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Diesel This is a forum dedicated to diesel engines and their applicable accessories.


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Old 06-22-2012
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4.108 Exhaust Questions

Dear all,
I limped into my final destination of Delaware City, Delaware recently after having discovered several growing leaks in the exhaust system. The mixing elbow was cracked; several hoses are in need of changing; etc.

So, I just received a new mixing elbow from Osco, identical to the one previously fitted to the engine. Here are my questions:

1. the exhaust flange is really dirty with soot/oil; what's the best way to thoroughly clean the flange. I assume soaking it in something.

2. When the flange is completely clean, do I just screw the elbow to the flange together using the supplied, threaded connecting pipe or should I use some sort of sealer?

3. There was no gasket between the exhaust flange and the engine; should I use high temp gasket material? what's best for this?

4. Is the the Walker Airsep arifilter/silencer worth the $500?

Thank you.

Chris
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Old 06-22-2012
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Re: 4.108 Exhaust Questions

I used a high temp pipe sealer, something like this: http://www.permatex.com/products/aut...et_Sealant.htm

Also I didn't think there was a flange gasket until I found it in the bilge just before reassembly... so maybe have a look around

Unless you have a real intake air noise problem I just don't really see the point of an elaborate air filter on a boat.. our engine simply has a screened 'snorkel' for the air intake. It's not like a vehicle where you might be driving on dusty roads etc....
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Re: 4.108 Exhaust Questions

Dear Faster,

Thank you for your reply! I will take a look for a gasket in the bilge!

The Airsep is reputed to reduce noise significantly and relieve pressure on the oil seals. Having read some of the threads from other 4108 owners, there seems to be some truth here. This is a new (very used) boat and engine to me so I am trying to make informed decisions.

Thanks again.
Chris
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Old 06-22-2012
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Re: 4.108 Exhaust Questions

Quote:
Originally Posted by ccolton View Post
The Airsep is reputed to reduce noise significantly and relieve pressure on the oil seals. Having read some of the threads from other 4108 owners, there seems to be some truth here. This is a new (very used) boat and engine to me so I am trying to make informed decisions.

Thanks again.
Chris
Experienced Perkins owners will be a good resource, of course. If a $500 dollar investment saves you a rebuild or serious repairs/maintenance in the future then it may well be worthwhile. My thoughts were not engine-specific... and by no means expert.
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Old 06-22-2012
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Re: 4.108 Exhaust Questions

Faster,

Well...I think you may still be right. $500 seems pretty steep. I think, for the time-being, while I refurbish this boat, I will focus on safety and structure before spending $ on the Airsep.

Thanks again.

Chris
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Old 06-22-2012
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Re: 4.108 Exhaust Questions

1. I would wire brush the surface clean, wipe with alcohol. 2. Use an anaerobic sealant on the threaded portion. 3. Regular gasket material will suffice. 4. A 4-108 has a machined grove in the crankshaft, so as the crankshaft rotates, it pulls oil back into the crankcase. The engine does this by having a slight vacuum supplied to the valve cover from the air intake. An air sep increases the vacuum available to the crankcase. I don't think it's worth it personally.
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Re: 4.108 Exhaust Questions

Hi Capnblu,
Thank you for the specific advice - exactly what I needed.

An engineer who is extremely knowledgeable about all things boats suggested an after-market tractor induction silencer for the air intake. Sounds like it is basically a big air filter. Are you aware of a specific one. He is in Europe and does not know of a supplier locally.
Chris
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Re: 4.108 Exhaust Questions

If you want sound proofing, install dynamat to your engine compartment. I don't think an air filter could achieve the decibel reduction the dynamat will.
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Old 06-23-2012
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Re: 4.108 Exhaust Questions

I have a Perkins 4108 that is 20 years old and has 4000+ hours on it. I WOULD NOT make any changes to the air intake system at all. The small air filter/screen does it's job just fine. I like the way the Perkins sounds...but then again, we sail as much as possible.

BTW, I replaced the back end of the exhaust manifold after 16 years, the mixing inlet was the first part to go. I also took the entire system, hoses, clamps, etc apart and gave everything a good cleaning. While your at it, take out the tube set in the heat exchanger and give it a good cleaning as well. Might as well replace the raw water inlet hose and all the clamps as well. Since they are probably all of the same vintage it will ensure your peace of mind.....Good luck!
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Old 06-23-2012
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Re: 4.108 Exhaust Questions

Chris,

Like other Perkins owners, I think you'll be satisfied with "Old Blue." It's a pretty reliable engine, based on simple engineering, and was widely used in industrial and agricultural applications -- which makes getting repair parts a little easier (and usually cheaper) than some of the other marinized engines out there.

Do a Google search for Perkins 4.108 manuals. There are several places that sell the manuals on CD, but they are also easy to find in free downloadable PDF format from owners' group sites (you can get started here). A couple of things to know about manuals:
- There are at least three versions of Workshop Manual (1972, 1978 and 1983). They are almost identical, but there are a few differences. I've found all to be useful.
- The Parts Book that's out there at lots of places all seem to have originated from one person's scan/upload effort. You can tell this is the one because it's got "overhaul" hand written on the cover page. The originator made one error -- he/she copied the diagram page for the alternator bracket & hardware twice, and failed to copy the corresponding part number & nomenclature page.
- Take the time to read the pages in the Workshop Manual that will help you decode your engine serial number. Anytime you go to buy parts, they will ask you for your "build list" and perhaps year of manufacture. That's info you can get from the engine serial number.

Other recommendations:
1. One of the best sources for parts and info is TransAtlantic Diesels (TAD). They have a great reputation for customer service, and know their stuff. If I can't find parts locally, they are usually my first "go-to" vendor for stuff I'm going to need to have shipped.
2. I just found another vendor in the UK -- ASAP Marine Supplies. For a few parts (like the rubber end caps for the Bowman exhaust manifold/heat exhanger), they may be less expensive than US vendors, even when shipping is factored in. If you contact them, they will set up your account to automatically remove the UK VAT (assuming that you aren't in the UK.)
3. Deal with Foley Engines at your own peril. I've found some decent info on their websites, but I would never buy anything from them. Unlike TAD, they've got a terrible reputation for customer service. No personal experience, but I've heard enough horror stories on numerous forums to know I don't want to take a chance.

Oh, almost forgot: Yes, there should be a gasket between your exhaust manifold and your engine block (two in fact). You can use carb cleaner to scrub the oil/soot off of your flange.
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Last edited by PorFin; 06-23-2012 at 04:39 AM.
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