David Mutch

Hi all. I have a leak from round the output shaft on my Delta 30 gearbox. The manual seems to suggest that to replace the oil seal, the box needs to come out and be pretty much fully dismantled. Is this really necessary just to change the oil seal, and if so, can anyone provide a bit more detail than the manual does on how to do the job? Thanks 🙂

Thanks (although I'm not sure what's silly about checking the PRV?!) Interesting about water boiling out of the oil. I could have sworn that after I got the engine hot the other day, the oil looked cleaner afterwards. I didn't mention this before, because I thought I must have been imagining it, but I guess if it's been chronically under temperature, it could have accumulated condensation in the oil, which boiled out and made it look cleaner. Maybe another tick in the box for a higher temp stat.

Thanks Tony. It usually never goes below 50psi, except the other day when I revved it for a long time and it dropped to 35ish afterwards, then climbed back up slowly, but I put that down to a lot of heat causing the oil to thin. The gauge and sender are new (well in the last 2 years or so), although I realise that doesn't guarantee working correctly. By and large its readings seem consistent with what I'd expect, but I've usually been too preoccupied with the smoke before now to pay attention to the gauge when I've got the hammer down, and the readings I saw today seemed on the high side. The fact there was zero smoke today on my cruise, plus good compression readings, makes it seem unlikely to me that the rings are bad. I guess the gunged up exhaust theory is still the most likely, but perhaps I'll investigate the relief valve anyway, as I've never had it out.

Thanks. I'll take a look then 🙂

So, went for our first cruise today since all the tinkering. Before doing so, I put the pump timing back to dead on the mark and replaced one of the pipes between the fuel filter and the injector pump, which was probably 30 year old copper, and didn't take kindly to being disturbed twice in one week. After a short warm up, I gave it some beans in neutral. Got a fair bit of smoke to begin with, but perhaps not as much as before, and this time it started to clear within 30 seconds or so, even without putting a lot of heat in the engine as previously. Set off, and wherever possible, opened up the taps. No smoke! Or none to speak of. The engine was also running noticeably smoother and quieter (the OH commented on this completely unprompted, so I don't think I was imagining it!). There's still one thing that I thought worth consulting the hive mind about. I wonder whether my symptoms could possibly be explained by a sticky oil pressure relief valve. I've not really had an eye on the oil pressure before when it's been billowing smoke, but I noticed today that when I first gave it some revs, the oil pressure shot up to nearly 100psi. I might have expected something like that with a stone cold engine, but I'd already run the engine for a while in the morning, so it wasn't completely cold. When giving it some welly on the cruise, it peaked at maybe 80psi, which seems more normal, although admittedly I probably didn't reach quite the same rpm, and that still seems higher than my previous BMC (although that could just be down to a different gauge to some extent, I suppose.) Could excessive oil pressure be forcing oil past the rings at high revs, perhaps? And could getting some heat/oil pressure in the engine help un-stick the valve, or just reduce the oil pressure enough due to higher oil temp, that the smoke subsides?

These modern marvels never cease to amaze!

Thanks. I'd never have thought to get that inventive!

Unfortunately, not all of us have have access to such good advice, especially for free. I suspect that's why a lot of folks come here looking for counsel. Indeed, my experience has tended to be that even if willing and able to pay, it's very hard to find a mechanic that good, especially when it comes to diagnosing something at all out of the ordinary. That's pretty much why I have learned as much as I have about engines and do as much of my own work as I can. If you can recommend someone on the Kennet and Avon with those kinds of skills, I'm all ears. I think it's a little unfair to say that I might as well change the gearbox, but perhaps I've not been 100% clear in articulating my reasoning. As @Tony Brooks points out, there did seem to be some improvement in engine sound when hot. However, that's not all. I have always believed that the stat is unnecessarily cool (I believe it's a 74 or even 72 degree stat). I'd never thought about cooler stats being used to regulate domestic hot water temperature, but I have heard they're often used in engines that have raw water cooling, especially if used in brackish or sea water, as this helps reduce corrosion, but that it's a bit of a trade off in terms of engine life, as running cool can cause other problems. I believe my engine may have been converted from raw water to a skin tank at some point in its life, so perhaps that's why it has a cooler stat. My current working hypothesis is that the smoke is due to prolonged periods where the engine is under insufficient load, just generating electricity, (especially over the last two years of working from home) and doing the occasional cruise with few locks and no flow requiring high power or rapid deceleration. I think this may have caused a buildup of a combination of carbon, diesel and oil (and perhaps even water, as the exhaust could conceivably collect condensation or rain water), causing smoke under higher revs, where there's more air flow through the engine to blow the gunk out, and increased exhaust temperature to help vaporise it. I'd reason that such a buildup is less likely to occur if any stray oil or diesel is ejected from the engine at a higher temperature in the first place, and that a higher temperature in the rings is likely to lead to expansion and therefore less oil and unburned diesel in the cylinders and therefore the exhaust system. Perhaps I'm wrong, but I guess I'll find out when I change the stat I like the cut of their jib!

@TheBiscuitsThanks (although needing a rev counter to calibrate a rev counter seems a bit of a catch 22 to me!)

I have a skin tank for cooling, and no calorifier (instant gas hot water), so I think I'll go ahead and change the stat. Thanks. I've always wondered with one that runs off the alternator whether they have to be calibrated somehow, as I'd have thought it depends on the pulley ratios to a great extent?

Well, something to report: This afternoon, to some extent out of frustration, I decided to give the old 'Italian tune up' a jolly good go, as a bit of a 'kill or cure'. I don't have a rev counter, so couldn't say exactly to what extent I gunned it, but I'd say I gave it at least 2000rpm, if not considerably higher (certainly more than I'd ever use for any longer than it takes to stop in a hurry), and just left it. The smoke was pretty appalling to begin with, but I held my nerve, and after maybe 3 or 4 minutes, it began to clear. It didn't clear completely (although my nerve didn't hold long enough to find out if it might, if left), but it reduces to what seemed to me a not completely unreasonable level for those RPMs. The temp gauge read considerably higher than I've seen it previously, and oil pressure at idle dropped below 50psi (to maybe 35-40, it's hard to tell on a dial with tick marks every 25psi), but crept back up as the engine cooled off. I'm beginning to wonder whether @Mad Harold might have been on to something after all. Although I've been on the river recently, there was precious little flow, and the smoking issue made me reluctant to really push it, although it still felt like I was pushing it compared to the canal. I think there could be a bit of a negative feedback loop there, with the smoke making me image the worst about my engine, and me therefore taking it easy everywhere, and allowing yet more gunk to build up in my exhaust. I'm also wondering whether @john.k might be on to something with a cold engine. Perhaps mine would be happier with an 82 degree stat? (Don't know if it was just psychosomatic, or whether I was just deaf from the revs, but I could swear the sound improved when the engine got some heat into it too.) I'm not calling it case closed yet, but thought it would be interesting to hear your thoughts on fitting a higher temperature stat, and doing more regular drag races!

Thanks Tony. Sounds like stem seals may be less likely then. I think I need to have a good look at how much oil it's losing, and at what's coming out of the exhaust. If I don't know if it's oil, diesel or steam (unlikely), then I'm flying blind as far as diagnosis is concerned. I think it's probably time to get some who knows their onions to take a look!

Thanks John. I think perhaps there's some confusion between my post and magnetman's, as I'm not aware of any worn rockers in my case. I'm hoping it's not rings, as at that point, I guess it's pretty much engine out, which probably means I may as well get a new one! Not quite sure how to proceed. Seems the only to confirm would be to at least have the head off... I guess I'll completely rule out timing first. Also still have a sneaking suspicion it may have to do with fuel delivery. I'd have thought that a tired pump could cause effectively retarded timing, if it meant the injectors didn't get to breaking pressure early enough in the cycle, perhaps? I realise that may be wishful thinking

Rock Oil is a major brand, stocked and recommend pretty universally in chandleries I've visited. Used it for 10 years now without complaint (perhaps, admittedly, until now, that is!). I'm assured it's supposed to help prevent bore glazing in the kind of low load application an engine has in a narrowboat. Pretty sure my oil filter is Bosch, and it gets changed at least twice a year. TBH, if doing the seals, I might get someone in who's more of a mechanic than I, but thanks for the tips.

That's interesting, as I guess a dodgy seal on an exhaust valve could well cause oil to get sucked into the exhaust, vaporised and blown out the tail pipe without actually combusting, which fits with the symptoms and the tests I've run so far pretty well...

Thanks. Because compression is good and there's no sign of combustion gas in the cooling system, worn rings/cylinders of failed head gasket seem unlikely. I guess there are places a head gasket could fail and let oil into a cylinder without letting combustion gas into the cooling system, but I'd have thought a failure like that would still cause lower compression. I use Rock Oil MP Lite D, and I can't say it's noticeably thinner than usual. What would that make you suspect? Fuel in the oil? I'm starting to lean towards the possibility of valve stem seals, as these could let oil into the cylinder without loss of compression, and it does seem it's not always just on start that you get smoke when these are gone. Is there any way to confirm this, though, other than changing them? And is that doable with the head in situ?

Will do, although I'm not sure it really smells like any of those. If it's oil, where could it be coming from, given that compression is good, so presumably the rings are ok? Valve stem oil seals? But from what I've read (no experience myself) that would tend to cause smoke on startup, but then clear? Fairly sure it's not steam, as it doesn't lose coolant. It does lose some oil, but so did my previous 1.5 (presumably mostly out of the breather), and it didn't smoke like this. The engine does seem to run coldish, although I'm not sure I'd describe it as stone cold. I don't think my temperature gauge is very accurate, but have measured the stat housing with an infra red thermometer before, and I seem to recall it was a bit below the stat rating ( which is I think is a low temperature stat - 72 degrees?). However, it's always run at the same temperature, and the smoke is new, so I doubt that's it, TBH No worries. Thanks for the explanation

Aarg! Seemed to be a bit of an issue with the submit button on that last one! 😆

Thanks Tracy. I've had a lot of diesel fills in the time it's been happening, and even run out once, so I don't suspect bad fuel (unless my supply is consistently bad, but then I'd expect others locally to have similar complaints) Thanks Tracy. I've had a lot of diesel fills in the time it's been happening, and even run out once, so I don't suspect bad fuel (unless my supply is consistently bad, but then I'd expect others locally to have similar complaints) Thanks Tracy. I've had a lot of diesel fills in the time it's been happening, and even run out once, so I don't suspect bad fuel (unless my supply is consistently bad, but then I'd expect others locally to have similar complaints) Thanks Tracy. I've had a lot of diesel fills in the time it's been happening, and even run out once, so I don't suspect bad fuel (unless my supply is consistently bad, but then I'd expect others locally to have similar complaints) Thanks Tracy. I've had a lot of diesel fills in the time it's been happening, and even run out once, so I don't suspect bad fuel (unless my supply is consistently bad, but then I'd expect others locally to have similar complaints) Thanks Tracy. I've had a lot of diesel fills in the time it's been happening, and even run out once, so I don't suspect bad fuel (unless my supply is consistently bad, but then I'd expect others locally to have similar complaints)

Hmm... That's an interesting theory, which I'd seriously entertain, were it not for the fact I had my exhaust replaced fairly recently, and it didn't improve. Also, I guess I'd expect it to smoke all the time when up to temperature if that were it. I will do the finger test though. Thanks John

Thanks Tony. Yes, replaced all washers (the atomisation/crush washers, large copper washers and spill rail washers). The top hats all remained in the head. It seems very unlikely to me that it's the injectors. It ran fine for years with the old ones, so I guess they were the right type, and it would seem odd for the new ones to be the wrong ones, but to cause the exact same symptoms as the faulty but correct old ones.

Thanks Magnetman. I have checked valve clearances and had a good listen to the top end and tappet chests, so I don't think it's that, although the sound kind of fits. Curious to know what you mean by the screws being soft? I guess something else in the top end could be the cause of the smoke, e.g. valve stem oil seals, but the smoke is definitely more white than blue, and it's only at high revs, so that one is lower down the list of suspects.

I suppose the question is: Is it excessive diesel knock? It certainly seems louder than my previous BMC, and I think this engine has got louder recently, seemingly coinciding with increased smoke. Could the timing being too far advanced cause smoke? (I've always thought advanced timing would cause knock and retarded timing would cause smoke/a misfire). When I first got the boat, it ran quite rough when cold. I found the pump timing was a couple of degrees retarded (by the timing mark), adjusted and it ran nicely for a long time. Just wondering if actually the pump should be a little retarded, and there was something else that was causing the rough running. If whatever that was (maybe bad fuel?) sorted itself out somehow, that might mean I'm now running too advanced. I realise I'm clutching at straws a little here ...

Hi Tracy. They're from Calcutt Boats, so I suspect they're the right ones. The noise and smoke were happening before I changed them, and haven't noticeably improved since, so it would be a bit of a coincidence if they were the incorrect ones, and happened to cause the same symptoms as the old ones

These videos give some idea of the sound, although I'm not sure they will capture it completely. Maybe just totally ordinary diesel knock, but I'm pretty sure it's not always sounded like that. Will try to get one of the smoke when I get a chance in daylight