"Harvey, Cole E" wrote:
> Hi all,
>
> I read some past posting about coolant overflow tanks, and made one for my
> SII. It is just a bottle with a hose that extends to its bottom with the
> other end connected to the pressure valve on the header tank. I ran the car
> and the bottle filled up, but as the car cooled the coolant did not return
> to the header tank. Am I expecting too much here? Is my pressure valve not
> functioning correctly? I was thinking that the coolant should be sucked
> back into the header tank.
>
> Thanks, Cole
Harvey:
I installed overflow tanks on my last Alpine and current Tiger, and they
completely solved the overflow problem. Plus, they allow you to completely fill
up your radiator all the way up to the radiator cap, and this might well improve
your overall cooling a bit too (it did on both my Sunbeams). In my opinion,
they are absolutely necessary for real world driving in a Sunbeam in warm/hot
weather.
You are correct in that the idea of the overflow tank/bottle is for excess
coolant to flow to it when the car is hot, and flow back into the radiator as
the car runs cooler.
I'm not that familiar with the Series II (I've owned Series Vs through the
years) and I know the radiator setup is a bit different, so I'm not sure what
you're referring to by "pressure valve". However, here's how your overflow
bottle needs to hook up: That hose from the bottom of the bottle needs to go to
the radiator fitting where you probably now have an overflow hose that just
spits the coolant onto the ground. Pull that hose off and put the hose from the
bottom of the overflow bottle there. Be sure you use a hose clamp around it
(clamping the hose to the radiator fitting, and you may also want to use another
clamp (I had to) where the hose comes out the bottom of the overflow bottle. Be
careful with that one if the bottle is plastic, as you want to tighten the clamp
enough to prevent any water/pressure loss, but not tight enough the crack the
bottle fitting.
That being said, for this to work, you must have a completely sealed cooling
system (no leaks anywhere, even very small "seepage"), or it won't work. If you
see any evidence of any wet, or dried coolant anywhere, you need to get that
fixed. When I installed the tank ($10 from Pep Boys) on my Tiger, it didn't work
at first and I discovered a pinhole leak around one of the radiator fittings.
Just enough loss of pressure to foil the coolant flow back into the overflow
tank. I had that welded up and it solved the problem. Also, make sure your
radiator cap is in perfect shape (maybe buy a new one, or have yours tested by a
garage to be sure), and I've heard that not all caps work with overflow tanks,
so ask the parts store about that, although I'm not sure about this issue. Also,
make sure you're using the correct radiator cap pressure. I use a 13 lb. cap on
the Tiger. If you use a cap with too high a pressure, though, you can cause your
heater core to leak, as that's the weak link in the system. I ended up having
mine re-welded and "end caps" welded on to it to keep it from bulging and
leaking. That could be a factor now, in that if you have everything under the
hood in perfect shape, the heater core could still have a very slight leak which
you might not be aware of. Do you ever get a coolant/anti-freeze smell in the
passenger compartment, especially when using the heater? That's almost a sure
indication of a heater core problem.
When you get the overflow bottle working properly, fill the radiator completely,
with the heater valve open, run the car to normal or hotter temps.(with the cap
on, of course), let it cool down (overnight is OK, you don't have to do this all
at once) and top up the radiator again, right to the top. You may have to do
this two, maybe three times. After you're all done, you'll probably want to keep
the overflow tank about 1/4 filled when cold, as this leaves enough room for the
coolant to expand into the tank, and then to be sucked back into the radiator as
the car cools.
Steve Sage
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