Engine surgery
When Geoff Higginbottom stripped down his underperforming Volvo Penta MD2030 diesel engine he uncovered some expensive repairs
Stripping the cylinder head from a Volvo Penta MD2030
During the summer of the 2019 our Bavaria 39 Tessa began producing black exhaust smoke and suffering a reduction in power from her 2005 Volvo Penta MD2030. Initial investigations covered the usual suspects such as fuel issues, blocked exhaust elbow etc, which resulted in the fitting of a shiny new stainlesssteel exhaust elbow.
But I was unable to isolate the exact cause before our annual cruise around the Channel Islands and northern France, so we simply kept the revs low while motoring and enjoyed our holiday.
However, while motor-sailing from St Peter Port to Cherbourg, the smell of unburnt diesel increased and just a couple of miles from the west entrance to the harbour we started emitting rather a lot of white smoke.
We limped into Chantereyne marina and were luckily able to berth on the hammerhead, which reduced the amount of time manoeuvring under power and kept the white smoke to a minimum. We obviously needed to address this tout-suite so cancelled our plans to continue onto St-Vaast-la-Hougue and set about investigating a possible defective or blocked injector.
Surprise breakage
I successfully pulled the front two injectors (of the three), but the aft-most one was surprisingly loose. Diesel injectors should be fitted with relatively high torque, so when I set to removing the retaining nut for the fuel leak-off pipe attached to the rear cylinder, I was genuinely surprised to see the whole injector rotate as well. Inevitably, the result of this rotation was that the brass leak-off pipe broke.
With the three injectors all pulled, a quick inspection of their ports highlighted that the rear injector port was completely blocked with carbon build-up, and I attributed the cause to the loose injector. We also noted that there was a lump of something that looked like calcified carbon still partially blocking the injector port, but this proved impossible to remove.
I cleaned the rear injector port, and made a temporary repair to the fuel pipe using JB Weld before reassembling the system. An engine test confirmed we had, at least, stopped the billowing white smoke.
Due to a lack of brazing equipment on board, which could have been used to affect a more permanent repair of the leak-off pipe, I decided to visit a few local garages and workshops to see if anyone could fashion some kind of repair for me. Unfortunately, I was out of luck.
Plan B therefore was to use the Volvo Penta Action Service (VPAS) to source a replacement part. This was now Friday afternoon before the August bank holiday and we had crew joining us on the following Tuesday ready for a sail back across the Channel. VPAS were very helpful with identifying the correct part number, locating a local dealer, dealing with translation challenges, and getting them to deliver it right to the marina on the Monday. However, I ended up having to pay r200 for a part you can get online in the UK for £50.
With the replacement fuel pickup installed and wine stocks replenished we enjoyed a lovely sail back across the channel stopping overnight in Yarmouth, before continuing on to Portsmouth. Engine power was still slightly reduced, but there was no billowing white smoke. I knew I’d need to remove the cylinder head in order to identify the foreign object in the rear cylinder injector port, and as the boat would be moving to her winter home in October, we enjoyed a number of weekends in the Solent without incident.
Getting to the root cause
Once the boat was in her winter home at Hornet, Gosport, I could focus on the task of pulling the cylinder head and investigating further. I removed the injectors and sent them off for servicing as well as ordering a cylinder head gasket kit in preparation for what I hoped would be a weekend-long job. Then I set about removing the cylinder head (see the step by step guide overleaf) and discovered the true cause of our loss of power.
The engine, which is actually a Perkins unit rebranded by Volvo Penta, has pre-combustion chambers. These make the engine easier to start and also improve fuel efficiency by partially igniting the fuel in a small chamber, before it gets squirted into the cylinder.
The chambers are sealed with conical inserts containing a number of holes which shape the charge as it enters the cylinder. The foreign object I’d earlier assumed was calcified carbon was in fact the remains of the conical cap for the rear cylinder. The good news was it had remained within the pre-combustion chamber and had not entered the main cylinder, as I’m sure this would have proved to be terminal for the engine.
The bad news was this was obviously not going to be a quick fix.
I needed to send the head off to a specialist for repair, so I made contact with a Perkins specialist who informed me that while it’s technically possible to replace pre-combustion chambers in a number of different engines, it was not possible for this particular engine. For my engine, the cylinder head is considered a single part, so Perkins do not make the individual component parts available.
I searched for a second-hand replacement for a couple of months but eventually had to stump up around £1,200 for a new Perkins head.
I did contact Volvo Penta who insisted their heads are machined differently so I should use a Volvo Penta version (at least 20% more expensive). Well I thanked them for their advice and then fitted the Perkins head. So far all is well...