Bukh 24 water temperature indication hot and cycling.

[Brian & Glenda]

For the benefit of future readers here is a copy of the link mentioned above, and below are instruction regarding how to post a link:
sadlerandstarlight.co.uk/forums/topic/boiling-bukh/

Yes, that article makes interesting reading ... but as in the linked article ... it seems that what is missing in many posts and requests for advice regarding cooling issues; is a statement regarding the type of cooling used on the engine under discussion (raw-water cooled, keel cooled, or fresh water cooled); and often the make and model of the engine is missing in the discussion! This is important info if one is to troubleshoot overheating.

I believe that my DV36 does not have a 'gas poker' as referenced in the linked article, while it seems that other BUKHS do. I don't know if a Bukh 24 such as Jonathon's, has a poker or not.

My DV36 engine ran cooler than it should ... about 130 degrees F with a 180 degree F thermostat (180 F = 82 C) so I began looking into the cooling systems of DV36s. I understand from my reading that the three different cooling systems of a BUKH DV36 use three different thermostats and three different plumbing configurations. I learned that the 50 degree C thermostat for a raw water cooled engine fits into an opening in the water cooled exhaust manifold, while the 80 degree C thermostats for the freshwater cooled BUKHs fit into the BUKH reservoir/heat exchangers. I also learned that while, the reservoir tank for a keel cooled DV36 is the same in appearance as the reservoir and heat exchanger for a fresh water cooled DV36, they are not the same internally, and the cooling systems operate quite differently.

My DV36 appears to have been originally raw water cooled, but at some time this engine was converted to fresh water cooling using a non-BUKH heat exchanger. If there ever was one, it appears that the water bypass system for my DV36 was removed at that time. None of the 80 degree C BUKH thermostats, will fit into the opening in the water cooled exhaust manifold; so no BUKH thermostat is available for my configuration. My cooling system now uses a $14.85 Cdn 80 degree C automotive thermostat. This proved to be much cheaper than the $259.99 Cdn that the Canadian distrubutor of BUKH parts charged me for the BUKH 80 degree C fresh water cooled thermostat (that I had to return), but as the earlier article I posted says, auto thermostats are not the same as marine thermostats, and my cooling system has apparently been altered to eliminate the bypass system.) The engine has run very well, although cooler than it should for the four years I've now owned the boat. To see if it made any difference in operating temperature I thought I'd change the thermostat and that caused me to do this research. My engine now seems to be working at the right temperature, although I haven't yet taken it out for a good run to ensure it doesn't overheat.

I'm keeping my fingers crossed now, and my wrenches close at hand.


For the benefit of any who want to know, I'll offer the following advice regarding how to paste a link:

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Regards to all,
Brian.

[jonathan]

Thanks, all, for your thoughts.
Here is a follow up of what I think may have been contributory to the temperature oscillation.

The engine is fitted with a calorifier, and earlier this season it stopped producing any hot water.
Investigation showed that the hot supply from the aft end of the exhaust manifold was blocked with debris. This was cleared but blocked again.
I then flushed the system with RYDLYME descaler for a couple of hours. Well worth doing I might add. There was a bit improvement in hot water supply but was only temporary before failing again. The water output from the exhaust manifold seemed to me to be very small, and insufficient to supply the circulation pump as the orifice is only about 4mm. So I swapped over the piping so that hot water was now taken from the cylinder block and returned to the exhaust manifold. This seemed to be effective for a while before failing again.

The water circulation pump was tested and seemed to work OK.
I was now out of ideas again and enlisted the help of a proper engineer who, after testing the water pump again suggested, by process of elimination, that I change the circulation pump as although there was good flow may not have produced it under pressure.

I found a Mercedes Benz car radiator 12v pump, from an online car recycler, at a reasonable price and it is identical to the Johnson marine version it was replacing.

This seems to have done the trick. I have hot water. AND the water temperature gauge seems to have stabilised back into the green range without excessive repetitive excursions into the red.

The other bit of good news is that with all the water sloshing around after messing with the water system is that the missing impeller blade floated into view in the bilge sump. That was a huge relief for me.

I found a lot of useful information from Cox Engineering at their website coxeng.co.uk Its worth a look if you have problems.

In summary it seems that the initial problem was masked by a series events and problems of an intermittent nature and coincidences.

My the wind blow fair on you.

Jonathan

[Sula]

Jun 29, 2018 20:04:40 GMT Brian & Glenda said:

I believe that my DV36 does not have a 'gas poker' as referenced in the linked article, while it seems that other BUKHS do. I don't know if a Bukh 24 such as Jonathon's, has a poker or not.

In case it helps anyone in future, my understanding is -


The DV10 and DV 20 (essentially the same earlier series engine, single and twin cylinder versions) is particularly prone to clogging with scale of its 'gas poker' cooling water inlet pipe into the block, as a a result of its small holes. 

The DV24 and DV36 (the twin and triple cylinder versions of a later series engine) also has a 'gas poker' which can clog, but its larger holes make this a less common problem (also there seem fewer of this series of engines in yachts).



   

[Sula]

Aug 2, 2018 16:18:44 GMT jonathan said:

Thanks, all, for your thoughts.
Here is a follow up of what I think may have been contributory to the temperature oscillation.

Well done for soldiering on, and glad you finally got it sorted.

Good also to hear the Rydlyme descaling was worthwhile: I am intending to have a go at that soon.

[tonyp]

Jonathan, how much Rydlyme did you use? It seems that a 1:1 mix is recommended, and I wondered if you managed to get away with just using 1 litre of concentrate and 1 litre of water? 

Incidentally this is what I'd called the gas poker from our DV24 in my posts on raw water pipe to engine block.  Apologies if I've got it wrong. Pipe from raw water pump goes onto pipe at bottom of picture. The rubber hose is the by-pass that goes to the top of the thermostat.  The serious blockage we'd had was in the lowest of the 3 holes in the "poker". The whole pipe was blocked solid at this point and the scale had to be chipped out with a nail!



Tony

[Sula]

Aug 3, 2018 19:16:17 GMT tonyp said:

Incidentally this is what I'd called the gas poker from our DV24 in my posts on raw water pipe to engine block.  Apologies if I've got it wrong. Pipe from raw water pump goes onto pipe at bottom of picture. The rubber hose is the by-pass that goes to the top of the thermostat.  The serious blockage we'd had was in the lowest of the 3 holes in the "poker". The whole pipe was blocked solid at this point and the scale had to be chipped out with a nail!



Tony

Apologies, I got that wrong, there is a poker in the DV24/36 (I'll amend my earlier post). But having read further around this, the one in the DV10/20 has rather smaller holes, and is therefore more prone to blocking.

[Sula]

Aug 3, 2018 19:16:17 GMT tonyp said:

Jonathan, how much Rydlyme did you use? It seems that a 1:1 mix is recommended, and I wondered if you managed to get away with just using 1 litre of concentrate and 1 litre of water? 

Hopefully Jonathan will be along shortly to give the benefit of his actual experience.  

My 'theory' is that the mixed 2 litres is unlikely to be enough, as you wouldn't be able to get the descale mix circulating, or even if you did it wouldn't reach the whole cooling system.  (The DV36 cooling system capacity is stated as 7 litres, and I doubt the DV24 is a lot less.)  Hence I bit the bullet, and bought the 5 litre bottle of Rydlyme (yet to see action).    That'll give me a 10 litre mix, hopefully leaving me around 3 litres in the bucket.

The other side of it is that the process of descaling 'uses up' the active ingredient in the descaler mix.  Even if it was circulating, would the descaler mix be depleted and inactive before the job was finished?

[chrismunson]

If an impeller has broken up, you have a real problem. In the raw water piping and engine block, passages have bends and restrictions that collect the bits of the impeller, and block the coolant flow. A mechanic who works on your engine type will know the most likely spots for such a clog. And, given the persevere nature of anything 'marine' by name, this will be at the very last location you tear into. There are very small nozzles in the pipes that manage the water flow, and that's where the impeller parts, and other crud, will end up. My Volvo mechanic pulled heads and manifold off my raw water MD17 and got out a nice collection of little black bits. Once the impeller has broken up, your goose is cooked. Of course check the thermostat and sensor wiring IF the impeller is sound and engine still has heat problems. BTW a temperature gun on Amazon can be had for $20 and they are fabulous to have on board.

Only once I have reused an impeller, and it broke up on start up at the beginning of the season. The rubber will deteriorate in the lay-up antifreeze, just like the little valves in the head pump. Replace the impeller every season before starting the engine. Period. They cost less than one hour of a mechanic's time. Even for Volvos.

[jonathan]

Regarding Rydlyme.  I bought a 5 liter bottle not knowing how much would be used. 

I diluted about 1 liter of Rydlyme 50:50 with water as per instructions to give 2 liters of fluid.

I filled a reservoir with about 1.5 ltrs of fluid which was gradually used up in filling the system, so I added another half ltr to the reservoir.

After about twenty minutes the return flow rate through the system suddenly increased and the reservoir nearly overflowed with the returning fluid.

The instructions say to keep flushing until the fizzing stops.  This is easy to see in the reservoir. I flushed in one direction for an hour, then the reverse direction for an hour by which time the fizzing was fading.

I would say one liter of Rydlime is marginal, two liters is ample.  I have enough remaining for a second flush in due course.

Rydlyme is excellent stuff.  It is expensive, but it does what it says on the tin, and it is not corrosive or acidic.

Tip - do remove the engine anode before flushing, as it says on the instructions.  I didn't and there was nothing left of it when I changed it at the end of the season.

[Peter Stembridge]

I have had persistently high operating water temperatures on a DV24 since new. I eventually tracked it down to partial blockage of the water injection tube (referred to as the poker) which is a copper (or bronze) tube, partially crushed at the aft end (furthest end from the flywheel) and with two holes drilled in the cylinder side of the tube to direct water supplied from the cooling pump into the block and onto the cylinder sides. Removing, cleaning, re-sealing and refitting the poker is a pig of a job and this design is in my view the Achilles heel of what is otherwise a great marine engine. I suspect the calcification build up may be speeded up if the engine anode is spent (due to dissimilar metals in the raw water cooling circuit) but the design of the poker is in my view extremely poor and rudimetary at best, particularly with the increases in water temperature we are now inevitably seeing. I tend to fresh water flush the engine at the end of the season but calcification and poker blockage still remains a bi-annual problem.

[andrew41]

According my my local Bukh engineer, the DV24 normally indicates the temp on the green /red border and is not an issue. On his advice I have flushed the engine thoroughly and water flow looks reasonable. For the moment I have stopped worrying and turned my attention to the fact the calorifier is not working! It has a new circulating pump but I cannot get hot water to flow through the pipe work. I suspect a possible air block. Any thoughts on this would be welcomed. Meanwhile I resort to the kettle when at sea in Livia…..