Heater Hose Routing from Engine - Mysterious T

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Joined
May 27, 2018
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38
Location
Washington
I've got a bit of a mystery that I am trying to figure out. I'm cleaning up the engine compartment of my 74 FJ40 (Late Model F engine aka 1.5) and I noticed that there is a T in between the heater valve on the engine (#1 in picture) and the heater valve on the firewall (#2 in picture). One end of the T has a hose that goes to the Heater Valve on the firewall (#2) and the other end has a hose that appears to be plugged in to the block (looks like the block drain). Am I confused on what I am seeing or is this something that you all have seen before and if so, what would be the purpose?

Screenshot 2025-03-07 at 12.34.00 AM.webp
 
Its likely to aid in flushing the system.


Just so I understand, so you preeminently have a line connected to the engine drain so that when the T is switched it will route the heater water to flush the engine cooling system?
 
#11 screws into the top of the head at the rear of the engine. Mine got rusty so I replaced it with a valve

View attachment 3854740

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@Pighead but do you have a hose permanently plugged in to the engine drain plug (just below the farthest back freeze plug) that attaches to the valve you showed above via a T? That is what I am trying to track down?
 
Do you have a photo of the area? The sounds like a homemade setup to reverse flush the block. But I might be misunderstanding you.
 
@Pighead but do you have a hose permanently plugged in to the engine drain plug (just below the farthest back freeze plug) that attaches to the valve you showed above via a T? That is what I am trying to track down?
Nope. just an ordinary drain.
I'll show you mine if you show me yours...

20230828_133145.webp
 
Nope. just an ordinary drain.
I'll show you mine if you show me yours...
@hobbes & @Pighead here are the photos. The line that heads right (RED hose) from the T terminates in the engine drain. Snapped a pic but hard to see. Also there are no valves on the T so purely meant to perpetually split the flow toward the heater core and also to the drain plug.

Image1_EnngineCooling.webp


Image2_EngineCooling.webp


Image3_engineCooling.webp
 
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Pighead's photo shows the stock engine block drain.

My GUESS is that is a homemade reverse engine block flushing setup. Or maybe someone lost/broke the block drain and rigged that up to keep going. But again, that's a pure guess.

The black plastic valve on the other end isn't stock either.

Matt has some photos of new unions and a non-OEM block drain linked below. (I'd contact him before ordering anything to make sure he has anything in stock)

 
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Pighead's photo shows the stock engine block drain.

My GUESS is that is a homemade reverse engine block flushing setup. Or maybe someone lost/broke the block drain and rigged that up to keep going. But again, that's a pure guess.

The black plastic valve on the other end isn't stock either.

Matt has some photos of new unions and a non-OEM block drain linked below. (I'd contact him before ordering anything to make sure he has anything in stock)

It seems like a bad idea. Curious, what if any negative impact there is from this setup.

Regarding the black heater valve on the left - I have already ordered an OEM valve for the firewall and plan to replace what's there. I was looking at Matt's Union Valve here: ( THE ULTIMATE UNION HOSE BIB CAT'S MEOW ) Cylinder Head & Early Threaded Water Pump Outlet Heater Shut Off Valve / Hose Bib / Fitting Assy. Pet Cock 100% Made in JAPAN Chrome Plated Main body ALL BRASS Internals and Moving Parts Part # 87240-10010 - VintageTEqParts.com - https://vintageteqparts.com/products/the-ultimate-cats-meow-cylinder-head-early-threaded-water-pump-outlet-heater-shut-off-valve-hose-bib-fitting-assy-100-made-in-japan-chrome-plated-main-body-all-brass-internals-and-moving-parts-part-87240-10010?variant=40516013391957, but haven't ordered yet as I'm not sure if I need it... yet. I've just ordered a new block drain and plug end drain from SOR. Does anyone know what size hose that is between the Union heater shutoff valve and the firewall valve?
 
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