Question - Engine Block Coolant Drain Plug Size (1 Viewer)

[Will Van]

Can anyone confirm? Is the engine block coolant drain plug on the drivers side of the motor 3/8” BSPT?

I realize most people have to chip out the debris when they remove.

TIA!

 

[Steamer]

It's 3/8 bspt. Close to 3/8 npt but different pitch. 3/8 bspt is 19 tpi and 3/8 npt is 18 tpi.

1/2" bspt & npt are the only two that share the same pitch but slightly different taper. Mixing 1/2 bspt & npt seem to go pretty well.

I got mixed up and thought it was 3/8 that had the same pitch and I ran a 3/8 npt tap into my block so I could use 3/8 npt fittings. I know it's not right but it worked out fine. It was helpful for installing flushing setups and I now have a 3/8 npt full port ball valve on there that stays. Every couple of months I'll drain a squirt in case anything has settled there.

 

[Steamer]

And if your looking to do some thorough flushing you may want to search up "Flush" with me as the poster. Myself and others have come up with some fairly elaborate flushing methods with good results. Depends on how bad it is on the inside and how much effort is needed or how much you care to put into it.

 

[Rigger]

I think the OEM Toyota drain plug is still available.

 

[GA Architect]

Should you want to replace the missing drain cock, Toyota still has them in stock: 96431-03833.

 

[Will Van]

Thanks guys! I will definitely flush the cooling system, since I’m going to Toyota Red coolant and an upgraded radiator.

But I need the thread pitch so I can run my Holley Sniper water temp sensor. It is 3/8” NPT. So I wanted to make sure I ordered the correct adapter (3/8” BSPT to 3/8” NPT).

Has anyone just cut/tapped the threads for 3/8” NPT directly?

 

[GA Architect]

But I need the thread pitch so I can run my Holley Sniper water temp sensor. It is 3/8” NPT. So I wanted to make sure I ordered the correct adapter (3/8” BSPT to 3/8” NPT).

Has anyone just cut/tapped the threads for 3/8” NPT directly?

May want to reach out to @FJ60Cam for advice on the water temp sensor at this location. I believe he uses this location for his Sniper installs.

 

[Steamer]

Has anyone just cut/tapped the threads for 3/8” NPT directly?

Hmmm. You started out with block drain and not your talking heat sensor. A bit confusing.
Where are you putting the heat sensor for the Sniper?

 

[Will Van]

May want to reach out to @FJ60Cam for advice on the water temp sensor at this location. I believe he uses this location for his Sniper installs.

Great minds think alike! I’ve already spoken to Cam. He couldn’t recall if it was 3/8” BSPT.

Hmmm. You started out with block drain and now you’re talking heat sensor. A bit confusing.
Where are you putting the heat sensor for the Sniper?

Apologies, I should have clarified. The Holley Sniper water temp sensor installs in place of the OEM Toyota block drain. I was trying to confirm that I need an adapter for 3/8” BSPT to 3/8” NPT to thread the Holley water temp sensor into the OEM block drain hole.

 

[FJ60Cam]

May want to reach out to @FJ60Cam for advice on the water temp sensor at this location. I believe he uses this location for his Sniper installs.

We’ve talked. I’ve seen mention of NPT used by the legends on here and have always threaded the Holley and the GM temp senders directly into the block drain and thermostat housing without issue myself.

Using an adapter may be the most correct solution.

 

[Steamer]

Apologies, I should have clarified. The Holley Sniper water temp sensor installs in place of the OEM Toyota block drain. I was trying to confirm that I need an adapter for 3/8” BSPT to 3/8” NPT to thread the Holley water temp sensor into the OEM block drain hole.

Got it. I didn't realize you could put it there.

 

[FJ60Cam]

I just ordered some bsp/npt adapters to test out.

 

[Steamer]

I guess with the sensor in the drain I'd want to pull it now and then since it's the place where sediment loves to build up and may affect the sensor in time.

I wonder if the addition of an adapter may move the sensor out of the water flow and affect accuracy or response time.

These are only just my thoughts, as "my" Sniper is still sitting on my living room floor.

 

[KimoTheBJ40]

Keeping an eye on this to see how it all turns out. My temperature gauge is out and have been wondering what direction to go in fixing it.

 

[Will Van]

Keeping an eye on this to see how it all turns out. My temperature gauge is out and have been wondering what direction to go in fixing it.

The 3/8” BSPT to 3/8” NPT adapter works quite well for the Sniper coolant temp sensor.

Is it your OEM temp gauge that is out? Or an aftermarket 1/8” NPT temp gauge?

 

[KimoTheBJ40]

Is it your OEM temp gauge that is out? Or an aftermarket 1/8” NPT temp gauge?

OEM temp gauge.

 

[Will Van]

OEM temp gauge.

I'm not sure the 3/8" BSPT coolant drain plug would offer you any advantage over the stock location for the OEM temp gauge. The OEM location for the temp gauge uses a factory 1/2" BSPT port adapter from the head to the metric OEM temp gauge threads (M16 x 1.5).

Unless you are thinking about adding an aftermarket 1/8" NPT temp gauge? If that were the case you would need either a 3/8" BSPT to 1/8" NPT adapter for the coolant drain plug location. Or a 1/2" BSPT to 1/8" NPT adapter for the OEM water-temp (head) location.

(The water ports in the head are 1/2" BSPT. And the coolant drain plug is 3/8" BSPT).

Also, pay attention to the depth/length of the water temp probe you choose. There is not a lot of depth at the OEM water temp head location. You could damage a new probe if it bottomed out on the tip before tightening up on the threads.