6CTA8.3m Overheat issue

[Bob Bonser]

I am knocking my head against the wall here. Any suggestions welcome.
Heres the timeline of this issue.

1. 4mos ago an impeller failed underway. Overheat to 210, I replaced the impeller at sea and all was fine

2. 2 mos ago I had the serpentine belt fail, Overheat to 210, replaced the belt at sea, all fine

3. 1 month ago random overheat at sea, towed in
a. I had some parts, all new so I replaced the fresh water pump, sea water pump and impeller, new serpentine, new thermostats, I removed the intercooler, opened top and bottom. I fished out the old rubber from the initial overheat issue. There was no corrosion on the tubes or fins from what I could see, Put it all back together.

4. Boat runs smooth, no oil in water, no water in the oil. Anti freeze 50/50 stuff from cummins (complete?) No smoke

5. temp gradually rises to 210

6. All the hoses on the sea water, intercooler side are cool , 80deg or so

7. Hoses on the heat exchanger side are empty till the thermostat opens at 180. then they get full and temps there match the temp guage. It seems like once open, the overheating rate rise remains constant. clicking up a degree at a time till alarm.

8. I used a laser to shoot the hoses. the thermo outlet hose enters the heat exchanger and the rearmost hose out the bottom tends to be as much as 130 deg cooler.

I haven’t opened the heat exchanger yet. Its the only part I haven’t inspected. Any ideas? I feel I checked and did everything. Air temps here are ok in the 80’s and sea temps are low 70’s

I am trying hard not to have a cummins tech out as that will be a $1000. I believe that the guage is correct because the numbers are matching what my laser is reading.

Thanks,
Bob

Topic

[Tony Athens]

1———————It’s a 480CE and you are over propped–that it something this engine cannot tolerate

2—————- The story just got thicker– I guess neither your aftercooler or HX has never been properly serviced since new– You pulled the “caps” without servicing properly? Very bad move as you now are most likely misting seawater into the engine.

You are playing with fire..

Read the article on aftercooler servicing and look at the disaster pics.. You’ll most likely be there shortly..

Tony

[Bob Bonser]

Dataplate

Can we tell for sure if this is the 480CE?

[Bob Bonser]

Thermostat

Corey, hit the submit button before I made it through.

7. The thermostats May have been 160. I used the part number found on quickserve and purchased them at Cummins. But, I really didn’t feel the outlet hose get warm until 180. I need to repeat that test.

8. Knowing the weight of the intercooler and the heat exchanger, does it make sense to ship them ? Would love to have you guys look at/service them.

Thanks again,
Bob

[Bob Bonser]

More info

Corey. Thanks again

1. I guess I need to ask if WOT always means underway/loaded or if you mean in neutral. Under load, not too heavy, I can hit 2650 with load shown as 100. I can’t really take it out to retest to make sure cause of the temps. I wouldn’t have time to get to wot and turn it about to get back to dock prior to overheat.

2. Is the heat exchanger something I service or something I bring to the local Cummins guy or ship to you? Tony says send some photos of it, this I can do too. Photos of the ends and the guts after I take off the end caps?

3. The raw water pump was from Cummins. Not sure if it was a Sherwood. But it was new in box. Installed last week.

4. Photos can be posted tmmrw . Working nights this week. Will be hit or miss. But will happen!

5. Water pump is a new in box, purchased at Cummins Southeastern Power in Tampa. Installed last week.

6. I have read the article on intercoolers and saw the comments on greasing them up.. When I had mine off the end caps opened fairly easy, but tapping the core with a wooden block didn’t make it move. I didn’t want to damage it so I rinsed it out. There really wasn’t any corrosion . Just a pile of old rubber fopeom a previous impeller failure. No tubing crud. The fins visible from the sides were not gunked up at all, but we’re discolored black.

[Tony Athens]

Let’s get the HX properly serviced and a new set/pair of 160 stats.. It’s been 14+yrs..

Tony

1 user thanked author for this post.

Bob Bonser

[Corey Schmidt]

the 480CE story…

Thanks for the reply…

No need to feel ignorant at all — we’re here to help you. These particular engines are very unique and deserve special attention.

1) Since you have a 480CE the game is a bit different. And there was no real KNOWN problem that caused the engines to drop valves, it was all install / engine load related. Read the following article carefully to better understand, ask more questions if you don’t:

Propping the Cummins 6CTA 8.3 480CE vs. 430/450 Diamond Engine

FUEL BURN will be your real indicator on the assessment of the engine and how it is currently propped. Can you hit 2650 or 2600 at WOT?

2) Re: the cooling issue, think of the heat exchanger as your engines “radiator” where coolant and raw water exchange heat from one another. If this component is not 100% up to snuff, then you could be experiencing issues as a result. We need to make sure everything is good with it…

3) Was the raw water pump replaced with an original Sherwood pump or one of our SMX pumps?

4) I think pictures of your engines as installed in the boat to start would be good, …once you remove the end caps from the HX, let’s have a peek at those with some pictures as well and see where we’re at.

5) Water pumps could be suspect if they are Sherwoods so we may also look there as well at some point.

6) When the aftercoolers were serviced, were they serviced via our maintenance protocol with lots of grease etc.?

7) I may be wrong but I’m pretty sure the 480CE factory supplied thermostats are 160F, not 180F so I’m a bit surprised you notice them opening at 180?

[Bob Bonser]

Components

Thanks for the reply.

1. The valve problem happened many years ago and it was a known mechanical issue that Cummins provided the parts and labor to repair. It’s 1000 hours of running since that occurred.
2. The engine is rated at 480hp
3. I think I am good about the raw water side. I change impellers, and the water pump is only a couple years old. I had the intercooler serviced 2years ago but I haven’t put more than 300 hours on it since then
4. I didn’t look at the heat exchanger cause I am totally unfamiliar with it. I can take it apart and see if it’s corroded
5. I have always been told by the Cummins tech that 2650 wot indicated I was propped correctly. Is that last 75 to 100 rpm so significant it means my engine is in poor condition ?
6. I am no mechanic, just a guy trying to not go broke owning a motor. I apologize if my comments may seem ignorant. Help and suggestions are appreciated. Even though you responded you didn’t suggest any way to correct. You mention looking more closely at the heat exchanger. Once I open the end caps how to proceed? Boil, scrape, replace ? I do t know.

Thanks

[Corey Schmidt]

A few things to think about:

1) “Sucked valve” at 1000 hours or 1000 hours AFTER valve drop? What happened there? Is this a mechanical 450C or an M4 480CE?

2) The component responsible for keeping your engine coolant cool (Heat Exchanger) is the only one you haven’t looked at? Might want to look at it and give it the MOST scrutiny?

3) How often are you maintaining the raw water components on your engine?

4) If your engine can only reach 2600 at WOT, it is in a poor condition. That engine needs to reach the governor break-point of 2725 – 2750 RPM under loaded conditions.

Propping a Cummins Mechanical Diesel Engine

[Bob Bonser]

additional info

I didn’t think it applied but here is all the particular information about the vessell

1. 2002 40ft Dorado Bluewater
2. Engine 6CTA8.3 with about 1000 hours post cummins haul out and rebuilt for a sucked valve
3. WOT attainable 2600RPM 18gph Cruising speed at WOT 24 kts
4. new oil and all filters
5. has been the most reliable motor I ever owned!!
6. Typical operating temp 164deg

[Author]

Replies