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Cummins 6BTA losing coolant

DIESEL engine, transmission and generator repair and maintenance discussion forum.
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KyleR
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Cummins 6BTA losing coolant

Postby KyleR » March 21st, 2024, 8:36 pm

I know this is a long read, but I was hoping to give as much info as I could. Thanks to those who make it through!! :-D

About 3 mornings ago as I was performing my pre-run checks, I noticed the coolant overflow reservoir on my STBD main engine (SN:46174828) was empty.  I checked the main reservoir and it was completely filled.  So I started looking for external leaks but could find no evidence of an external leak anywhere.

I turned to looking for internal leaks and checked the oil and transmission fluid but neither had any abnormal level or visual indication of contamination.  At this point I was thinking I probably had a heat exchanger leak and was slowly losing coolant to the seawater side via a tube/sheet leak.  So I refilled the overflow reservoir, warmed the engines then started our cruise at 1050rpm @ 7knots, our typical cruising speed.

Within 10 minutes, the STBD engine started producing thick white smoke from the exhaust – and a lot of it.  I went and verified the coolant overflow reservoir level and I could definitely see that the level had lowered.  Typically I see level go up an inch or so, but it had dropped about a quarter inch.  Given the lowering level and thick white smoke, the heat exchanger leak seemed less likely.  During all of this, temperatures were normal at the helm indications (165F) as well as temps taken locally on the engine with an IR gun.  I was comparing them to the PORT engine and both were as matched as they ever are (within a couple of degrees).

We continued to slowly make our way and I kept checking the overflow reservoir every 5-10 minutes and could definitely see a lowering trend, but nothing drastic.  The white smoke sometimes got a little less, and sometimes would get worse.  Finally, I saw the helm temperature start to rise pretty rapidly and I turned off the engine immediately as the temp was passing 200F, but it continued to rise to around 220F before stopping.  No alarms were ever received.

After putting the other engine in neutral, I went down and saw that there was still coolant in the overflow reservoir, but it was lowering pretty fast as it was being drawn into the main reservoir – and it was empty within just a few minutes.  I didn’t want to open/check the main reservoir at that point as everything was pretty hot.  We finished our trip on the PORT engine and once the STBD engine cooled I checked the main reservoir and it was completely empty.

My research of the symptoms seems to suggest a potential coolant to exhaust manifold leak and based on my research I thought I would go after the two most obvious locations first: the exhaust manifold cap gasket and then the turbo charger to exhaust manifold gasket.

I am attaching pics of the exhaust manifold cap after removal – before doing any cleaning other than wiping off the gasket.  You can see what looks to be a loose sealing surface on the gasket hanging down in the pic with my hand, but there was no evidence of external leakage from the cap so I am not sure if that tear was the result of removing the gasket or a potential failure mechanism. 

Also I definitely found what appears to be residual coolant in the exhaust manifold.  (I stuck a paper towel inside and it came back soaked with a yellowish liquid which is the color of the coolant I use (Valvoline Zerex G05).  It didn’t fill the manifold, just some traces of it that I was able to see.

I haven’t removed the turbo from the exhaust manifold yet.  I basically wanted to attack this one step at a time so I started with the cap gasket replacement (the easiest) to see if that works.  If not, I will proceed to the turbo to manifold gasket and replace it and see if that works.  If not, then I am guessing I will have to remove the manifold and have it inspected/tested.  And the final attempt would be a head gasket replacement if all else fails. Basically after each step, I'll pressure test the coolant system and see if it holds.

My questions so far that I would like help with are:

• Given my symptoms and indications, am I on the right track?

• Does my work progression (1. cap gasket, 2. turbo gasket, 3. manifold removal, 4. head gasket) seem reasonable?

• Is there anything specific I should be looking at to confirm the source of the leak or which component likely failed? Nothing jumps out at me on the manifold exhaust cap and gasket, but maybe the pics reveal something to more experienced eyes.

Thanks for reading and any feedback is greatly appreciated!

Kyle
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Re: Cummins 6BTA losing coolant

Postby bud37 » March 22nd, 2024, 10:56 am

Whatever you decide,.....if you are going to replace the gaskets and try again if that is the finding , be sure to clean those surfaces very well and check them with a machinist grade level/ straight edge. They need to be quite flat to mate and seal properly, especially important after any over heat/leak situation.

FWIW, there is one area there where that gasket has very little purchase at the edge of the one port. Right hand side of first pic.
The above is strictly my opinion always based on years of doing...remember to support local business , it pays back.
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KyleR
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Re: Cummins 6BTA losing coolant

Postby KyleR » March 30th, 2024, 11:36 pm

Thought I'd follow-up for those who may find themselves in a similar situation.

So, after removing the exhaust manifold cap I decided to go ahead and pull the turbine based on recommendations from Seaboard Marine as they thought the turbo gasket was more likely the culprit.

So I removed the turbo and what a mess I found! I'm attaching pics of the as-found condition. I found a reputable turbo shop here in Miami who disassembled it and actually said there was almost no corrosion internally - just a lot of oil/dust/sludge buildup.

I'm not sure how much was before we owned the boat as I try to be pretty consistent taking the engine to WOT near the end of a trip, but I'm sure I've contributed to it by not doing every time.
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KyleR
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Re: Cummins 6BTA losing coolant

Postby KyleR » March 30th, 2024, 11:40 pm

And here are a few pics of the rebuilt turbo all cleaned up and ready for installation. I sure hope this fixes it and it's not something worse Iike a cracked manifold or blown head gasket!

I hope to have everything installed tomorrow and start it up and see what happens. I'll update then.
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Topic author United States of America
KyleR
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Re: Cummins 6BTA losing coolant

Postby KyleR » April 3rd, 2024, 7:20 am

Got everything installed and fired it up....more thick smoke and coolant t loss. :banghead:

So, now I'm on to the next step of my troubleshooting plan which is to remove the exhaust header and have it pressure tested. I took two days - one day of just hitting the bolts with PB Blaster and then a hammer, repeat, repeat, etc... And then the second day of just going loose, tight, loose, tight, etc. very carefully and slowly and I was able to remove all 12 exhaust manifold bolts without snapping a single one! I was so thankful!!

Anyways, we've rented a truck and we're off to a diesel shop in N. Palm Beach that specializes in Cummins to have the whole manifold/turbo unit pressure tested. I did hook a hose up to one port and put my hand over the other port and when I blew into the manifold it sounded like I could hear air. The shop said they'd pressure test it for free so we'll know for sure later today.

That's all I've got for now.... Thanks for following along on my saga!
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Re: Cummins 6BTA losing coolant

Postby km1125 » April 3rd, 2024, 12:12 pm

Sorry to hear that!

While that's off and out to be tested, I'm wondering if you could plug the hoses that were attached to it and then pressure test the whole rest of the coolant system to see/verify any other leaks in the system?
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KyleR
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Re: Cummins 6BTA losing coolant

Postby KyleR » April 3rd, 2024, 8:25 pm

Good suggestion - I've actually already tried that before all this other hoopla since I already own a coolant system pressure tester that I used for pressure testing the aftercoolers and heat exchangers.

Unfortunately, the design of this 396 has an electrical chase that runs almost directly over the radiator cap and only gives me a couple of inches or so between the cap and the chase. I can't get the tester attached. :-(

But, on the good side, when the manifold was tested today it definitely leaked so it was definitely cracked internally. So, at least now I've identified a smoking gun!

So, I picked up a new manifold and will be installing it over the next few days as I work around other projects as well! And all this being done on anchor just off the Biscayne Bay south Florida!!

At least I have an amazing view each day!! :-D
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Topic author United States of America
KyleR
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Re: Cummins 6BTA losing coolant

Postby KyleR » April 13th, 2024, 2:34 pm

Well, it looks like I might have gotten lucky and only had a cracked exhaust manifold.

I ended up getting a new manifold, new gaskets, new manifold bolts and even decided to get a new starter and mag switch while I had everything on that side removed. It was the starboard engine so getting to the starter is a royal pain, and it looks like it is the original Cummins starter.

Anyways, I changed the oil and put everything together and barred the engine over a couple of revolutions and she started right up!

No leaks, no unusual smoking, no abnormal noises or temperatures. Just waiting for everything to cool down and then check all fluids and connections for leaks.

But, so far so good. Thanks to those who chimed with advice!
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