740/760 heater control valve

James Sweet · Aug 29, 2009

Does anyone sell a *metal* vacuum operated heater control valve? The
valve in my brother's 760T appears to be original, and I'm getting ready
to go through the cooling system.

I have seen places touting superiority of the plastic ones, but I have
personally had one snap clean in half, heard of others, and seen several
warped heads due to plastic radiator tanks failing. The problem is that
failure is catastrophic and coolant is lost before you even realize
something happened.

/g · Aug 30, 2009

James Sweet said:
Does anyone sell a *metal* vacuum operated heater control valve? The valve
in my brother's 760T appears to be original, and I'm getting ready to go
through the cooling system.

I have seen places touting superiority of the plastic ones, but I have
personally had one snap clean in half, heard of others, and seen several
warped heads due to plastic radiator tanks failing. The problem is that
failure is catastrophic and coolant is lost before you even realize
something happened.

I've never seen the metal ones, but sort of resolved to run the plastic
ones
a max of 100k miles. They seem to last that long. My routine when I buy
a new used brick, is to completely replace the cooling system. All hoses,
heater valve, water pump, thermostat. I've even pulled the metal heater
line
that wraps back around the engine, just to make sure it's ok.

My last replacement radiator was for the turbo, and I specifically asked
for
a full metal nissan, and got the nissan, but it still had the plastic end
caps. I was
in a hurry to take a trip and took it anyways. I have had original
radiators snap
the neck on me.

The other often forgotten weak spot in the cooling system is that damned
rubber seal for the thermo switch (electric fan?) on the passenger side. I
lost my
last 740 that way. Only hint I got was the enormous white cloud behind me
as
my coolant left. By that time, the guage was pegged, and it was over.

Do let us know if you find a metal one. Is there a possibility of
subbing in
something from another car?

good luck, /glenn

James Sweet · Aug 31, 2009

My last replacement radiator was for the turbo, and I specifically asked
for
a full metal nissan, and got the nissan, but it still had the plastic end
caps. I was
in a hurry to take a trip and took it anyways. I have had original
radiators snap
the neck on me.

Nissens, and yes, I've seen far too many plastic tank radiators fail
like that. When I got my 740, it had a shiny clean cylinder head and a
brand new looking Nissens radiator in it, I can guess why.

The other often forgotten weak spot in the cooling system is that damned
rubber seal for the thermo switch (electric fan?) on the passenger side. I
lost my
last 740 that way. Only hint I got was the enormous white cloud behind me
as
my coolant left. By that time, the guage was pegged, and it was over.

Do let us know if you find a metal one. Is there a possibility of
subbing in
something from another car?

That's a part I've never had fail. You can install that switch (for the
aux electric fan) in an inline adapter that goes in the lower radiator hose.

As for the valve, all the ones I've found so far are plastic, the plan
is to just replace it regularly with the timing belt.