[Aaron65]

OK, these may be dumb...sorry!

I'm going to replace the old heater hoses on my '74 Firebird, and I'd like to install a shutoff valve (just in case the heater core would start to leak).

What direction is the coolant flow to the heater? I'd like to install the valve on the inlet hose, of course. It seems like it would come from the back of the engine into the heater and return to the water pump, but I might be all wet. HA!

Finally, what size is the heater hose to the water pump? The other one looks like a standard 5/8" hose, but the water pump one seems larger.

Thanks!

[form74]

The Water Pump hose is 3/4'".

I think the water returns to the head and flows from the water pump

[kate`s67gto]

Here is a pic of Buick water flow. Pontiac is the same as Buick.

[Aaron65]

Thank you both!

[dmac]

I wouldn't use a shut-off valve, unless you put one in each hose. Generally, you can just bypass the heater core using one hose going between pump and head.

If you put in a valve, there will still be water pressure on both sides of the valve. Maybe not much, but enough, especially at higher temps.

[Overkillphil]

Feed from the passenger side head to heater core connection (buried behind wheel well) is 5/8", while return from heater core to timing cover is 3/4".

[77HANDMEDOWN]

When it's hot there is pressure. So even if there weren't pressure on the return with the valve closed and the engine running, as soon as you killed the engine the pressure would push it back to the heater core.

[STEELCITYFIREBIRD]

Do you know to split-cut-peel the hoses off the heater core and not pull and twist etc to get it them off w/o damaging the core?
If not I'll explain.

[Aaron65]

Originally Posted by 77HANDMEDOWN

When it's hot there is pressure. So even if there weren't pressure on the return with the valve closed and the engine running, as soon as you killed the engine the pressure would push it back to the heater core.

That makes sense...didn't even think of it.

As far as the split, cut, peel technique, I'll get out the carpet knife before I begin. Those heater cores are fragile, and those hoses are old!

[HWYSTR455]

I use anti-seize on the heater nipples to prevent stick/damage.

Why block it off? What's the intended goal? I can't see a good reason to do so, other than maybe reduce interior temps some. (which it really doesn't do by much)

.

[TedRamAirII]

Water flows OUT of the head to the core and from the core TO the water pump. The larger hose is 3/4" . I think it helps cool at least the right side head to flow coolant through it to the core. Maybe to have both heads flow to the core would be even better? I would not do it with a stock type. engine though. Running the heater will in fact help a overheating engine cool. As was said, be careful not to damage the heater core pipes. treat them like they are glass, or you will be putting a core in. ; )

[Aaron65]

Originally Posted by HWYSTR455

I use anti-seize on the heater nipples to prevent stick/damage.

Why block it off? What's the intended goal? I can't see a good reason to do so, other than maybe reduce interior temps some. (which it really doesn't do by much)

.

The car's been sitting around, and probably has the original heater core. I was just thinking of a way to shut off flow in case it were to rupture (that happened to me once!) or otherwise start leaking.

[HWYSTR455]

Just carry a hose reducer and put the two hoses together if it fails. You can just cut the hoses right at the core nipples at that point, or even pull to your' heart's content. (No worry of damaging the core at that point). Oh, and carry some spare antifreeze too.

.

[LPete]

I remember working on a car with a heater valve that looked like an "H" -- it had a leg in each hose, with a valve in the connecting piece that opened to allow bypass flow. I'm thinking it was a Chrysler or GM, but that's a guess. You could look in a book at a parts store if you have some time. No idea if the hose sizes would be right.