Bukh DV20 woes... hard to start, and now....

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stevie69p

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My 1975 vintage Bukh DV20 has been difficult to start for the last month or so. The boat is fairly new to me (Sept last year) and I just put it down to being an old engine and the rather cold snap we have had of late. I could eventually coax it into life and then it would run ok, but I did notice that the exhaust smoke was quite grey. Anyhoo....

I changed the oil & filter about 6 weeks ago; all was normal with what came out. Changed the engine anode at the same time. I took the boat out weekend before last for a little motor across to a nearby bay just to give it a run. Oil level was fine before that run. At the start of this week I replaced both fuel filters. The primary filter was fairly cruddy looking, and I though there may be some improvement after replacement, but alas no... Decided tonight to remove the stop solenoid, just to check it wasn't stuck against the fuel rack, and removed the high pressure injection pump to check the rack wasn't stuck, etc... only to discover GREY engine oil. Aargh...

So, in making the assumption that the starting issues of late, the grey smoke, and now the discovery of grey engine oil are all related, I'm thinking blown cylinder head gasket. Does the assembled panel here have any nuggets of wisdom as to common failure issues on these engines? I will be honest and say that my diesel engine experience is rather less than petrol stuff, but I did rebuild my last boat's single cylinder Volvo 2001, so I feel fairly confident about tackling this myself.

Thanks in advance for any advice forthcoming. I could do with this like a hole in the head at the moment!
 
Before taking the head off check the water pump The neck of the pump body between the pump casing and the engine flange should have a weep hole to allow any water that gets past the pump shaft seal to drain into the bilge. If this hole is blocked or not there then the leakage water can get to the engine sump. This is not unknown.
 
Re the grey oil, my I suggest you check the water pump seals are not leaking. This is a fairly common problem with BUKH DV10/20 engines. If the seals fail water travels along the pump shaft into the chaincase and contaminates the lub oil. You can usually tell if this is happening because water comes out of the tell-tale holes in the pump body. They are almost hidden by the u-shaped clamping piece that holds the pump in place and can get blocked with crud.

Ah Bilgediver, you took the words out of my mouse. :D
 
Yes, I did consider the raw water pump for the oil contamination issue, however that wouldn't explain the starting problems. They could, of course, be entirely separate issues.

On giving this some more thought... a couple of times recently I have gone to start the engine, only for the starter motor to give a big 'clunk' and not turn the engine. I had assumed the bendix on the starter was sticking and was another thing on the to do list, but it may be another sign of water ingress. Suspect this job could get messy...
 
As others have said, there appear to be two problems. The grey oil is almost certainly the result of water ingress is either through a knackered head gasket or defective water pump seals. If the latter then that wouldn’t affect starting.
Does the oil level on the dipstick appear to be rising? That was exactly the sign when my pump poured water into the engine.
You also do need to check compression, either by hiring someone to do it or you buy a tester. Not huge money https://www.machinemart.co.uk/p/clarke-cht693-8-piece-compression-tester-kit/ and worth having in the toolbox.
Whatever you do, inaction isn’t a good idea. Water in the oil will start to cause real damage.
 
Champagne Murphy said:
As others have said, there appear to be two problems. The grey oil is almost certainly the result of water ingress is either through a knackered head gasket or defective water pump seals. If the latter then that wouldn’t affect starting.
Does the oil level on the dipstick appear to be rising? That was exactly the sign when my pump poured water into the engine.
You also do need to check compression, either by hiring someone to do it or you buy a tester. Not huge money https://www.machinemart.co.uk/p/clarke-cht693-8-piece-compression-tester-kit/ and worth having in the toolbox.
Whatever you do, inaction isn’t a good idea. Water in the oil will start to cause real damage.
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Yes, the oil level in the sump is up by about 1cm on the dipstick top mark.

Inaction isn't an option. My intention was to get the milky oil sucked out tomorrow night and get the head off, but a compression test prior to that would be helpful analytically; though not having a reference compression figure from before the starting problem began, it's only going to tell me if the head's going to have to come off if the figures are low now.
 
If it has been taking a fair bit of cranking to get her started then the engine may have back flooded through the exhaust. A lot of Bukh starting issues can be cured by regrinding the valves which tend to coke up something awful. I will bet your exhaust valves will be in a particularly sorry state. Quick injector service will also do wonders.
 
On Vyv Cox's website he has a simple DIY method for compression testing without a gauge. Might be worth a try. If your engine has a starting handle, you should be able to feel if it's got decent compression.
 
robmcg said:
If it has been taking a fair bit of cranking to get her started then the engine may have back flooded through the exhaust. A lot of Bukh starting issues can be cured by regrinding the valves which tend to coke up something awful. I will bet your exhaust valves will be in a particularly sorry state. Quick injector service will also do wonders.
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+1. A large part of the expense is the head gasket (good old Bukh, reliably expensive) so while youre there......
 
stevie69p said:
Yes, I did consider the raw water pump for the oil contamination issue, however that wouldn't explain the starting problems. They could, of course, be entirely separate issues.

On giving this some more thought... a couple of times recently I have gone to start the engine, only for the starter motor to give a big 'clunk' and not turn the engine. I had assumed the bendix on the starter was sticking and was another thing on the to do list, but it may be another sign of water ingress. Suspect this job could get messy...
Click to expand...

Water ingress into the engine cannot affect the starter in the way you describe. It's most likely an old Bosch starter with a sticky drive, the drive can be replaced by any decent auto starter repair centre.
 
PaulRainbow said:
Water ingress into the engine cannot affect the starter in the way you describe. It's most likely an old Bosch starter with a sticky drive, the drive can be replaced by any decent auto starter repair centre.
Click to expand...

No, it was more ingress into one of the cylinders I was thinking about, but that wouldn't make a lot of sense if repeated vtries of the starter suddenly makes it spin over... I guess if it's locked hydraulically, then it would just clunk and never spin up.

I'm going to make a start on this tonight - get the oil out and flush and some fresh oil in to protect the bottom end as much as possible. Then head off and see what's what hopefully...
 
My DV20 is reluctant to start in winter temperatures, despite valve re-grind and replacement piston rings. That part of your troubles may just be par for the course. You can get a 'cold start' air inlet stub to help with this. I have found, though, that the engine will start in the end. You just need to give it a good minute or so spinning with the compression lifters. This may be in several bursts of a few seconds each to allow the starter motor to have a rest.

If your water pump has been leaking into the chain case you will have a big corrosion clean-up ahead. In my experience, the first sign of this would be an oil leak at the front crankshaft seal because the water trickles down and rusts it out. Only a little leak will do this - not enough to make the oil grey.
 
I already have the cold start element fitted. Before the new year, my winter sailing involved 20 seconds of preheat and then the engine would fire up within about 10 seconds of cranking, so I think something has gone south over the winter to make it a pig to start, plus the engine never used to be particularly smokey.

I don't think the raw water pump is the culprit. I checked it last night and the little hole at the seal was bone dry. I'm hoping it's not a cracked block or head, but will report back with any findings once the head is off.

Thanks all for advice so far...
 
Well I have made a start this evening but rather slow going trying to get the contaminated oil out via the Pela vacuum pump, so I am just going to let it continue to drain out overnight. I plan to then remove the raw water pump to check the seals just in case, then fill the engine with 50/50 mix of clean oil and diesel and hopefully get the engine started to flush that through before contemplating the next steps. I still think I will need to remove the head, but would like to see what's the source of the water in the oil, i.e. if it's not the pump seals. I have read online about cylinder liner seals going... I think if it's anything like that, I would just stop on a 43 year old engine. I don't want to throw good money after bad!

As regards white smoke... yes this engine and I believe other Bukh's are famous for that, but what I was getting was more grey smoke.
 
stevie69p said:
Well I have made a start this evening but rather slow going trying to get the contaminated oil out via the Pela vacuum pump, so I am just going to let it continue to drain out overnight. I plan to then remove the raw water pump to check the seals just in case, then fill the engine with 50/50 mix of clean oil and diesel and hopefully get the engine started to flush that through before contemplating the next steps.
Click to expand...

That doesn't seem like a good plan.

Drain the oil, fix the problem, fill with new oil. Run the engine and drain/refill with more new oil. I most definitely would not put any diesel in oil and i certainly wouldn't want to start the engine with a fuel/oil mix.
 
I’m very nervous about contradicting such a knowledgable poster, but when my pump seals went Al and Norm were still running the Bukh show in Poole. They were extremely helpful and would always offer good, experience based advice on the phone(‘don’t drop the flywheel on your foot’ was a particular gem). They advocated flushing with an oil diesel mix (don’t run the engine, then oil only and run.
 
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