D2-55 (2002)

[CRYSTAL]

Has anyone heard of any issues of 'Electrolysis' on VP D2-55 Heat exchanger casing (2002 year) or any other type of issues around heat exchangers.

Stupid questions: how is the Heat exchanger protected from the circulating sea water?
Also hoping the HE Insert is made from Bronze but not sure if it's also aluminum (better heat xfer but not good for salt water).

any ideas anyone as I'm trying to help out a good friend of mine (B44).

my friend needs to replace his HE and looking at around Eur2.5K for complete unit. (location is Cyprus)
I'll be gettting further details tomorrow once I pay his engine a visit.

thanks,
Hratch

[Willi Cinque]

I would be interested to know what the end result of this was. I have a 2002 Bav 44 with a D2-55 and there is sufficient corrosion between the rear of the Heat Exchanger case and the exhaust elbow for it to seriously leak. I pulled it down and repaired it temporarily by rebuilding the metal with a commercial grade aluminium 2 part compound but it is a temporary fix. (That said, it was done 6 months ago!)
Did your friend buy another unit or was it possible to repair the original?

[s/y Susanne]

I have just discovered serious corrosion at the junction between the Heat Exchanger to Exhaust Injection Elbow on my 2003 D2-55. This unit has been pampered and always drained as per Penta Spec so it is the cause of some anger tome that this has occurred.

The aluminium casting of the exhaust manifold has eroded either through electrolysis or acid corrosion. The result is that sufficient metal has been lost to cause a serious leak of exhaust gases into the engine bay with no easy remedy other than a new H/E unit at around £2500.

My suspicion is that an electrolytic cell is formed between the H/E casting ( Aluminium ) the gasket ( Stainless Steel) and the  exhaust elbow ( cast Iron) in the presence of sea-water. The sea-water is directed by the elbow away from the joint but it may be assumed  that in certain circumstances , such as engine shut-down, that sea-water spray can get deposited at this junction of metals.

I notice that Volvo have changed the part number from 3808561 to 21404796 for the H/Exchanger. Anyone else with this problem?  If so anyone with a remedy or information about the best welding rod choice for use on the Aluminium casting which appears to be a contract item from MOTA as an OEM supplier?

All replies appreciated

[tiger79]

In fairness, it's 12 years old.  Surely it's reasonable to expect some parts to need replacing after that time?

[Tony]

I have a D2-55 also in a 42 Cruiser, and have not been able to find a sacrificial anode in the raw water circuit which i have seen in other makes. Can anyone tell me if there one hidden somewhere and/or has anyone retro fitted an anode that may help to slow down this process. I can understand that it is a 12 year old engine and that some parts need replacement after that time but a heat exchanger imho need not necessarily be a consumable item if protected properly.  I am interested to hear the result of any repair attempt. Good luck with it.......

[s/y Susanne]

In fairness, it's 12 years old.  Surely it's reasonable to expect some parts to need replacing after that time?

Sorry Tiger but I disagree The VP D2-55 H/E costs about £3000 + and that equates to about £2/hour  of my cash going in Volvo's direction for the use of my engine.

An injector elbow made of stainless steel, or a bit of internal baffling in the exhaust would probably avoid the issue altogether (see my later post) but a 3 metal junction with the possibility of hot sea-water in the mix needs better design ab-initio does it not?

[tiger79]

In fairness, it's 12 years old.  Surely it's reasonable to expect some parts to need replacing after that time?

Sorry Tiger but I disagree The VP D2-55 H/E costs about £3000 + and that equates to about £2/hour  of my cash going in Volvo's direction for the use of my engine.

An injector elbow made of stainless steel, or a bit of internal baffling in the exhaust would probably avoid the issue altogether (see my later post) but a 3 metal junction with the possibility of hot sea-water in the mix needs better design ab-initio does it not?

The heat exchanger fitted to your engine has been superceded by a revised design, which may or may not be better.  And it costs less than £2500 inc VAT.  But I still reckon that it's reasonable to expect some parts to need replacing after 12 years' use.  The 2003T in my last boat suffered corrosion of the oil cooler, necessitating a £1000+ repair, but fortunately I discovered the leak before the engine lost all its oil and seized!

[MarkTheBike]

Tiger, I see what you're getting at but I can't agree with you. I drive a Volvo and it would be the last one I ever touched if my radiator only lasted 12yrs and cost me a couple of grand to replace. Bearing in mind how much you use a car and how little you use a boat engine, I think we're poorly served. This appears to be quite a common problem and I have personal experience of just how disastrous the failure can be. Before it failed, we'd motored from Guernsey to Plymouth in very poor weather in December and a failure then would have put the 3 of us in serious danger. Not acceptable. Needs a redesign or better quality materials.

[Salty]

100% agree with you Mark, a breakdown in such circumstance is totally unacceptable. On my previous boat the engine fitted was a Beta conversion of a Kubota diesel. Within its exhaust manifold/heat exchanger it had an anode fitted precisely to prevent such corrosion. The engine on my B36 is a Volvo conversion of a Perkins labelled engine that started life as a Japanese engine for something probably agricultural. Nothing against that, it works well, just like a sewing machine only a lot more reliable, but still no anode to protect the heat exchanger. When I bought the first service kit for the engine I specifically asked for an anode to be included with the kit, and one was supplied, but as I found out later there was no provision for fitting the anode. Has anyone converted their manifold to enable an anode to be fitted?

[MarkTheBike]

Salty - is your supplied anode a rounded zinc body with a threaded stud through it? I asked the same questions as you when getting all the bits to replace the HE that had failed. I was told that my engine (MD2030D) absolutely didn't require an anode. However, I couldn't help but notice on the blown HE casing that there's a tapped hole (plugged) that looks like it was designed for exactly that purpose. Curious.

[Salty]

Hi Mark,

It's five years since I bought that first service kit for the engine on my boat (MD2020), and I'm not sure what happened to the supplied anode. It's somewhere in my garage (read needle in a haystack), so when and if I find it I'll take a photograph and post it here.
Going back to a subject touched on earlier in regard to the longevity of heat exchangers, heat and salt water make for a very corrosive situation that has to be seen to be believed. Years ago while at sea, most of the ship's I served on had steam driven mooring winches, and the combination of them being wetted with sea water which takes an age to dry out, and then being heated with steam resulted in very rapid corrosion until a suitable substance was found that could be painted over the heated parts to prevent the sea water from coming into contact with them. Since then there has been a changeover from steam driven winches to hydraulically driven with a consequent reduction in maintenance time and costs and improved reliability.
Inside a heat exchanger you have exhaust temperatures and a cooling system which if it works reduces the exhaust temperature to the point where when the water is injected into the exhaust things should be cool enough for corrosion not to be a problem. In the event of any reduction in the cooling water flow, there is where the problem begins. Last year I had a loss of coolant where barnacles had got into the sail drive leg, and had been able to migrate past the filter and the pump and along with bits of broken impeller had caused a partial blockage of the tube nest in the heat exchanger. Running the engine on very low revs while still maintaining some flow of water through the system, I got back into harbour where I stripped the system down, and thoroughly cleaned it out. The broken impeller parts had not occurred during my ownership of the boat and until that time I'd not opened up the heat exchanger. As a result I purchased a thin bottle brush from eBay and cleaned all of the tubes and hoses, but was not able to get the brush to go down through the opened water inlet valve on the sail drive. With the boat very recently ashore I've used the brush from below through the opening in the bottom of the sail drive as well as through each of the side openings and also used a pressure washer on it as best I can. More barnacles were removed, leaving the system clean, I hope !! I've also fitted an ultrasonic antifouling system which should hopefully contribute towards keeping the nasties at bay. The point I'm making is that there may be more than one factor resulting in degradation of the heat exchanger.
Later in the day - found the anode, by chance I happened to look in the right place early on in the search, see photos below. There are no markings on the anode which might otherwise provide some clue to which machinery it belongs. At one end it has a spindle that protrudes with flats on two sides and with a thread cut into the remaining part, while at the other end there is a hole drilled into the anode with a thread cut into it.

[s/y Susanne]

I can only refer to the corrosion in my case which has occurred at the exhaust gas outlet from the heat-exhanger aluminium casting where it joins the cast iron "wet" elbow at the aft end of the engine.

This corrosion, from a mixture of hot sea-water and hotter exhaust gases, now seems to be a direct consequence of chemical reaction caused by injected sea-water splashing backwards towards the exhaust ports,  and that is exactly what the "wet" elbow" is supposedly designed to avoid.

The elbow is cast  in iron with a cavity and two "injection ports" to jet pumped sea-water in the same direction as the exhaust gases and away from the engine.

The problem is that the elbow is simple, plain, humble cast iron. This corrodes nicely with the hot sea-water over time. The injection ports become enlarged and then new holes appear that  also inject water, BUT not necessarily in the correct, aft direction. Hot seawater  plus warm dilute sulphuric acid, you can see what is going to happen!

This whole process of corrosion is hidden to the owner. I have not seen it written anywhere that it is advisable to periodically inspect the elbow by running it with a hose connected to a water-tap to determine if the injection path is correct and that there is no splash-back.

IMHO the problem was foreseeable. The solution would not necessarily be complicated as the cast elbow could have been vitreous enamelled inside. A relatively simple process used in water heating boilers throughout the world. Fabricated stainless steel elbows seem to be popular as replacement for Yanmar and some VP engines but none yet for the D2-55 or 75 variants.

That said, the welding on these aftermarket components will always be a source of potential corrosion and I would be interested to hear from anyone else if they have evidence that these S/S fabrications are holding up.

I am hoping to commission for delivery in July 2015 an investment moulded, cast-stainless component as a replacement for my repaired Cast Iron VP elbow. Anyone interested in a group-buy please let me know. (price as yet unknown, but lower price than the VP part!)

[MarkTheBike]

S/Y Suzanne - more very interesting insights into the problem, and the enamel coating idea would go a long way (IMO) to prolonging the life of the elbow (and in the coolant side of the HE!) for a very low cost (although I'm sure VP profits would drop). I would certainly have joined a group-purchase idea had I not replaced my elbow six months ago. Grrrrrrrrrr.

Salty - I can certainly see how the blockages you found would have led to the failure and your method of clearing it sounds pretty thorough. Little blighters. You were lucky to limp back into port. I think most of us would like to hear how effective the ultrasonic A/F is, perhaps you'd update us from time to time. I am guessing that the anode is about 40-50mm long. It does look as though it would fit although the tapped hole in my old casing is in the coolant side - does that matter? Any idea of the thread size?

[aquapore]

Hi all

I had a similar trouble with a corroded exhaust manifold with large hole blown near the elbow. 

I repaired the engine by having a welder grind out all the corroded aluminium, cut of the outlet flange off and weld on a new flange made out 15mm alum plate.

Having spoken to Volvo, they regard the elbow as a consumable to be replaced every 5 years. My boat is 12 years old and the elbow was totally caked with carbon.

I chipped/ground/bashed all of the carbon off and soaked to elbow in a strong solution of EDTA to get it down to bare metal wihch showed pits about 1 mm deep.

I dip coated the whole elbow in a high solids epoxy paint blowing it through and clearing the passages. I then built up the machined mating flanges with more epoxy and on curing linished it flat. The idea was to produce a proper corrosion barrier and electrical isolation from the aluminium.

It has been going for more than a year now. The elbow does not get hotter than about 50 deg C. Industrial epoxys can take you to 120 deg C.

I note that there was a stainless steel shim piece about 0.5mm thick between the aluminium manifold and the elbow that I have no idea why - perhaps someone can shed light.

On a more general note I understand that the problem of corrosion is made worse with higher sulphur fuels that give rise to sulphuric acid and also long down time is also said to be bad. My boat was part of a deceased estate and lay idle for 3 years. That is what probably caused the problem.

Hope this helps.

Regards

Aquapore

[Salty]

Hi Mark,
Regarding the anode, the overall length is 40mm of which the protruding threaded part occupies 10mm. That protruding part has a flat section on opposite sides while the remaining part has a 12mm metric thread cut into it, this was checked with a die. Internally there is what appears to be a 6mm thread cut into the anode and while this was checked with a 6mm tap, some metal was very easily removed by the tap such that there may be another thread size that is more or less similar. As for the ultrasonic antifouling, I intend to post information about it in due course but assuming I do, it will be under a specific heading. At present it is too soon to tell whether it is providing any significant benefit.

[MarkTheBike]

Hi Salty

Thanks for the feedback. I'll dig out the old HE and check it for thread size and depth, but it sounds about right. Perhaps the two flats are for a spanner poked in to tighten.

Looking forward to your experience of the ultrasonics; yep, definitely a separate topic...

Cheers