8V-71N - Coolant in bilge, where do I start!?

[drewread]

New to me vessel with twin Detroit 8V-71Ns purchased in the fall, winterized then stored on the hard for the winter.

I finally got into the vessel this past weekend, now that it is warmer, only to discover a substantial amount of CAT EC-1 coolant has leaked into the bilge below my port engine.

Does anyone have any suggestions as to where to start looking, or how to find where this has leaked out from? I'm like a deer in the headlights of a Mack truck.

I did check the petcocks that I could find and none I found so far are leaking. There are a few silicone hoses around the heat exchanger that I can tighten up next time I am at the vessel (this weekend.)

I did my best to clean up drip marks from all around the engine but it is hard to tell what is from spilling while filling, what is winter antifreeze (it is the same colour, and actually what I thought the fluid was until I discovered the empty heat exchanger), or what could potentially be from the leak.

Thanks for any help on a starting direction that anyone can provide!

 

[Moonfish]

Before panicking I would check the pressure cap overflow hose right at the pressure cap neck.
Then check ALL hose clamps., they only have to be a little loose to leak.

 

[drewread]

Before panicking I would check the pressure cap overflow hose right at the pressure cap neck.
Then check ALL hose clamps., they only have to be a little loose to leak.

Thanks, will do - I need to clean the overflow containers anyway.

The overflow hose is well above where the coolant has leaked down to though, which makes me think it is probably something lower down the line. I will tighten all the hose clamps for sure, "easy" job (except for the yoga that is likely involved! )

 

[Moonfish]

I undersatnd, but this actually happened to me. I searched everywhere, until I found that leak at the neck and it was running down the side of the engine and getting into the bilge. I couldnt believe it either. Just something you should check.

 

[drewread]

I will 100% check them, quick and easy.

But just to be clear, this happened over the winter and the engines haven't run since she was put up on the hard and winterized. This coolant leaked out while she sat over the winter - I don't see how it could get up to the overflow port without heat (in fact it was freezing cold.)

Thanks!

 

[jgmo]

I won't argue about the overflow....it's easy to check. But, since this happened while just setting I would start at the bottom and work my way up.

And, the bottom is the air box drains. They may be just open tubes but if they are routed/plumbed to a container, look in there.

Check around the parting line for the cylinder head to engine block. These don't have 1 piece head gaskets. Instead, they have individual seal rings at water jacket (and oil gallery) passage openings. As a result, external leaks at head to block interface can quite often occur.

Check the "weep hole" in the bottom of the waterpump housing.

If you have a conventional type radiator cap, you can pressurize the system there. Most big box auto parts stores have the pressure tester to loan out.

I would keep the pressure under 10 psi. Start at 5 psi then 8 just to be cautious. These systems won't take the 20 psi that most car engines will.

Good luck.

 

[drewread]

And, the bottom is the air box drains. They may be just open tubes but if they are routed/plumbed to a container, look in there.

I think you are using the proper name for what is affectionately referred to as the "slobber tubes"?

Those are both routed into a black can, no sign of coolant in there.

Check around the parting line for the cylinder head to engine block. These don't have 1 piece head gaskets. Instead, they have individual seal rings at water jacket (and oil gallery) passage openings. As a result, external leaks at head to block interface can quite often occur.

Sounds potentially... ugly. Fingers crossed it is something else entirely!

Check the "weep hole" in the bottom of the water pump housing.

I'll see if I can find that. Can't seem to find it in my manual.

If you have a conventional type radiator cap, you can pressurize the system there. Most big box auto parts stores have the pressure tester to loan out.

I would keep the pressure under 10 psi. Start at 5 psi then 8 just to be cautious. These systems won't take the 20 psi that most car engines will.

Will look for a pressurizing cap, I assume that with that I will be able to see and hear where it is leaking once the system is pressurized, that would be great if I can get that working. Thanks for the idea.

 

[jgmo]

Yes, though I've never used the term "slobber tubes", I've no doubt some folks do.

Pressure testing is typically one of the best ways to pinpoint an external leak. You will likely not be able to hear the leak as the pressure you would be using is very low.
It really only works if the system is completely full of water or coolant.

There are also dyes that could be added to aid you, some of them iridescent and visible under ultraviolet light. The "black light" dye will leave a trail that can be detected even after the leak trail dries up.

The waterpump is about 10" in diameter located pretty much at the front upper center of these engines and has three hoses attached. At the very bottom of the round casting is a 1/8" hole where coolant will leak from if the shaft seal is bad. That seal can be replaced without removing the pump. Access is through a removable plate held in place by a large snap ring that you can easily see and remove with the correct tool.

It is also a good idea to remove the valve covers when pressure testing because the fuel injectors are surrounded by coolant and the seals for them can leak but you won't see it if the covers are left on.

Just my opinion but a shop manual, tools and some well chosen spares are pretty much indispensable to have handy for guidance and repair when owning these wonderful old engines. Especially on a boat where making it back to port can be a pretty big deal.
Save the tow...prepare before you go.

Good luck.

 

[drewread]

Thanks @jgmo the boat and Detroits are completely new to me. I have been reading through the Detroit (and other) manuals all winter long - lots to learn from them.

Stupid question, but is it safe to remove the valve covers and not worry about needing new gaskets for them every time? I know they are rubber, but I assume they will need replacement at some time.

I read about the dyes in the manual and if the pressure test doesn't work I'll be going that route next.

I know exactly where the water pump is - I was looking at it this weekend as I was trying to follow the path of all the coolant hoses and clean up the pink drips as much as possible (they seem to stain the paint) so I can see where it is coming from better. I'll re-topup the coolant with what I have aboard before I pressure test. The coolant may be drained down to the leak level already.. Which will make it hard to see coolant flow out. Thanks for the info on the water pump hole, I'll look there this weekend when I get to the boat.

I'm a tool geek - no worries there, other than my garage being too small for all the toolboxes. In fact I'm having a spanner socket machined right now so that I can hopefully pull the output shaft for a reseal. That is going to be another debacle in a too small engine room with two too large engines in it. Lol.

Thanks again.

 

[jgmo]

Well....
...at the risk of being completely wrong....

If the covers are the cast aluminum type and not the old stamped sheet metal type...
...yes, they should have the molded synthetic rubber gaskets that are typically reusable.

That is though if you take care to pull the covers off carefully and ensure they haven't gotten stuck to the head so as to be pulled free of the cover as you lift them off. Because, when they pop out of the slot they can be stretched and deformed in the process and difficult to put back correctly. So go slow there with that in mind.

Agree the 8V-71 is BIG and heavy. It is also one of the finest diesel engines I have known. Powerful, rugged, reliable and near bullet proof.

They have their "quirks" (like slobber tubes) and can be a challenge to learn how to work on. But, if you do take the time to learn them, they really aren't that hard to work on at all if you have the tools. No intake valves helps make them simple and pretty dang efficient for as old as they are.

I've always said, the Detroit 71 series will always get you home.

 

[drewread]

Well....
...at the risk of being completely wrong....

If the covers are the cast aluminum type and not the old stamped sheet metal type...
...yes, they should have the molded synthetic rubber gaskets that are typically reusable.

That is though if you take care to pull the covers off carefully and ensure they haven't gotten stuck to the head so as to be pulled free of the cover as you lift them off. Because, when they pop out of the slot they can be stretched and deformed in the process and difficult to put back correctly. So go slow there with that in mind.

Agree the 8V-71 is BIG and heavy. It is also one of the finest diesel engines I have known. Powerful, rugged, reliable and near bullet proof.

They have their "quirks" (like slobber tubes) and can be a challenge to learn how to work on. But, if you do take the time to learn them, they really aren't that hard to work on at all if you have the tools. No intake valves helps make them simple and pretty dang efficient for as old as they are.

I've always said, the Detroit 71 series will always get you home.

Thanks!

 

[drewread]

Quick update.

We were pulling abandoned wires from various areas of the vessel today. There are lots.

One of the abandoned "wires" was a small copper pipe inside of a black jacket - we pulled it back to the engine and cut it off for further investigation.

Turns out it was carrying coolant through it and was some sort of thermal "sensor" that went into the cooling system beside my overheat alarm sensor, into the housing for the thermostat.

Anyone know what that was? I have to find a way to cap it off.

 

[drewread]

If the covers are the cast aluminum type and not the old stamped sheet metal type...
...yes, they should have the molded synthetic rubber gaskets that are typically reusable.

Also @jgmo, I didn't take off the rocker covers this weekend - I want to have a gasket set in hand just in case I need to replace them, and I have another 5 million projects to look into.

There is of course some confusion though - My options plate sheet (there are no actual plates) say Type 44 head covers - which I think were the stamped type , but I'm pretty confident that I have the cast aluminum ones. See image.

The parts manual is also saying I need 4 per engine for the stamped type - I have two rocker covers on an 8V-71. Are they doubled up?

Thanks for any help!

 

[drewread]

Reporting that it appears that the decommissioned coolant temp sensor was likely the culprit. I removed it and sealed it with a plug earlier this week.

I haven't seen anymore coolant below this engine since I plugged it. Will add more coolant next week and hope that this is actually solved.

Thanks for the help and suggestions.