This is topic Radiator cap pressure ? in forum Tech Talk at Northern California Ford Owners  .


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Posted by SnakeBit (Member # 8871) on :
 
So I just received my new Alum. Radiator from Mishimota it included a 19 lb cap. By using a higher pressure cap, what does that do to the system. I have a new hoses with new Ford Racing Alum water pump also.
 

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Posted by sydewayzLX50 (Member # 10217) on :
 
I believe it makes the boiling point of the water higher but also puts more pressure on the hoses, radiator, etc. if the cooling system is in good shape u should be ok

[ January 26, 2011, 09:56 AM: Message edited by: sydewayzLX50 ]
 

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Posted by racsirx (Member # 1710) on :
 
Trust me, you dont want to put a high pressure radiator cap, I learned the hard way. I put a Moroso high pressure race radiator cap and to keep the water from filling up the reservoir quickly. Well the pressure was so high when I blew a headgasket during a pass, that it found the weakest link, the radiator hose, blowing a hole in the radiator hose and water went everywhere causing me to hit the wall.


 

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Posted by sydewayzLX50 (Member # 10217) on :
 

quote:

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Originally posted by racsirx:
Trust me, you dont want to put a high pressure radiator cap, I learned the hard way. I put a Moroso high pressure race radiator cap and to keep the water from filling up the reservoir quickly. Well the pressure was so high when I blew a headgasket during a pass, that it found the weakest link, the radiator hose, blowing a hole in the radiator hose and water went everywhere causing me to hit the wall.

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quote:

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Originally posted by JohnB:
Straight from Stewart Components website:

"In a cooling system, a higher pressure equates to a higher boiling point for the coolant. Higher coolant pressures also transfer heat from the cylinder heads more efficiently. We recommend using a radiator cap with the highest pressure rating that the radiator is designed to accept. In general, performance radiators will accept 22-24 PSI, and professional racing radiators will accept a 29-31 PSI.

The coolant will typically only build to 16-18 PSI, due to expansion up to 200°F. However, if the engine does overheat due to external factors, the pressure inside the cooling system could reach as high as 28 PSI. Once the radiator cap has opened and vented coolant, the engine will not cool down until it has been turned off. The radiator cap is basically a "safety valve", so always use the highest pressure radiator cap that the radiator will tolerate. If you are unsure of the pressure rating for your radiator, check with the manufacturer for the maximum recommended operating pressure."

Layman's terms? Radiator cap is for the radiator...not the cooling system. Bursting pressures, in SAE ratings, are applicable to all hoses...no matter the size. Of course, rating pressures and capacity decrease when diameter is increased (a 1/2" hose will be stronger than a 2" hose) but a radiator hose, for example, is supposed to hold a minimum of 90 psi on a SAE20R5 rating (the lowest rating allowed..)

With that being said, and the example given above...where did the problem occur? Had nothing to do with the radiator cap, and everything to do with a cylinder head gasket that either failed/head that lifted/or a block that is transferring cylinder pressure into the coolant system...or a bad hose/bad clamp.

To the OP, you will be fine running the cap supplied with your radiator.

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Thanks for taking me to Radiator Cap Pressure 101

 

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