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Radior Cap Pressure


Guest Mr. Solutions
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Guest Mr. Solutions

Hi<P>The original radiator cap pressure on my car reads 7 pounds. What would the effect be if this was replaced with lets say a 15 pound one????<P>Reason for asking is I just had my engine overheat, and I mean **overheat**. It also appears that there is no water in the rad hoses; something I'll be confirming over the weekend. The only saving grace was that the temp. outside is currently -15C, so I could drive her a bit in this state, but never the less, the walk back was not nice!<P> frown.gif" border="0

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Well we're in the same boat it seems. Our car is a '51 Super and like you say the original cap was like 6 pounds as I remember but I have a new one that holds 15. The car was running hot earlier but that was due to a timing problem (too advanced). Ever since I got the timing right, the car has been running cool. We did however replaced the radiator, the water pump and we put in a 160 degree thermostat (the manual calls for a 151 degree but I couldn't find one that cool). So if it's overheating I don't think it's the higher pressure cap. If anything the higher pressure would make the water/antifreeze boil at a higher temp so it really can't be the cap (unless it's faulty). I would suggest checking the timing and reverse flushing the cooling system to make sure all the passages are open. I went to a local readiator shop and borrowed a tool that's like a power washer. It had a hook-up for a garden hose and one for an air hose so when you hit the trigger water came shooting out under pressure from the air hose. It worked quite well.<BR>Good luck.

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Guest Mr. Solutions

Hi Crin & Teresa <P>Thanks for the reply. I maybe should have added this in my earlier post, but I just had the entire cooling system flushed, but NOT reverse flushed. Do you think this could possibly have made any difference?

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I was told that it does. I reersed flushed it without even knowing that I was "reverse" flushing it. It was just easier for me to pump the pressurized water through the top hose than the bottom. It turns out that I was pumping water in the block in the opposite direction to the normal flow. Better to be lucky than good.<BR>Well, like I said, I was told by other members of this club that it does make a difference. But again please make sure to check your timing. On our car, after driving it for about 30 minutes the temp would just keep creeping up and if we had to stop at a light or soemthing it would really go up. Once we started moving it would not come back down. This is what prompted us to replace all the cooling items. It still did it. I then retarded the timing (by feel - maybe a degree or two) and that's what did it.

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Guest scott mich bca # 6619

Johan,<P>Have you replaced the 7 pound cap? I had an overheating problem with my '55, and believe it or not a new cap made a difference.<P>The reason I know this is I bought a new cap with the flip lever. It worked fine. When I was at the Buick National, I put my old plain proper cap back on, so I would not loose any points in judging.<P>When I left to go home I forgot to change the cap back to the new one, and experienced the overheating problem.<P>After it cooled down, I added more fluid, put the new cap back on, no more overheating.<P>So this would work, only if your cap is bad.<P>I also reverse flushed the heck out of the system, and it helped tremendously.<P>I would not use a different size cap, as you may damage something else.<P>Scott Mich<BR>Assistant Director<BR>Chicagoland Chapter<BR>1955-76C<BR>1959 Olds SS-88

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The radiator cap will raise the boiling point of the coolant.The radiator is like a pressure cooker. The more pounds of pressure the higher the temp will raise before boiling!Stant makes a cap checker to see if your old cap is releasing pressrue to early or late.your anti freeze to water raito could also be off. Thats what it sounds like to me. when its that cold your coolant can freeze in the block or radiator leaving the motor with no way to cool itself until the heat from the motor melts the coolant in the block and then in the radiator by this time its to late the motor has already over heated itself/ no water can flow to cool it. Im a machnic and have seen this first hand. But dont change the cap pressure your just asking for trouble. Hope this helps Tim

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Guest Mr. Solutions

Hi All<P>Thanks for all your replies.<P>64 Buick:<BR>Who / What is "Stant"; any web site?<BR>I was also running with a 50/50 coolant mixure, so I doubt that this is causing my [lack of heating] heating problem. I guess I can go up to a 60/40 mixure in my neck of the woods, but I've never had a problem prior to this.<P>I have also now replaced all my hoses on the cas... approx. 24 foot in all! I'll do a test run this coming Wednesday & we'll see then!<P>Thanks

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Johan:<BR> In anothr post you are asking about a block heater. If you remove a freeze plug you will have a good oppertunity to see how much debris is in the engine block and to clean it out...This will increase coolent capacity and heat transfer...and after 50 years there is usually an embarassing amount of junk in an engine block.<BR> bill

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