yanmar 3gm - annoying fuel weep from filter area- solution?

PaulR

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our yanmar has been superb but has developed a minor fuel weep from the area of the fuel filter - we have replaced the O ring - tried tightening the knurled nut that holds the filter case on but the leak is still there - it is not easy to get to (tucked between starboard side of engine and part of boat so no good view) and now beginning to wonder if leak is actually from one of the fuel supply pipe connections rather than the filter housing - how is best way to trace source of leak and are the pipe connections made with copper type washers which if so presumably are readily available to replace ? guidance welcomed -thanks all
 

vyv_cox

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I have this problem also. The filter is very difficult to access on my installation but it doesn't seem to be simply a problem of inadequate tightness. I have assembled it using a tiny smear of 'Instant Gasket' over the O-ring and sealing faces, which seems to have done it. If you do this, make sure it is a very small amount or you could get solid goo in the injectors.
 
A

Anonymous

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There is often a fibre washer on the bolt at the bottom that secures the bowl in place. There should be some kind of washer, anyway. If yours is hard to get to, might the washer have gone AWOL? Are you sure that you've put the correct filter in (if over-sized it might cause a leak)?

As for tracing leaks, clean carefully with kitchen paper (actually blue workshop paper is better as you can see the wet patches better) and a solvent such as IPA, meths, etc. Put a few sheets of blue workshop paper under the weeping area -- you might have to put a board down first. Any drips become evident. Starting with a clean degreased system, it is usually possible to feel where the leak is coming from.

By pipe connection, I assume you mean the brass connectors? It is usually possible to take up the brass connectors -- nip them up carefully with a spanner of the right size but if you have an in-line connector or T, make sure that you use a second spanner to hold the body otherwise you will damage the line or unscrew the other end. It is very unlikely for a brass connector to 'fail' unless it has been opened and not put back properly. You don't use jointing compounds with brass. Inside the connector you have a brass ring, called an 'olive' ( that's it rough shape) which fits onto the copper pipe. The copper pipe has to be straight, burr-free and undamaged or the olive won't go on. When you assemble the connector, the olive is distorted forming an interference fit onto the pipe and the olive, which is made to close tolerance, sits snugly into the fixed part of the connector. It is DIY-able but get some bits and make up one or two on the bench before working on the job. You will need a pipe-cutter -- very cheap at local markets and a cheapo is fine for copper. If you don't use a pipe-cutter you are unlikely to get a decent end.
 

affinite

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I bet that it's the copper washers on the fuel lines into the filter housing. I had this weeping problem on my 3GM, I replaced the washers and Bob's your auntie - no more leak! Generic copper washers were available at first chandlers I asked (in Greece)
 

vyv_cox

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<<< There is often a fibre washer on the bolt at the bottom that secures the bowl in place. There should be some kind of washer, anyway. If yours is hard to get to, might the washer have gone AWOL? Are you sure that you've put the correct filter in (if over-sized it might cause a leak)? >>>

Different filter. The filter on the block of the Yanmar 3GM has a solid bowl with a screwed collar at the top that attaches it to the housing above. There is an O-ring in the joint. My engine, and presumably the OP's, is fairly tight in its compartment, with about an inch side clearance in which to fit a new (secondary) fuel filter. It's very difficult to tighten this collar in the limited space.

Much the same applies to the pipe connectors, although in my case these are definitely not the source of the leak.
 
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Anonymous

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I know the type. Horrid things. Would an oil filter wrench help to nip it up? I don't mean the rubber or chain strap type but the type that looks a bit like a water-pump wrench (which is the only type I use now)? You might be able to get that end-on. Almost makes you want to make up a special tool for the job, which I've had to do to replace the raw water impeller on my Yanmar -- utterly impossible job unless you have the sort of hands that a professional mechanic develops by daily use.
 

awol

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Copper washers - pair of long nosed pliers, heat washers to dull red in cooker gas flame, quench in coffee mug (keeps coffee warm!), refit.

Filter - nice stepped ring, tighten with screwdriver and hammer (but not too hard).
 

Blue Fox

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I solved this problem by removing the filter from the engine block and (with a lengthened fuel pipe) put it in a more accessible place in the engine room. Otherwise it is indeed difficult to fasten the bowl (btw, don't overtighten the bleeding screw! It's very soft aluminium).
And you can reach the impeller much more easily if you remove the entire waterpump - well, in fact the only way to do it with my Yanmar.
 

biscuit

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I had a similar annoying leak on my 2GMF. It wasn't immediately obvious where the leak came from and I had done the thing with the copper washer without success, as advised. Eventually I found a stripped thread on the aluminium body of the filter where the central (specialised) steel bolt holds it on. I bought a whole new filter unit, but was told that I could have fixed it with a Helicoil insert.. of which I have no experience. Both the bolt and the bleed screw are liable to strip the threads if they are overtightened.
 

steve28

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fit an oversize o-ring to the filter bowl, many users of the yanmarhelp forum have this problem, its to do with the way the tightening ring is threaded.
By over size i mean in section size. the yanmar ones are about 1.5 mm, 2.5 is fine.

all this is assuming is coming from the bowl seal and not from the bleed screws.





steve
 
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