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O-ring for MD2030C sea-water pump

WalshamUK

Member
Joined
14 Jan 2011
Messages
108
I have purchased, and intend to fit, a new sea-water pump for my Volvo Penta 2030C engine. The pump requires an O-ring which is Volvo part number 3580380. It looks likely that the O-ring that has been supplied is the wrong size. Does anybody know what the dimensions of a 3580380 O-ring should be? Or failing that, if anybody has a 3580380 O-ring lying around, could they please measure its dimensions please and let me know what they are. Thanks in advance. Keith Jackson
 

duncan99210

Well-known member
Joined
29 Jul 2009
Messages
5,992
Location
Winter in Falmouth, summer on board Rampage.
I came across the same problem. The VP o ring isn‘t an exact fit, it’s a bit loose and you have to take care to avoid pinching it when you refit the pump. I got annoyed paying VP prices so measured the old one and bought just smaller, same size and just bigger from here O Rings & O Ring Kits: O Ring Cords, Adhesives, Lubricants & Gauges
I bought, 3mm section, 70mm diameter; 3mm section, 68mm diameter and 3mm section; 65mm diameter nitrile o rings. IIRC the 68mm ones did the job nicely.
 

WalshamUK

Member
Joined
14 Jan 2011
Messages
108
I came across the same problem. The VP o ring isn‘t an exact fit, it’s a bit loose and you have to take care to avoid pinching it when you refit the pump. I got annoyed paying VP prices so measured the old one and bought just smaller, same size and just bigger from here O Rings & O Ring Kits: O Ring Cords, Adhesives, Lubricants & Gauges
I bought, 3mm section, 70mm diameter; 3mm section, 68mm diameter and 3mm section; 65mm diameter nitrile o rings. IIRC the 68mm ones did the job nicely.
That is really useful information. Many thanks. The O-ring that came with my replacement seawater pump (original Volvo Penta pump from Keypart), and another 3580380 O-ring bought from the Volvo Penta dealer in La Rochelle, are both 3mm X-section, and 75mm diameter. And they both look too large diameter for the job. In fact they are larger than all of the 3 sizes that you quoted. Why would Volvo Penta supply oversize O-rings?
 

WalshamUK

Member
Joined
14 Jan 2011
Messages
108
Is it possible to measure the groove?
I would love to measure the groove, but I don't want to start the job with what are very probably wrong parts. Does anybody have photos and/or dimensions of the inside of the housing that the seawater pump goes into? Especially photos/dimensions of the O-ring groove?
 

duncan99210

Well-known member
Joined
29 Jul 2009
Messages
5,992
Location
Winter in Falmouth, summer on board Rampage.
The problem is that there isn’t a groove. Although the seal is an o ring, it isn’t being used in the normal way an o ring is: ie, a groove cut in the item which the ring seats in. The pump has a plain surface which mates with a flat surface on the engine, hence the ease of nipping the o ring when reassembling the pump. Also why the discussion on the best size of the o ring. The 70mm ring is the “correct“ size but is large enough to slip easily during assembly, hence my use of the smaller one which retained its position better.
Incidentally, when I nipped the o ring, I was in a remote location and could not get a replacement. Instead I made a paper gasket from several thicknesses of cartridge paper, liberally smeared with gasket gloop. Worked well enough to get me back to civilisation and a VP dealer.
 
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