Perkins 4-108 oil leaks solved

[model 10]

Maybe everybody shouldn't try to re-assemble an engine. There are basic things you need to do and making sure the water pump slides into place is one of them. You didn't.

[Deltasailor]

Originally Posted by Qayaq

Really. You got a 4108. After re fitting my timing cover and not aligning the water pump">raw water pump flange, the ear snapped off the impeller shaft and dropped into the drive gears. Fortunately the gears survived but it did stick a hole in the timing cover.Which is when I found out about the need to align. So in my mind I would say to not bother aligning is somewhat fool hardy. Nobody needs that T shirt, I certainly didn't.

I bought a " re coned" 4108 in 1988 to install in my Endurance 37 that I was building on a shoe string. I drove from Liverpool to Peterborough to meet a man who told me it was a factory test engine. He said it was "factory re conditioned" (possibly with a can of spay paint) I knew "knowt", It looked OK so I took it back to Liverpool and installed it. We sailed "Mr Orion" to Greece in 40 days (Biblical?) and started a charter business, That boat ran for 10 years with little or no problems. I had no issues, it was a very dirty engine, you could tar the road with the oil after a few weeks, but it ran and ran. We took her back to the UK through the French canals with no problems. A great tough engine proud to be British.

[Qayaq]

Originally Posted by Guy

Maybe everybody shouldn't try to re-assemble an engine. There are basic things you need to do and making sure the water pump slides into place is one of them. You didn't.

Ho ho. Your funny. Those drives do damage if they are not set up correctly, which is why there is an alignment tool, though it is easy to make your own. Check the 4108 manual. I've been an apprenticeship served marine engineer for over 25 years so I was quite surprised when I damaged my own engine. And yes I did turn the engine over before final tightening of the flange bolts. Ho hum

[Maka]

If my 4-108 stops leaking oil, I know I'm outa oil.

If I implemented this complicated fix... how would I ever know when the engine was out of oil?

[Kekaimalu]

We have a Perkins 4-236 about 20 + years in our yacht. Compression ratio is 16:1. It cannot compare in noise & vibration to more modern engines such as the new Volvo Marine Diesels (which are about 23:1) but so far it has proved extremely reliable. We normally run it at 1000rpm for 5kn up to 1400rpm for 6.5kn and so far it has never let us down. After reading the posts about oil leaks on the 4-108 I thought I'd add that we haven't experienced any oil leak problems with this Perkins model.

[Capt Gill]

Originally Posted by sv.antea

My friend's Perkins 4-108 always leaked oil. Two years ago he took it to a yard, they pulled the engine and replaced all the gaskets and seals. It started leaking badly again in few months. I have installed a nice fiberglass pan under the engine, so the oil doesn't end up in the bilge. Oh my hubris. I pulled the engine again, replaced all the seals and gaskets. Looked beautiful. Started leaking all over the front few months later. I don't give up. Pulled it again.

Aside. I put myself through college fixing MG at the local British Leyland dealership. I have rebuilt few Perkinses over the years since I switched to sailing and sailboats and always noticed how superficially similar the design of the 4-108 was to an MGB motor. The relevant similarity is that the front motor mounts are attached to the front plate. When I disassembled the 4-108 this time, it finally struck me. The front plate on the MGB went on the front of the block over two big locating pins. The Perkolator has no such pins. It weighs twice as much and (some owner refer to them as "rock crunchers"): add shock loads and vibration. What really drove the concept in was noticing the Perkins engine block had provision for hefty motor mounts brackets, forward and aft, unused in the marine version. I bet the famous London cabs use THOSE to mount the engine. Not the front plate.

Before you install the timing cover, the front plate is held to the block by five or six measly 5/16" bolts. A bunch of 1/4" and 5/16" bolts go through with the installation of the timing cover, but the torque specs and common sense prevents you from honking down on those. The timing cover is easily distorted and leaks would be all but guaranteed. The gasket set you get these days is all of one material and it is foam of some kind. So, as the engine bounces around and shakes, the block starts twisting behind the front plate coming to stops on the threads of those measly five bolts.

The proper answer would be to install sturdy locating pins. A machine shop could probably do that. You would need to find suitable location as not to compromise the block.
As I didn't have the time or money for the machine shop, I came up with different solution. First I made a hard paper gaskets instead of the foam one in the gasket set to go between the block and the front plate and one for the timing cover. I used hard setting Permatex on the block to plate gasket. Tightened the aforementioned 5 or 6 measly bolts, but temporarily added all the timing cover bolts as well without the timing cover and tightened everything lightly and evenly and in a fanciful sequence, so the gasket got compressed evenly. Let it set overnight.

Before installing the timing gear and cover, I tightened the 5 bolts properly.
Now the hard part. Out of some high tensile Al alloy plate, I cut and drilled a frame in the shape of the timing cover gasket, but narrower. I used 1/4" plate and made it in two pieces because I didn't have enough material for the complete circuit. Thicker and one piece would be better. I used it instead of the good-for-nothing original oval washers when installing the timing cover.

Anyone confident enough to install the timing gear and set the backlash probably knows the timing cover is made to float a little and has to be positioned just so, so the front crank shaft seal is concentric with the shaft. There was a special tool for that operation for the MGB, A ring, temporarily installed instead of the oil seal, before the bolts of the timing cover were tightened. Now to be sure, after centering the timing cover by feel and tightening few of the bolts lightly, I drilled and tapped two #10-24 locating screws through the timing cover into the front plate.

With the proper paper gasket and the stiff aluminum frame instead of the handful of oval flat washers, the timing cover can be tightened down (with longer bolts of course) as much as the bolts and threads can handle, providing the extra needed support for the plate to block joint. To say nothing of the now leakproof timing cover gasket.

Well done, I suspect you've also reread and edited making your's an easy read, too often not done here leading to much head scratching.
My 4-108 has similar,but minor issues. Understand that these are Gremlins of the British sort and they DO NOT go away they simply move to another place. Having much experience with British vehicles of all sorts I've learned it's better to live with them than fight them. In this case,as long as it's manageable, I will do as zeehag does, keep a supply of nappies & drip pan, this way I know where the Gremlin is and not have to be concerned about it relocating and causing havoc, usually at the most inconvenient time. A reasonable accommodation I believe.

[cottonsail]

Why don't the British build computers? Because they can not figure out how to make them leak oil.

[UNCIVILIZED]

So then the same people that built fighter planes out of wood, & came up with a positive ground wire system for cars, that nobody on the planet understands, also build boat engines? No wonder they leak oil.

Regarding gasket material, are we referring to using Admiralty nav charts type paper? And might there be a better location on the engine to attach engine mounts to? Ones not directly connected to any sealing plates on the engine.

[Capt Gill]

[QUOTE=UNCIVILIZED;2445026]So then the same people that built fighter planes out of wood, & came up with a positive ground wire system for cars, that nobody on the planet understands, also build boat engines? No wonder they leak oil.

Kinda begs the question, why would anyone buy such things ? Beauty, a sense of uniqueness and finally seduction. Critical thinking takes a back seat; this is how it was for me and I don't believe I was alone in that regard, it's similar to romantic love. Take a E type Jag ,which I had for awhile, first it catches your eye, get closer enter the cockpit, the aroma of the leather is first to disarm your critical thinking then the bucket seats they fit you as a fine kidskin glove fits your hand, then gently laying your hand on the s/wheel inlaid w/fine wood one notices the highly polished walnut dashboard sporting a multitude of Lucas (AKA The Prince of Darkness) gauges; you feel as if you're in another realm, a contemporary Camelot ,you not only want it you need it and if not totally seduced by now peering through the windshield there's this v. long front hood that must surely house a powerful engine, so you get out, lift the bonnet which exposes all, since it's the entire front enclosure, but v. light. The engine is brilliant, all but the block is highly polished aluminum including the three carbs.
Oops, sorry got caught up in the reverie of a past love affair, in any case it's how infatuation can trump logic.

[model 10]

[QUOTE=UNCIVILIZED;2445026]So then the same people that built fighter planes out of wood.


They were not fighter planes, they were bombers. They had 2, a big bomber and the Mosquito. Just about biggest plane we ever built was wood. Wood is just about the strongest composit there is. The oil leak is not the mounting plate, it's the timing gear cover.

[sv.antea]

You are right, Jamhass, it's been a while since the MGs, I remember now one bolt per side went to the block, two to the front plate. Perkins 4-108, three 5/16" bolts through the plate only. So on top of everything, thrust tries to bend the plate.
Quayaq, did not have any problems with misalignment of the raw water pump before, strangely enough just discovered that problem on my Universal M25. One time however when I had to fit a new timing cover, as the old rusted through, the new part was so poorly made that the front seal could not be aligned because the crank timing gear would touch the cover and keep it from moving any higher. Had to take a torch and a ball peen hammer to it to make room for the teeth. Your problem may have been due to poorly made timing cover, too.

[sv.antea]

Uncivilised. There are the four bolt bases machined and threaded I mentioned, and some kind of weldment could be designed to fit these, but lot of other stuff would probably have to be shifted around. They probably opted for the plate because it is further forward for better mount load distribution.

[Mistress Sirena]

well my solution to most of the oil leaks was to simply tighten all the nuts and bolts back down starting at the oil pan on up to the valve cover. just snugged them "all" up surprised how slack they all were.

[TKDSailor]

Originally Posted by zeehag

perkins are brit engines. brit engines always leak. leaks make em run. pretend it is a diesel mg B. hahahahaha
even brand newly rebuilt will leak. buy oil absorbant engine diapers and place one under engine. run engine.
breathe and live life. engine will leak oil.
if it stops leaking, it will blow up.,

Sorry, Zeehag, but not true!! I've had a Perkins 4-108 in our Roberts Spray 38 "Ark" since 1995, and it NEVER leaked a drop, having motor/sailed the ICW 3 times (along with other sailing), until 2017. It was a PERFECT engine (except I had problems bleeding it...). Then, in 2017, on our 4th trip up the ICW, she developed a leak. 1 quart every 8 hours. The pan caught it, and (much to the admiral's dismay) I would suck it out with a turkey baster, and put it back in the engine. Turned out, Perkins, in their infinite wisdom, made a plastic cover for the mechanical tachometer hole, which I did not use. The plastic cracked, and, after putting on a cap from a medicine bottle and hose clamp, it stopped leaking. Unfortunately, now it started leaking from elsewhere, but only 1/4 quart per 8 hours motoring... I have plenty of diapers now for this senior engine, and it's still awesome!!
(1993- last year they were made)!

[Capt Gill]

Originally Posted by TKDSailor

Sorry, Zeehag, but not true!! I've had a Perkins 4-108 in our Roberts Spray 38 "Ark" since 1995, and it NEVER leaked a drop, having motor/sailed the ICW 3 times (along with other sailing), until 2017. It was a PERFECT engine (except I had problems bleeding it...). Then, in 2017, on our 4th trip up the ICW, she developed a leak. 1 quart every 8 hours. The pan caught it, and (much to the admiral's dismay) I would suck it out with a turkey baster, and put it back in the engine. Turned out, Perkins, in their infinite wisdom, made a plastic cover for the mechanical tachometer hole, which I did not use. The plastic cracked, and, after putting on a cap from a medicine bottle and hose clamp, it stopped leaking. Unfortunately, now it started leaking from elsewhere, but only 1/4 quart per 8 hours motoring... I have plenty of diapers now for this senior engine, and it's still awesome!!
(1993- last year they were made)!

I agree with Z, maybe not all Perkins leak, however, when 99%(anecdotally) of those Brit engines leak to say "all" is ok. Maybe you had one of the exceptions – for awhile! I've had many Brit cars and one m/cycle, a Norton, in my time and can't recall a one that didn't leak oil; I used to have an auto shop and one of the quips we'd make re. Brit engines is, "if it's not leaking it's probably out of oil", one even tends to supernaturalize to explain the issue as I have with my Perkins 4-108, this can also apply to you, it's the Gremlin theory, i.e. the Gremlin(s) is/are embedded in the boat, one can't get rid of it w/o destroying the boat so you learn to live with it and appease it, e.g. in our case, the Gremlin is residing in the Perkins, so ya fix the leak, however the Gremlin relocates and the engine leaks elsewhere (remember, can't get rid of the Gremlin it only relocates). In my case, I've resigned to accept this as fact, so we get along ok as long as I appease the Gremlin, although the engine still leaks it's v. little and manageable; you may ask, "how does one appease the Gremlin?" well, this works for me: the Gremlin is at its best behaviour when given a clean, tidy environment and proper maintenance. Of course, since perfection is not possible, the Gremlin will let its presence be known, e.g. the same oil leak that wasn't fixed properly the first time or something else that has been neglected. The Gremlin also has times when it's evil, vindictive or just out of sorts and will cause problems that have nothing to do with you, in that case, it's best to take a deep breath then go about what needs to be done to remedy the issue, try to refrain from getting angry, yelling at your mate or kicking the dog as this will provoke the Gremlin, it sees this as a weakness so steps up the game, perhaps by sabotaging the work such as allowing a unique piece of hardware to slip from your hand into the hinterland of the bilge,but the trick is to maintain a calm attitude take a break if need be, that will keep the Gremlin at bay as you're no longer any fun. If this all sounds a bit anthropomorphic so be it, however, I think most of us can recall a time when we struck, banged on or spewed epitaphs at the object of our frustration, if so you're being Anthropomorphic.
Seems like you've come to terms with your "awesome" Perkins as I have, so much so that I'm going to give it a first name, any ideas? Maybe Anthony?