Rear main seal - amount of work?

[frankn88]

I have a bad oil leak when the engine is running. The mechanic is supposed to look at it tomorrow. He said it could be a leaky oil sender, or a rear main seal, or ? I am confident, with my luck, it will be the rear main seal. I looked it up in the Seloc manual and for a 1994 5.7l it says you don't need to remove the engine. I mentioned this to him and he pretty much scoffed at the idea and said he couldn't imagine how you could do it without removing the engine. Anybody have any experience with one of these?

 

[KC_Sundancer]

The bell housing and flywheel need to come off to get to it.
With the bell housing having the rear engine/transom assembly mounts I'm not sure how you could without removing. :smt017

 

[Creekwood]

You could probably do it with engine in place if you used a chainsaw to cut out the transom and then glass her back up after. :wink:
Might be easier to pull the engine though. On small boats with hatches that easily remove, its not that major a task to pull the engine. Probably less than a boat dollar.

 

[Ten Years Gone]

edit

 

[1990-270-da-lover]

Another possibility is if you have the remote oil filter on top of the engine (usually fastened to the riser elbow ) the cap that is put on the original oil filter attachment can work it's way loose and can be a source for a good volume leak. Don't ask me how I know. LOL

 

[frankn88]

They were supposed to look at it yesterday. Since I didn't get a call, they probably haven't yet. Thanks for the tips, I'll see what they say.

 

[boatrboy]

Another possibility is if you have the remote oil filter on top of the engine (usually fastened to the riser elbow ) the cap that is put on the original oil filter attachment can work it's way loose and can be a source for a good volume leak. Don't ask me how I know. LOL

I have had to replace this gasket as well - don't know if you have the same setup but it's a relatively easy fix. Good luck - hope it's not the rear seal - as others have said it's really not practical to do this in the boat.

 

[frankn88]

Ok, hundreds of dollars and weeks later the latest diagnosis (by a mechanic that DIDN'T do the upper end valve job last year) is that the mechanic that DID do the valve job did not properly seal the intake manifold and oil is leaking out of the back through a gap where there should be sealant. The mechanic who DID do the valve job is saying, "well, it looks like you are having blow-by and I should do a compression leak-down test and then re-seat the manifold". My question is, why is an engine that you rebuilt last summer having issues less than 2 engine hours after you finished? If it had blowby, shouldn't he have figured that out when he was doing the valve job?
The engine has two breather tubes that run from the PCV up to the air cleaner - both have a little oil on them, but not much. I don't seem to have any loss of power - I can still stay on plane easily at 3200, where I always have. I'm pretty sure the guy who did the valve job is going to try and weasel out of fixing it "under warranty" (without going into details, it's been about 10 months, but less than 8 engine hours, since he worked on it).
Is blow-by easily diagnosed without doing a leak-down test, or do you think it's warranted? I'm tired of dealing with this guy and ready to just hand it over to the other guy, who I trust.

 

[Bt Doctur]

I`d lose the second mechanic. blow-by comes from compression gasses getting past the rings into the crankcase and is visable coming out the valve covers.The best test is a leakdown test.
Without sealant there oil will be blown out, perfectly normal happening from crankcase pressure.
The fix is to remove the intake manifold, clean the surfaces, lay a 1/4 inch bead of black RTV front and rear, and now the trick to keep it from leaking
Set the manifold in place, start all the bolts AND COME BACK THE NEXT DAY
The sealant will have cured and now you have a semi-solid surface for the manifold ends.Torque to spec, install dist and hoses and your done.
Shame you that far away or I`d do it for you

 

[frankn88]

Bt Doctur, if I understand correctly, you're saying you don't think it's blowby, and the intake just needs to be properly seated, right? I moved the boat yesterday and I rechecked the breather tubes while it was running - they have some oil residue on the inside, but nothing's coming out and the flame arrestor and carb do not appear to have any oil on them. I revved it up and took off one of the valve cover oil fill caps and there was just some hot, moist gas wafting out - the 1st mechanic said if I did that and had blowby it should feel like a steam train chuffing out of there and splattering oil all over, and same thing with the breather tubes.
The engine has 520 hours on it. It's going to cost $500-600 to get it reseated. I'd do it myself, but I just don't have the time right now. My boat's been out of commission for the most part since this time last year, and it's getting pretty frustrating...