Leaking filter assembly bleed screw - Yanmar

Dalestr

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Inherent Yanmar Leakage
Some of the GM series Yanmars built before 1998, before they added self-bleeding to the multi-cylinder models, will ooze a bit of fuel at the secondary filter bleed screw, or at the lift pump on days with large ambient temperature swings. The lift pump allows fuel to pass through as it contracts when cooling but then blocks its retreat as it expands on a warm day. An abnormally high pressure is then reached and the weakest gasket lets a bit of fuel pass to relieve the pressure. This is an intermittent weep. Some of the fuel piping on the earlier 2GM20F, for example, is steel tubing instead of hose. Hose can expand somewhat under pressure but not steel.
The owner detects a weep of fuel and tightens the small bleed screw on the filter more and more. This screw uses a nylon washer of a specific size, so buy these from Yanmar. There is a landing surface under that washer with an elevated ring like a donut, to help it seal (it is not a flat surface). Too much torque applied and the threads can get stripped but it is a good design in a bad situation.
How to fix the thermo-siphoning problem?
  1. I’d consider replacing the steel pipe going from the lift pump to the secondary filter with a good length of hose to allow more expansion. 1/4” hose is sufficient and the less fuel volume, the less expansion there is. The fuel pump uses M8 banjo bolts but the inlet/outlet of the filter uses M12. You would need to buy banjos with hose barbs.
  2. A more sure-fire fix allows you to leave that steel piping but essentially adds an expansion tank at the unused large port on the filter top. This is designed for an M8 banjo fitting and you would run a hose from this, about 24” long, filled mainly with air, locked in a steep upward direction, with a sealed plug in the end.
  3. One more complex fix would be to make the fuel pump check valves imperfect by filing/grinding a very slight notch to the valve seats. A slight-passageway is enough.
I didn’t attempt any of these cures but wish I had tried #2. I lived with bits of paper towel stuffed around the filter head for a few years as this is right over the forward engine mount. This captured the occasional ooze well but required attention. For my own cure, I created a self bleeding circuit for continuous, controlled flow into the return line — I already had supplanted the lift pump with an electric pump with greater capacity (Facet 40163). I still bleed at the primary and secondary filters after servicing but don’t need to bleed at the injection pump inlet as I finish purging by running the pump for 15 seconds. This was fairly tricky and can’t recommend it to others.
If one strips the threads of the bleeder you can plug it for life with epoxy and then use the M8 bolt for bleeding.
 

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IanCC

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The bleed screw doesn't have a copper washer under it. If it did it would need replacing or annealing every time you used it. It has a nylon washer which is rebated into the top of the filter. In the picture above, the bleed screw is the small yellow headed one.
 
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IanCC

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The larger screw, with copper washer under it, is completely redundant and can be epoxied in if stripped.

I understand it is where, in a previous version, the fuel return from injector pump came in. But was abandoned because fuel became too hot.
 

Dalestr

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That port is now used in the YM series engines as an additional location for automatic air purging since air tends to collect there. You see it well in the YBW video instruction on bleeding. Too bad they used a self bleeding engine for that.
 

Halo

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With a OEM nylon washer it only needs tightening with a screwdriver. Doing so avoids stripping the soft threads.
If you buy the Baldwin equivalent filter it comes with the slightly thicker washer which seals nicely.
A hook wrench is a real bonus for getting the castellated type thread ring which holds the filter bowl in place on and off.
Catching the fuel when you are changing the filter and bleeding is made much better by using a cut off wide plastic bottle pushed up and around the filter so that it catches the fuel and filter bowl
 

DinghyMan

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With a OEM nylon washer it only needs tightening with a screwdriver. Doing so avoids stripping the soft threads.
If you buy the Baldwin equivalent filter it comes with the slightly thicker washer which seals nicely.
A hook wrench is a real bonus for getting the castellated type thread ring which holds the filter bowl in place on and off.
Catching the fuel when you are changing the filter and bleeding is made much better by using a cut off wide plastic bottle pushed up and around the filter so that it catches the fuel and filter bowl
Using a bleed screw with an outlet where you can put a length of pipe and a container is even better, no diesel spilled and no diesel smell afterwards

Diesel filters have to be one of the worst designed parts on older non-self bleeding engines due to the design which just seems to encourage diesel getting spilled whenever a filter is changed or bled, and making the filter housing out of the softest available aluminium and not bothering to fit an insert where the bleed screws go doesnt help
 

ducked

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I'd probably try a nylon washer first. Maybe supplement it (or copper washer if you use that) with a smear of RTV

Copper might have some electrochemical incompatability with the aluminium in damp salty conditions, corroding thread, and is harder, putting more tightening stress on possibly marginal threading.

Also PTFE and/or polythene thread tape, and/or thread sealant
 

DinghyMan

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I'd probably try a nylon washer first. Maybe supplement it (or copper washer if you use that) with a smear of RTV

Copper might have some electrochemical incompatability with the aluminium in damp salty conditions, corroding thread, and is harder, putting more tightening stress on possibly marginal threading.

Also PTFE and/or polythene thread tape, and/or thread sealant

There is no issue using copper washers on aluminium fittings in diesel systems, they have been standard fittings for a very long time - people putting way too much force when tightening the bleed screws is the issue

You never put PTFE tape anywhere on a diesel system
 

ducked

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There is no issue using copper washers on aluminium fittings in diesel systems, they have been standard fittings for a very long time - people putting way too much force when tightening the bleed screws is the issue
Er...So thats an issue (not "no issue") then. Perhaps its an issue here, and could be mitigated by using a nylon washer.
You never put PTFE tape anywhere on a diesel system
I suppose due to the risk of blocking injectors and such, which is worth pointing out

I have had some concern over this in relation to my practice of using PTFE tape on brake nipples, which (in Scotland especially) otherwise rust solid and also suck air when brake flushing with a syringe.

I decided that, with care, the benefit justified the risk.

If thats true for my safety-critical brakes, it might be true in some circumstances for my less safety-critical engine.

Of course it might not be true in any circumstances for your engine. That'd be up to you.
 
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Dalestr

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Since the bleed screw and that spare port on top are both (I think) on the outlet side of the final filter, I would not be adding sealants or tape which could possibly create debris that travels to the injection pump and inhectors. For the same reason, I don't try to prefill a secondary filter if there's another option. I only pump fuel towards it. That said, it's feasible to prefill this bowl partially, maybe 3/4 full before slowly snugging it up around the element. You then must bleed from it and the injection pump inlet, unless you have a self bleeding -YEU version.
The spin on type secondaries can be prefilled if you know the inlet port location. If a replacement secondary element is not in sealed packaging, I would toss it out.
The Yanmar element is rated for 250 hrs so most seasonal sailboats can get 2-3 years from one.1000001503.jpg
 

DinghyMan

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Er...So thats an issue (not "no issue") then. Perhaps its an issue here, and could be mitigated by using a nylon washer.

I suppose due to the risk of blocking injectors and such, which is worth pointing out

I have had some concern over this in relation to my practice of using PTFE tape on brake nipples, which (in Scotland especially) otherwise rust solid and also suck air when brake flushing with a syringe.

I decided that, with care, the benefit justified the risk.

If thats true for my safety-critical brakes, it might be true in some circumstances for my less safety-critical engine.

Of course it might not be true in any circumstances for your engine. That'd be up to you.
The issue is not the use of copper washers, the issue is people who dont follow the instructions and overtighten everything stripping the threads

If you need to use PTFE on brake fittings and they "suck air when brake flushing with a syringe" then they arent sealed - fix the cause not the effect, using PTFE, RTE, etc. is just a bodge - again lack of sealing is usually down to overtightening of the fittings - use proper stainless or titanium brake bleeders if you are worried about them seizing
 

ducked

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If you need to use PTFE on brake fittings and they "suck air when brake flushing with a syringe" then they arent sealed - fix the cause not the effect, using PTFE, RTE, etc. is just a bodge - again lack of sealing is usually down to overtightening of the fittings - use proper stainless or titanium brake bleeders if you are worried about them seizing
"Proper stainless or titanium brake bleeders", eh? :ROFLMAO:

I used the OEM brake nipples that came with my cars, the last one being a 1986 Daihatsu Skywing that the cops got a couple of years ago.

Different World

I dont expect I'll ever see a titanium brake nipple, but if they are the same shape as the OEM's I'd expect they'd suck air when -ve pressure bleeding just like real ones do, because I think its inherent to the design and situation.

I imagine they would be fairly immune to corrosion though.

And SHINEE.
 

Dalestr

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Brake bleeders are a great way to vacuum bleed a primary filter that's higher than the fuel in tank. I use a hand vacuum pump to remove air from a Racor 110A but the same suitability for the Racor 120 filter exists; you use a spare inlet port and fit a "brake bleeder repair kit" which has an NPT adapter (in the USA).
Adapting bleeders to secondary filters can more challenging but adapters can be found or made, for example, for the M8-? top port on the Yanmar filter. This could end the need for manual lift pump operation --a torture for some folks1000001509.jpg. With a bleeder, you get a valve plus a hose nipple. It is also a cleaner more controlled process.
 

DinghyMan

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Brake bleeders are a great way to vacuum bleed a primary filter that's higher than the fuel in tank. I use a hand vacuum pump to remove air from a Racor 110A but the same suitability for the Racor 120 filter exists; you use a spare inlet port and fit a "brake bleeder repair kit" which has an NPT adapter (in the USA).
Adapting bleeders to secondary filters can more challenging but adapters can be found or made, for example, for the M8-? top port on the Yanmar filter. This could end the need for manual lift pump operation --a torture for some folks With a bleeder, you get a valve plus a hose nipple. It is also a cleaner more controlled process.
The picture I posted above is a small set of the range of bleeders we make - as you say the bleeders with a brake nipple and a length of pipe make for much cleaner filter bleeding

We have made some for M6 injection pumps as well as a wide range of metric and imperial for pumps, filters, and some replacement banjo bolts with bleeders in them for troublesome installation's
 

rogerthebodger

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A break bleed nipple is an interesting of making engine bleeding quick easy and clean.

I fitted some small ball valves into my bleed points with a quick connector and pipe to bleed the diesel into a jar which is less messy
 
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