getting ready to go out for a spin the other day, I popped the rad cap to check the coolant and the spring and inner cap fell off ... I had not noticed the rusting ... so off the the parts store.

I easily found a size match but the cap on the car was 15 lbs and the one I found is 16 ..... I'm thinking no problem as the car's cooling system is FINE and a seldom see the temp go over middle on the (stock SMITHS) gauge.

I'm thinking no biggie .... and believe I'm actually seeing lower water temps (because the old cap's rubber seal was old and cracked so I was prbly losing pressure ...????) ... but this is really a seat of the pants feeling and could be a result of really nice weather on my last couple of drives.

This is a 1275 with stage 1, standard rad' (for a MINI 1000) with an overflow tube, but no recovery tank .... 1979 M-1000 set up with an A+1275 now .... 25% anti-f solution and regularly flushed ... a lil watter wetter for taste. A Florida car ... Cape Canaveral.

does the 1 lb make a significant difference????? Should I find a 15 lb cap?

 

I think OEM was actually 13 lbs......use the 16 till you can buy a 13?

 

by what's for sale at MiniMania

13psi up to 80, 15 later ....

7 for early 850 . . .

Haynes says 74 and beyond 1.05 bar, that's 15.22 psi

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found an article: Beating the Heat: Advantage of a High Pressure Radiator Cap

For a daily driver, the extra pressure would only be particularly helpful if running a modified coolant ratio. Installing one won't hurt anything. If you ever do approach boiling point, they'll give you a little more insurance against it, and they'll keep the coolant doing its job longer before the bubbles in the fluid create problems. ... How much does the pressure raise the boiling point? Well, it's about 2-3 degrees for every psi that we increase the pressure of the system.

since no hoses have blown and my temps are well with the 'normal' range, I'm not gonna worry about it.

 

Yeah, I think 1 pound over won't blow anything up.

 

and if the system is working well as I believe from the temps I see, aka I'm not getting close to boiling (under pressure) I'm not taxing the system . . . .

I'd repeat that I think the new cap has improved my system and lowered the engine temp.

WHY?

The old cap was at least 12 years old and when it broke and I looked at it, the rubber seals were cracked ... breaking down. Was the radiator doing its job or blowing off steam early ???????

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new item on my check list .... when checking coolant level ALSO check condition of the cap rubber!!!!