How long to bleed?

[prv]

The time obviously varies considerably by engine type. After filter changes I mostly get away with no bleeding, just start up. Always starts but if it does stop before all the air is automatically bled out, then the amount of air remaining is small and just a few strokes on the lift pump with the bleed screw on the secondary filter slackened does the job.

What kind of filters do you have, and do you part-fill them with diesel before fitting them? The internal volume of my primary filter and its bowl, allowing a bit off for internal structure, is probably about a coke can or 300ml. That's got to be several feet of empty hose once sucked into the system, and while I've never tried it I struggle to believe my engine could keep going through such a gap.

Pete

 

[Plum]

What kind of filters do you have, and do you part-fill them with diesel before fitting them? The internal volume of my primary filter and its bowl, allowing a bit off for internal structure, is probably about a coke can or 300ml. That's got to be several feet of empty hose once sucked into the system, and while I've never tried it I struggle to believe my engine could keep going through such a gap.

Pete

I have a CAV primary filter with the glass bowl section, the type that is tricky to reasemble in a confined space, and there is no easy way of adding fuel to the filter other than pumping it through so it starts dry and mostly fills before the engine stops. The secondary engine mounted filter is a screw-on cartridge so because it is easy i usually pour some diesel into the new one before fitting. Its a Vetus (Mitsubishi) engine.

If you have a Racor 500fg type filter then you really must completely fill the housing with fuel otherwise only the bottom half of the filter element gets used and a big airpocket remains at the top of the housing, although this does not usually result in a bleeding problem and you should not need to bleed at all.

Www.solocoastalsailing.co.uk

 

[prv]

If you have a Racor 500fg type filter then you really must completely fill the housing with fuel otherwise only the bottom half of the filter element gets used and a big airpocket remains at the top of the housing, although this does not usually result in a bleeding problem and you should not need to bleed at all.

I do have Racor filters, but not that model. The ports on mine are at the top, so I assume any airspace remaining (as a result of bleeding via the return line rather than the screws) is minimal.

Pete

 

[RupertW]

About 0 seconds. Just start the engine. Very occasionally it might splutter to a stop, in which case I top up the secondary filter and start it again. I make sure I run it for about 15 to 20 mins after the primary filter change before putting myself in a position where it stopping could be an issue, but that's just being extra cautious.

Yanmar seemed to have figured out self-bleeding engines at least 25 years ago.

I wish they had done it for starting again after refilling an empty tank as well, like a petrol engine. I've had 5 Yanmars over the last 20 years and they all took bleeding after running out of fuel. For 3 of them I only know this because I always run an engine dry as soon as I can after buying a boat so I can be 100% sure that I know how to quickly bleed it. For the other 2 I shamefully have actually unexpectedly run out of fuel.

 

[RichardS]

If you have a Racor 500fg type filter then you really must completely fill the housing with fuel otherwise only the bottom half of the filter element gets used and a big airpocket remains at the top of the housing, although this does not usually result in a bleeding problem and you should not need to bleed at all.

I have two 500FGs and, from the design, would have expected that to be true but whenever I unscrew the lids off mine they appear to be brim full even though I don't fill them to the very brim when I change the filter as I don't want to risk any spillage.

I wonder if they do, in fact, flush out any trapped air over time?

Richard

 

[Plum]

I have two 500FGs and, from the design, would have expected that to be true but whenever I unscrew the lids off mine they appear to be brim full even though I don't fill them to the very brim when I change the filter as I don't want to risk any spillage.

I wonder if they do, in fact, flush out any trapped air over time?

Richard

Interesting. From your experience then sometimes they do flush out the trapped air. I have seen instances when an old filter is removed it is dirty on the lower half of the element and like new on the upper half . Not a big deal other than the part of the filter element being used will clog up in half the time.

www.solocoastalsailing.co.uk

 

[<152587>]

A lot of problems when bleeding systems is the reluctance to really open the venting device to provide sufficient flow because of the smell and mess.

 

[RichardS]

Interesting. From your experience then sometimes they do flush out the trapped air. I have seen instances when an old filter is removed it is dirty on the lower half of the element and like new on the upper half . Not a big deal other than the part of the filter element being used will clog up in half the time.

www.solocoastalsailing.co.uk

Yes, that is true. The filters are always lighter at the top and get darker and darker towards the bottom of the paper mesh .... but that's not because the filter body is not full as mine are always full but the filters are always graduated. I think it something to do with the slight swirl action coming up from the glass bowl but I don't know.

Richard

 

[lpdsn]

I wish they had done it for starting again after refilling an empty tank as well, like a petrol engine. I've had 5 Yanmars over the last 20 years and they all took bleeding after running out of fuel. For 3 of them I only know this because I always run an engine dry as soon as I can after buying a boat so I can be 100% sure that I know how to quickly bleed it. For the other 2 I shamefully have actually unexpectedly run out of fuel.

You could just top up the secondary filter to get it started, which would get a fair bit of the air out whilst it ran on that fuel. In fact if you were able to stop the engine and top up the secondary filter periodically you should be able to get it going without any bleeding. Defining 'periodically' would involve trial and error. My secondary filter is very conveniently placed unlike the primary.

I also keep an oil extraction pump next to the primary filter - long pipe run so I use it to clear the pipes if I suspect any blockages and am reasonably practiced at fitting it and getting a seal. If I believed the pipes from the tank to the primary were full of air I could use that - lot quicker and easier that flicking the lift pump.