Why is my Studebaker radiator cap not a pressurized cap and every other vehicle I've ever owned pressurized? What is the advantage of a modern pressurized system? Lee Aanderud ------ I believe your '61 should have a 7lb. cap. oldcarfart@aol.com (Oldcarfart) ------ Early cars were not designed to operate under pressure or at higher temps. The boiling point of water increases under pressure. i.e. no pressure 212, 5l b 227, 10 lb 240 degrees. John Poulos ///And older cars with unpressurized systems had even a tougher time at altitude. You lose 2 degrees for each 1000 ft of altitude, so LOTS of cars overheated on the way to Tahoe. 7000' at Donner Pass lost them 14 degrees, so they were boiling over at 198, which was really easy to achieve driving up the grades. Those were definitely the bad old days!!! tom99999@pacbell.netwrks ///Dunno if they are still there, but when I drove to San Diego on I8 some 20 years ago they had 'Radiator water ahead' signs on that last westbound grade going up to the Roosevelt(?) National Forest area. After that it's downhill into town AFAIR. randee /// They still have such signs on some moutain overpasses. Also have signs advising you to turn off the car's AC while ascending. "Robert Kabchef" ------ What year Stude is it? Pressurized systems came into use by every manufacturer around 1940 (to pick a year, your mileage may vary slightly). The first systems were about 7# pressure. This lasted thru about '55 (to pick a year, your mileage may vary slightly). Then the systems were upped to 15#. ///My '50 Champion has the original,non-pressurized cap. /// It should be mentioned that while you can find pressure caps to fit earlier cars, installing one can cause damage to a radiator that wasn't designed with pressure in mind! That said, I've been running a 7lb. cap on the Transtar for several years now. While the Transtar would've had a pressure cap on it when it was built, I have a radiator from a 1950 2R16 in it because the original 1957-style radiator was destroyed in an accident. When I initially installed it (the cap) on the old style rad, the upper tank ballooned a bit. But that was 7 years ago and I'm still driving it like that! ///Along this line, has anyone tried putting an auxiliary cooling fan on an older Stude. My 37 runs fine on the highway but is lousy for slow cruising. Even the service bulletins warn that they will overheat. I'm thinking of getting an after market cooling fan. Converting it to 6 volt and trying it out this summer. Mike --------- Use as low a pressure as you can or you'll be blowing out at the seams. Some of the rad tanks will baloon and flex with each cycle. Solder will loosen and water will dribble... Ditto with heater cores... DJLevesque@webtv.net (David Levesque) --- I use 12-14 PSI caps on all three of our Hawks, always have. Also have overflow tanks, six blade fans, HD radiators (3 core on the GTs, 5 core on the 56J) and AC on all of them. I also use 195% thermostats year round. Never had a cooling system problem yet. Engine temps with AC on, in the desert (Palm Springs area) were usually around 210-220% when outside temps were 110-120%. When I lived there I had electric pusher fans in all of them. In stop and go traffic, on hot days, I'd turn the AC off and fans on. High pressures should not be a problem if the entire system in in good condition. When the engine temp exceeds the thermo opening temp: 160, 180, 195, whatever, the thermo has done all it can do (open up). Temps above the opeing point of the thermo are then caused by something else. jhall20613@aol.com (JHall20613)