Does anyone know what size the plug in the tstat housing is? I thought it was 5/16" hex but cannot really tell. It could be square. Its 15 years old probably.

Its super tight and wanted to try and be sure before laying into it.

 

Checked Bob's site to see if he mentioned the size. He only says it's a 3/8" NPT plug. That should at least mean it's a standard alan wrench (of socket) to get it out.

That plug has been out of my truck for years, and my recent water pump replacement I don't remember what size it needed to remove it.

If 5/16" feels like it fits, I'd go with that. If it's too loose, try something metric.

 

It's a 5/16 square fitting

 

Plug drive configurations can vary. My OEM water pump (replaced at 98k miles) had a 7/16" external square head 3/8'' NPT plug. I still have the pump and could verify this. I replaced the pump before later adding a DIY coolant filter set up. The replacement pump had the allen head plug, if I'm not mistaken, that was removed during the filter install.

 

Coolant filter? Sounds like a great idea. I love this place. Where does one put his hands on said filter system? Is it like a flow through fuel filter, or is it a canister, or what? Sorry about the hijack... as far as I know the plug is 7/16" NPT.

 

Welcome to guzzle's Coolant Bypass Filter Mod Web Page

 

That is why i want to remove the plug. Sinister and riffraff both have the filter kit premade for sale. I got some really nasty stuff when I did the flush and hose change

 

Thanks!!!!