dirty coolant in 6414DF marine diesel

[Labrador Coaster]

Good evening,

I have a 6 cylinder John Deere motor in my boat. It has over 6000 hrs, but burns no oil, 38-40 lbs oil pressure, water temp is 185 degrees, ( has a copper keel cooler, with a separate salt water pump supplying water to a wet exhaust

Over the years I have periodically flushed the coolant with fresh water. every time I do this the water come out very black and muddy. After leaving it in a bucket for a day it eventually clears leaving a brown greasy residue in the bottom of the container.

This summer I seem to be losing coolant and have had the motor overheat and boil over, as a result I have been putting in a lot of fresh water ( instead of antifreeze) today I flushed the motor again, and the water was very dirty.

a friend has an identical motor in his boat ( with less hrs.) he tells me that his water is always clear.

A side note , when I drained/flushed her today some of the coolant was still fluorescent green, ( the color of last years coolant. I would have thought that with all the water I put thru her this summer that coolant would have be gone already.

I haven't changed the impeller for many years, think I will take a look at it,

Any advice would be appreciated,

thanks,

Wilson

 

[beenthere]

Maybe a small crack or a small leak in a seal that is letting oil get into the coolant. But then sounds like possibly more than just oil in the coolant.
Those are a lot of hours. What year is this diesel model?

 

[Labrador Coaster]

The motor is around 20 years old, I run the motor at 1700 1900 rpm max. For the past 8-10 years I put only 100 or so hours pr. season.

If I fill the base to the mark on the dipstick she will burn oil down a 1/4 inch, I used to refill, now I leave it and the motor doesn't lose or burn more than a qt/liter a year.

I thought that the coolant might be leaking out into the exhaust manifold ( water jacketed), and with my wet exhaust going out thru the stern I wouldn't have noticed. But I put colorant in the motor thru the expansion tank but didn't see anything the next day when I started the motor.

thanks for your interest

 

[JD 4520]

You have at least two different issues going on:

1. You have a closed coolant system so you are obviously drawing water in from the outside, therefore you have a leak or crack of some sort. The coolant is cooled by the outside water in your manifolds.

2. Overheating...probably or possibly the same issue, a crack or leak is letting coolant out, creating air pockets and therefore hot spots. It could also be a lack of circulation in the outside water and therefore the impeller.

If you are really drawing oil in, you are also getting water in your oil. That would be obvious. Doesn't sound like that is the issue.

I would be checking your manifolds as those could be rusting out after that much use over that long of a period.

Good luck!

 

[JD 4520]

The oil that you are observing is likely just residue from the engine burning a little oil and being sucked in through this "leak". That is not your issue, it is the leak or crack that is your issue.

Try loosening the radiator cap and see what happens. Put some coloring in your sealed water system and see if you can observe it coming out.

 

[jenkinsph]

Lots of ways to loose coolant and wind up with oil in the coolant too. Do you have a crankcase breather where you can see it? If it has much blow by you may have issues with the liner seals. Might be an oil cooler pin hole too.

 

[Labrador Coaster]

Just getting back from the wharf where I removed the water pump from the front of the John Deere. First thing I noticed when I removed the Alternator belt was a wobble in the bell pulley, second thing was that the cute little rubber replacement impeller that a JD dealer had sent me would NOT be fitting in that unit.

After using an impact wrench and some heat I got all the bolts out, and... everything looks fine, obviously the wobble is a problem but it spins really smoothly and the cast iron impeller seems tight and in good shape.

I have to figure out a way to unscrew the impeller, check out the bushing (which didn't leak...) maybe it sucked air which caused airlock/boilover?

Had a chat with some of the boys at the wharf tonight, wondering if there was a hole in my manifolds interior water jacket, would this cause the exhaust gases to turn the coolant black, but would this put coolant into the cylinders.

In the boat the motor is tipped back somewhat with the end of the manifold going down to the wet exhaust.
Anyone have a rough idea of the cost of a new water pump for a 6414df JD, ballpark... 200-300-$ ??, or is it as simple as ordering a new bushing? there are no wear marks anywhere.

 

[jenkinsph]

Just getting back from the wharf where I removed the water pump from the front of the John Deere. First thing I noticed when I removed the Alternator belt was a wobble in the bell pulley, second thing was that the cute little rubber replacement impeller that a JD dealer had sent me would NOT be fitting in that unit.

After using an impact wrench and some heat I got all the bolts out, and... everything looks fine, obviously the wobble is a problem but it spins really smoothly and the cast iron impeller seems tight and in good shape.

I have to figure out a way to unscrew the impeller, check out the bushing (which didn't leak...) maybe it sucked air which caused airlock/boilover?

Had a chat with some of the boys at the wharf tonight, wondering if there was a hole in my manifolds interior water jacket, would this cause the exhaust gases to turn the coolant black, but would this put coolant into the cylinders.

In the boat the motor is tipped back somewhat with the end of the manifold going down to the wet exhaust.
Anyone have a rough idea of the cost of a new water pump for a 6414df JD, ballpark... 200-300-$ ??, or is it as simple as ordering a new bushing? there are no wear marks anywhere.

I think you might get alot more help from a marine forum such as The Hull Truth - Boating and Fishing Forum this is one of the busiest marine forums I can think of and I have been a member there for years. Lots of knowledgeable people there who can provide you with the information and help you need.

 

[Glen Watkins]

Nice site jenkins but 250 pages of
864 Attachment(s) Post the best picture of your lady on your boat Would never get anything done!

 

[Labrador Coaster]

Thanks, I will register at the new forum.

I'm in the process of downloading the shop manual for the motor. I have been trying this morning to get the impeller off the water pump shaft, with out success, it turns a half turn with heat, but very stiff. I assumed it was a counter rotational thread set up, but perhaps it is pressed on?.

thanks for the advice.

Wilson