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Old 02-09-2012, 17:27   #1
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4108 perkins rear main leak :/

Have a 4108 Perkins that NLT has about 300 hours since the previous owner did a total rebuild. The motor is mounted to a v-drive in my 44 islander. Seems to leak about 1/2 qt in 24-36 hours. Do you have to drop the crank to replace the rear main ? Sheesh , this thing is really ago horned in there , and I don't want to have to pull it just for the leak :/
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Old 02-09-2012, 17:41   #2
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Re: 4108 perkins rear main leak :/

The rear main seal leaking is a classic problem for this motor. When I had mine re-done spent some extra bucks to by Foleys special seal for about a $100.00. So far no leaks, although I don't have anywhere near 300hrs since the service was done. I believe the work can be performed with the motor in the boat. Foley Engines | Marine & Industrial Engine Products
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Old 03-09-2012, 06:17   #3
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Re: 4108 perkins rear main leak :/

The rear seal can be repaced with motor in place. You will have to remove the transmission with adapter plate, the flywheel and bell housing. The seal, bolts to the rear of the block around the crank. Be certain that leak is not also from the front seal (under the main shaft pully) or the front cork seal at the front of the oil pan. These other places are common leak points, not to be ignored when you suspect the rear seal.
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Old 05-07-2016, 13:53   #4
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Re: 4108 perkins rear main leak :/

My perkins 4108 is leaking from the front and rear. Can the front seal be replaced without dropping the pan?
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Old 05-07-2016, 14:17   #5
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Re: 4108 perkins rear main leak :/

The front seal is in the timing cover. With the pulley removed you could dig out the old seal, but it's easier to remove the timing cover. Make sure that the pulley shaft doesn't have pits or is rough where the seal rubs. If it is, it will just eat the new seal. Better bearing suppliers have a sleeve, I think teflon, that slides over the shaft to form a new surface.
The rear seal is held in place by a 2 piece seal housing. The housing has a gasket between it and the block. I believe the seal housing can be removed without removing the pan.
In this old post - Foley's rear main seal works for me. I have a 4108 generator engine.
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Old 16-09-2016, 18:50   #6
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Re: 4108 perkins rear main leak :/

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Originally Posted by cburger View Post
The rear main seal leaking is a classic problem for this motor. When I had mine re-done spent some extra bucks to by Foleys special seal for about a $100.00. So far no leaks, although I don't have anywhere near 300hrs since the service was done. I believe the work can be performed with the motor in the boat. Foley Engines | Marine & Industrial Engine Products


Now that 4+ years have passed how is the Foley redesigned rear seal holding up? Does it seem to be the fix (hopefully for good)?
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Old 16-09-2016, 19:17   #7
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Re: 4108 perkins rear main leak :/

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Now that 4+ years have passed how is the Foley redesigned rear seal holding up? Does it seem to be the fix (hopefully for good)?
The standard seal lasts 10-20 years easily. All this bs about the Perkins rear seal is silly. It's easy to change and it should be part of regular maintenance . The damper plate is going to be dead by then anyway and that's not perkins fault.
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Old 16-09-2016, 19:23   #8
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Re: 4108 perkins rear main leak :/

One of the causes of rear main seal leak in many engines is excessive blowby into the crankcase. If the increase in pressure can't be relieved enough through the crankcase breather, the pressure can blow out seals. If you have too much blowby, changing the seal won't help the problem.
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Old 20-09-2016, 15:55   #9
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Re: 4108 perkins rear main leak :/

Were literally putting in the new foley style units tomorrow. Motors on the engine stand and turned upside down for the install. I'm thinking my associate, " master mechanic" ordered a special tool that looks similar to a " Chinese handcuff" like when some of us were kids.

Haven't been their since friday, so not sure what the tool is exactly, or if it's needed. Anyways I'm wondering what would the solution to excess pressure in the block be, is their some sort of relief valve OR cap, that can be used.

Dirk
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Old 22-09-2016, 18:44   #10
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Re: 4108 perkins rear main leak :/

No special tools needed. Straight forward, install, the secret tool was a large socket to press the rope bearing into place. Motor is out of the boat , on a stand, which is really easy.

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Old 10-12-2016, 14:08   #11
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Re: 4108 perkins rear main leak :/

where can I buy rear seal for 4-108 besides expensive Foley?
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Old 10-12-2016, 14:21   #12
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Re: 4108 perkins rear main leak :/

I ended up using TAD Diesel exclusively. In my humble opinion a fantastic company to work with for info, and sourcing parts. The ladies their were fantastic to work with.

I spent a pile of money with Foley. Very unhappy, with customer service. In fact I'll go without, before I EVER purchase from them again.



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Old 10-12-2016, 14:29   #13
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Re: 4108 perkins rear main leak :/

I finally finished my rebuild. Got two separate one hour test runs on the 4-108m, the second with a diesel machinists at his shop. It's good to go. We went over it after a couple 1/2 hour runs, found a couple minor leaks, and we pulled the timing gear cover off.

The mechanic wanted to apply a sealant along with the gasket. He's been a diesel mech for 30 years on logging equipment, he didn't want me to develop a leak at sea. With the sealant and the test runs no leaks, the motor,runs smooth at low rpm and at high rpm.

Turns out I didn't wire the intake glow plug, and the air fuel was cold, as soon as we wired that it fired first time.

Still in my garage, I'm not excited about driving 8 hours south. I'll go early Jan.

Thanks again toall he provided input.

Dirk Williams
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Old 15-02-2017, 23:54   #14
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Re: 4108 perkins rear main leak :/

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Originally Posted by Dirk Williams View Post
I ended up using TAD Diesel exclusively. In my humble opinion a fantastic company to work with for info, and sourcing parts. The ladies their were fantastic to work with.



I spent a pile of money with Foley. Very unhappy, with customer service. In fact I'll go without, before I EVER purchase from them again.







Dirk


I had the same experience. Very very RUDE at Foleys. I"ll never buy from them. TAD is SO MUCH better.
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Old 16-02-2017, 04:12   #15
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Re: 4108 perkins rear main leak :/

It's a 4-107/108... If the seals don't leak, you're out of oil
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