Had the radiator cleaned and a small leak fixed. The guy at the shop gave me a 7lb radiator cap and told me I should use it instead of the 13lb cap I had been using. Put the rad back in today fresh coolant in and fired it up. Ran for a while then the temp started climbing and went past 210 so I turned it off figuring maybe a problem with thermostat. Checked the thermostat on the stove and it worked fine. Took all the hoses off checked for possible problems there and everything looked fine. Ran for awhile w/o a cap figuring maybe it needed burped. Put the cap back on ran it with the same outcome. Just kept climbing never went down as it should when the thermostat opened up. third time I tried running it but put the 13lb cap back on. Ran it till it hit 180 stayed there for awhile then started climbing. Hit the throttle once and the temp started dropping and stayed around 170-180 and ran as it should. Could the problem have been caused by having a cap with too little pressure or was the problem possibly an air pocket that finally got cleared out when I hit the throttle. Haven't tried running it with the 7lb cap again figured I check here first and save the gas. thanks for any input.
Probably you burped an air pocket. All the 7 lb cap does is cause it to boil @ a lower temp than the 13 would.
the 7 lb cap is to keep the tanks from getting messed up, older cars have large tanks, and since force = pressure X surface area, they can get bent up with too much pressure. Probably had an air bubble in it. I'd put the 7 lb cap back on. 210 is lower than the boiling point of water at sea level, so even with only a 7 lb cap it will have to get a lot hotter than that to boil over.
Before putting the 7 # cap back on do this. Get the front of the car up higher than the rest, such as car ramps or even a steep driveway. Let it idle until the thermostat opens, and allow the system to burp itself. Quickly shut it down, allow it to cool and fill to the recommended level. Cap back on and take a test cruise. As cold as it is in PA. today, you might have other issues that need to be addressed, good luck, TR
Yeah I was thinking it might have been a big burp. Next decent day I'll give those ideas a try.. Thanks for all the advice.
Someone once told me for every pound of pressure, you reduce the boiling point 3 degrees? That sound right?
3 degrees is about right, but it INCREASES the temp at which water will boil. Somthng I always do is drill a small hole - 1/8 or less - in my thermostats, allows air to bleed thru. I had a Cobra kit car that I could not get all the air out of the cooling system till I did that.
That is correct, You should run a 7# cap. It will keep the tanks from "swelling". But... If you want the coolant recover system to work. You won't find a 7# coolant recovery cap. Solution..... Take your 14# cap, and carefully heat the spring on the cap slowly cool in water immediately and you can lower your cap to 7#'s. Take it slow and everytime you check it (borrow a pressure tester). I have done hundreds of them. Also run a 160-180 Thermostat. Make sure nothing blocking front of radiator. If running conventional fan, make sure its at least 2in from core. If possible put shroud on it. Another hint. If you want to make a color scheme shroud. take a plastic garbage can heat up a knife and cut the garbage can the depth you need leaving "tabs" on the side to mount unit. Have fun guys. Just a OL Radiatorman LOL
huh? http://www.amazon.com/Stant-10228-Radiator-Cap-PSI/dp/B000B8N3FK I have one on my truck....it has the gasket.
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