# Coolant Flow Direction



## DTM (Oct 25, 2007)

All,

Installing a Vintage Air system and need to install an inline value. Which connection is the "output" on a '70 455? The rear 5/8" one on the drivers side head or the 3/4" on the waterpump housing. I am thinking it si the one on the head... Can someone please confirm...

Thanks in advance,

DTM


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## DTM (Oct 25, 2007)

No one can answer this?


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## Billybobracing (Nov 24, 2016)

The water pump pushes coolant out to the heater core and the radiator. The port at the rear of the head is the return from the heater core.
Bill


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## PontiacJim (Dec 29, 2012)

DTM said:


> No one can answer this?


Well, here is what I found doing an internet search:

Coolant flows into the water pump thru the bottom radiator hose, into the block from the water pump, up into the heads, and then to the intake crossover (or heater core from the back pass side head), then back to the radiator via the top hose. Coolant from the heater core is returned to the water pump not to the radiator.

And this:

Hot coolant flows out of the nipple from the rear passenger side head. The return is on the timing cover.


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## brdngtn (Feb 1, 2020)

My radiator was boiled out and pressure tested outside the car I still see gunk when I drain so I wanted to flush the engine. I installed a flush kit, "T" in the heater core bypass hose and fitting for rad cap opening connected to a hose and ran the engine until discharge was clear (and warm). Upper rad hose remained cool, and after draining again I was unable to get even half of the original fluid back in.

My question is - did I flush the engine or just the radiator? I need to figure out the coolant flow path possibilities.

Warmed fluid obviously runs through the heater core long before t-stat opens. Engines should not self destruct due to plugged heater core so there must be an alternative path back to pump. Since we want the hottest fluid going to the heater core and also as a trigger for the t-stat, I assume t-stat resides in the alternate path. Coolant in the manifold flows past the t-stat and once the fluid is warm enough to open the t-stat, some is diverted through the radiator and is then combined with what did not do through the radiator and the heater core return. This means there are actually three sources for the inlet side of the pump right?

Ok, so garden hose water in the heater core return path is mixed at the pump inlet with the other 2 sources. Since I was adding a few dozen gallons of hose water to the heater bypass hose, and the only place it could escape is top of radiator, (and obviously not hot enough to open t-stat), one possible path can be through heater return directly to lower rad hose, flowing up (backwards) and out the top (and not flushing through the block at all). *This would eliminate the lower rad hose as a pump inlet.

Incoming hose water in the heater core return path is mixed at the pump inlet and that mix is pushed through the system or down lower rad hose and out, so discharge water getting warm but never hot is evidence of mixing and at least some of what passed through the block. My hypothesis is actual replacement of all the fluid in the system is gradual and asymptotic (never complete, just increasingly weaker mixture).

So asking the experts here, having run until discharge is clear, have I "flushed" the engine as well as is possible?


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## Lemans guy (Oct 14, 2014)

You can also open the two plugs or petcocks on each side of the lower block to completely drain the antifreeze from the block....the radiator lower peacock as well...


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## BearGFR (Aug 25, 2008)

Those plugs on the lower sides of the block can be hard to get to, especially with headers. The last time I had my engine out I replaced them with valves. I put short lengths of copper tube on them that exit at the base of the oil pan. Now it's easy whenever I want to drain the block, and coolant doesn't get into the starter or the solenoid.




















Bear


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