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Technical Engine Engine Core Plugs - Volvo Penta MD22L

The Volvo Penta MD22L fitted to the Maxi 38 has a 18mm diameter core plug fitted to the heat exchanger... and is virtually inaccessible. The plugs rarely (if ever) fail and so they are not available as spares. So read how Caorann spent £166 searching for a solution that did not necessitate removing or replacing the whole heat exchanger. The solution is to tap the plug hole and fit a new threaded plug...

My Volvo Penta MD22L fitted to CAORANN, my Maxi 38, developed a small leak of coolant mixture from a nearly inaccessible 18 mm dia. core plug in the heat exchanger. Well, one might think it should not be too difficult to replace a small piece of metal (around £0.50 worth). Just need to contact a Volvo dealer...

The first three dealers said they had never been asked for this particular core plug. On checking their Volvo manuals, this part of the heat exchanger is not shown, nor are any parts listed. Even the Volvo dealer web site had the same answer – nothing! Not to worry, Volvo H.Q. Watford will have all the answers! But it wasn't until two weeks later after numerous phone calls that we got an answer from Volvo Sweden: "Core plug no longer available. Suggest you fit a new heat exchanger". The heat exchanger costs around £300 and apparently, the whole reason for having core plugs is so they can "pop out" to prevent the heat exchanger cracking if the coolant freezes!!!

Well, surely motor accessory suppliers could identify a suitable core plug? After more than 100 miles of searching, something was found but even after trying various sealants, the leak persisted. So yet more phone calls led to Volvo finally proposing to fit a 1/2" - 14 NPSF tapered thread plug. However the only answer regarding recommended sealants was "no sealant is mentioned in the manuals". And since the core hole needs to be tapped to accept this "new type" plug, the heat exchanger should ideally first be removed even though its fixing bolts are obstructed by "glued" finished timber work.

In the end, my local marine engineer managed to tap the hole (working upside down!) with the heat exchanger still in situ. He was then able to fit the tapered threaded plug supplied by Volvo Watford with sealant applied and I'm pleased to report no more leaks! This whole saga meant the boat was out of commission for 4 1/2 weeks and cost £165.67 just to find an alternative for 51 pennies worth of core plug.

CAORANN

Last Updated (Thursday, 25 February 2010 00:02)