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Radiator cap on a BN1

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bighealeysource

bighealeysource

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Hey all,
Quick question - I replaced my older and non original radiator
cap with one rated for 7 lbs and higher boiling temp and think
I made a mistake. Should I go back to the standard cap
which is rated for 4 lbs ? Seems like now if the car sits
for any period of time I start to become a steam locomotive
which was not a problem before replacing the old cap.
Any suggestions ?
Thanks,
Mike
 
The radiator cap for a Healey needs to be 1" long as opposed to the normal 3.4"--if you have the short one you will not get a good seal. NAPA makes a proper cap but I do not have the number--take your old cap to the dealership and have a sharp-eyed parts guy find you the correct one which should be 7psi. If you do a BCF search in the Healey forum putting in "radiator cap" and "Dave Russell" you'll probably find a post with the correct NAPA number.

Dave knew just about everything....
 
Mike -

To be honest, there is no need for a 7 lb cap on a 100 if your car is in proper working order.

Before going to something like increasing cooling system pressure (which the 100 motor was originally designed to work with an open atmosphere cooling system), you should really make the relatively small effort to get your cooling system in order.

The 100 motor, when as set up from the factory, will be very cool even in the warmest of conditions, even in stop and go traffic.

Most importantly:

1) Get your radiator core rodded. This is a cheap thing to do and makes a HUGE difference.
2) With the radiator out, remove the thermostat and put a strong force of water through the bottom hose first (to blow out scale through the top hose) and then reverse the direction. It may take a few minutes but there will be alot of crud in your block.
3) Go to British Car Specialists and get one of their 160 deg balanced sleeve thermostats. It's a little over $30 but to be honest because the throat is so big, it removes any restriction on the water flow, allowing hot water to get out of the motor faster. This thermostat makes a big difference.
4) I see you live in Hilton Head. It doesn't get that cold down there, so run 80%to90% distilled water to 10% to 20% coolant. Add Redline Water Wetter. Use a very high quality coolant and flush and replace annually. Water works MUCH better moving heat than coolant... trust me on this one.
5) A good thing to do is have the header & little heat shield Jet Hot coated w/ Extreme Sterling. This reduces heat under the bonnet and reduces problems with boiling fuel. It also helps keep the motor cool by pushing heat out the back rather than heating up the engine bay & your engine.

I run my A90 (exact same set up as a 100, but with an open atmosphere cooling system) in heavy traffic in tropical Hong Kong, and the car runs cool under most conditions. I do have a supplementary electric SPAL fan, but to be honest it only engages on rare occasions.

Alan
 
As an aside, if I reside in a temperate zone at sea level with an ambient min temp of around 30C then the expansion of the water in the rad would not be as great as say someone who is in a colder zone, just wondering if I need a 7lb, or would a 5lb suffice?
 
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