4-108 OIL LEAK

[roberttigar]

Rear seal on a 4-108...Its the only fluid leaking from the engine. Has anyone had success using any of the aditives that are available to expand the seal and stop the leak? Bob

[svHyLyte]

Originally Posted by roberttigar

Rear seal on a 4-108...Its the only fluid leaking from the engine. Has anyone had success using any of the aditives that are available to expand the seal and stop the leak? Bob

I take it you are not too well acquainted with 4-108's. Unfortunately, it is a property of the engines that they all have leaky rear seals. The question becomes, how much of a leak. Given the time, effort and cost of replacing a rear seal, and the fact that, if not from the start, within a few months, the new seal will also leak most often they are not worth bothering with unless the leak is material. And, given the size of the galleries in that engine, IMHO a leak preventive additive might prove unwise sooner than later.

FWIW...

[Rubicon King]

Agree on the above. My 4108 leaks about a 1/4 cup an hour. I simply monitor every 4 hours, replace the leaked oil and change the catch blankets to keep the drainage from becoming an issue. remember Captain Ron.."Diesels love oil like sailors love rum"

[roberttigar]

I'm very familar with the 4-108 and aware of the problem. I have owned the boat 30 years. Replaced many parts and done my own service. My question was will any of the additives avail, that claim to treat this kind of problem, (like Castroil "Stop leak") help. I dont loose 1/4 cup an hour. Its more like 2- 3 oz in 6 hours. Bob

[svHyLyte]

Robert--

I don't know of anyone using something like "Stop Leak" in a 4-108 tho' we know many 4-108 owners (all with greater or lesser leaks!). I do know several diesel mechanics that insist such additives are unwise for the reason I mentioned earlier. In our case, with 3500+ hours on the engine, we use about 1/4 of a quart in 100 hours which is rather less than you're experiencing so my "wait and watch" might not work for you. I guess it depends upon the amount you have to motor at a clip. N'any case, good luck. I will be interested to hear your results if you elect to give the stuff a try.

FWIW...

[jimbunyard]

My understanding of how the stop leak additives work is that they soften and slightly expand the polymers that make up the sealing parts of lip and o ring seals. Since the rear seal in the 4108 is a 'rope' seal, it doesn't seem likely that these type additives will work very well to stop or lessen a leak in this application...

I have used them as a stop-gap solution in automatic transmissions, and have noticed a definite improvement, but I think they're far from a permanent solution.

There is an 'upgrade' available that uses a PTFE impregnated 'rope', but, having never used it, I can't vouch for its' efficacy---though I know that PTFE impregnated stuffing box packing works very well indeed.

[Lepke]

Stop leak products don't work on rope seals.

You can stop the leak with a proper install of the rope seal. I use the new seal on my 4108 running a generator. It doesn't leak. The old rope seal needs to be soaked in oil before installing. The trick when installing is to grease either the seal or crank journal where it rubs. Otherwise on the first start the seal can get pulled out of place or gets too hot before enough oil soaks into the seal. Once it gets too hot the contact point becomes hard and is forever too big and doesn't properly close the gap.
While it is a job to change the seal, it's easier on the 4108 than an engine where you have to remove the pan and rear main bearing cap.