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Old 28-10-2011, 02:25   #1
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Perkins Losing its Blood

Hello to everyone,

I have a perkins 4108 from 1985 with 3000hrs on the clock. The engine runs great, does not smoke, and does not overheat (80c running temp). My only problem is oil loss, I know perkins are famous for leaking oil but mine goes from Max to Min on the oil gauge in about 20hrs of engine time. There is always a lot of oil in the bilge after running the engine. Based on your experience is this more or less normal and I should live with it or totally crazy indicating a serious problem to come?

Thanks for your help

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Old 28-10-2011, 02:45   #2
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Re: Perkins loosing its blood

Our mechanic says that the Perkins 4108 is known as a leaky engine and he has never seen one that did not seep oil from somewhere. However, he says that most of those leaks might have been prevented with regular maintenance. Our engine is the same vintage as yours and predominately leaks from the valve cover gasket (just changed for the third time and yes we checked to make sure it's not warped); the timing cover gasket; the old tach drive (the one in use comes off the alternator now) and a bit where the oil filter attaches. We don't use up oil as fast as you report though. Our mechanic suggested that we degrease the engine and look to see where the predominate leaks are and then fix them one at a time (or as you can afford them) and monitor the oil level closely.

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Old 28-10-2011, 05:53   #3
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Re: Perkins loosing its blood

Greetings and welcome aboard the CF, Liber.
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"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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Old 28-10-2011, 05:56   #4
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Re: Perkins loosing its blood

Liber, your engine's oil consumption (and leaks) is excessive and unless you do something about it, you will end up stranded somewhere. Your bilge should not be full of oil and you cant pump that oil out using your bilge pump.

I suggest that you clean and degrease your engine and run it to see where the leaks come from before making decisions on what to do. If necessary it is possible to remove the engine and replace the various gaskets and seals and refit the engine and get many more years out of it.

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Old 28-10-2011, 06:26   #5
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Re: Perkins loosing its blood

The 4-108's 'famous' leak is at the rear seals. It seems they all leak there to some extent or other. The mechanic who worked on the warped head on mine said it's common and, except in the worst of examples, simply lived with (a lot of the fishers and shrimpers here in the Gulf have 4-107s or 4-108s in their boats so he saw a lot of them). It's generally controlled by an oil absorbant pad under the engine.

I'm not sure what you are describing by "Max to Min on the oil gauge" though; I assume oil pressure? That may tell you oil levels are dropping but it doesn't tell you how much oil you actually in the engine or have lost. I chiefly rely on the dipstick as the most reliable indicator of the amount of oil in the engine (and oil loss over time). Are you losing a considerable amount of oil per the dipstick in the 20 hour runtime you describe?

On my 4-108 the rear seals seep. But it's surprising how just little oil seepage has the appearance of a LOT of oil in the oil absorbant pad (on my engine, in a pan beneath the engine), flung around the engine compartment and occasionally ultimately draining down into the bilge (where I have a bilge sock as a backup). Even just a few drops gives a considerable amount of oil film on the pad and the engine itself; and it doesn't take much to give a sheen on bilge water.

That said, I've seen a bit of an increase in oil in the bilge of late - more than I think is accounted for by the rear seals. But there's no appreciable loss in the engine oil level per the dipstick. As already suggested here, I've already bought a can of degreaser. My plan is to first check around the engine where I can see some oil runs at fittings, and check for tightness (my engine mounts have a tendency to work loose over time, leading to vibration, and I'm thinking leading to things loosening up); tighten where necessary; degrease, and monitor for leaks.
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Old 28-10-2011, 08:35   #6
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Re: Perkins loosing its blood

When I went into the shop in Australia to buy a new rear seal for my 4108, the man there said that I might as well plan on changing the oil pan gasket and the front seal too. He was right, as the leaks ( it got up to a quart a day) continued until I replaced the oil pan gasket. The oil pan gasket is cork, and after 25 years it loses its ability to hold oil. I was able to replace it in the boat by lifting both ends of the engine up about 12 inches.

The rear seal is designed for 'controlled leakage', and the manual devotes half a page on how to install it. Replacement can be done in place, buy a lot of stuff has to come off. The front seal is relatively easy, but it is a more modern design and never leaked on my engine.

If you ever pull your perkins out of the boat, plan on replacing the rear seal and the oil pan gasket while its out--its MUCH easier.
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Old 28-10-2011, 21:11   #7
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Re: Perkins Losing its Blood

This is just the reason I re powered with a Beta. The Perkins/westerbeke rear seals are ancient technology that always leak. I am a great deal poorer but my boat is a great deal cleaner, and it doesn't smell like oil now.
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Old 28-10-2011, 21:37   #8
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Re: Perkins Losing its Blood

my 4-108 is a 1979 model. i bought the boat in 2005 with an unknown number of hours on the engine. clock hadn't worked in years so i just keep an engine log.

yes it leaks to some extent. i would guess that i put in one half to one quart of oil every 20 hours or so. but it starts easily, runs well, doesn't smoke except when starting, and the engine oil pressure is up where it belongs.

not going to do anything about it except keep maintaining it as usual and hope for the best, although i will clean it as you suggest and see if i can find some obvious place where it might be leaking....
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Old 29-10-2011, 22:29   #9
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Re: Perkins Losing its Blood

I replaced a thoroughly dead 4.107 with a 4000 hour 4.108. I took the 108 to my auto shop and replaced all of the seals and gaskets. It doesn't leak.
This is, however, not a fair comparison because I did the work in a clean and well lit, well equipped shop on an engine stand. Not in a boat. Also I am accustomed to working on Porsche air cooled engines which tend to do 2 things; leak oil and have bitchy owners. I've learned a lot over the years about stopping oil leaks and I put it all into play on that Perkins.
I will tell anyone who's trying to stop their oil leaks 4 things.
1. Don't cut any corners. Everything must be perfectly clean and it must fit together well or it will leak.
2. Loctite 574 anerobic sealant or the Volvo equivalent (cheaper) works wonders on many gaskets and on all metal to metal joints.
3.RTV is not a cure-all. I only used it in one place, on the 4 corners where the 4 piece oil pan gasket meets.
4. Don't over tighten gaskets.
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Old 29-10-2011, 22:41   #10
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Re: Perkins Losing its Blood

Check the hoses to the oil cooler as this could cause your problem and would be an easy fix.

I have a 1969 perkins 4-107.
It has 500 hours on a rebuild by previous owner who put in a one piece rear main seal. The oil level on the dip stick never changes. It does not leak, it does not smell.
Do I have the only one that does not leak oil?

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