radiator cap
- Thread starter JanP
- Start date
petehoovie
Well-known member
What is the year of your car? Is the radiator original/stock?
If your loosing water with a 7 lb cap either the cap is no good
or not seating at the bottom or there is a compression leak. G.M.
Jan P. I have no idea what year radiator you are talking about, but here goes, with my thoughts on a mid 40's era radiator.
My guess is that it depends on what your radiator was built for. Here is a snippet on Canadian Ford military radiators.
Early in WWII they were not pressurised
With the introduction of a 3.5 lb pressure valve in (Bren carriers and likely trucks, brought on by the need for a closed system in the North African desert) they found that the seams in the tanks were letting go, so they modified the components in production to have wider laps (for the soldered seams)
Radiators of that era were well made of relative heavy materials, but the top tank design does not lend its self to high pressure, in my opinion.
I think that if you have a radiator that wasn't made for a pressure system, that you are going to split seams and crack top tanks etc. If you have a rad that was built to be pressurised, that it is probably still only good for a 4 lb system.
From an open system to a 4 pound pressure system raises the boiling point of the system about 3 1/2 degrees per lb, About 14 degrees F. at sea level, from 212 to 226 F. which is significant if you think about it.
My guess is that it depends on what your radiator was built for. Here is a snippet on Canadian Ford military radiators.
Early in WWII they were not pressurised
With the introduction of a 3.5 lb pressure valve in (Bren carriers and likely trucks, brought on by the need for a closed system in the North African desert) they found that the seams in the tanks were letting go, so they modified the components in production to have wider laps (for the soldered seams)
Radiators of that era were well made of relative heavy materials, but the top tank design does not lend its self to high pressure, in my opinion.
I think that if you have a radiator that wasn't made for a pressure system, that you are going to split seams and crack top tanks etc. If you have a rad that was built to be pressurised, that it is probably still only good for a 4 lb system.
From an open system to a 4 pound pressure system raises the boiling point of the system about 3 1/2 degrees per lb, About 14 degrees F. at sea level, from 212 to 226 F. which is significant if you think about it.
4 lbs pressure is not going to hurt a radiator in reasonably good condition.
Skip has been selling a 3.5 lb pressure valve that is fitted to the bottom of
the over flow tube on early radiators that were not made for pressure caps.
Raising the boiling temperature has nothing to do with making the early
Ford radiators pressurized. The flow in these radiators is restricted by the
length and the 144 tubes causing the water to back up in the top tank and
then is lost out the overflow tube. The answer is not less water in the
radiator which causes the engine to run hotter. The solution is a pressure
cap with a low operating pressure that keeps ALL of the water in the
radiator AND also act a safety valve to release pressures over 3.5 in the
case of Skips valve or 4 lbs on the early Ford pressure caps. An engine
running under 212 degrees will have less than 3.5 lbs and no water will
be added for over a year. Another problem is most old Ford engines have
some slight internal water leak, a bottle of Barr's heavy duty stop leak
in almost all cases stop this leakage. One indication of a leak is water
out the exhaust at start up or air bubbles in the radiator. There may be
a little from condensation for a few minutes but if it continues it is a leak.
Even water pumps can have a pin hole casting leak or a slight crack on
the 32 to 36 pumps from a freeze up. These cracks are hairline and
usually on the curve right behind the pulley and can be welded. G.M.
Skip has been selling a 3.5 lb pressure valve that is fitted to the bottom of
the over flow tube on early radiators that were not made for pressure caps.
Raising the boiling temperature has nothing to do with making the early
Ford radiators pressurized. The flow in these radiators is restricted by the
length and the 144 tubes causing the water to back up in the top tank and
then is lost out the overflow tube. The answer is not less water in the
radiator which causes the engine to run hotter. The solution is a pressure
cap with a low operating pressure that keeps ALL of the water in the
radiator AND also act a safety valve to release pressures over 3.5 in the
case of Skips valve or 4 lbs on the early Ford pressure caps. An engine
running under 212 degrees will have less than 3.5 lbs and no water will
be added for over a year. Another problem is most old Ford engines have
some slight internal water leak, a bottle of Barr's heavy duty stop leak
in almost all cases stop this leakage. One indication of a leak is water
out the exhaust at start up or air bubbles in the radiator. There may be
a little from condensation for a few minutes but if it continues it is a leak.
Even water pumps can have a pin hole casting leak or a slight crack on
the 32 to 36 pumps from a freeze up. These cracks are hairline and
usually on the curve right behind the pulley and can be welded. G.M.