Cooling system pressures are controlled by the radiator cap. The cap has a small disc at the bottom of the cap that is a vacuum valve. GM has changed the part number for the radiator surge tank cap on vehicles that came from the factory with Dex-Cool. The radiator cap is often overlooked in common engine overheating problems. Coolant that is boiling cannot transfer as much heat and overheating is likely to occur. … If the pressure on the system drops because of a failing radiator cap, the boiling point … I believe for a 383 2 barrel a 16 lb is the standard. That same mix at 16 pounds per square inch (psi) of pressure boils at approximately 250 degrees. Allstar Radiator Cap Small Stant 16 PSI ALL30124. The sudden decrease in pressure causes the boiling point to suddenly drop down, so that the entire contents of the radiator is suddenly boiling and spraying out all up in your face and all over everything else. It is designed to add pressure to the cooling system and increase the boiling point like grandma's pressure cooker. I have a buddy who's car would over heat in the texas weather. And the boiling point increases 2-3 degrees for each additional psi of pressure in the system. I've no idea what is listed for SBF. of pressure raises the boiling point about 2 degrees, over 2 at 212 and a little less per lb. ... all the 16 pound cap does is raise the boiling point of the water. cap gives at least a 250 F boiling point. ACDelco RC85 GM Original Equipment 15 P.S.I. If your gaskets, hoses, radiator are in great shape, that pressure should keep it from puking out coolant when shut down hot. This means that a cap rated at 13 lbs. Higher pressures are used to increase the boiling point of the coolant under arduous conditions i.e. The radiator cap actually increases the boiling point of the coolant by about 45 F. Functions of Radiator Pressure Caps. For every pound of pressure in a closed cooling system you raise the boiling point by three degrees. To understand why the cooling system is pressurized, consider that for every 1 psi over atmospheric pressure, a liquid’s boiling point is raised 3°F. A faulty radiator cap can cause your car to boil-over at a lower temperature, but is an easy and inexpensive DIY repair. At that point, the system is pressurized and helps control overheating and enhances system efficiency. Stant 10231 Radiator Cap - 16 PSI Vented. Below are functions of radiator caps in automotive engines: A radiator pressure cap keeps the system pressure at 16 PSI, which avoids the coolant from boiling off even when it gets hotter considerably. will increase the boiling point in a system by 39° F. High-performance caps range from 19 – 32 psi. I live at 6150' and a 13 psi cap boils at 250 for me. Sunday at NHMS we epoxied the radiator back together, put a 16 lb cap on it, and ran cool all day long. Each lb. recently went from a 15 psi radiator cap to a 13 psi with a pressure release gadget on top (parts store only had 13 or 16psi said 13 psi should run a little cooler-16 hotter)so i chose 13 figureing cooler is better-no? I always knew opening a hot radiator cap was a bad idea, but I guess I never thought about it much in these scientific terms before. Recovery system caps allow coolant to exit the cooling system into an overflow or recovery bottle as coolant heats and expands. A faulty radiator cap can cause your car to boil-over at a lower temperature, but is an easy and inexpensive D-I … This Stant 10231 Radiator cap 16 PSI with a Vented in case of over presser. However, straight water has a lower boiling point than a mixture. higher (3 psi times 15 psi cap). at atmospheric pressure, if exposed to 15 psi (a common radiator pressure cap), the boiling point will now be 45°F. Water boils at 212° F, increasing the pressure in a closed system increases the boiling point. My current radiator cap is a 13 psi cap and im looking at replacements that are either a 16 or 18 psi. Or does it really make a difference? Whereas water boils at around 212°F. 7 lb cap will work just fine. The radiator cap maintains system pressure to 16 pounds per square inch (psi) on most vehicles. A slowly failing, worn out or faulty radiator cap can result in overheating, loss of coolant or even major engine damage. A faulty radiator cap can cause your car to boil-over at a lower temperature, but is an easy and inexpensive D-I-Y repair. or NO…any comment on the difference between mfgrs 15 … I'd suggest running a normal overflow recovery cap and tank and make sure the radiator is full when up to operating temp, fill the overflow tank to about 1/3 with coolant and call 'er good. as the pressure and temp rise. At sea level, water boils at 212 degrees. Standard size caps fit 2-1/8" O.D. How does an increase in pressure affect the coolant is boiling point? This is because for every pound of spring pressure, the boiling point is increased by 3° F. Water boils at 212° F, increasing the pressure in a closed system increases the boiling point. Radiator caps hold pressures between 6-16 PSI for most automotive systems. Otherwise I can't see any real reason they didn't use a more standard 15 psi cap. Stant 10231 Radiator Cap - 16 PSI Vented. Higher cooling system pressure raises the boiling point of coolant to reduce the risk of overheating. So the over-simplified answer to the tech quiz is that, yes, a higher pressure radiator cap can help prevent overheating. The radiator cap ensures that this pressure remains constant. Also, they raise the coolants boiling point, about 3-degrees F for each additional (psi) above atmospheric pressure. ... raising the pressure at which your radiator cap releases is raising the boiling point of the fluid in your cooling system. So you should be good to around 240 degrees depending on coolant boiling point. And yes you should be running a 16psi/lb cap. You could use a 15 or 16 lb cap, all cooling system components should be tested to say 30 psi. Traditionally radiator cap pressures are generally in the 6 to 15 psi range. At higher elevations the boiling temperatures are all lower since atmospheric pressure is lower up here. x 3/4" deep necks unless otherwise noted. This allows the coolant to reach much higher temperatures without boiling away. The radiator cap controls this expansion and provides constant pressure on the system. A 20 lb cap will bring the boiling temperature of your coolant (water) to about 255 degrees. ... Hi Luigi, 16 psi is 16lbs, the PSI is "Pounds per square inch" Hence a 16lb cap. A faulty radiator cap can result in engine overheating, loss of coolant or major engine damage. For every pound of pressure exerted on the coolant in the system, the static boiling point of the coolant is increased by 3 degrees F. Keeping coolant in a liquid form allows the fluid to do it's job transferring heat to the radiator to be dissipated. I'm looking for a new radiator cap so as usual I go to look at Rockauto. 50/50 mix with a 16 lb. Ford might have been afraid that 16 psi would burst the heater core or maybe the radiator(?). Boiling point is rated at 133°C/271°F for Expert, and 136°C / 277°F for Factory Line, but only with a +1.5 bar (22 PSI) pressure cap! umm, hes talking about radiator caps not turbos. But because a radiator cap maintains pressure in the system, the boiling point is raised and the system is capped off. It is designed to add pressure to the cooling system and increase the boiling point like grandma's pressure cooker. By adding 16 pounds of pressure to the system you will raise the boiling point … That vacuum valve hangs down in the open position until the cap is subjected to rapid expansion of coolant or steam, which closes the valve in a sealed position. Compare that with typical coolant boiling points in my graph on post # 5 (138°C with 50/50 mixture). Higher pressure caps can boost the boiling point even more. The system is pressurized to increase the boiling point of the coolant, by doing so you allow the engine to run hotter without boiling off the coolant thru the overflow. racing or desert conditions. A high-pressure radiator cap is used to raise the boiling point. In all actuality, the formula is: for every 2 PSI increase (at sea level) you increase the boiling point 1* above 212*. It is designed to add pressure to the cooling system and increase the boiling point. Ideally, car cooling systems should maintain a pressure of around 13 to 16 PSI. Which one do i need? A radiator cap is the part of a vehicle responsible for containing engine coolant and ensuring that the cooling system remains under pressure. Radiator Caps are manufactured using either metal or plastic design depending on the vehicle manufacturer’s specifications. Every PSI increases boiling point 3 degrees. I don't remember ever seeing a 16 pound radiator cap before (really high PSI in my mind), I was thinking 8-10 would be more appropriate. The manufacturer told us that 20 psi would be no problem...it appears they were wrong. With the 1.3 the higher pressure is going to circulate coolant coolant faster, so it will cool the motor better at higher speeds. High-performance caps range from 19 – 32 psi. Stant 10227 Radiator Cap - 13 PSI. But anyways, you should be fine with either the .9 or the 1.3 cap. Radiator Caps are designed to seal the top of the radiator filler neck to prevent coolant loss, pressurise the cooling system and raise the boiling point of the coolant. This protects the system from boiling over at the top of the operating temperature range. So, pressurized cooling systems help prevent overheating and coolant loss. By increasing the pressure in the cooling system, the boiling point of the coolant is increased to 245 degrees Fahrenheit at 8 PSI. A radiator cap keeps the cooling system pressured which raises the boiling point. The cooling system uses pressure to further raise the boiling point of the coolant. Standard size caps fit 2-1/8" O.D. The new cap is 18 PSI (RC87 - part number 25713160), the old one for many vehicles was 15 PSI (RC75 - part number 10296465). FENIX: CAP1021.Upgrade your cooling setup with a Fenix performance radiator cap.Rated to 1.1 Bar / 16 PSI, this radiator cap will raise the coolant pressure and subsequently its boiling point - increasing your cooling system's heat capacity and performance. Radiator Cap. x 3/4" deep necks unless otherwise noted. The caps pressure rating varies by engine application anywhere from 13 – 16 psi. Higher cooling system pressure raises the boiling point of coolant to reduce the risk of overheating. 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