Coolant leak, not the Bypass hose

[g8rb8t]

Hey guys -

Getting deeper into the mechanical side of my truck and learning a lot as I go thanks to this board. Recent update is last year or so I replaced my radiator and upper/lower hoses. The truck has been running great ever since.

Yesterday I noticed a coolant leak at what I thought was the bypass hose and replaced it ('74 302 and as I understand coolant capacity is 4 gallons).

A few items I noticed:

1. Draining with the radiator cap removed only yielded approx 1 gallon of coolant, expected a lot more?? Got the hose replaced and it only took just over a gallon to top off the coolant... Any ideas why it tops off with only a gallon?

2. After replacing the hose and topping off, it appears the leak is in the gasket where the bypass hose connects (Thermostat housing). Wondering if I should just replace the entire housing with a cast Thermostat housing or just go with a new Thermostat gasket? See the attached picture for the drip location

Thanks for thoughts.

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[toddz69]

Very common area for a leak - many of us have horror stories with leaks from that juncture. I'd start with a new gasket and see if that fixes it. There are a lot of tips and tricks to get a good seal there. I like to use a paper gasket with a thin coat of some type of gasket sealer/maker on both sides. I use the Right Stuff AND let it set up overnight before I refill the cooling system.

Todd Z.

 

[g8rb8t]

Thanks a ton Todd! Appreciate the help (as always).

Any thoughts on the 302 coolant capacity? Only appeared to drain about a gallon? Searching the site appeared to show 4 gallons(?)

 

[Broncobowsher]

As stated, common leak point. Rarely will it need a new housing. The shiny chrome ones leak worst.
The housing can warp, usually with dropping the thermostat out of the groove and over torqueing the bolts trying to stop the leak.
Corrosion can also be an issue.

As for the only a gallon, you didn't actually drain the cooling system. You only drained the radiator. There is a lot of water left in the engine, heater core, etc.
Add the assumption that you are dealing with something that is stock and in like new condition. If the cores are plugging up with corrosion, that will displace coolant as well.

 

[nvrstuk]

What everyone said but you can flatten the gasket sealing surface easily with a block of wood with sandpaper wrapped around it. Clamp the block down and then slide the tstat housing back and forth till the wear pattern is even.

Then use excellent quality sealant and follow the dang directions! lol

 

[DirtDonk]

And if all you did was pull the bypass hose, you didn't even drain the entire radiator.
I've had my doubts about the 4 gallon reading over the years myself, but as said there's a lot more to it than just the radiator. The tubes are small, but you also have an entire engine block and intake manifold, a modest size heater core and hoses. So there are a lot of other areas for liquid to hide.

 

[g8rb8t]

Thanks!

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