6CTA Coolant leak on top of exhaust manifold

[Bob Foster]

Hello,

I’m hoping to get some advice regarding a coolant leak that I noticed today while checking on my boat.

I have a 1999 Formula 41pc fitted with twin Cummins 6CTA Diamonds. After the cold snap that we just had in Philadelphia I decided to check on the boat as it is on the hard for the winter.

During my inspection in the engine room, I spotted engine coolant resting ontop of the port exhaust manifold. It appears to be coming from some type of plate, water cover perhaps? And also leaking from what looks like an auxiliary heater line bung just aft of the cover.

I am assuming that it is called a water cover or manifold cap because it has the same dimensions as the turbo flange and after reading the article on here regarding replacing the turbo gasket Tony mentioned that the turbo to manifold gasket replacement is the same procedure as the manifold cap gasket replacement.

I’ve read the marine age article and found that to be very informative. Correct me if I am wrong but this appears to be a failed gasket due to marine age? Nothing appeared to be cracked and the boat never ran hot as I ran her back from MD to Philadelphia around 2 hours and never ran hot prior to me taking ownership ( I am close friends with the previous owner, I know the history of this boat very well ).

I’ve attached two images. One picture is of the obvious leaks as they were when I first saw them. The second is what appears to be a part number which I have looked up and cannot find anything. I did loosen that bung after that picture was taken to confirm it was indeed engine coolant in the manifold and not RV antifreeze from winterizing and to my surprise it was pressurized. Please note that the boat has not been run since we winterized in October.

Any help identifying that part and more importantly which gasket to buy would be much appreciated. I apologize for any ignorance as I am new to this boat and these engines so I am trying to learn as much as possible.

Thank you,
Bob

Topic

[Bob Foster]

Back to the topic of this post

I finally had some free time to stop by the boat today and get the exhaust manifold cap gasket done. I got completely sidetracked and did the Aftercooler service but the whole purpose of this post was regarding the manifold cap gasket leaking.

I started by draining about 3 gallons of coolant from the exhaust manifold. I was able to drain the mainifold by removing the bung plug on the turbo. I circled it in the picture. To ensure that the coolant level was low enough in the manifold prior to pulling the cap, I visually checked by looking into the auxiliary bung next to the cap. Once I pulled the cap off I was fortunate to see that the mating surfaces were in very good condition and requires minimal sanding. I made sure to use high temp copper rtv on both sides of the gasket and that the “ turbo side “ was facing the cap. The install was very self explanatory, big holes to big holes and small holes to small holes. I tightened the 4 bolts and used pipe dope on the threads.

I could see where the coolant had leaked from on the old gasket. It appears that the gasket rusted from the outside in from I assume condensation over the years.

The coolant was only 2 years old so I re used it along with a gallon of fresh coolant since I lost about a gallon while draining.

Here are the pictures:
( Pardon my mug in the one pic )

– Bob

[firehoser75]

Thanks as Well

Tony,
I too just serviced my aftercooler (and other items) thanks to all the info that you, Rob, and all of the members of this forum provide freely to us mechanical “newbies”.
YOU GUYS ROCK!
Thanks again,
Tom

[Bob Foster]

Tony Athens wrote:

Just proves again the point beyond any doubt————————–FRESH WATER FLUSHING adds decades of life to the engines “mixed metal aftercooler” that runs in salt water ( normally)

OH, BTW, you are doing a 100%+ job..

Tony

Tony,

Thank you very much for the kind words and also for writing such detailed articles on the subject. All of the advice and literature gave me the confidence to take this on.

– Bob

[Tony Athens]

Just proves again the point beyond any doubt————————–FRESH WATER FLUSHING adds decades of life to the engines “mixed metal aftercooler” that runs in salt water ( normally)

OH, BTW, you are doing a 100%+ job..

Tony

[Bob Foster]

Today I had the time to go to the shop and knock out to Starboard Aftercooler. The core came out pretty clean with the brake clean and spray nine and compressed air. The number 3 Aftercooler and heat exchanger maintenance kit provided the perfect amount of grease and all of the essentials to make this job simple. In this cooler I did find a light amount of deposits in the core tubes along with smaller chunks of rubber.

I pressure tested the port Aftercooler and aside from my test rig having a slight leak, it appears to be good to go. I pressurized the air side and capped off the water side to make an extra confirmation that the rig was leaking. I am currently testing the starboard one now. Once that is complete they will go back on the boat and I will attack the original subject of this post which is that manifold cap gasket leak.

Here are some pics from today.

[Bob Foster]

Stephen Oliver wrote:

Bob Foster wrote:

Rob Schepis wrote:

Good pics. Tailgates do always make for a good workbench. Yes, on the water side. Here’s some pics when I did the same and I did it twice, once with air, once with water, just for fun.

Haha! It is actually the perfect height for it!. My garage is packed full of stuff at the moment… we just had a baby shower so as you could imagine it’s chaos in our little one car garage.

That is super helpful Rob. Thank you very much for sharing those photos and I see that you went to 15PSI which is also very helpful as I was concerned about over pressuring it on the water side. I may also hit it with water just to have the extra assurance.

Thank You!

– Bob

I Did the same as rob – Both sides 30 PSI for the water side as the fittings are smaller and had less need to blow themselves off, and 25 psi for the air side – left for 24 hours.

Interestingly I used some dish soap to find any leaks – and on one there was a small leak on the test rig fitting, I couldnt stop it but it was 1psi in 24hours and the other aftercooler had a porous casting.. I ended up grinding the hoses back and casting some JB weld over the top (at the suggestion of Tony).. it survived the 24 hours pressure test nicely.

Steve

Steve,
Thanks for sharing what you did and that definitely is comforting to know that you went up to 30PSI. I just did my first pressure test and my rig is also leaking using the same method as you did. I sprayed some soap and found a leak at the coupler to the Aftercooler. The crazy part is that I never detached it before so that means that it was definitely leaking boost!. I happen to have enough brand new 2.5” Mishimoto turbo piping couplers from a car that I was building a few years ago so I will be replacing all 8 couplings.

– Bob

[Bob Foster]

William Walter wrote:

Bob great decision to take that apart. Good pictures and I’m surprised at how well your cores and aftercoolers look. First thing I did when I got my boat 2 years ago was to take my whole salt water side apart.second thing I did was address my overpropping.was a busy winter.what I’m curious about is the environment your boat was in before purchasing.were you up the Delaware in fresh water or on the coast.im surprised at the condition but fresh water would explain for an engine with 1000hrs.Disregard as I read up a few post and saw that indeed you were mostly in brackish water.Bill

Bill,
Once I saw the debris left behind from a failed impeller and getting close to 1000 hours I figured that it must be done. This coming season will be my first full season with this boat so it is definitely nice to do all of this now and get familiar with it. I am hoping that this helps alleviate some of the smoke during the cold start ups as well but we shall see.

The only thing that I have left to do is to get the valves adjusted. I will have Cummins come out to do that as I do not want to liability if god for bid I drop a valve or something.

-Bob

[Stephen Oliver]

Bob Foster wrote:

Rob Schepis wrote:

Good pics. Tailgates do always make for a good workbench. Yes, on the water side. Here’s some pics when I did the same and I did it twice, once with air, once with water, just for fun.

Haha! It is actually the perfect height for it!. My garage is packed full of stuff at the moment… we just had a baby shower so as you could imagine it’s chaos in our little one car garage.

That is super helpful Rob. Thank you very much for sharing those photos and I see that you went to 15PSI which is also very helpful as I was concerned about over pressuring it on the water side. I may also hit it with water just to have the extra assurance.

Thank You!

– Bob

I Did the same as rob – Both sides 30 PSI for the water side as the fittings are smaller and had less need to blow themselves off, and 25 psi for the air side – left for 24 hours.

Interestingly I used some dish soap to find any leaks – and on one there was a small leak on the test rig fitting, I couldnt stop it but it was 1psi in 24hours and the other aftercooler had a porous casting.. I ended up grinding the hoses back and casting some JB weld over the top (at the suggestion of Tony).. it survived the 24 hours pressure test nicely.

Steve

[William Walter]

Good find

Bob great decision to take that apart. Good pictures and I’m surprised at how well your cores and aftercoolers look. First thing I did when I got my boat 2 years ago was to take my whole salt water side apart.second thing I did was address my overpropping.was a busy winter.what I’m curious about is the environment your boat was in before purchasing.were you up the Delaware in fresh water or on the coast.im surprised at the condition but fresh water would explain for an engine with 1000hrs.Disregard as I read up a few post and saw that indeed you were mostly in brackish water.Bill

[Bob Foster]

Rob Schepis wrote:

Good pics. Tailgates do always make for a good workbench. Yes, on the water side. Here’s some pics when I did the same and I did it twice, once with air, once with water, just for fun.

Haha! It is actually the perfect height for it!. My garage is packed full of stuff at the moment… we just had a baby shower so as you could imagine it’s chaos in our little one car garage.

That is super helpful Rob. Thank you very much for sharing those photos and I see that you went to 15PSI which is also very helpful as I was concerned about over pressuring it on the water side. I may also hit it with water just to have the extra assurance.

Thank You!
– Bob

[Rob Schepis]

Pressure Test Aftercooler

Good pics. Tailgates do always make for a good workbench. Yes, on the water side. Here’s some pics when I did the same and I did it twice, once with air, once with water, just for fun.

[Bob Foster]

So we finally caught a break in the freezing weather in Philly and I had some spare time yesterday so I decided to get one of the aftercooler’s done. I had already taken them apart at the shop last week so the cores are free and make it easy to work on them at home. I received the maintenance kit #3 in the mail so I was armed with all of the essential’s that Seaboard Marine provided. I was able to clean a good amount of oil residue out of the fins using brake clean and simple green and also compressed air and a garden hose. It took about an hour to clear out all of the ” crud ” that was trapped in the fins but overall I am happy with the final product and comparing running the hose water through it when I started to when I finished, it appears to flow a lot better/un-restricted. I was very fortunate that the boat is a brackish / fresh water boat and there was really no deposits in the tubes which I used the supplied rod to clean so that was simple. The only thing that I was up against was the oil residue on the fins.

During reassembly I used a generous amount of metal lube which was also supplied with the kit. I ended up using about half of the tube which was supplied. I lubed up both ends of the core and also about an inch into the housing itself. Once I installed the O ring that was supplied I applied more lube on top of that and also on the mating surfaces of the end cap.I used the supplied Rectorseal on the threads of the supplied pencil zincs.

I did also make a pressure test rig borrowing a friends pressure tester that he uses for residential pluming and heating and some PVC fittings. Unfortunately I am experiencing a leak where the PVC fitting is clamped to the turbo pipe coupling ” I think it’s time for new couplings “.

Once I confirm that the aftercooler is not leaking I will then re-paint and it will be done!

Tony,
Hopefully you can shed some light on this for me. Could I also pressure test on the water side? and if so how much pressure would you recommend? I obviously wouldn’t want to damage anything.

Thank You,
– Bob

[Bob Foster]

Tony Athens wrote:

This boat most obviously spends its “time off” in fresh water, correct?

Your aftercooler says it all, and these are early 6CTA’s (pre-2000 ish?) ..

Tony

Tony,

Yes that is correct. Since 2003 when the p/o purchased it, it has been in the brackish waters of the upper Chesapeake and also the fresh waters of the Delaware River in the Philadelphia area. The first owner was in CT so that would be salt.

Also correct in saying early 6CTA’s they are original with the boat 1999.

I will post more updates and pictures regarding the original issue of the leaking manifold cap gasket once I tackle that. I’ve got some time until I splash her in April.

– Bob

[Tony Athens]

This boat most obviously spends its “time off” in fresh water, correct?

Your aftercooler says it all, and these are early 6CTA’s (pre-2000 ish?) ..

Tony

[Bob Foster]

Here are some pictures of my engine room and both engines.

[Bob Foster]

Update:

I went down to the boat today to replace the exhaust manifold cap gasket and left with both Aftercoolers in my truck. I still need to drain the engine coolant and change the cap gasket. The reason why I pulled the Aftercoolers was because I went to drain the pink stuff that I winterized with from them and found chunks of rubber.

Being that they are approaching 1000 hours and the previous owner told me that they have never been serviced and the chunks of rubber I found I figured now would be a better time than ever to take them apart , clean , and reassemble. Once I got them to the garage I took them apart to find about a half of an impeller amount of rubber in the port cooler and a few chunks in the starboard cooler. Other than the chunks of rubber I am impressed on how clean they are.

I spoke with the previous owner and he confirmed the the 1st owner did have both impellers go out on him and that he ( the previous owner ) removed a lot of chunks from the starboard cooler and did not have room to pick out the chunks on the port cooler.

I just purchased the #3 Aftercooler and heat exchanger kit for both engines. Once it arrives I will dissemble again , clean , and reassemble per Tony’s instructions. I have a set of brand new impellers that I will be installing prior to re-installing the coolers.

I’ve attached photos of the port and starboard coolers. I will attach photos of my engines and engine room in the next post.

Also as a side note. I am learning a lot about these engines and I appreciate everyone’s input here! You guys rock!

– Bob

[Bob Foster]

Rob Schepis wrote:

Bob Foster wrote:

I have experience in a prior life as a Nissan Tech

Well if the 6CTA fails you, you could repower with a pair of LD28M’s !

Keep us updated with pics and progress.

Hahaha YES!

[Rob Schepis]

Bob Foster wrote:

I have experience in a prior life as a Nissan Tech

Well if the 6CTA fails you, you could repower with a pair of LD28M’s !

Keep us updated with pics and progress.

[Bob Foster]

Tony Athens wrote:

In the diesel boating world,IMO there is nothing better than a “hands-on” operator. Tony

Thank you Tony. I would not be able to afford a boat if I did not have a mechanical background LOL!

All joking aside. Being in the auto repair trade for the better part of my life has saved me thousands in boat repairs and maintenance on my previous boats and will with this one as well.

Thanks again for all of your advice!

-Bob

[Tony Athens]

In the diesel boating world,IMO there is nothing better than a “hands-on” operator. Tony

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