How to flush a diesel Bukh DV20?

[grjfield]

Tinkering with my diesel, rocker cover off, YIKES...some junk dropped into it (paint chips, rust, dirt!)
I have drained the oil but now want to flush it to get all the crap lying in the cracks.
Does anyone have a suggestion on what to use to properly flush the engine?

Thanks
Gerard

[stevec195]

Uhmmm. If it were metal shavings I’d be a little concerned, but from the sound of it, you may do more harm than good by “flushing” the motor.

[parkstone bay]

Belatedly, when you say "Flush" - you're referring to the lube oil? Go to local discount store get a can of their generic diesel oil (but NOT synthetic or semi-syn). Drain the old oil, it'll be black as old boots - after running the engine up to temp. Fill with the discount store oil. Don't change the filter at this stage. Repeat the process (that is to say, you're using good(-ish), nominally road quality oil, as a flushing medium. Most compounds sold for flushing either THIN the oil, or are thinner oil as such and aren't recommended under load/prolonged use. ) When you've given her a good run with the discount store oil, then drain, change the filter, and refill with a proprietary mineral diesel oil (no need to go for "formulated for turbo's, etc). take the opportunity to run her under load and change the gearbox oil at the same time: it's the same oil as the lube oil . Though the gearbox oil doesn't take anything like the bashing the engine does, (much cooler temperature, no combustion products) when was it last changed? - it should be done every 5 years or so. I know a little bit about Bukhs, they are great little engines, I have a DV24 in my little MB in England. PM me if you like for more info. Andrew

[Winchfodder]

What is the oil capacity of the dv20 engine and gearbox?

[parkstone bay]

Hi the nominal capacity of the DV20 sump is approx 2.8 litre; and that of the gearbox approx 1.0 lit. BUT - especially if you're using a drain system that sucks sump oil out through the dipstick hole, you'll never get the whole capacity out. Same applies to the gearbox (BTW, it's the same oil). when I change the oil on my DV24 (the newer, up-rated, replacement engine; but engineering-wise very similar), I always pump out the old oil, then use discount store oil "good for all diesels" as a flushing oil, run for an hour or two on that, then chuck it before refilling with good quality "real" oil. DON'T use synthetic or semi-synth oil on these engines. Top tip: reading the sump dipstick level with nice fresh oil is quite difficult; reading the gearbox dipstick (which is only a thin steel rod) is impossible. Make up a piece of wood dowel to the correct dimensions - the oil level is much easier to see against on a piece of flat matt wood than a thin rod. (The Mkii version is painted matt black; the oil shows up well.). Finally, you don't need to flush the gearbox, it doesn't get the combustion products contamination that the sump oil does; that's also why the gearbox oil needs changing less frequently than the sump oil. (and if you're in a country that doesn't use litres 1 litre = 1.76 imperial = 2.11 US pints) Hope this helps Andrew

[Winchfodder]

Thank you Andrew for the comprehensive reply.

The dv20 in by new (to me) boat looks like it has not been serviced for years. It runs (with white smoke after 10 minutes) ok. So I only want to approach gently as all the bolts are tight/rusty/seized.

Also all the wiring is a mystery, old, corroded, and some ends just hanging and going nowhere.

So far I have replaced the alternator, but have no voltmeter as it had rusted and I have no idea which wires to use.

The gearbox dipstick is very tight and very thin. Any theories on how to access without damage.

Dv20 is a tight fit it my Centaur. Access almost impossible to oil and fuel filters on the sides. I have a pela pump for the dipstick. I can also feel under the engine to the back of the sump and think I can feel a sum plug on the vertical back plate (if you see what I mean- no plug on the underside. I am going to use the pela, but wondered how safe it might be to try and disturb the sump plug. (Because resecuring might be stressful if it is tight, washers etc.) Have you undone yours in the past?
Also question about the engine anode. Do you change, I read somewhere that they can end up inside the water jacket if you make a mess getting them out. Any thoughts.

[Winchfodder]

The gearbox dipstick with the sort of Allen key head is very rusty and reluctant to move so far by hand with a couple of wd40 doses.

Is it screw fix or straight pull up and down. I don't want to force it. Any thoughts?

[parkstone bay]

Hi - the gearbox dipstick has, as you say, a right - angle "handle". Unless someone's done something REALLY odd in a previous life, it's a straight pull.
There are rubber seals (tight fit into a hole) which should come out with the rod. End of the rod are the dipstick markings.

As regards the anode (apologies for not coming back to you) if the anode rots and drops into the water jacket, that's not an issue - it won't get into the rotating parts.

PM me if you like. I'm in Poole, Dorset. Andrew

[Winchfodder]

Originally Posted by parkstone bay

Hi - the gearbox dipstick has, as you say, a right - angle "handle". Unless someone's done something REALLY odd in a previous life, it's a straight pull.
There are rubber seals (tight fit into a hole) which should come out with the rod. End of the rod are the dipstick markings.

As regards the anode (apologies for not coming back to you) if the anode rots and drops into the water jacket, that's not an issue - it won't get into the rotating parts.

PM me if you like. I'm in Poole, Dorset. Andrew

Thank you for the notes.

Gearbox dipstick very tight and not wanting to lift. Rusted in I guess. Tapping around the base with a chisell after soaking in diesel seems best bet. I dont want to snap off the handle.

Managed to extract the anode bolt. No anode left. Have bought a new one.

Main problem now is the bolts to the thermostat housing. I wanted to clean the thermostat, but the four bolts dont want to move. They have 5mm hex top and the wrench does not want to move them at all.

[parkstone bay]

The thermostat cover is - as you say - the socket head cap screws. The Gearbox filler/dipstick "should n't " be rusted in. The dipstick is just a pushfit into the casing. If you look at ebay there's a DV20 gearbox for sale with great pictures. The disc, where the L-shaped handle goes is, is part of the dipstick - you don't want to turn the handle/rod, relative to the disc, (which is the top of the rubber bung into the casting). I've tried to attach the picture.

[parkstone bay]

brilliant - it worked. the dipstick is really clear. You must not turn the rod/handle relative to the disc/bung. The whole lot has to come out in one.

[Winchfodder]

It is very solid. I have been trying vertical lift with grips. I think I will chisell around the base.

[parkstone bay]

Yeah, remember that the disc - highlighted on picture - MUST come up with the rod/handle; and in fact it'll come up with the bung. -- DO NOT try to separate the rod from the disc, which as I said before is the top of the rubber bung which is a push fit into the gearbox casing.
I SUSPECT that some dork has really sweated the thing in, without realising it should only be a firm push fit by hand.
What you've got is the classic yacht auxiliary engine problem. "It's difficult to get at, so I'll leave it this year, next year CBA, etc... etc" before long it's 5, 6, 10 years down the line. 99.5% of yacht auxiliaries suffer from lack of regular maintainance, and 100% of then suffer from lack of use.
On the Centaur, can you take up the cockpit sole to improve access to the engine - I thought that on some Westerlys, they had that feature.
All Best
Andrew

[Winchfodder]

Still struggling to free the dipstick!

I am fitting a new exhaust elbow on the DV20. Should I apply anti-sieze compound when bolting back the flange to the manifold or screwing the elbow into the flange. Also when screwing on the water hose fittings.

Same with refitting the engine anode screw.