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Old 22-08-2017, 11:41   #1
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volvo penta metal tube disassembly

Hello,

We need to remove our thermostat. Today, in looking at the engine, it occurred to me that there is a metal tube connecting the heat exchanger and the thermostat housing. I'm fairly confident I can disassemble the unit, but how to re-assemble without leaks.

The parts diagram shows a "sealing washer". Does that washer require permatex or some or sealing agent to seal the metal tube to the thermostat housing? Is the contact pressure from the housing on the tube enough to ensure no leaks?

My engine has many of these metal tubes, so I imagine there is a way to do this. Neither the service manual nor operator's manual mention anything useful. I have some experience working on cars but metal on metal is usually welded.

Any help appreciated.
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Old 22-08-2017, 14:48   #2
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Re: volvo penta metal tube disassembly

The sealing washer is in fact a rectangular section "O ring" and you will have the best chance of a successful job if you get a hand full of new rings and replace any of them that you disturb. While you are in there, install a new seal ring for the thermostat as well.

Depending on the condition of the surrounding housing a sealant may or may not be necessary.

DougR
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Old 22-08-2017, 15:00   #3
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Re: volvo penta metal tube disassembly

DougR is the expert on these. I assume this is a 200x Volvo. The seals can be a real pain to get sealed and to keep sealed. In theory they go dry. There were two slightly different sized Orings on my 2003. Get new ones if you can. Also the heat exchanger mount has a slot in it allowing it to slide a bit for and aft. This eases making the hardpipe connections.
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Old 22-08-2017, 19:04   #4
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Re: volvo penta metal tube disassembly

Thanks Doug,

I'd already got seals for the thermostat and tube, I'll make sure to get them for any other tube i might move around.

Any recommendations on sealant brand?

Thanks Paul,

Engine is a vp 2003b. Thanks for the tip on the exchange slide.
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Old 22-08-2017, 23:15   #5
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Re: volvo penta metal tube disassembly

For me, if the mating surfaces are still in tack with no corrosion or worn down area's the simple use of Vaseline or O Ring rubber"grease" or white lithium grease all help with location of the pipe and seating of the O Ring,

As with many lovely Volvo engines and there use of copper pipes/ rubber O Rings and Aluminium housings many suffer from Galvanic corrosion leading to pitting and in many cases severe under cutting of the Aluminum Housing where i have seen numerous attempts to repair using epoxy fillers/RTV sealants all having limited success depending on the severity,

Personally i had the best success using DURALAC www.llewellyn-ryland.co.uk/downloads/duralac.pdf in these worn damaged aluminium housings

This is paste used for dissimilar metal combinations (yes including rubber) and works very well as it stops Galvanic corrosion issues and also seals and fills in the worn area's it never gets rock hard but hard enough to seal and allow minor movement, it's like placing a Zinc anode around your joint

Cheers Steve
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Old 23-08-2017, 20:05   #6
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Re: volvo penta metal tube disassembly

Also ... Make sure you get the old seals out. It is always possible that one got left in place from a prior job. They can be hard to see.
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Old 23-08-2017, 21:39   #7
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Re: volvo penta metal tube disassembly

Thanks all,

Given potential for leaks and given our sailing season ends in less than 2 months, we will add this to our growing fall winter do to list. I'll update with our success at that time. Thanks again.
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Old 23-08-2017, 23:16   #8
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Re: volvo penta metal tube disassembly

Hi Redbeard
I have the same engine and my mechanic swears by Three Bond RTV Silicon smeared on any such surface. We used it on those tubes, the exhaust elbow which I replaced and the rocker cover gasket etc.
Dave, an ex red beard!
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Old 24-08-2017, 02:18   #9
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Re: volvo penta metal tube disassembly

Although yes many mechanics do use RTV silicon along with O ring installation as per my earlier input BUT there's very mixed success due to the following.

1) The RTV depending on actual chemical breakdown can react with certain rubber type's of O rings and soften them to the point they dissolve over time.
2) If the RTV hardens prior to the O ring finding it's correct working location (why they use O rings) it can prevent sealing and will ultimately leak
3) If a lube is used it MUST be compatible with the "O" ring material.
4) You have know what you've got to do a correct installation.

Cheers Steve
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