Reply to "Overflow tank"

A few notes: the two OEM tanks -at least in the late '72s & newer, were nickel-plated both inside & out under that flat black paint . Careful paint removal produces a nice bling at zero cost. They may still corrode, though.

The small-tank clamp was welded to the rt. inner fender panel, and was lined with some type of foam. It rots & falls apart, leaving the tank not well retained. I've seen those tanks fall thru the stock clamp and literally drag on the ground- visible from behind the car! Check yours and use some type of rubber glued in (hi-temp glue) if necessary.

Replacing the big recovery tank with a plastic tank from a generic auto parts store should be done carefully. I did this a while back, and within a month, it started leaking. Because heat off the right header MELTED IT!

The connection from the rad cap overflow is 1/4" while the connection to the base of the big recovery tank is 1-3/8" and I've seen the most gawdawful conglomeration of amateur hose adapters down there to hook this up. Most of which leak air so the vacuum produced by a cooling engine will not pull water back into the main cooling system. Thus the engine "uses & loses water"....

The hose routing at the rad in the early Blue Owners Manual (and the TSBs) may not be how your car is plumbed. I tried it both ways and it made zero difference in stable operating temp on a 500 mile run whether colder water went into the top or in the bottom of a stock rad, regardless of theory.

'Vented' thermostats with two little air bleed holes drilled in them probably make the 8 extra feet of bleed hose from rad to tank superfluous. It may take a LONG time on the road to purge all the air either way. Quite a bit gets caught inside the cylinder heads.

Be sure you've replaced the swirl (small tank) radiator cap neck with a U.S-made one if you're using a U.S made cap. They are shorter than Euro caps and will not develop their rated pressure in an OEM tank neck made for longer Euro caps. A 16 lb U.S cap opens at maybe 12 psi. FWIW, a stock Euro cap was rated at 0.9 bar or 13.2 psi. The base of stock soldered cap-necks were often rough and won't seal except temporarily with a brand new cap; replacing the neck fixes both problems.

Do not try fixing boil-overs with an 18-22 lb NASCAR radiator cap. A 43-yr-old stock rad (and some aftermarket aluminum ones) was only tested to about 16 psi when new. First the rad tubes swell, then rupture at higher pressures and even good (not stock) hose clamps won't hold.

When upgrading the hoses and clamps, don't forget the 3" long section of heater hose under the dash. Often neglected, this one may rupture and scald your (or your passenger's) ankle while fogging up the windshield at high speed! This is the reason for manual cut-off valves in the heater lines.