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Old 19-02-2006, 19:32   #1
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Fresh Water Pressure Caps

I have 2 18 hp Volvo Sail Drives - Some work was done on one engine at River Bend Marina in Ft. Lauderdale (Avoid if possible) in which the exhaust manifold was replaced and a new "radiator" cap installed. I have continued over heating on that engine (a prior issue) but the last time I had coolant in the bilge. The Original cap reads "75 kph" - the replacement cap reads (a US cap) "6.0". Does anyone know for sure, what pressure is "75 kph" in US terms?
I am thinking that the 6.0 cap may release at too low a pressure.


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Old 19-02-2006, 22:13   #2
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I assume the pressure is actually read in kilopascals on the old cap "kpa" 75 kpa equals around 11 psi so yes, seems to be too low if that is what the engine manufacturer calls for.


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Old 19-02-2006, 22:20   #3
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Named after the scientist Pascal.

Pascal was the first man to mess around hydraulic's, back during the circa late 1500 or 1600's?

Pascal's Law was derived from his findings about pressure within the chamber etc.

When I went to vocational school a number of years ago. This was the first chapter in our diesel book!!


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Old 19-02-2006, 23:06   #4
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I can't think of anything that the "6.0" would relate to. And it is surely too low for a radiator cap pressure. Even 11PSI is a little on the low side. I also would ahve thought the 75 would have been Kpa, not Kph, but I will take it as a typo. As Pete said, 75Kpa = 10.875 PSI or near as darn it to 11PSI.
The pressure won't "stop" the over heating, pressure allows a higher temp to be achieved before the water boils. But if you lose pressure early, the water will boil out and thus you will then get over heating. I would get a correctly rated cap on there pronto before you go doing some big damage.

Now why is it that the "so called proffesionals" are dropping the ball all the time. Darryl on here is having a nightmare over a Volvo install and bad bad workmanship, not to mention some seriously wrong advice from the Volvo agent and I have just been helping some very poor boatie with a major problem with his alloy prop and stern leg. The yard has painted copper based anti-foul on the things and they have eaten away. I will open a new thread with a photo of the prop.

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Old 20-02-2006, 19:40   #5
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Thank you all for your comments - I agree I must get a new cap. Volvo wants over $50 for the cap! I will look locally for a closer match.

Best Regards,


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