Coolant Block Drain Plug - don't skip this during a coolant flush
 

I'm sure plenty of people here already know this, but a surprising amount of coolant stays inside the engine after you drain the radiator. The 14mm drain plug on the center iron helps get it out.


Apologies for the sound levels, my phone has seen better days.

Good video - thanks!

Thanks for this, I do annual flushes but have never removed that plug. Is there a gasket on it and if so can it be reused?

It has an aluminum crush washer. It can be re-used a number of times but it's probably good form to replace it.

Dale

Thanks, good info. Any chance it is the same diameter as the oil drain plug?

Nope it's quite small. Probably 8mm ID I would guess.

Dale

I've been ignoring the block drain plug (changing AF every year) for years and no issues - related post:
https://www.rx7club.com/3rd-generati.../#post12338981

By design, coolant enters and leaves the block at quite a high level, so if you only remove the radiator plug you won't drain hardly any of the coolant from the block.

I know exactly how much coolant drains when draining only from the radiator drain plug: 5 quarts. This is more than 1/2 of the total coolant capacity (9.2 quarts - from the 1993 Service Highlights) with the OE radiator, etc.

If you are changing coolant once a year I don't know if it's totally necessary to do the block drain every time. The big thing is I think that gets more of the junk/sediment out since a lot of it settles in the block. It is a good idea, but I wouldn't lose sleep if you haven't done it this way in the past.

Dale

Bumping this to ask if anybody knows the torque specification for that 14mm bolt? I couldn't even find this bolt referenced in the service manual(in either the cooling or engine sections).

Personally I don’t think it’s super critical. Has an aluminum washer for sealing. I might tighten it only slightly more than the oil drain plug. If you don’t get out a torque wrench for that, you shouldn’t need one for it.

Yeah, just snug it up so you feel the crush washer taking a good seat. I would guess 20-30 ft-lbs, in that neighborhood.

Dale

Just for posterity, it's M10*1.5 and quite short. Maybe 8mm long max. Just got a 3 year project up and running for the first time. Car has been dead since 2006 at the latest. Probably longer.

Didn't even know the drain existed until I added coolant.

A bolt with the same part number 995101000 is also used in the side of the manual transmission, The 1994 FSM gives a torque spec for it there of 19-25 Nm (14 - 18 ft lbf).

A quick note for future reference:
Coolant Drain Plug Crush Washer Gasket part number 9956-41-000 replaces N326-10-323.

I will measure the inner and outer diameter of this washer whenever I get the chance...

I've always wondered if a block drain valve from other cars or trucks might fit.

This looks like the block drain on my daily-driver LX470, with the right size hose it was completely mess-free to drain the coolant. I haven't tried it yet, but might get one the next time I need Toyota parts.
https://absolute-wits-end.com/block-...de-14mm-plugs/

As best as I can tell, this aluminum gasket/washer was also used in the transmission, fuel, clutch, brake and other systems of various other Mazda vehicles up until 2013. Ford also used it in some models. And yet, my local Mazda dealer had to order some for me.

It'll be great if the petcock fits and if they can withstand the frequency of use. I recently did an engine swap on my Camry and have dealt with those valve, they are definitely mess-free but that's about the only good thing I can say about Toyota lol. The valve uses a 10mm bolt to open the petcock, after a few flush cycle it begin to require more torque to form a leak free seal, a bit more torque than I'm comfortable with for a 10mm.

in a part number for hardware, 9956 tells you its a washer, 4 = aluminum (2 is copper) and then 1000 = 10mm ID

so like the oil drain plug is 9956-41-400 is an aluminum 14mm ID washer. 9956-21-000 is the turbo oil feed, copper, 10mm etc etc
Mazda has washers from i think 6mm to something like 24mm

Thanks for the additional info. I just measured the coolant drain crush washer gasket and can confirm that the inner diameter is 10mm and outer diameter is 14mm.