4.108 Oil Pressure

[cburger]

I recently purchased a twenty year old Perkins 4.108 with 5000hrs on it. The engine was in the previous owners boat so I was able to sea trial it under load for about an hour. Motor had a couple of issues, but nothing that seemed out of the ordinary. As the motor is currently in my garage waiting to be dropped into our vessel next year I want to go over it a throughly as possible.

One of the issues of major concern is that everytime the motor was started the low oil pressure alarm came on. After about 20seconds the alarm goes off and during the alarm period there is no abnormal running of the engine, no smoke, knock etc, smooth as silk. Needless to say I still want to investigate the cause and rectify the problem. Is there a high proability that the oil pressure alarm itself is faulty and before I go throught the trouble of just swapping out a new oil pump is there a way to check to see if the alarm is the cause. If it turns out to be the pump is this something a fairly experienced guy can do himself, I have all the shop manuels? Would it be a good idea just to swap out the oil pump as GP considering the ammount of engine hours and the accessability of the pan now? I am also going to have the injectors serviced and replace the rear main seal whilst doing all of this, thoughts? Any other service points that I should think about?

Thanks,

CB

[Pblais]

After about 20seconds the alarm goes off and during the alarm period there is no abnormal running of the engine, no smoke, knock etc, smooth as silk.

There may not be anything wrong. 20 seconds seems only a bit long.

[ssullivan]

I agree with Paul. I had a 4.108 in my last boat and the pressure alarm was audible for maybe 3 seconds after startup.

20 seconds is longer, but as you said, the sensor could be sticking or something. Not really worth all the effort to fix. Also, just watch the oil pressure gauge and see if it is corresponding to the audible alarm. If not, don't worry about it.

Say hi to the Tappan Zee for me.

[cburger]

Thanks Sully, the TZ says hi back. No oil pressure gauge on this panel, I plan to install one as part of the refit. Go Giants!!

[never monday]

go to AutoZone and buy a cheap mechanical gauge. install is where the oil pressure alarm switch is. Read the pressure when you start the engine. There will be a normal delay and ramp up in pressure, but it should reach 40psi in less than 10 sec.

I'd inspect and replace as necessary every piece of sheet metal on the engine. Oil pan, timing cover, valve cover. All of these are thin and corode easily.

[Maddog]

I think your fine. Go with the advice on the mechanical gauge. If you need a new alarm, go wiht the Cole Hersee 4112-RC. I belive it is standard with most panels. Dual alarm for Oil and water. They make a kit that sells through WM that includes the alarm and the senders. Enjoy the perkins.

[cburger]

As usual, tahnks all for the great insights, nice when you don't have as much work as expected!

[Pblais]

nice when you don't have as much work as expected!

You really don't think this is the end do you? It's all just one problem at a time.

[cburger]

A quick thought, the boat origionally had a Perkins 4.108. The old panel is really nice VDO gauges, panel that came with the new old engine has a panel out of an 80's era Benetau, not as nice. The new old engine is a 4.108 low profile type, the origional was a standard model. Will the old wiring harness match with the newer engine and should I be able to keep the older gauges??

[cburger]

Hey Paul I would welcome one problem at a time, its the twenty at a time that has been the challange lately. How's your weather, warming a little??

[Kanani]

Man.....if I were in your shoes, I would take this opportunity to pull the crankshaft out of that thing and put in all new rod and main bearings and new seals & gaskets. I mean......it's sitting on the floor....in the wide open. Heck, I'd do that even it didn't have the symptoms that you describe. Pulling the crank on that engine is no big deal.....unless the engine is in the boat. It's a one day job and less than $200 in parts. Unless you put in a new oil pump (good idea too).

Low oil pressure on those engines is often a sign of worn bearings.

Trust me....you'll kick yourself if you don't do it. Especially if you plan to cruise this boat. At the VERY LEAST.....replace that main crank seals on both ends. If it isn't leaking now, it soon will.

[GordMay]

The Cole Hersee 4112RC Dual Alarm combines a warning light and buzzer:

Lo Oil/Hi Temp Engine Wiring: http://www.colehersee.com/04resource...nfo/IF-132.pdf

And:
http://www.colehersee.com/pdf/IFs/IF-119.pdf

[donradcliffe]

Chris,

As the PO of your 4108, let me add a little history to the oil pressure and see if the experts can shed more light on things.

Around 2,000 hours ago, I noticed that the oil pressure alarm would stay on longer than expected on startup if the engine had not been run for a day or so. If you shut down the engine and start it up within a few hours, the alarm goes off within the normal 2-3 seconds. Then I found that if I used oil filters without a built-in non-return valve the filter (spin-on mounted with the hole on the bottom) would lose all its contained oil within a few hours, requiring the pump to refill it before the oil pressure came up. I could take the filter off after it sat for a day and it would be dry.

The genuine perkins filters have non-return valves, and helped, but even using them things aren't quite right. Once the motor has been run for a minute or so the pressures are normal, indicating the bearings etc. are in reasonably good shape. My suspicion would be something like a sticking internal one-way valve in the engine internal oil system, or an internal leak in the filter housing which allows the oil to drain back out of the filter into the crankcase, but maybe the experts can help. If the problem got too bad, I was going to look at an external oil filter system where the hole is on the top of the spin-on filter, but I never had the engine out of the boat where I could tear into it...a new oil pump certainly wouldn't hurt, and maybe it would cure the drain-back problem.

[never monday]

If the filter is mounted horizontal or thread down. This could be the cause of the problem. Some aftermarket filters have poor drain valve designs. Theres plenty of info all over the web. If it's mounted threads up. I have a harder time with this being the answer. A new oil pump won't cure a filter that's draining. the empty space is still there and needs to be filled first before the oil pressure sender knows it has pressure.

[drh1965]

Maybe you have a bad Oil Pressure Relief valve? Mine is screwed into the oil pan and is very gummed up. I suspect these parts must fail frequently.