Cummins C8.3 325 hp running too warm

Topic: Cummins C8.3 325 hp running too warm (Read 1829 times) previous topic - next topic

Cummins C8.3 325 hp running too warm

August 04, 2020, 06:18:30 pm

Just got back from a trip to Antonito CO which included a long run through west Texas and then climbing Raton Pass. Tempt gauge showed 225 at one point running flat but slowly climbing towards Dumas TX in 100 F and towing pickup. Next morning it started running hot up Raton Pass. Sometimes it runs fine around 185 to 200 then starts climbing up to 210 or 215 for no apparent reason (same speed, conditions. On the way home ran hot up the pass, but then settled down to 195/200 and below for rest of trip. No alarms went off and I climbed at a reasonable speed manually shifting down to keep water pump speed up a bit, no lugging.

Last summer changed out thermostat with Cummins 195 degree thermostat, flushed radiator as per Wolfe and switched over to Cummins Fleetguard OAT coolant. Fresh oil change, new fuel filters right before trip to Colorado. I'm wondering if my fans are going into low speed instead of high sometimes and then back up to high. How does one test the fan operation is my first question? I've checked radiator for obstructions, dirt, and there was no loss of coolant except for changing out the coolant filter before the trip. I use a blank coolant filter.

If I can't figure this out, would it best to start at MOT or FOT to make sure fans are working properly? I've got a small film of oil on both fan motors and below hydraulic pump, but no change in fluid level in the reservoir tank over 12,000 miles since filter change in 2017. My home is sold and we have to be out of it by end of month. In November we hope to be full time on the road when wife retires. This has got to be resolved by November.

Re: Cummins C8.3 325 hp running too warm

Reply #1 – August 04, 2020, 07:22:06 pm

Quote from: Realmccoy – August 04, 2020, 06:18:30 pm

I'm wondering if my fans are going into low speed instead of high sometimes and then back up to high. How does one test the fan operation is my first question?

You'll need to locate the device that controls your fan speed. Search the Forum for pertinent threads that may help point you in the right direction. Once you have found the speed controller, you can fiddle with it.

If it is one of those wax capsule controller valves, I'm not sure how you would make it change speeds to see if both modes are working. I'm not familiar with those devices.

If it is a electric solenoid valve, turning the power to it on and off should cause it to change speeds.

If you can't tell what the fans are doing by sound alone, you could pick up a non contact tachometer to check the actual RPMs. I bought one at Harbor Freight several years ago. Probably sell them at Lowes or HD also. Example below:

https://www.harborfreight.com/digital-photo-sensor-tachometer-66632.html

Re: Cummins C8.3 325 hp running too warm

Reply #2 – August 04, 2020, 07:36:56 pm

Mine has the wax capsule fan controller, no electrical connection.

Re: Cummins C8.3 325 hp running too warm

Reply #3 – August 04, 2020, 07:47:48 pm

Factory fan control on ours turned the fan on high as soon as the motor warmed up. Replaced with the same controller as source engineering in Oregon sells. 50hp loss on high if not needed. Full speed at 185 vs 199. Better mpg. Better power

Re: Cummins C8.3 325 hp running too warm

Reply #4 – August 04, 2020, 07:52:08 pm

Bob, was/is yours the wax controller or the Saider one like mine as I seem to remember if it is turned off it jumps to high speed. I think you said disconnecting it will activate high
John h

Re: Cummins C8.3 325 hp running too warm

Reply #5 – August 04, 2020, 07:55:03 pm

Piloted wax capsule. Variable speed. Low to 170. Ramp up to full speed at 185.

Replacement industry wide used is low to 185. Ramp up to full speed at 199 degrees

Re: Cummins C8.3 325 hp running too warm

Reply #6 – August 04, 2020, 08:04:50 pm

When it was running hot were you on the top half of your fuel tank,that could make a difference also,my advice would be to check the fan speeds like the above says,that may not be the problem.have you ever had the fuel pump return valve spring replaced or
reworked,many of us has had done or done it ourselves.

Re: Cummins C8.3 325 hp running too warm

Reply #7 – August 04, 2020, 08:07:10 pm

195 thermostat? Shouldn't it be a 180?

Re: Cummins C8.3 325 hp running too warm

Reply #8 – August 04, 2020, 09:22:36 pm

Here is my valve

Re: Cummins C8.3 325 hp running too warm

Reply #9 – August 04, 2020, 09:38:26 pm

On top half of fuel tank.

Re: Cummins C8.3 325 hp running too warm

Reply #10 – August 04, 2020, 09:54:27 pm

I would think that a 180 thermostat would be a better choice but that would not address the overheating problem. You encounter the heating even going over Raton Pass. I looked up the elevation and it's just over 7,800 feet. If the ambient was high, the density altitude (the altitude your engine, radiator fan, radiator thinks it's at) could easily have been 10,000 feet. Your radiator fan, intercooler, radiator are much less efficient at this altitude and especially with a mechanical engine, the injection pump does not do a good job reducing the amount of fuel injected so your EGTs soar. Bottom line is your cooling system can't do the job heading up a grade at high altitude, especially in summer weather.

So, you need to downshift to keep the RPM up toward the top of the normal limits rather than trying to pull a grade in a lower gear and if it still is hot, slow more and if necessary downshift another gear. The coolant circulates best at high RPM and the EGTs will be less. Remember, the damage from excessive EGTs is cumulative so may catch up with the engine even years later.

Probably nothing wrong with your cooling system but you got caught out with a combination of high altitude, high temperature and a cooling system that can't keep up. This has killed hundreds of pilots, counting on a normal length takeoff run and don't have the power or wing to overcome the conditions. Plus, many are overloaded.

Our Detroit is the same. Grades that I can charge up in three seasons, cause a drastic slowdown and gear dropping in summer.

Pierce

Re: Cummins C8.3 325 hp running too warm

Reply #11 – August 04, 2020, 10:01:57 pm

I put in the one listed in cummins, thermostat 3913028. (Found old thermostat: 180 degree). Yes, high altitude with mechanical engine is more of a challenge for sure. Generator was a little slow to start the first time at the campground when my two-year-old granddaughter turned it on.

Re: Cummins C8.3 325 hp running too warm

Reply #12 – August 04, 2020, 11:24:59 pm

The temps posted seem very normal. My dash gauge is almost 10 degrees higher than the engines computer shows on TPMS

Re: Cummins C8.3 325 hp running too warm

Reply #13 – August 05, 2020, 08:45:09 am

Have been helping another RVer with his overheat issue.

You can eliminate the fan motor hydraulic controller as an issue with these two steps.

Take the lines off the wax valve and cap both lines and see if the fan runs wide open.

Then put a union on the 2 lines and see if the fan runs at low speed.

If the above works, would suspect the wax valve is the issue.

Re: Cummins C8.3 325 hp running too warm

Reply #14 – August 05, 2020, 11:42:09 am

Towing a pickup, high altitude thin air, high ambient, high density altitude as Pierce says all play a part. Driving technique is critical, these conditions will reveal any system weakness when running full output. Keeping revs up is important, but there's always the option to drop another gear, lose a few mph, take some load off powerplant/cooling.

Re: Cummins C8.3 325 hp running too warm

Reply #15 – August 05, 2020, 01:22:03 pm

We pulled a horse trailer filled with household goods to Ohio with our RAV4 several years ago. My 4107 Greyhound with rear side radiator has also been on long trips. Neither vehicle ever moved the temp gauge off the thermostat in hot weather. With the fore/aft drivetrain setup in most diesel pushers, there is no way to use a PTO like GM did 80 years ago. Good idea then and now too. The idea of the complex system we have is beyond my comprehension. Foretravel realized they had a problem after the side radiator U300 in 1992 didn't make it so they added another motor/fan. It's still marginal in the mountains here in the West in summertime. Not only is the radiator too small but it uses lots of horsepower and creates more heat doing it. In the case of the GV series, there was so much room up front, radiators could have been installed here and taken advantage of ram air also. Porsche, VW Vanagon, etc have done just that very successfully.

If I were buying an expensive RV, I have to say I would be looking at the front engine Freightliner Cascadia RV. Bet the temp gauge does not move on grades and it gets better fuel mileage than our coaches.

Pierce

Re: Cummins C8.3 325 hp running too warm

Reply #16 – August 05, 2020, 08:00:46 pm

Foretravel over cooled original U280's and made up a kit to block part of the rear radiator

Re: Cummins C8.3 325 hp running too warm

Reply #17 – August 05, 2020, 09:10:00 pm

Sorry you have seen high heat on Raton.

Raton Pass for our coach pulling 5,500 lb Jeep Grand in warm weather is 30mph 3^rd gear with light steady throttle. We also keep pyrometer EGT below 950 degrees, and coolant stays below 190 degrees. If needed, we have had some 20mph climbs at 2^nd gear for some steep slow drives. Never can go too slow for these few moments of driving. Keeping Tachometer below 1,800 is also a guide on these climbs. We used to overheat approaching 210 when not paying attention to RPM, EGT, no more once we learned to be light on throttle. Every push on the throttle that does not move tach, just puts more fuel into the system, increasing heat gain, without any benefit.

Re: Cummins C8.3 325 hp running too warm

Reply #18 – August 05, 2020, 09:13:42 pm

I was in 4th gear with more throttle and speed. Thanks for sharing your experience.

Re: Cummins C8.3 325 hp running too warm

Reply #19 – August 06, 2020, 10:26:31 am

That last sentence in Barry's post is critical for mountain driving. If you are not able to accelerate in a given gear with more fuel, drop a gear manually.

Re: Cummins C8.3 325 hp running too warm

Reply #20 – August 06, 2020, 11:45:31 am

Barry, Wolfe & Amos, just curious if you perform that manual down-shift under full load or if you back off the throttle before making the shift?

Larry

Re: Cummins C8.3 325 hp running too warm

Reply #21 – August 06, 2020, 12:37:10 pm

I just punch the button regardless of throttle position.

P

Re: Cummins C8.3 325 hp running too warm

Reply #22 – August 06, 2020, 12:48:46 pm

Quote from: Caflashbob – August 05, 2020, 08:00:46 pm

Foretravel over cooled original U280's and made up a kit to block part of the rear radiator

This had to be in the dead of winter to keep coolant circulating while not introducing cold coolant into the warm engine. I had a Volvo with a canvas blind in front of the radiator that pulled up with a small chain. I've seen big rigs with movable louvers for winter driving. In normal weather, how can you over cool an engine if the thermostat is working? Certainly not applicable this time of year.

Pierce

Re: Cummins C8.3 325 hp running too warm

Reply #23 – August 06, 2020, 12:59:04 pm

Cats never fully warmed up was what I heard. When where and why I have no idea. Sheet of plywood

Re: Cummins C8.3 325 hp running too warm

Reply #24 – August 06, 2020, 05:01:44 pm

Larry,

Transmission will generally take care of itself, but better to not manually shift up or down under hard throttle. So, the better answer is let up a little when the transmission is going to shift.

If Allison wants to automatically shift down, under hard throttle that needed shift may be delayed for a while.

All shifts under hard throttle may be a bit harder on the tranny, but necessary during some situations.

Affiliate Notice