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Old 20-08-2012, 09:05   #1
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Perkins 4.108 Rebuild?

I think I already know the answer to this but I am hoping I am wrong. I am and ex-navy nuc mechanic and have pretty good mechanical skills, but this is a first for me and I want to be sure before I start thinking about ripping apart my Perkins 4.108.
Yesterday we were heading out for a day of sailing when I got a drop in RPMs without touching the throttle. I throttled back up to 2000 RPM and a few minutes later I got another RPM drop followed by loud mechanical "banging" coming from the engine. I throttled down and limped back the dock. When I tried to throttle back up I got the same banging just before making it back to the dock. Engine temp hit 220 during the process.

After shutting down, I checked oil level and it was about 5 times higher than max on the dipstick and extremely thin. The oil was not emulsified so water in the oil was ruled out. I'm assuming the sudden rise in oil level is due to Diesel fuel being introduced into the sump. I noticed a high oil level several weeks ago which I just attributed to overfilling during the last oil change. I should also note that the oil pressure guage has never read above 10 psi which I assumed was due to a faulty sensor or guage (now I think wrongly).

This morning I drained 8 quarts of VERY thin oil (should be only 4 quarts) and replaced with fresh oil. I started the engine and place it under load at 2000 RPM while at the dock. The oil pressure guage read 40 psi at 2000 RPM (so evidently the whole time I was getting 5 or 10 psi it was accurate). After 10 minutes or so I again got the sudden RPM drop, and the engine began to heat up to 220 at which time I shut it down. I never got the "banging" but to be honest didn't let it get that far.

I believe I am looking at two distinct issues:
Firstly, somehow I am getting diesel fuel into my oil sump which caused my oil to thin drastically and lead to low oil pressure. I thought maybe a faulty injector but the engine has always run smoothly with no perceptible misses. I read somewhere of a faulty lifter pump could cause this (?). Could that be a possibility?

Secondly, I believe that the oil issue has led to a far more serious problem with the "banging", loss of RPM and overheating. I hope I am wrong, but I am guessing that I may have damaged my engine bearings, and that this is causing the engine to bog down (RPM loss) and over heat due to the increased friction and work load. The engine still starts very easily.

What do you think?

I know that there are some VERY experienced people on this forum and hoped you might be willing to offer your opinions and advice.

If a rebuild is necessary, do you think it is feasible (if necessary) to do a rebuild with the engine still in the boat? With the boat down, I have no way to get it to a yard which is 10 miles away. I am a pretty good mechanic but have never done a diesel rebuild, though I believe I could pull it off. Would I be better off re-powering. If so, how much do you think each would roughly cost (rebuild vs. repower).

Thanks for taking the time.

Scott
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Old 20-08-2012, 10:34   #2
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Re: Perkins 4.108 rebuild?

There are only 3 places where your engine might admit fuel to the crank case: At the lift pump through a blown diaphram; at the drive to the Injection Pump with a blown seal; or, at the Injectors. From your description, however, I would guess that you might have blown an injection nozzle tip that may be/have been sculling around in the top end of the engine with your "banging" being an obstructed valve being bashed by a piston. I'd start by pulling the injectors to see if they are all intact. If not, pulling the head is the next move, which can be done in place. Unfortunately, a rebuild "in-place" would be pretty difficult, if not impossible, on any boat due to the difficulty of reaching the bottom end which will be necessary if you have damage to a piston. Sorry old son...

FWIW...
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Old 20-08-2012, 10:42   #3
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Re: Perkins 4.108 rebuild?

Major overhaul is in order, drop in oil pressure when hot is worn bearings. The fact that you had 40PSI on fresh oil when cold, and then a drop when warmed up indicates that your bearings (one or more) are warn. Your rings are obviously worn as well as diesel is finding its way pass the rings and down into the crankcase washing off the lubrication and causing increase in friction, and heat.

I rebuilt two atomic 4s, before rebuilding my first diesel 4.108. It is doable to do what you're intending. But be prepared to spend a LOT of time. When compared to simplicity of Atomic 4, I have to say i spent 5-10x more time on same task when rebuilding 4.108 as opposed to A4. So plan on spending significant amount of time.
I ended up re-building it at home. Me and a friend loaded the major assembled components into his SUV, then I hoisted it up with a main halyard up and into the cabin. Then i put on Injection pump, tranny, fresh water circuit, starter, alternator and pumps. It took, like i said about 10 times longer then what would have taken me with Atomic 4.

So far i got about 50 hours on it this summer, and its running like champ. I love how little fuel i am using. About 1/2 gal/hour.
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Old 20-08-2012, 11:47   #4
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Re: Perkins 4.108 rebuild?

I had a similar issue. Oil level increased and got thin. I also sent a sample to Blackstone for analysis. They confirmed diesel in fuel plus antfreeze.
Start with the simple cheap causes first.
Remove the manual fuel pump and check the diaphragm.
Next do a compression test to see if compression is good. If you are lucky the banging was due to an over filled crank case.
I never found what my leak was due to but TAD perkins people told me 99% chance it is a bad seal on injector pump. So I pulled it and injectors and sent out for rebuild. Just got them in and fired the engine up last weekend so we will see.
When I had my problem I might note the engine oil level was stable but only increased in level slowly (after sitting for a week not being used).
I dread the day I ever have to remove my engine but if I did I would remove starter, alternator,injection pump, transmission (of course) and head. I think At that point it could be manhandled out.
Hope this helps..... We all feel your pain.
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Old 20-08-2012, 11:52   #5
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Re: Perkins 4.108 rebuild?

Quote:
Originally Posted by svHyLyte View Post
There are only 3 places where your engine might admit fuel to the crank case: At the lift pump through a blown diaphram; at the drive to the Injection Pump with a blown seal; or, at the Injectors. From your description, however, I would guess that you might have blown an injection nozzle tip that may be/have been sculling around in the top end of the engine with your "banging" being an obstructed valve being bashed by a piston. I'd start by pulling the injectors to see if they are all intact. If not, pulling the head is the next move, which can be done in place. Unfortunately, a rebuild "in-place" would be pretty difficult, if not impossible, on any boat due to the difficulty of reaching the bottom end which will be necessary if you have damage to a piston. Sorry old son...

FWIW...
Yes I had this happen on Perkins 4-236. I had diesel in the oil. Amazxingly , the engine seemed to run good although that one cylinder was obviously not firing. With the crankcase full, your pistons were having trouble moving! It pays to check your oil often. Have you tried running again since you removed the excess? maybe you'll get lucky..... If the engine is damaged, it needs to come out, and a pro needs to check the crankshaft etc for damage....
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Old 20-08-2012, 12:00   #6
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Re: Perkins 4.108 rebuild?

Had the same problem
Injector pump rebuild fixed it
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Old 20-08-2012, 13:26   #7
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Re: Perkins 4.108 rebuild?

My advice is do the easiest simple cheap things first before talking yourself into a rebuild and there are already rebuilt engines on the market.

If you do want to rebuild then it can be done aboard if you have room above the engine to lift it high enough to get to the bottom end or if you have space to roll it to one side. If you can remove it from it's engine bed and move it forward into the cabin you also might have a chance at a rebuild aboard. It would all be much easier to rebuild in a shop at home.

kind regards,
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Old 20-08-2012, 14:06   #8
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Re: Perkins 4.108 rebuild?

I would work from the top down.
First remove the injectors and have a look at those,
Then do a compression test since the injectors are out,
The compression test will give you your next lead and you might need to pull the head.
If all that fails it could be rings or even bearings: complete overhaul...
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Old 20-08-2012, 15:22   #9
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Re: Perkins 4.108 rebuild?

From what you tell me you have some serious problems as recognised by othe forumites.

I would personally not waste time checking any further, with the forlorn hope of a possible magic solution... the 4108, and i have one, is a very reliable engine but do wear over time. I would not be to scared of stripping her out, go slowly, make notes as you go along, and get her rebored, crankshaft reground, and fit new end and main bearings which will be available to whatever the pins were ground to, rebore and fit oversize pistons, and rings, reassemble with a quality build graphite or similar to all working parts, cleanliness here is next to godliness. Take injection pump to a diesel engineer who will set up the injectors at same time. a new lift pump would be good,done properly you will have a new engine. I really dont think there is an alternative less expensive, if you have the time go for it.
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Old 20-08-2012, 16:09   #10
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Re: Perkins 4.108 rebuild?

You're looking at the worst case scenario.

Best case is that the lift pump diaphragm failed and pumped diesel into the crankcase?

In this case the basic fix is to rebuild the lift pump, replace the oil and see if the engine works...

Since it's going to be difficult to rebuild the engine where you are this fix (or fixing the injector pump or whatever caused the original problem) could buy you enough time to line up a replacement block/engine and to get your boat to where it can be fixed.

You don't say how old the Perkins is, but they're getting to be old engines, and other components like the transmission may be reaching the end of their service life. If cost is not a problem repowering with a modern engine may be a better option.
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Old 20-08-2012, 16:34   #11
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Re: Perkins 4.108 rebuild?

sapadeni, Slow down! Much of the times that there is excessive fuel in the oil , it is a bad diaphram in the lift pump. It only costs you the price of a gasket and an hour or so of your time to check it. I have had it happen on 3 differant diesels in my life time. One of them ran away and made the most godawful noises that could be imagined. I replaced the lift pump and it was still running good 700hrs later when I sold it. Check for tiny cracks or pin holes in the diaphram with a light and a magnifying glass. If you are lucky, that will be all there is wrong. If the pump is OK then pull the injectors and rent a borescope and diesel compression tester. That should tell you if a piece of valve broke off and damaged a piston. If it ran smooth between problems then that is an unlikly cause, but should be checked for, along with doing the compression check. The compression test should give an idea of if you really need to tear down the engine. If the compressions are fairly equal and the bore scope doesnt show damage, then dont tear it down yet. At this point you are probably into it for 150-200 dollars and maybe 4 hours of your time. Get the injectors tested and maybe overhauled anyway. While the injectors are out, aim the injector pipes in a safe direction with a big old towel to catch the fuel, and turn the engine over, be very careful since the fuel will come out a something like 1500PSI and can do major injuries. Turn the engine over for long enough to see if the spray from all 4 pipes is even, or if 1 or 2 are differant from the rest? Do this at about half throttle. If you havent found the culprit by now, you start on the bigger buck things. If the tests so far havent shown an obvious problem, then the next step I would take is to take the injector pump off and have it tested for a leaky front shaft seal. This is less likly than a bad lift pump, but certainly can happen. Might as well get it overhauled while it is off. You might be into it for 1000_1200 dollars, and you have tested just about everything that can cause the problems that you have described. You may have to have a tech retime the injection pump, but other than that ,most of the labor is your own. If in all of this you have found the problem, then I would run it and watch the oil pressure and level closely and have oil analysis done at maybe 20 hr intervals to determine if there has been any actual damage. Perkins are extreamly tough engines and can take some real rough treatment.____Good Luck with it and keep us posted as to the outcome._____Grant.
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Old 20-08-2012, 17:12   #12
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Re: Perkins 4.108 rebuild?

Hope for the best and prepare for the worst.

Giving in at this point, before a thorough troubleshooting is not the cheap solution.

The first step is to isolate the cause of increasing oil level.

After the oil change and you restarted the engine, did the oil level go up again? In that short period of running how much did it go up?

The RPM fluctuation could be a result of mechanical problems but it could just as easily be another symptom of a failed lift pump.

If there is no knocking after the oil change you could be OK. The continuing symptom that concerns me is the high temperature.

It is really important to be observant of everything and try to understand how they repate to each other. At this point, if I read right you have the following symptoms - forget what happened before - only focus on what happens now.

- Oil level still increasing?
- RPM fluctuates
- Water temperature goes high
- Does oil pressure go low?
- Pull the fresh water cap - when water temperature goes high do you get bubbles/pressure in fresh water system? (sign of head gasket)
- I presume there is a good stream of raw water in the exhaust? (i.e. no failed raw impeller)

Let's say the lift pump is blown. This can thin the oil and cause low oil pressure. The oil level can rise to the level of the skirts. The oil would be seriously foamed by the crank shaft and foamy oil does not pump well = low oil pressure

The banging is a bit of a mystery. I would expect the high oil quantity would not do this. When the case got full the downward stroke of the piston should pretty much pump it out the breather. There should have been an oily mess in the bilge.

I suspect the banging could be related to high temps. A very high temp on the engine could result in combustion starting early and like a gasoline engine you get what sounds like a ping or in the case of a high compressed diesel a big knock/bang.

So the second thing to understand is why is it overheating.

If you can isolate these two issues you can decide whether the engine needs to be overhauled or whether you are looking at a lift pump and perhaps a cooling system repair.
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Old 20-08-2012, 17:20   #13
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Re: Perkins 4.108 rebuild?

Thanks guys. I really appreciate you all taking the time.
As I mentioned, one of my biggest concerns is the sudden loss of about 500 RPM and subsequent high temp when I tested the engine under load (albeit at the dock) at around 2000 rpm, even after I changed the oil. Could placing it under load at the dock cause a high temp?
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Old 20-08-2012, 17:26   #14
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Re: Perkins 4.108 rebuild?

Troubleshoot the high temp separately - Are you getting the regularly scheduled amount of water out the exhaust - do the bubble check with the fresh water cap open.

Also check for flow in the fresh water system - you could have a stuck thermostat (maybe from the high temps) - when cold there should be no flow in the fresh system. The thermostat will crack open and water will start to circulate. No circulation = stuck thermostat.

The RPM fluctuation could simply be related to the lift pump being failed (if it is failed) and unable to supply enough fuel under load.

Try not to think of one failure only - you could have multiple things going on at this point.
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Old 20-08-2012, 17:47   #15
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Re: Perkins 4.108 rebuild?

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Originally Posted by Ex-Calif View Post
Hope for the best and prepare for the worst.
Quote:
Originally Posted by Ex-Calif View Post

After the oil change and you restarted the engine, did the oil level go up again? In that short period of running how much did it go up?

I ran the engine 10 minutes or so after changing the oil and saw no noticeable change in oil level.


The RPM fluctuation could be a result of mechanical problems but it could just as easily be another symptom of a failed lift pump.

Understood.

If there is no knocking after the oil change you could be OK. The continuing symptom that concerns me is the high temperature.

There was no knocking after changing the oil, in fact it sounds smooth as always. Though I never brought it above 2000 rpm. Could the high temp be due to placing it under load while tied to the dock (personally, I don't think so).

It is really important to be observant of everything and try to understand how they repate to each other. At this point, if I read right you have the following symptoms - forget what happened before - only focus on what happens now.

- Oil level still increasing?
- RPM fluctuates
- Water temperature goes high
- Does oil pressure go low?
- Pull the fresh water cap - when water temperature goes high do you get bubbles/pressure in fresh water system? (sign of head gasket)
- I presume there is a good stream of raw water in the exhaust? (i.e. no failed raw impeller)

Water flow is excellent. I just checked the impeller a couple of weeks ago.

Let's say the lift pump is blown. This can thin the oil and cause low oil pressure. The oil level can rise to the level of the skirts. The oil would be seriously foamed by the crank shaft and foamy oil does not pump well = low oil pressure

Oil pressure has evidently been low for several weeks (maybe 30 hours run-time, as I thought the guage was faulty. I know, big mistake.

The banging is a bit of a mystery. I would expect the high oil quantity would not do this. When the case got full the downward stroke of the piston should pretty much pump it out the breather. There should have been an oily mess in the bilge.

There was an inordinate amount of oil in the drip tray after I shut it down before changing the oil (approximately a pint).

I suspect the banging could be related to high temps. A very high temp on the engine could result in combustion starting early and like a gasoline engine you get what sounds like a ping or in the case of a high compressed diesel a big knock/bang.

Could the banging be due to a faulty injector?

So the second thing to understand is why is it overheating.

If you can isolate these two issues you can decide whether the engine needs to be overhauled or whether you are looking at a lift pump and perhaps a cooling system repair.


The boat hasn't overheated before this incident.
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