Slight overheating. Running hot. 195 degrees.

[Bill Stenger]

Thank you all in advance. I have been reading endlessly. And havent found my answer yet.

Ok guys I’m having an overheating problem with my 250hp cummins. Cpl # 1570. It has been running 191 degrees @2300 rpm and 195 degrees @ wot about 2850 rpm. Any low rpm below 1200 it hangs around 180 -185. I verified the gauges accuracy with a IR. Temp Gun. I found 190 and 194 degrees.

Since I bought it a few months ago I have replaced the following items related with the cooling system with new parts. Sherwood 1.5″ raw water pump, Cummins oem Tstat, most all hoses with silicone, Coolant circulation pump, Heat exchanger just cleaned and gone through by radiator shop, also inspected gear cooler and it’s free flowing.

I seem to have good flow from the raw water through hull fitting. With a garden hose. Idk about underway. Strainer is clean as I remove it and freshwater flush nearly every use. Elbow was recently off those holes are clear. I don’t loose any coolant to speak of. It was black from soot in the cooling system. Which was fixed by replacing turbo gaskets and flushing.

Any ideas would be greatly appreciated! I’m running out of ideas.

I an debating running it without the tstat to see if that changes anything. Maybe the cummins replacement doesnt have enough flow? Like I said I’m coming to a lose here.

Topic

[Bill Stenger]

130 mile round trip run. All seems well.

Just wanted to thank you guys. We finally got to put some hours on this boat and enjoy it Saturday. Ran about 130 miles round trip to West End same day. Everything seemed good. temps held @ 191 @ 2300 and coolant after cooled down seems to be @ the exact levels. I will get the Jwac serviced after summer break. And will order 160 Tstat with my next order as well. It can’t hurt in my eyes.

I did how ever hit the prop on the trailer bunk pulling it on after the trip like a dummy. So now its time to get a prop that fits like it is supposed to. This prop only had .25″ clearance between prop and hull.

[Roger Franklin Williams]

I have not installed 160 Stats yet will advise once I do.

1 user thanked author for this post.

Bill Stenger

[Tony Athens]

Pretty normal to run below the cap after it is cooled down..

Tony

1 user thanked author for this post.

Bill Stenger

[Bill Stenger]

Awesome Kevin! I will make some trips and monitor temp and coolant levels very closely. Then after summer I will pull off the Jwac and have it serviced. It surely can’t hurt. And yes I figure it will be @ high cruise speed pretty regularly. Unless in an idle zone.

Yes I did find one old impellor fin in the HX. And one or 2 in the gear cooler. This was while I was first working on the boat before I even realised it ran warm.

Tony, I totally agree I think the 160 is the way to go. I just don’t want to mask a real problem. I have some suspicion that I may have a slight head gasket leak or something abnormal going on. Hopefully just jwac or heavy funk in the block not allowing heat tranfer like you mentioned. This coolant was very dark when I first got it. Seems much better now.

One more question guys. Is it normal for the coolant level to remain 1″ low in the tank? Even if I top it up completely it will push out a little and remain consistently. .75 – 1″ below the rad cap. If I don’t top it up it just stays there.

[Tony Athens]

Bill,

Kevin is 100% right in his take on running temps in relation to thermostat opening temps……………………… But what I have learned over the last 30 yrs of dealing with “marine engines” is that as the years go by ( like 15 to 25++) things just never seem to work as they did when new, even after shop cleaning of the heat-X and or related components….Maybe a coating remains in the heat-X or in the block that just does not transfer the heat is used to transfer?

All I know is that if you have run out of solutions and answers, switch over to our 160F hi-flow stat, and 99+% of the time, your issue goes away….That is one of the reasons I developed it…………………… It just plain WORKS..

Just an FYI–All of the new Cummins engines ( since 2005-ish) come with 160F stats. Maybe they leaned something too? ………………

Tony

[Anonymous]

Bill,

You should only need the base mounting gasket (3938152) and maybe the intake gasket (3914856). You should be fine to make a couple more trips, unless you notice that the temps continue to rise, then it needs to be addressed immediately. If you are always going to be running hard, yes a switch to the 160 thermostat could be a good thing.

I would say to make some trips, keep a close eye on it. If everything continues to be okay, service it at the end of the summer and see if it makes a difference. If it doesn’t, well talk more about the issue and switching thermostats.

Out of curiosity, when you had the heat exchanger and such serviced, did you find any impeller or anode pieces?

Thank you,
Kevin

[Bill Stenger]

Thank you Kevin! I want to make some 60 mile runs very soon since I am loosing summer quickly. ( my wife is a teacher we want to take some trips before she is back trapped at work unable to escape). I have no issues continuing to attack this issue. But I have 3 weeks to make a few trips before school starts again.

What gaskets are required while removing jwac? I assume a simple base gasket. My local rad shop has a quick turn around time. And I have no issues getting it done. But I would love to make a trip or two in the mean while. Think that is feasible or should I keep chasing this issue before making any real trip with the boat? I also show a 40 degree drop in temps between coolant into jwac and out temps via IR GUN. Also the jwac looks very clean from what little I can see through the air inlet with a mirror. Although Im sure it hasn’t been cleaned for a long time or ever before. Since this engine screems neglected all over it.

Also the way I run this boat it is likely always running @ 23-2400 rpm all the time unless in an idle zone for a short time. I rarely idle around its always running from one point to another. So I feel the 160 tstat is likely a better option for me regularly. Your thoughts?

[Anonymous]

Bill,

Normal operating temperature is up to 15 degrees over whatever the thermostat opening temperature is. So, if you were to switch to the 160 thermostats, no you would not see the same operating temperatures (190-195). You would probably see 170-175. However, this is not the best way to fix the problem. That engine is designed to run optimally between 180 and 190 degrees. We need to isolate and fix the underlying issue.

As you said, the pressure feeling the same on the hoses is not as scientific a test as we would like to do. Also, we need to check the air side of the aftercooler.

Yes, you could continue to run and keep an eye on it, but at some point, that aftercooler needs to be removed and cleaned.

Thank you,
Kevin

[Bill Stenger]

Roger 160 tstat temps.

Roger once you installed the 160 tstat did you notice any differences then? I feel since my temps are well beyond the 180 tstat that they would easily climb from 160 – 195 just the same. Any input? I regret not installing the 160 tstat while I had it apart a few months ago.

[Bill Stenger]

Kevin, No I have not had the JWAC cleaned or checked. The two 3/4″ hoses seem to have the same in and out pressures felt by hand. I know thats not very scientfic. Have you seen a Jwac cause overheat issues? Also is it normal to run 190 – 195? Am I chasing a ghost? Should I just run it and keep an eye on it? Or throw in a 160 stat and see what happens after that. My assumption is that the tstat will not change anything except idle temps. The temp would still climb to 195 while running?

[Roger Franklin Williams]

Cummins cooling issues

Have 2-1998-5.9 BTA’s fresh water only, have always run 190-198 D if running over 2400 RPM, not often, over the last 17 yrs. All systems completely serviced several times and verified but it has never made any difference. I just bought SBM’s 160 D thermostats as I do not like running that close to overheating temps. I seem to think I read on here at one point Tony said those temps are not an issue except for minimal margin for overheat temp safety.

[Anonymous]

Hey Bill,

Has any inspection been given to the JWAC aftercooler? If there is any corrosion/calification/gunk buildup that could be causing restriction, this could easily be contributing to your cooling system running hotter.

Thanks,
Kevin

[Author]

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