3 replies to this topic

[johnnyblaze]

hi eveyone

 

im going to put an expansion tank on my race mini 1330cc, one of these

 

 expansion.jpg   5.33K   1 downloads

 

what i dont know about is what radiator cap to run with it , i beleave it needs to be a recovery cap on the rad and i take it the same cap on the tank?

 

also what poundage cap 13lb,15lb more pounds? both caps the same poundage?

 

will be using a thermostat blanking sleeve is this makes any difference .

 

any advice be more than appreciated thanks

 

kerrin

Edited by johnnyblaze, 20 September 2013 - 10:07 AM.

[KernowCooper]

With a 88c Thermostat the normal is a 15lb Cap, I cant see a 15lb cap will cause any problem without one.

[johnnyblaze]

vizard says a 13lb i cant see how 2lb would change do much else so mayb try the 15lb caps then are they both ment to be recovery caps?

[dklawson]

The cap rating has two purposes.  It increases the boiling point of the coolant and provides a safety/relief valve for the system.

 

As the system pressure increases it move the boiling point of the coolant a little "higher".  That simply means that the engine can run hotter before coolant starts coming out of the overflow.  It does NOT mean that engine runs cooler.  Once the system pressure exceeds the rating on the cap the coolant will be released out the overflow as a safety mechanism.  

 

Therefore, you can run a higher pressure cap if you want to, all you are doing is moving the boil over point higher along the temperature curve.  However, doing so increases the stress on other parts of the system like hoses.  For example, if you are running old stock rubber hoses and a 15 PSI cap on an engine that tends to overheat, you are very likely to have a burst radiator hose at some point and a little less likely to burst a hose if you fit a lower pressure cap.  In short, a higher pressure cap increases the pressure of the system, raises the boil over temperature slightly, and increases stresses on other system components.