[Robert Epsten]

Now that the after-cooler is no longer a potential issue, it seems your salt water side from the through hull to the heat-exchanger has been addressed and functioning properly. If you have an IR gun shoot the sender housing and see if it correlates with the gauge.

[Robert Epsten]

Hi Tony,

I’m not familiar with that model after-cooler, but I am sure it works on the same in principle as the newer 6BTA’s. Regardless, even if your current problem is not an after-cooler issue, your way past due for service. If your gear cooler and heat exchanger are original to the motor, best to replace them before you get water into the gear oil or loose coolant out the heat exchanger or even worse get water into the motor from a worn out after-cooler. A good radiator shop should be able to advise you on this issue. Also, don’t ignore the exhaust elbow especially if its from the 90’s.
The fix may not be cheap, but you may of lucked out by finding the problem before it finds you.

Regards, RME

[Robert Epsten]

Tony, the other circuit you may want to check is the fresh water pump. In my experience they leak before failing. You need to remove the belt (take a pic first of the belt in place because it can mess with your mind putting it back on) then spin the pump and it should spin with little resistance.

Good luck, RME

[Robert Epsten]

Hi Tony,

I am not a Cummins mechanic but feel like one after spending considerable time and $$ looking for a overheating issue on my Cummins 6BTA. In your case I would suggest the following.

1-be sure there’s no restriction from the thru hull to the the salt water pump including hoses and valves

2-you didn’t mention the after-cooler, has it been serviced or flushed in the past 3 years??

3-did you replace the tstat or at least check it to be sure its fully opening in boiling water at the correct temp?

4- are you sure the coolant system was properly purged upon filling?

Also look to see if the hose between the salt water pump and the fuel cooler, and the hose between the fuel cooler and after cooler are bulging under load. If so, the problem is in the after-cooler, oil cooler, heat exchanger, exhaust elbow or all the above.

I use the salt water acidic flush between servicing my after-coolers, oil coolers and heat exchangers but always pull off and have them professionally cleaned and tested every 3 years.

Lastly you can get an IR gun and shoot the motor at the thermostat to see if its a gauge or wiring issue. In my experience its the motor and not the wiring.

Good luck, RME

[Robert Epsten]

Been awhile since I checked in about my overheating problem. I installed the 160 tstats and all’s well. I would still bet the problem is in the new design of the cummins tstat and not in the remainder of the coolant circuit.

RME

[Robert Epsten]

Thanks for all the input. I will update you when I finish the 160 stat install.

RME

[Robert Epsten]

Thanks for the reply. I’ll change it out.
In your experience what engine temp would I be looking at 2400 RPMS if im currently at 185 to 190 degrees with the 160 tstat in place??

RME

[Robert Epsten]

Hi Rob, i am back.

Since we last chatted I have replaced the heat exchanger and oil cooler. I also swapped out the gauges port for starboard. I placed the thermostat with the rattle pins in the 12 and 6 o’clock position. I did a slow fill, a purge or two but still have the same problem. I also checked the spitters and they are open.

At this point I feel I may just need to live with it. If I let the motor fully warm up no problem. I havent looked at the impeller but it was changed last year and I have no heating issue at a load.

My only other thoughts that maybe the new design housing design could have something to do with it?? I wish I had my original tstat.

RME

[Robert Epsten]

Thanks, Rob I will give it a try in the next week or two and get back to you. My last questions;

1- I noticed on Seaboards site the 160 tstats have a single drilled out hole maybe 3/16 of an inch at the base of the tstat flange. The Cummins OEM tstats have 2 tiny holes with a brass insert in the flange, I am assuming to get trapped air out? Should I remove one of the brass insert and drill a larger hole like 3/16 of an inch??

2-any value in testing another thermostat to see if the old and new open at the same temp?

Again, thanks for the helpful advice,

RME

[Robert Epsten]

1-to belch the system I use the petcock when filling. I do squeeze the hose between the heat exchanger and the stat housing.

2-I then take the expansion cap off, bring the motor to temp to allow it to vent. Recently did it twice. I removed coolant as it heated up so it wouldn’t spill into the bilge. I do have reservoir tanks

3- I would say 30% of the time I’m at cruise, otherwise trolling

4-the motors are usually about at 160 when I go to cruise. If the motor is shut off while still warm, I don’t believe the overheat occurs.

I’m thinking about getting another 160 stat and comparing the old with the new in hot water to see if they open at the same temp. Possibly if the stat fully opens at say 185 degrees it wouldn’t overheat. Maybe.
When I replaced the coolant, fill a little slower and do the radiator cap belch under a load.

[Robert Epsten]

Thanks, sorry for the power flush confusion,

The part number on the thermostat is 5292738 – 180F – 54mm
Motor serial number if it helps is 46181279

I have not spent a lot of time looking at the 160 tstats. Do they interfere with performance or cause more smoking?? I would imagine it would be a good idea to get a sender that maybe alarms earlier like 190? Is this available from cummins or Seaboard??

Thanks, RME

[Robert Epsten]

Thanks Rob,
1- yes the coolant easily drains out of the small fitting on the heat exchanger tube
2-it’s clean blue being the 50/50 Cummins mix
3- i haven’t pressure tested it since I’m not loosing coolant
4- the strainers are clean, the raw water pump isn’t leaking, new 3 years ago and impeller was changed last year;hull strainer removed and cleaned last spring

I would think if it was a salt water issue the engine would always run hot.Also if it was a heat exchanger issue wouldn’t it run warm all the time? The way the needle on the temp gauge goes from about 200 back to 185 so quickly sounds like a sticking thermostat. It’s been changed twice so getting a defective one twice is unlikely. On the bench it doesn’t fully open to about 195 but I bet that’s normal.

Thanks,RME

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