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10-01-2008, 17:08
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#1
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Registered User
Join Date: Mar 2004
Boat: Pearson 323 Vision Quest
Posts: 40
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Heat exchanger pressure cap size ?
Hi Everyone,
I have a 1977 Volvo MD11-C 23 HP Diesel. I think it may need a new pressure cap, I'm loosing coolant. The existing cap has engraved on it
7 lbs, this sounds low to me so can anyone give me some feedback before I buy a new one ????
Thanks again - Bob
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10-01-2008, 17:40
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#2
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Now on the Dark Side: Stink Potter.
Join Date: Aug 2003
Location: Palm Coast, Florida
Boat: Sea Hunt 234 Ultra
Posts: 3,962
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Don't know about Volvos, but the Perkins has a 7 lbs cap..Not on the heat-exchanger, but on the reservoir tank.
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Life is sexually transmitted
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10-01-2008, 18:53
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#3
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Registered User
Join Date: Mar 2003
Location: Philippines in the winters
Boat: It’s in French Polynesia now
Posts: 11,368
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7 to 10 pounds is average for most cooling systems. What it does is raise the boiling point of the coolant to around 250º F.
Without a pressure cap and recovery tank it allows the coolant to vaporize and dissipate.
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Faithful are the Wounds of a Friend, but the Kisses of the Enemy are Deceitful! ........
The measure of a man is how he navigates to a proper shore in the midst of a storm!
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17-10-2008, 18:13
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#4
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Registered User
Join Date: Apr 2005
Location: Apollo Beach, Fl
Boat: Privilege 37
Posts: 537
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Volvo Pressure Cap
Quote:
Originally Posted by delmarrey
7 to 10 pounds is average for most cooling systems. What it does is raise the boiling point of the coolant to around 250º F.
Without a pressure cap and recovery tank it allows the coolant to vaporize and dissipate.
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I have a Volvo 3cylinder diesel (MD2030B) and I need a new pressure cap. The existing cap has "09" stamped on one of the ears. Can I assume that means 9 lbs and not some metric unit of pressure?
Also, I found caps in the auto parts store that fit, but their pressure ratings are 16, 18 & 20lbs. I wonder why autos would use higher pressures than marine diesels? Mostly because I can get them for 4 bucks and no shipping.
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Greg, SV Cat Tales
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17-10-2008, 18:25
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#5
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Registered User
Join Date: Jun 2005
Posts: 1,901
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Quote:
Originally Posted by svcattales
I have a Volvo 3cylinder diesel (MD2030B) and I need a new pressure cap. The existing cap has "09" stamped on one of the ears. Can I assume that means 9 lbs and not some metric unit of pressure?
Also, I found caps in the auto parts store that fit, but their pressure ratings are 16, 18 & 20lbs. I wonder why autos would use higher pressures than marine diesels? Mostly because I can get them for 4 bucks and no shipping.
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probably 0.9 Bar
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17-10-2008, 18:51
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#6
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Registered User
Join Date: Apr 2005
Location: Apollo Beach, Fl
Boat: Privilege 37
Posts: 537
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Quote:
Originally Posted by never monday
probably 0.9 Bar
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Thanks. Converting to PSI, that should be a little over 13. Would the auto parts store 16psi cap work or could I do damage to heat exchanger? (I don't have an expansion tank. Cap fits on top of heat exchanger)
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Greg, SV Cat Tales
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17-10-2008, 20:16
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#7
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Eternal Member
Join Date: Aug 2006
Location: North of Baltimore
Boat: Ericson 27 & 18' Herrmann Catboat
Posts: 3,798
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Shipping a pressure cap by USPS should cost much more than a buck and a half
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18-10-2008, 05:20
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#8
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Registered User
Join Date: Jun 2005
Posts: 1,901
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Quote:
Originally Posted by svcattales
Thanks. Converting to PSI, that should be a little over 13. Would the auto parts store 16psi cap work or could I do damage to heat exchanger? (I don't have an expansion tank. Cap fits on top of heat exchanger)
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you should either have a tube from the rad cap neck going to an overflow tank or the bilge. I wouldn't run a 16# cap.
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18-10-2008, 06:47
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#9
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Registered User
Join Date: Apr 2005
Location: Apollo Beach, Fl
Boat: Privilege 37
Posts: 537
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Quote:
Originally Posted by never monday
you should either have a tube from the rad cap neck going to an overflow tank or the bilge. I wouldn't run a 16# cap.
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Thanks for the advice.
__________________
Greg, SV Cat Tales
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18-10-2008, 08:22
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#10
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Registered User
Join Date: Mar 2003
Location: Wherever the boat is!
Boat: Marine Trader 34DC
Posts: 4,619
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Quote:
Originally Posted by bob_deb
Hi Everyone,
I have a 1977 Volvo MD11-C 23 HP Diesel. I think it may need a new pressure cap, I'm loosing coolant. The existing cap has engraved on it
7 lbs, this sounds low to me so can anyone give me some feedback before I buy a new one ????
Thanks again - Bob
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Bob, My first question would be, are you sure you are loosing coolant from the pressure cap? If you can physically see it then OK, otherwise look at all possibilities also.
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18-10-2008, 21:53
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#11
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Eternal Member
Join Date: Aug 2006
Location: North of Baltimore
Boat: Ericson 27 & 18' Herrmann Catboat
Posts: 3,798
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What is the fluid level when engine is cold?
A lot of people fill their heat exchangers to the top.
If you don't have an overflow, expansion will cause it to drain out.
When the engine cools....you will have air there.
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