What'* that you say? The best way to drain the block is to remove the knock sensor? Well -- where were you two hours ago?!

seriously though, I'll try to thread-chase the hole in the block, but I may end up rethreading it now

It is a 7/16 head and seems to have a tapered thread...the nipple on the end is 5/16. Would anyone happen to know or have some direction about the thread size/count on this thing, i cant locate my thread counter (even if these mashed up threads could be counted) or a comparable bolt.

maybe i'll be re-tapping for an alternate plug. Would anyone have a part number for a suitable alternate?

The brass radiator plug in the picture is close in size, but naturally it is pipe thread.

Your suggestions/insight is most welcome. a temporary fix could be good enough.

Thanks so much.

It'* a standard plug for a pipe. Take it to your local hardware.

Thanks so much for responding but could you please be more specific?

We are talking about NPT, yes? If so, then we may be talking about 1/8in. NPT...same size as most steam radiator vent connections.

My local hardware doesn't have the thread chaser for that size so I'll be heading to the plumbing supply soon.

Thanks so much.

My mistake, i'm not actually sure if household steam vent connections are IPS or NPT.
But I'm guessing this plug from the engine block is NPT.

Here'* the service manual.
https://charm.li/Buick/1990/LeSabre%...VIN%20C%20SFI/

I used that brass steam radiator plug, which has the correct thread, and some PTFE sealant paste for good measure.
It is a temporary fix, but probably would last.
Two carbon steel hex head plugs are on the way.
Cleaned the threads with this 1/8-27 NPT tap from the local plumbing supply.

While you have the knock sensor out, order a new one. Then you can get that replacement over with and also can test-fit it in the sample jig at Home Depot or the like. I see you've already chased it, so this would be for confirmation at this point.

Taps are NOT the proper tool to chase threads. While it technically works, and in the case of Pipe thread, which seals with the taper design, its less an issue. but do NOT chase threads with taps, buy thread chasers when you can.

So, this is an image of the sparkles in my pan after I drained some of the FRESH fluid out.

It had been raining coolant under my car for weeks...i'd gone through at least six gallons of coolant and had to change the pump cause the belt wouldn't stay on the pully...And it was raining fluid.


Seems like I'm going to need a fire hose to get all those shavings out. SMH.


Groovy

Sparkle



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You could drain into a clean pan through a shop towel or similar repeatedly to get it all out. OR a dirty pan if you don't pour it back in (and recycle appropriately of course).

They make coolant filter kits, that could be an option as well.