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]

Rob Schepis wrote:

Sounds good Bob, and congrats!

Thank you Rob!

Tony Athens wrote:

Think positive..

The RTV makes the steel gasket very forgiving–That’s why we changed the Cummins “dry assembly” Protocol , & use RTV as it has a 100% track record as to working very well except in very surface pitted applications.

Using the composite gasket requires not less that 3 re-torques after installation/initial use hot/cold cycles.

I even re-torque the steel gasket after the first start-up when I check for leaks.. BTW, all torquing is done with a box end wrench by “feel” & experience as to what is tight use a grade 12.9 alloy bolt/nut w/ RectorSeal # 5 as the assembly lube.

Tony

Tony ,

Thank you again for all of the advice and I agree that the RTV makes the steel gasket forgiving as I have experience in a prior life as a Nissan Tech and Nissan swore by that stuff on pretty much all of their gaskets.

You answered my next question regarding torque specs, I’ve always done these type of things by feel
( unless doing a head gasket ) so that is great to hear from you as well.

I just placed the order for the gaskets about an hour ago and they should be here in Philly on Tuesday so my plan is to drain the coolant and replace the gasket on both engines on Wednesday ( my day off ) unless it is freezing cold. I will certainly post an update on how things went along with pictures.

Thank you!
– Bob

[Tony Athens]

Think positive..

The RTV makes the steel gasket very forgiving–That’s why we changed the Cummins “dry assembly” Protocol , & use RTV as it has a 100% track record as to working very well except in very surface pitted applications.

Using the composite gasket requires not less that 3 re-torques after installation/initial use hot/cold cycles.

I even re-torque the steel gasket after the first start-up when I check for leaks.. BTW, all torquing is done with a box end wrench by “feel” & experience as to what is tight use a grade 12.9 alloy bolt/nut w/ RectorSeal # 5 as the assembly lube.

Tony

[Rob Schepis]

Sounds good Bob, and congrats!

[Bob Foster]

Rob Schepis wrote:

Bob,

Pop the caps first before ordering and clean up the surfaces so you know all is good and smooth for the steel gaskets.

Rob ,

Thank you so much for offering your suggestion as it makes complete sense. However I ordered the steel gaskets already as I am limited on time to when I can work on the boat ( work and baby on the way ). I will certainly inspect the mating surfaces prior to installing the new gaskets. If the surfaces are indeed rough, I will just need to bite the bullet and order the composites. Due to the water where the boat has been for most of it’s life I am optimistic of the surface’s being smooth.. Hopefully my intuition is correct and if not than I suppose having a spare set of gaskets is not the worst thing either.

Thank you!
-Bob

[Rob Schepis]

Bob,
Pop the caps first before ordering and clean up the surfaces so you know all is good and smooth for the steel gaskets.

[Bob Foster]

Tony Athens wrote:

Look at the article again………………It is very clear as to what to use………………….. STEEL GASKET with RTV………..The year vintage of the engine is not important.

The mention of a composite gasket is referring to “if you have crappy surfaces” and until you have it apart and with cleaned surfaces, neither of us knows that………………………….If you are not sure, post pics..

Tony

Thank you for clearing that up Tony. I am going to order the steel gasket for both engines as I prefer to do things in pairs. If I have any questions I will be sure to post detailed pictures along with said questions.

Warm Regards ,
– Bob

[Tony Athens]

Look at the article again………………It is very clear as to what to use………………….. STEEL GASKET with RTV………..The year vintage of the engine is not important.

The mention of a composite gasket is referring to “if you have crappy surfaces” and until you have it apart and with cleaned surfaces, neither of us knows that………………………….If you are not sure, post pics..

Tony

[Bob Foster]

Tony Athens wrote:

Let’s think positive here.. All you have a a failed gasket due to age and nothing else.. It happens…

This is really a simple fix.. Drain about 3-4 gallons of coolant and follow the pics and advice on the link..DO NOT rethink what is in that article nor let a mechanic do that either………………… No rocket science here, just simple “Mechanics 101” ……

Bet you a 6-pack that if you inspect the gasket when its removed, you’ll see the issue.

Tony

Tony,

Thank you for the bode of confidence regarding the leak that I am experiencing. As previously stated I am new to these engines so the advice that I am getting from you is greatly appreciated. I see that there are two different types of gaskets, one composite to be used in conjunction with high temp RTV and the other appears to be a crush style gasket. after reading the description of the composite gasket, it says from year’s 1985 – 1991.

Being that my engines are from 1999 would you recommend that I use the non composite gasket and no RTV?

I really appreciate all the help and I look forward to making my parts and maintenance items purchases through you.

Warm Regards ,
– Bob

[Tony Athens]

Let’s think positive here.. All you have a a failed gasket due to age and nothing else.. It happens…

This is really a simple fix.. Drain about 3-4 gallons of coolant and follow the pics and advice on the link..DO NOT rethink what is in that article nor let a mechanic do that either………………… No rocket science here, just simple “Mechanics 101” ……

Bet you a 6-pack that if you inspect the gasket when its removed, you’ll see the issue.

Tony

[Bob Foster]

Philip ,

I really appreciate the help so far! I will definitely post some pictures when I can so that you guys can see what I am working with. I look forward to hearing some feedback once I post the pictures.

I have been doing some research on here regarding the aftercooler service since I bought the boat back in late September. I’m sure that I will be on here picking everyone’s brain in addition to reading the articles over and over.

Warm Regards ,
-Bob

[Philip]

Post up the pictures when you get a chance, some very good eyes here that can help you! A couple of pictures in good definition from all four sides and the top would be great. Also close ups of the end caps on the aftercooler and heat exchanger are helpful. We are not judging a contest here, just using the pictures to help you.

Acid flush vs bench service are two different animals. Definitely do the service with the items removed from the engine and NEW o rings. DONT skip the pressure testing part as it’s the most critical. If you have questions about that process do ask and we can help.

I wouldn’t worry about the pressure for now…

[Bob Foster]

Philip ,

Again, thank you very much for your input regarding this issue as it is very much appreciated. I do not have any photos of the engine’s in they’re entirety yet but I can certainly take some the next time I am down there ( perhaps on Sunday ).Overall they are visibly pretty clean for being 20 year’s old compared to some of the photos I’ve seen not only on SBMAR ( marine age article ) but also from looking at listings from other vessel’s equipped with these engines.

I do know that the previous owner had the thermostats replaced and also the sea water side acid flushed on both engines 3 or 4 years ago and the boat had always ran great for him 180* on both engine’s ( and for me the 3 times I had it out ). The boat since 2003 has been berthed in the upper Chesapeake ( light brackish ) & Delaware River ( Fresh ) with the very occasional trip to the Jersey shore ( Salt ). The engine’s and all of the components in the ER for that matter show very well and do not have that green corrosion or rust visible to me. I will certainly take some pictures and upload them to this post as my description is no substitute.

I will definitely buy the required gasket kits to not only replace both manifold covers but also to disassemble the cooler’s noted. I am just baffled on how a cold engine could pressurize the coolant system, could it be perhaps residual pressure from the last time she ran?. I do however recall checking the coolant level on my previous boat ( 454 BBC ) over the winter and found it to be pressurized as well. To be clear, on both occasions It was not like 6-7 psi of pressure but enough to spew a couple of ounces of coolant out when I cracked that bung loose.

Maybe I am thinking too deeply into this whole thing but one thing is for sure, I’d rather be safe than sorry.

Thank you again Philip and I will post pics as soon as I can.

Warm Regards ,
– Bob

[Philip]

Bob –

I’m a warm weather guy in California so asking me about winterizing has its limits. But the symptoms sure do point that way…

The best thing would be to remove the entire cooling system in the spring, disassemble all, clean, new o-rings and LOTS of grease, and then the most important part would be to pressure test each item as assembled before installation. That would cover your “coolers” ie aftercooler, heat exchanger, gear cooler, fuel cooler, etc. for both maintenance and integrity.

Replace the gasket on the exhaust manifold cap. Remove the bung and reinstall with some rectorseal. Give a good visual of the entire exhaust system before spring commissioning and go run her and see what you have.

What’s the maintenance history of the engine? Be detailed….

Got any pictures of the engine from all sides?

[Bob Foster]

Philip ,

Thank you for the quick reply. Living in the NE, freeze damage is always a concern and that is why I decided to run down and check things out.. I used the same procedure to winterize this boat as I have done with my previous boat, the only difference is that the previous boat was a gasser and had twin 454 BBC that were also raw water cooled. I run 6 gallons of Pink through each engine making sure that it is all pink flowing out of the exhaust. Although I am confident that it was winterized correctly, those nights where it is single digits certainly weigh heavy on my mind.

Is there a certain way for me to check the heat exchanger for possible damage?. Could it be possible that even though I had pink flowing through my exhaust that there may be residual water in the system?

Again I apologize for any ignorance as these engines are new to me.

Thank You!
-Bob

[Philip]

First off I’d be concerned about where that pressure is coming from. Any chance you aren’t winterized properly and have some freeze damage someplace (maybe inside the heat exchanger).

As for dealing with the leak… pretty straight forward.

https://www.sbmar.com/articles/changing-a-turbo-to-exhaust-manifold-gasket-on-a-cummins-mid-range-engine/

[Author]

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