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S&S Swan Maintenance - Perkins 4108 Oil cooler leakin water
26 April 2016 - 09:18
Join Date: 06 January 2012
Posts: 67

Perkins 4108 Oil cooler leakin water

Hi, I just noticed that the oilcooler is leaking water from the back end of the cooler unit. Not much but annoyingly a drop of seawater in every 5 to 10 seconds. As it is located at the most unreachable section of the engine I'm wondering how serious is that leak and what is the common reason for it. It might have leaked already during the last summer as there was always some seawater under the engine. Because of that I changed all the seals of the seawaterpump during the winterlayup last winter and thought this was the only reason to the sewater leak. The seawater pump was dripping seawater at the same interval of one drop in every 5 to 10 seconds.

The engine has been totally reconditioned by the PO around 10 years ago and it is running very smoothly, not overheating, starts immediately after winter, no oil leaks, etc. Nothing to complain with it. The oil is clear, no water in it.

Of course I tried to tighten the hose clamp without any change to the leak. So what do You think I should do next?



Swan 431-12 "CAID"


"Do I really need my freshly installed Marine Air Conditioning System here in Finland?" Photo taken yesterday.

26 April 2016 - 10:32
Join Date: 30 January 2007
Posts: 461


there are two oil coolers in the 4.108, one for the sump oil and another for the transmission oil.  At different times I needed to change both of them because, usually, a sea water leak means ongoing destructive corrosion of the aluminum; in my case, a 411, they are both reachable without displacing the engine - I cannot affirm that they are in confortable places, but it is a feasible job.

New heat exchangers which match closely the original ones are still available and some easy fiddling with the connecting rubber hoses is the only necessary thing to do. In all cases I used Bowman heat exchangers and they can be bought on internet: 1) Transmission, Bowman model DC60 XBB, 28mm bore; 2) Sump, Bowman model EC80.

Regarding the snow you show, it is probably a close relative of the one that passed through København last Sunday.  It is pretty cold here for an expat from Italy like me and I am longing for summer to arrive!  :-)

Daniel, 411/004

26 April 2016 - 11:40
Join Date: 29 January 2007
Posts: 1018

Dear Daniel and Ihe,

yesterday it was quite cold even in the Med, with a fresh Mistral (as you can see Julia is wearing gloves...)...

Fair winds!

matteo (47/069 Vanessa)

27 April 2016 - 09:04
Join Date: 06 January 2012
Posts: 67

Dear Daniel, thank's a lot for Your answer. I'll try to uninstall the oilcooler next weekend and find out whats wrong with it. The engine of CAID is one of the few parts that did not need any attention during the restoration and I find it bit difficult to concentrate on that after the Yacht is already floating. But ones got to do what ones got to do.


Matteo, very nice teak decks You have!



CAID 431-12

03 May 2016 - 01:13
Join Date: 31 July 2007
Posts: 88

Check the elbow where the seawater enters the oil cooler. Mine was brass and corroded and leaked. Hard to find the leak.

18 May 2016 - 17:28
Join Date: 06 January 2012
Posts: 67

Hello, I just found and fixed the problem. It was the rubberpart Bowman 3366 that was leaking for some reason. See the pic where the leak is clearly seen. I changed it to a new one  from the new Bowman oilcooler ( and the engine bay is finally TOTALLY dry!

The oilcooler I already had was totally clean and did not show any wear or tear. I suppose it was replaced during the engine renovation as told bu the PO.  Why this rubberpart did not seal is a mystery to me. It was not harder than the new part, the rubber had no cracks, ...

Bowman 3366

21 May 2016 - 19:50
Join Date: 30 January 2007
Posts: 461

I am glad that you succeeded in fixing the problem.

Those neoprene caps can indeed leak if they are not correctly and cleanly fitted on the metal body of the heat exchanger and/or the clamp used is not of the right size.

Fair winds and happy Perkins running!

Daniel, 411/004

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