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Old 20-08-2012, 18:08   #16
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Re: Perkins 4.108 rebuild?

The good news is it runs and it runs smoothly.

Do the fresh water cooling check. You could have a stuck thermostat.

The overheating should not happen at the dock under load. I presume there is no smoke or other symptoms while doing this "load" check.

I doubt you have an injector issue but one way to check is to crack off the supply nut at the injector one at a time at idle. There should be a change in RPM as each cylinder goes "dead" - If one cylinder does not go dead you can suspect the injector or you can start worrying about the injector pump but I doubt that is in play here.

The lift pump is my prime suspect for the rpm loss. It also explains the increasing oil level and thin oil/low pressure.

The oil in the drip pan can be correlated with the high level and the oil blowing or pumping out the breather or oil disptick tube.
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Old 20-08-2012, 18:44   #17
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Re: Perkins 4.108 rebuild?

Please do check the water pump">raw water pump, hoses, seacock and even the heat exchanger again. Just because you checked it a few weeks ago doesn't prove that it hasn't failed since. Make sure you are getting the proper amount of raw water flowing through the system. Catch the exhaust water in a bucket for a set amount of time and compare the amount you catch with the engine specs.
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Old 20-08-2012, 18:47   #18
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Re: Perkins 4.108 rebuild?

I generally now pull mechanical fuel pumps off my marine diesels, plate the hole, and replace with a 50 dollar inline electric for this very reason.

You may even find, depending on the location of your tank, that a lift pump is not even needed.

For emegencies, you can plumb a second intake into your CAV filter with a cock and snap fitting, then keep a 10 litre outboard tank aboard which can be placed high and gravity fed to the engine. This may then logically progress to a 20 litre tank which you will fill on the way to the dock and run as your primary tank.
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Old 20-08-2012, 18:47   #19
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Re: Perkins 4.108 rebuild?

The banging could be from a faulty injector, but it is a very common sign of an over full oil sump. What happens is that the crankshaft on a modern engine is not designed to run in the sump oil like the old splash system of lubrication. The high oil level causes excessive oil to be thrown up against the cylinder walls and that gets past the rings and causes the engine to run away. That can be a full blown runaway or intermittant banging. When my own Perkins 4-154 ran away(bad lift pump) the noise was so bad that I thought it is going to physically blow out the sides. The kill button did nothing, I turned off the fuel valves and tried to get the air cleaner off, but could not do it. I came back up to the cockpit figuring that the engine was going to explode, and tacked becouse we were too close to the beach, and the engine went to a smooth idle and stoped when I hit the stop button. The differant angle of the engine stopped the oil from being thrown against the cylinder walls, and it ran normal. I was pretty sure that the engine was toast, but a new(rebuilt) lift pump and it purred like a kitten for about 2 monthes and then died. The new lift pump had quit, but not leaked into the sump. I changed to a 12 volt automotive fuel pump and never had a problem again. YES I HATE LIFT PUMPS. I hope your problem can be solved this easily.____Good Luck____Grant.
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Old 20-08-2012, 22:49   #20
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Re: Perkins 4.108 rebuild?

After my recent experiences with cheap electric lift pumps I have been impressed by my Walbro FRB-22.

Just one tick every few seconds.
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Old 21-08-2012, 05:56   #21
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Re: Perkins 4.108 Rebuild?

No significant smoke of any color coming from the exhaust, and as I mentioned, the engine starts very easily with the first crank. No abnormal knocking like the other day (though I only ran it for 5 or 10 minutes under load at the dock, and shut it down when it hit 220 degrees). Plenty of cooling water, and 40 lbs of oil pressure (vs. the 5 to 10 lbs I had been getting).

I'm still concerned about the high temp at 2000 RPM seeming to come just after the drop in RPM. Is it possible to have bearing damage without knocking in the engine?

The worst part of this is that it may have been avoidable, and even worse, I know better. I should have caught the thinning and rising oil level (though I'd never heard of deisel in the oil sump), and should not have ignored the "faulty" oil pressure guage.

Well, you guys have given me much more hope than I'd had 24 hours ago. I'm going to pull the lift pump and check the injectors, and keep my fingers crossed that I didn't cause much more serious damage. Just in case, anyone know of any sources for rebuilt diesels in the Tampa area?

Thanks again, I'll keep you all posted.
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Old 21-08-2012, 14:58   #22
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Re: Perkins 4.108 Rebuild?

Ex Navy Nuc. Thanks for your service. I was a non-Nuc on a Nuc Cruiser in the late 80s and really admired the education you folks endured. Got my ESWS pin aboard the Bainbridge and several nuc Chiefs sat on my board so that I got a thorough grilling on nuclear power.
A 4-108 is child's play comparatively.
Good to have you posting here.
kind regards,
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Old 21-08-2012, 16:34   #23
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Re: Perkins 4.108 Rebuild?

Thanks SkiprJohn. I appreciate your post.
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Old 21-08-2012, 16:40   #24
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Re: Perkins 4.108 Rebuild?

Quote:
Originally Posted by sapadeni View Post
No significant smoke of any color coming from the exhaust, and as I mentioned, the engine starts very easily with the first crank. No abnormal knocking like the other day (though I only ran it for 5 or 10 minutes under load at the dock, and shut it down when it hit 220 degrees). Plenty of cooling water, and 40 lbs of oil pressure (vs. the 5 to 10 lbs I had been getting).

I'm still concerned about the high temp at 2000 RPM seeming to come just after the drop in RPM. Is it possible to have bearing damage without knocking in the engine?

The worst part of this is that it may have been avoidable, and even worse, I know better. I should have caught the thinning and rising oil level (though I'd never heard of deisel in the oil sump), and should not have ignored the "faulty" oil pressure guage.

Well, you guys have given me much more hope than I'd had 24 hours ago. I'm going to pull the lift pump and check the injectors, and keep my fingers crossed that I didn't cause much more serious damage. Just in case, anyone know of any sources for rebuilt diesels in the Tampa area?

Thanks again, I'll keep you all posted.
Don't forget the freshwater circuit check and the thermostat.

Depending how easy it is to remove you could simply pull the thermostat temporarily and do another dock check before pulling the lift pump and injectors.

PS - The thermostat can be dropped in a pan of water and heated up on the stove. It should start cracking around 130-140f and be fully open before 180f.

Cheers
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Old 21-08-2012, 17:33   #25
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Re: Perkins 4.108 Rebuild?

I replaced my lift pump after the same problem and found that it was the injector pump seal leaking. a $600 repair. I also now use a electric pump instead of the mechanical lift pump.
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Old 21-08-2012, 18:38   #26
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Re: Perkins 4.108 Rebuild?

If you have much bearing damage, you wont likely have good oil pressure. That's pretty much all the oil pressure really indicates.... it could care less if the rings are worn out...... wont be indicated by oil pressure.... Get teh fuel leak solved and run it.
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Old 21-08-2012, 18:59   #27
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Re: Perkins 4.108 Rebuild?

Just a tip on bearing damage.

Oil pressure as pretty much established by the clearances in the bearing supply circuit as Cheechako indicates. The oil pump is a gear pump where pressure is directly related to RPM. There is a spring loaded "pop-off" set at whatever spec the engine has - usually around 40 psi but could be much higher.

The viscosity of the oil is the second factor. Very low viscosity will result on low pressure. Dilution of the oil with diesel is a key in this case and would have resulted in very low viscosity.

The fact that the oil pressure was recovered after oil change is encouraging.

Bearing distress is another key factor in low oil pressure. If bearing distress of this amount is present there will be evidence. If the old filter is available it can be cut open with a filter cutter and the internals inspected for metallic debris.

The idea of the injector pump causing the oil contamination is not ruled out at this point but the lift pump is the more likely culprit.
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Old 21-08-2012, 19:10   #28
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Re: Perkins 4.108 Rebuild?

I think svHyLyte has it nailed. My bet is bad injector. let us know.
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Old 21-08-2012, 19:38   #29
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Re: Perkins 4.108 Rebuild?

I would put my money on the fuel lift pump diaphragm, followed at a distant second being the shaft seal on the injector pump. As far as the overheating I think that is a whole different issue. start with the salt water system but my bet is your mixing elbow is coked up (easy fix) or heat exchanger needs a clean(when was the last time you pulled that apart? zinks leave a lot of crap behind) finally look at the engines fresh water pump, these vanes have been known to let go. Good luck .
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Old 21-08-2012, 19:44   #30
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Re: Perkins 4.108 Rebuild?

Hopefully one or more of the suggestions the wise folks that responded will work for you.

If not, I am just buttoning up my repower with a 75hp Yanmar that I purchased from Mastry Engine Center there in Tampa. The original Ford/Lehmann had been rebuilt twice and I was not interested in doing it a third time. Changing engine manufacturers present many unique challenges. Propeller and shaft, engine bed supports, exhaust, alignment and gear controls to name a few. To top it off I had to give my cockpit a "C" section to lower the engine down.

To answer your question about costs, the Yanmar set me back about 13K and the labor will easily run you half as much again depending on your circumstances.

Let's hope it it is an easy fix and if not a quality rebuild to keep things simple!

Best of luck...
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