Tom, thanks for the comments!
I'm still chasing the prob. Current situation is: Still have the original
hose
to the water pump connected to the fitting on the head; system in that
configuration is tight, no leaks. Does not lift the old 14# cap, but running
too
hot.
> >I recall some time back you posted info about the pressure cap for the
> >cooling system recovery tank. Looked for that e-mail, but couldn't find
> >it.
>
> Actually the 7# cap is original.
>
> If the radiator has been recored with a modern core, it can withstand
> a 15 psi cap. The later caps, for the 1970 Datsuns (240z, 510, etc are
> all 14 psi... and work fine).
My radiator WAS either recored or replaced about 15 yrs ago, (don't remember
which). Running hot as I am, that new 7# cap just doesn't cut it, going to
exchange it for a new 14.
> Yep, heater hose is metric. 1/2" sounds correct.
>
> I like to buy the heater hose from an INDUSTRIAL SUPPLIER. Someplace
> that sells it for Kenworth or 18 wheelers. There is a GOODYEAR silicone
> hose that runs $3 to $4 a foot. Cheap insurance as it really does
> have a 20 year life. It pays to make sure the hose is Goodyear, Gates,
> anything quality.
>
> Avoid the hose from "discount auto supply" or what ever. About 50c/foot
> but horrible quality.
Interesting, the "wrong size" heater hose NAPA sold me was 54c/ft. I'll
definitely
look for good quality hose IF I decide to keep the heater functional.
> >As a temporary measure I've bypassed the whole mess by connecting the
> >return hose to the water pump directly to the outlet from the head.
> >(Actually, in Hawaii, this could be the final solution, since all I use
> >the heater for is VERY occasional "demisting").
>
> NO! I would NOT recommend doing this. Reason is the coolant normally passes
> through the heater, which is really a small radiator. The coolant is usually
> cooler returning back to the engine.
>
> You are better off just capping off the heater tubes in this case. This
>prevents
> hot water from bypassing the radiator.
>
> >BUT, with that bypass in place and the old (14# ?) cap in place, I'm
> >still running hot. The system is tight, now--no coolant loss. I just
> >used a Prestone flush for the cooling system, following their
> >directions. I had been running hotter than usual coming up the
> >mountain, for quite a while before the leak developed. A lot of the
> >cooling fins on the radiator front face have flaked off.
>
> Remove that "bypass".
Don't quite understand that, Tom. In the stock (1600) configuration, the
coolant
flow to the heater goes from a connector on the head, through the intake
manifold,
through a manual "diverter" valve, then through the heater exchanger, and
returns
via a pipe under the carb. heat shield, connected by hose to the water pump. It
seems to me that the flow through the intake manifold and back through the heat
shield pipe would essentially negate any beneficial heat exchange from the
heater
core. Anyhow, in doing my temporary bypass, the hose is kinked, thereby
limiting
flow, probably almost as effective as "capping" the head and water pump
connections.
> Good time to do a full tune up. Adjust valves, mixture, and timing. Make
> sure all the basics are covered first.
>
> You do not have one of those "thermostatic" fan clutches, do you? Fan
> should be locked to the water pump.
Nope, I have a spacer where the fan clutch was.
I had just accomplished ALL of the foregoing tune up items (remember my valve
adjustment messages?) Guess my big mistake was "bragging" that the Datsun was,
"running a lot better than it had in a long time!" thereby challenging Murphy
and
incurring a jinx ;-).
Until about a year or so ago, the engine would routinely operate with the temp
gauge indicating about 1/8th inch above the "140" mark. The "T" connector at
the
top of the radiator developed a leak at the brazed joint, and I removed the
radiator and had it rebrazed at a radiator shop. The guy at the shop remarked
about the deterioration of the fins of the front face of the radiator, and said
it,
"could affect my cooling". I said, "no problem, it tends to run cool, anyhow"
:-).
Until this most recent leak developed, it would routinely run at about 1/2
scale of
the temp gauge, even coming up my mountain. Now it is running with the gauge
indicating about 1/4-1/8" of the 240 mark as I pull into my garage after
driving up
the 1000 ft. elevation. No leaks or "dumping" at shut off, but I wouldn't want
to
go any higher up the road!
I guess I've never had a radiator "rodded" (whatever that is) or "backflushed".
Flush the cooling system as I did a 2nd time? Recore or a new
radiator?--alternatives I'm pondering.
Dave
'68 1600
Kailua-Kona
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