Official Cummins 6cta 450C thread

[Forrestkk]

I am sure I am not the first, but had started noticing some steam in my port engine (no change engine temp at all). Well, thought I had dirty coolers, but they look great (doing the maintenance anyway). Pretty sure I found the culprit, look what I found on the inlet side if the gear cooler...the whole top zinc out of the aftercooler. Not sure how long it was there, but I have a brand new gear cooler as my IR gun showed my port trans running 20 degrees hotter than my starboard. Will probably pull this one, clean it, pressure check and keep as a spare. Lesson, if you think your zinc completely dissolved, maybe it didn't.

 

[Irie308]

Even the threads are intact. How does that happen?! I eliminated the top zinc as it doesn’t sit in water and I’d rather not replace the transmission from overheating due to lack of flow.

 

[Forrestkk]

Even the threads are intact. How does that happen?! I eliminated the top zinc as it doesn’t sit in water and I’d rather not replace the transmission from overheating due to lack of flow.

My only guess is that it wasn't tight enough in the brass fitting.

 

[Alex F]

My only guess is that it wasn't tight enough in the brass fitting.

100% agree. The first thing one should do is always make sure every new zinc is snug tight. Since 99% of the time I replace the zinc element (the heads stay fine for years), it's never an issue.

 

[Forrestkk]

Driveway Cummins Marine shop...my 10 year helping me out. We are close, one aftercooler core is STUCK...letting kroil penetrate and flipping every so often and reapplying, hopefully it frees up.

 

[becnme]

Are you pouring the Kroil down the air side too? It helps and I have had them where it needed 3 days to loosen up.

 

[Forrestkk]

Are you pouring the Kroil down the air side too? It helps and I have had them where it needed 3 days to loosen up.

Was not pouring it down the air side. Will try that.

 

[ZZ13]

Was not pouring it down the air side. Will try that.

All the corrosion is from the air side. The salty condensing air eats away the inside of the aluminum housing where it meets the core. The aluminum dust/corrosion packs into every nook and cranny and packs into the air fins at the bottom of the core and bends the blades of the fins. The amount of the fins affected depends on how long it’s been together and whether metalube grease was in there protecting the aluminum housing. You probably know all this.

Good luck. I’ve serviced a lot of these that were never greased and never cleaned. Most of them that took Herculean effort to get apart, had to be replaced. Once you start the greasing and cleaning every two year regiment, the core just pushes out easily by hand.

 

[Forrestkk]

All the corrosion is from the air side. The salty condensing air eats away the inside of the aluminum housing where it meets the core. The aluminum dust/corrosion packs into every nook and cranny and packs into the air fins at the bottom of the core and bends the blades of the fins. The amount of the fins affected depends on how long it’s been together and whether metalube grease was in there protecting the aluminum housing. You probably know all this.

Good luck. I’ve serviced a lot of these that were never greased and never cleaned. Most of them that took Herculean effort to get apart, had to be replaced. Once you start the greasing and cleaning every two year regiment, the core just pushes out easily by hand.

That is all good info and wasn't tracking all of it. Thank you for sharing.

Supposedly, the port AC was serviced when the strb engine was replaced. We will see; sure hope I don't need a new insert. I have been able to get it to move back and forth about 1/8" of an inch. I hope that I can get a little more wiggle and get it loose.

 

[ZZ13]

That is all good info and wasn't tracking all of it. Thank you for sharing.

Supposedly, the port AC was serviced when the strb engine was replaced. We will see; sure hope I don't need a new insert. I have been able to get it to move back and forth about 1/8" of an inch. I hope that I can get a little more wiggle and get it loose.

The pitting and loss of metal at the bottom of the aluminum housing is something to also check closely. You can’t loose any metal from the housing edge where the big o-ring seals it to the core. Pitting, even significant pitting down inside the housing isn’t an issue. Packing all those pits full of metalube before assembly will keep those from getting any worse. Once you get it all put back together it’s easy to rig up a go/no-go pressure test.

 

[Forrestkk]

The pitting and loss of metal at the bottom of the aluminum housing is something to also check closely. You can’t loose any metal from the housing edge where the big o-ring seals it to the core. Pitting, even significant pitting down inside the housing isn’t an issue. Packing all those pits full of metalube before assembly will keep those from getting any worse. Once you get it all put back together it’s easy to rig up a go/no-go pressure test.

Well, managed to get the core about 33% out, but fear it may have met its end. After using a pry bar to get it moving out of the housing, I noticed the brass plate looks like it had pulled away from the fins a bit. Assuming that can't be good.

Should I just brute force it the rest of the way out and order a new core now?

 

[ZZ13]

Well, managed to get the core about 33% out, but fear it may have met its end. After using a pry bar to get it moving out of the housing, I noticed the brass plate looks like it had pulled away from the fins a bit. Assuming that can't be good.

Should I just brute force it the rest of the way out and order a new core now?

I drive them through. I took a 4” pvc coupler from the plumbing section. It’s just a hair too big to fit inside the housing. But run your table or mitre saw one swipe through the side of the coupler to take a blade width out of the circumference. Now it will fit inside just right. Then rig up a way to drive the coupler through. Like a 3/4”-1” thick piece of wood cut to the right diameter. Then a 2x4 on end wacked into that with a sledgehammer. Anyway, that’s the pusher I rigged up.

 

[Alex F]

... The Cummins mechanic who I work with was all set to go and then Cummins released a bulletin saying to stay with the 160. Seaboard Marine seems to agree with this revised point of view...

Could you please share that article. I'm a bit puzzled which thermostat to go with. Based on how I'm using the boat I'm leaning towards 180. But I rather be safe than sorry and go for 160.

 

[Forrestkk]

Could you please share that article. I'm a bit puzzled which thermostat to go with. Based on how I'm using the boat I'm leaning towards 180. But I rather be safe than sorry and go for 160.

I am using 160s with no issue.

Here is the SBMAR reasoning. I find it sound even though this focuses on the BTA, the same logic applies to the CTA.

https://www.sbmar.com/articles/choosing-the-160f-or-180f-thermostat-for-your-cummins-6bta/

 

[ttmott]

Could you please share that article. I'm a bit puzzled which thermostat to go with. Based on how I'm using the boat I'm leaning towards 180. But I rather be safe than sorry and go for 160.

I am using 160s with no issue.

Here is the SBMAR reasoning. I find it sound even though this focuses on the BTA, the same logic applies to the CTA.

https://www.sbmar.com/articles/choosing-the-160f-or-180f-thermostat-for-your-cummins-6bta/

I'm curious about the issue using the correct thermostat per Cummins. The thermostat doesn't affect the cooling system's capability or reliability; all it does is regulate the coolant temperature by varying the coolant flow through the engine and heat exchanger. Typically, a higher engine temperature is desired to reduce carbon buildup on the cylinder head and reduce carbon contamination in the oil.

 

[Forrestkk]

I'm curious about the issue using the correct thermostat per Cummins. The thermostat doesn't affect the cooling system's capability or reliability; all it does is regulate the coolant temperature by varying the coolant flow through the engine and heat exchanger. Typically, a higher engine temperature is desired to reduce carbon buildup on the cylinder head and reduce carbon contamination in the oil.

I'd argue the way to keep carbon build-up out of the head is to not idle or operate for lengthy periods under light load which leads to wet stacking. Combustion chamber (head, pistons, cylinder) temp is determined by fuel flow (load) and engine speed, not coolant temp.

As far as oil, the same issue above applies to carbon build up as that is caused by incomplete combustion during low load conditions.

Oil temp is important to make sure fuel (blow by and incomplete combustion again) and moisture are removed, but running at 80% load gets it to the necessary temps at least on my engines as evidenced by oil samples verifying that there is no fuel/moisture contamination. Also, why labs have you run under load for 15 to 20 mins before sampling, get that oil hot.

Additionally, oil cools the bottom of the piston, and coolant cools the oil which helps keep you pistons cooler.

This is why the SeaBoard article resonates with me, boats are always going uphill.

Just my $0.02.

 

[Alex F]

I am using 160s with no issue.

Here is the SBMAR reasoning. I find it sound even though this focuses on the BTA, the same logic applies to the CTA.

https://www.sbmar.com/articles/choosing-the-160f-or-180f-thermostat-for-your-cummins-6bta/

Many thanks for the link. Very good article and definitely helps with the decision.

I didn't expect any issues with 160s t-stats, as it's preferred for the most applications. It's just a while ago, I read somewhere (don't recall if it was BD thread or SBMR article) that when cruising at trawler speed 180 t-stats is preferred for keeping the temps higher to help minimizing carbon build up and the blow by.

I had a situation when temp on the port engine went up to a hair over 195. I saw it climbing and was able to catch it in time. As soon as I saw it going past 195 I pulled the throttles back and came off plane. The temp dropped pretty quickly at trawler speed. No alarm went off. According to Tony's article, the alarm would be going off at 205*. But I don't want to take any chances and get the engines to this temp.

This leads to the question regarding Tony's statement. "When running the 160F tstat you can have your redundant a.k.a “sleepyhead” alarm system triggered by a 190F switch. Therefore, your alarm is alerting the operator that something is amiss while the engine is still in a safe temperature range before irreversible damage is done."

Do you guys know how to rig this type of redundant alarm to go off at 190*?

 

[ttmott]

I'd argue the way to keep carbon build-up out of the head is to not idle or operate for lengthy periods under light load which leads to wet stacking. Combustion chamber (head, pistons, cylinder) temp is determined by fuel flow (load) and engine speed, not coolant temp.

As far as oil, the same issue above applies to carbon build up as that is caused by incomplete combustion during low load conditions.

Oil temp is important to make sure fuel (blow by and incomplete combustion again) and moisture are removed, but running at 80% load gets it to the necessary temps at least on my engines as evidenced by oil samples verifying that there is no fuel/moisture contamination. Also, why labs have you run under load for 15 to 20 mins before sampling, get that oil hot.

Additionally, oil cools the bottom of the piston, and coolant cools the oil which helps keep you pistons cooler.

This is why the SeaBoard article resonates with me, boats are always going uphill.

Just my $0.02.

"Wet Stacking" is really an issue of the past and more typically a condition with non-electronic Detroit Diesel 2-stroke engines in the small yachts like we have. I wouldn't be so bold to say that my engines run at 80 percent much at all, it is more low throttle settings and speeds in our area. About the only time we get to cruise loads (which is about 70 percent on my boat) is open water like running down the ICW or over to the Bahamas. As far as the QSM engines and discussions with the Cummins certified service center that does the major work on mine, the thermostats are replaced with the Cummins specified units. Not that I think this is a major issue to run a bit of a cooler thermostat, I think the factory that tests these engines in all conditions is the authority. Nothing against Mr. Athens as he has the school of hard knocks to back his decisions up. I don't understand the importance of the piston cooling - we are talking about a small differential in oil temperature between two different coolant thermostats. Explain that better for me. I know of no one that runs engines at load to extract oil samples - the engine is brought up to operating temperature and the sample is pulled. The key to oil analysis isn't one data point but a collection of many to determine conditional trends.

 

[Forrestkk]

Many thanks for the link. Very good article and definitely helps with the decision.

I didn't expect any issues with 160s t-stats, as it's preferred for the most applications. It's just a while ago, I read somewhere (don't recall if it was BD thread or SBMR article) that when cruising at trawler speed 180 t-stats is preferred for keeping the temps higher to help minimizing carbon build up and the blow by.

I had a situation when temp on the port engine went up to a hair over 195. I saw it climbing and was able to catch it in time. As soon as I saw it going past 195 I pulled the throttles back and came off plane. The temp dropped pretty quickly at trawler speed. No alarm went off. According to Tony's article, the alarm would be going off at 205*. But I don't want to take any chances and get the engines to this temp.

This leads to the question regarding Tony's statement. "When running the 160F tstat you can have your redundant a.k.a “sleepyhead” alarm system triggered by a 190F switch. Therefore, your alarm is alerting the operator that something is amiss while the engine is still in a safe temperature range before irreversible damage is done."

Do you guys know how to rig this type of redundant alarm to go off at 190*?

Yes, the alarm is driven by a thermal switch(one wire), not the transducer (two wires) that drives the guage. Change the thermal switch to a lower temp. They can be ordered in almost any temp pretty sure McMaster-Carr carries them, but probably summit or jegs as well.

 

[Forrestkk]

"Wet Stacking" is really an issue of the past and more typically a condition with non-electronic Detroit Diesel 2-stroke engines in the small yachts like we have. I wouldn't be so bold to say that my engines run at 80 percent much at all, it is more low throttle settings and speeds in our area. About the only time we get to cruise loads (which is about 70 percent on my boat) is open water like running down the ICW or over to the Bahamas. As far as the QSM engines and discussions with the Cummins certified service center that does the major work on mine, the thermostats are replaced with the Cummins specified units. Not that I think this is a major issue to run a bit of a cooler thermostat, I think the factory that tests these engines in all conditions is the authority. Nothing against Mr. Athens as he has the school of hard knocks to back his decisions up. I don't understand the importance of the piston cooling - we are talking about a small differential in oil temperature between two different coolant thermostats. Explain that better for me. I know of no one that runs engines at load to extract oil samples - the engine is brought up to operating temperature and the sample is pulled. The key to oil analysis isn't one data point but a collection of many to determine conditional trends.

I disagree on wet stacking as a thing of the past, especially if you have a mechanically controlled engine. Newer electronically controlled engines are lenss likely to suffer, but even those log idle time in the computer for a reason.

I run nearly all of my time at 80% load on plane with the exception of a few no wakes, and combustion chamber temps terrify me. My dad had an RV business (where I learned to work on diesels) and even in automotive applications I have pulled apart engines and have seen pistons melt due to long heavy loads up a hill. Of course, if you are over propped, you are "lugging" the engine causing a fuel flow to engine speed mis-match creating higher combustion chamber temps. The cooler the oil that is sprayed on the bottom if piston the better, IMO. 20 degrees is a 11% delta on coolant temp which translates to reduced oil temps.

I'm not suggesting you sample while running at load, but the engine should be brought to temp and run at load or the oil likely will not reach operating temp. Here are blackstones instructions.

https://www.blackstone-labs.com/information/sampling-procedures/marine-sampling/