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One Crap Can fills up faster- Why?

  • Thread starter Thread starter bobk
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bobk

bobk

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  1. OWNER - I own a Hatteras Yacht
Hatteras Model
48' MOTOR YACHT-Series I (1981 - 1984)
The starboard crap can on the 6V92TA's fills up in 100-150 hours, while I get nothing in the port can. Both engines were majored and have about 800 hours. Where does the oil come from? Why the difference and should it be fixed? Sounds like a pricey thing to do. Certainly vs. the cost of a couple of quarts of oil.

Bob
 
My best guess would be: the engine that does not have any crap in the can is the problem. Make sure you don't have something clogging the line or the check valves. It should be slobbering at idle. This is normal for DD.
 
If I am not mistaken at idle the airbox check valves should be open and there should be some air coming out. At least this is the case with 6-71's.
 
You have one can per engine then? Do you have 2 check valves per eng, one on each side or did you modify the oem checkvalve setup and use a single check valve with a "T" to both airboxes on each engine?

In any case, are all your pipes/hoses checkvalves oriented vertically so that they all drain equally well? Sometimes the oem checkvalves came from the factory NOT oriented vertically even though the DD service manuals state they are to be vertical. Are you sure ALL the hoses/pipes, whatever, are connected so that you are not getting a false indication from the engine that's producing very little in the can?

Obviously checkvalves could be clogged. As pointed out, at idle you should get a definite stream of air from each valve. The valves can be easily opened (unscrewed) and cleaned in solvent. If the valves were clogged on what is seen to be the good engine, then there would be nothing in the cans, the slobber would eventually build up and be sucked into the combustion chamber. In this case, an empty can could give the wrong impression of which engine had a problem.

If all this is OK then the consideration has to become, why is one engine pumping more oil? Is the crankcase ventilation functioning properly? If clogged, this could be the problem, forcing oil/air mist into the airbox that otherwise would not end up there.

The other possibilities are less pleasant to consider so ruling out airbox drain/crank ventilation issues is the first thing to do.

Out of curiosity, how big are the cans? 150 hours is a fair amount of time; depending on the size of the can, maybe the "bad" engine isn't actually out of spec at all - perhaps the good engine is just closer to optimum.
 
Good questions MikeP. On the trip south last year the check valves were pretty much horizontal. There are two cans, one per engine and two drains and check valves each. The cans are about a one quart capacity with small air filters on top. Methinks they are Walker Airsep products. Running south, mostly at 1000-1100 rpm the starboard can was nearlly full after 170 hours. I removed each of the check valves and cleaned them (you may recall I found a piece of a ring in the outboard port check valve) and then re-routed the hoses so that the valves were verticle for the return trip north.

The valve covers have vent hoses that run to the Walker Airseps on the turbos. I don't know if the hoses are clear. Is there a special test, or just blow through them. I'll do that asap.

Anyway, where does this take me?

Bob
 
You may have a blower seal starting to leak; that's the most common place for the oil to come from.

If the turbo induction wheels are clean then its not coming from crankcase blowby. This leaves you with two possibilities - a blower seal (unpleasant if it fails entirely, but not horrifyingly expensive to have fixed) and a problem with oil control from the bottom end (e.g. oil control rings); that one sucks.

Nonetheless, 1 quart in 170 hours isn't enough for me to get really hyper about. It does, however, bear watching and if it gets much beyond that level I would get worried.
 
Thanks again for the advice.

I just checked the last suggestions. Crankcase vent hoses are clear and the turbo wheels look clean, but there is a bit of an oily film when you rub a finger on them. I suspect this is normal as the mechanic who surveyed the engines found the same thing before purchase and wasn't concerned.

So now the question is how to I determine if this is a blower seal? I had the aftercoolers cleaned last fall and the mech didn't suggest doing anything with the blower seals, and I guess he was almost there in the dissasembly. Could he hae seen evidence of a seal leak at that point? If it is rings, is it worth fixing, or just keep running it until oil consumption gets out of hand.

Bob
 
The way to determine blower seals requires removing the top of the airhorn and running the engine (at IDLE!) while shining a light at the blower end plates. You will SEE the oil leaking if it is.

Note that if anything gets sucked into the blower - including you - during this procedure - it will be destroyed (along with the blower)

This is not a safe procedure, but it is the only damnfoolproof one I know of to determine if the blower seals are leaking.

I was reamed a new butthole for suggesting this procedure on Boatdiesel; it is, however, the one that is printed in my DD Service manual!

If its an oil control problem (and not a blower problem) I wouldn't fix it until it gets out of hand, assuming the engine is otherwise ok.

But that's me.
 
Genesis said:
The way to determine blower seals requires removing the top of the airhorn and running the engine (at IDLE!) while shining a light at the blower end plates. You will SEE the oil leaking if it is.

This is not a safe procedure, but it is the only damnfoolproof one I know of to determine if the blower seals are leaking.

I was reamed a new butthole for suggesting this procedure on Boatdiesel; it is, however, the one that is printed in my DD Service manual!

.
Click to expand...
LOL, wait Karl, isn't Boat Diesel where the real experts are? I find it amazing that I can usually find the answers I need right in the Detroit manual. LOL
 
Thanks again for the advice. Sounds like for now I'll just keep an eye on it.

Bob
 
Well guys, I now have two more round trips under my belt and can report that the starboard crap can collects about 16 ounces in the 170 hour run at 1000-1100rpm. Seems OK? The port can collects about one ounce. Great? All four check valves were cleaned and re-oriented to as vertical position as possible.

Also I'm seeing increasing oil seepage from the manifold/block joint and the bolts are tight. My very experienced DD mechanic calls it slobbering and attributes it to running slow. The manual says stay above 900 if I recall right. He also says changing the gaskets may not help, and advises I just run faster (too expensive) or use more diapers.

I think I have 160 degree thermostats as that is about the operating temperature (165F on the mechanical gages). Would switching to 170 degree t-stats help this. Any and all advice welcome.

Bob
Chateau de Mer
1981 48MY
about to head to Florida again
 
Check your blower and turbo seals on the engine that is slobbering oil into the crap can. Those are (often) not overhauled when the engine is.

To check the turbo seals pull the air pipe to the airhorn and see if there is significant amounts of oil in it. To check the blower seals the BEST way is to remove the airhorn and piping and start the engine at IDLE and shine a flashlight on the end plates.

Note that this is an extremely hazardous operation - anything - and I do mean anything - that gets into the open blower WILL BE EATEN, including you. If you're uncomfortable with the risk DON'T ATTEMPT IT - call a mechanic.

Sometimes you can see the leaking without starting the engine. Sometimes.

If you have airseps make sure your vacuum regulators are not stuck closed as that will pull over an INSANE amount of oil from the top end and into the turbo which then goes through and into the airbox, causing the same problem. Since you're reporting this with relatively low-speed operation it is UNLIKELY the airseps and vacuum limiters are responsible (if you have them) as that particular problem tends to show up most of the time at higher RPM operation (on boost) where there is more significant vacuum developed in the Airsep system.
 
Check valves? What check valves. I have 8v53N's and don't have any check valves on the slobber lines. Anybody have a part number on these little guys and where I can buy them? What is the risk in running the engines without them? Sorry, don't mean to hijack the thread.
 
8V53's do not use them.

It is the only one without check valves. I converted mine to copper and ran the line into water bottles with a hole in the top. I can see the level easily and they were saved from going to the landfill. I am not sure how the 2 engines compare as I did them at different times and have not emptied them yet.
 
Ns don't need them; they are there so that when on boost you're not bleeding off huge amounts of air into the crap can (or oil pan if you have the - shudder - OEM setup)

Naturals before they routed the slobber back to the crankcase don't have or need them, and if yours route back to the crankcase you should change that.
 
Hey karl...
My 12-71Ns have the crap cans way down south in the bilge. I doubt like hell if they have EVER been serviced. That is on the agenda for this winter as well. If they are full, were does the crap go?? Is it blown into the cylinders at that point? ws
 
The cans I've seen have are open so if the can gets full it sprays it all over the bilge . The cans have to be vented by design . I took mine and re routed both sides to one check valve and into 1 gallon jugs as Karl I think had suggested. When dirty just put the cap on the old jug and stick new jug in and change out the check valve to the already cleaned check valve that's in the toolbox. Takes about 10 mins ..........................Pat
 
I’ve got the same cans. When I opened them up the first time, I found dried slobber in there, a brick about an inch thick. I had to use a screwdriver to break it up.

If your engines are healthy, I think it would take quite a while to fill ‘em up. If that were to happen, you’d know it as the slobber would be leaking down the outside of the can.
 
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