolant drain plug?

Hey everyone. I'm new to the whole Corvette scene with my 1985 Corvette, also being my very first car.
I'm doing a full coolant flush on my car because I just know it hasn't been done in decades. It's full of junk, aside from being at a dangerously low level.

I got my hands on the '85 FSM and it says to open up the engine block drain plugs for a more thorough flush than just flushing the radiator. Unfortunately, my first experience with the FSM isn't so nice as the manual never seems to make mention of the block drain plugs again, anywhere. I have no idea where they would be. I assume there are two for both sides of the engine block. I found one of them, cracked it open and had to stick a brush up there to remove the gunk before the coolant started to flush out.

Now for the life of me, I can't find that other drain plug (on the passenger side) I've been looking for nearly an entire day and found nothing.
Where could it be? If anyone has pictures too, that would help me so much. Thanks!
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Old Oct 31, 2024 | 08:59 PM
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On the passenger side you have to remove the knock sensor, it's threaded into the block drain hole.
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Old Nov 1, 2024 | 01:45 AM
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If you have the same 1985 FSM that I have, there is a picture of the location of the knock sensor on the passenger side on Page 6E3-107. Section 6E is Driveability and Emissions Fuel Injection (Port).
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Old Nov 1, 2024 | 04:59 PM
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Originally Posted by Ryravux

Where could it be? If anyone has pictures too, that would help me so much. Thanks!

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Old Nov 1, 2024 | 05:50 PM
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Thank you all for the replies! I've gotten to it finally
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Old Nov 1, 2024 | 05:52 PM
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From the FSM 6E-107



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Old Nov 2, 2024 | 06:24 PM
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Thank you. I didn't realise that the passenger side block coolant drain plug was just the knock sensor itself
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