Low engine temperature

[bneukam]

Its warming up here in Boise, so I decided to go take the coach out for a good test drive. Its a 02 Intrigue 36' with the 400 ISL. Its been in storage for 4 months. I had turned off both main battery switches, and disconnected the negative cable on house batteries only. Everything fired up great, and everything was in good working order. House batteries showed 94% on the inverter panel.

I took it out for a 45 min drive and the engine temp stayed between 159 and 162 degrees. I did both stop and go traffic, and interstate driving. Outside temp was around 45 degrees. The fan did turn on high when I first started it, and I believe it ran there for about 3 min before it went to low. After the 45 min drive I checked the fan and it was still running on low. I had the heat set on high, but only got a little warm air out from the floor vents.

During the heat of the summer last year the temp ran around 182 to 185, and the highest it ever got to was 198 climbing a pretty long and steep pass. These readings are from the silverleaf.

Should I replace the t-stat or can this be normal driving in colder temps?

[FunGus]

Definitely not a normal operating range. In fact, running too cool can be very harmful to a diesel engine because the heat necessary for a complete fuel burn is not there and can cause a "washing" of the cylinders from the unburned fuel causing excessive wear. I would replace the thermostat asap.

.

[smlranger]

Generally, if a T stat sticks open, it can keep the engine from getting to proper operating temp. My vote is a bad T stat.

[bneukam]

Thanks Fungus, so were the temperatures last year at 182 within normal range? Is the fan supposed to run on high for several minutes, then switch to low like mine did?

[dons2346]

The '02 ISL should run at 195 normal temperature. At a 45 deg OAT, it might take 20 minutes to get to the 195 but it will get there under normal operating conditions. I would suspect a bad T'stat. Even at 180+ during the summer is to cold for the motor

[smlranger]

Originally Posted by dons2346

The '02 ISL should run at 195 normal temperature. At a 45 deg OAT, it might take 20 minutes to get to the 195 but it will get there under normal operating conditions. I would suspect a bad T'stat. Even at 180+ during the summer is to cold for the motor

My 07 ISL 425 with DPF lopes along at 186-188 (per Silverleaf) and will go up to +/- 195 on harder pulls. I thought that was a bit cool but when I talked to Cummins, they said 185 was OK. I've always suspected my fan is running on high all the time but the folks at CC checked it last summer and said it was operating as designed.

[bneukam]

I drove the coach down to Rush Truck center this morning to have a new T-stat installed. Service tech said the t-stat in a 400 ISL is a 180 degree, so anything above that is good, but you would get better mileage at closer to 190 or 195. But with my setup being a shorter rig, and I travel pretty light, I may not get much higher than my normal running temps of 182 to 184. I've driven the rig now a little over 5k miles, and I always fall in the 9 to 11 mpg.

I will post again after they change it out, and see what difference it makes.

Thanks everyone for your comments

[lshew]

Are you certain your fan is operating correctly? When the engine is cold, even on a warm day, the fan should not be on high after you start the engine. It should be on low speed because there is no heat build up in the engine requiring the radiator to cool the coolant. In fact you can often drive the coach for 5 to 8 miles before the engine coolant temp gets high enough to cause the fan controller to engage the fan hydraulic motor to a faster setting. Thus cooling the coolant in the radiator for recycle back into the engine block. I believe your fan controller is the problem. It's easy to trouble shoot the fan controller. The fan will default to high speed if the fan controller electrical plug is disconnected. So start the engine, look at the fan for fan blade speed. Shut the engine down. Disconnect the fan controller. Start the engine back up and check the fan speed. If the fan is on high speed both times, the fan controller is probably bad or the wiring has an issue. Normal operating temp should be 195 deg. unless someone put a cooler thermostat in. The best fuel and diesel engine performance is about 190 to 200 deg. The fan controller has 2 parts. One is a hydraulic valve and the other part is the electronic control module. Mostly likely only the electronic control module is bad provided the wiring is all ok. Or you can change both as an assembly. The latter is a lot more expensive and requires a lot more labor. The electronic module takes only a few minutes to change. Of course dependent on where its installed.

[bneukam]

So had the T-stat replaced, they performed the test on the old one and it was bad. I then took her out for a 40 min test drive. Temps stayed in the 178 to 182 per the silverleaf. I pulled over and checked out the fan and sure enough it was on high speed. So I turned it off for a couple of minutes and fired back up, the fan stayed on low speed. I then proceeded home, and again, checked the fan speed and it was on high again. Repeated the same process, and it went back to low when I started it back up.

So I am thinking that not only did I have a bad T-stat but also a control module on the fan. Any suggestions, on what I should do next?

[CountryFit]

prior to oat coolant change over, i typically saw around 180 deg. with final charge oat coolant in, most time it stays in 170-175, in rare occasions it reaches 180 deg. yours in 178-182 sounds like a perfect range. i wouldn't do anything with it for now.

[birdhunter]

If you were truly getting 9 - 11 miles per gallon that's pretty fantastic.

[bneukam]

So I do believe that my fan controller could be a problem, as it does seem to be running on high more than it was last year before storage. I would bet here on my next trip that i could lose some mpg because of this.

I do have a trip planned to the Oregon coast this summer, so I am planning on scheduling to stop in at CC to have them check this out.

Ive heard of people cleaning the wire harness to the FCU, can anyone describe where they are located? I just quickly looked under there and only saw the controller sitting at the lower right cornor of the radiator. What do they clean them with? Is there anything else I can try?

[bneukam]

I took the coach out yesterday on some back county roads and monitored my fan speed in reference to my coolant temp.

I pulled over with every 10 to 15 degree jump in temperature starting at 120, and checked the fan speed. The fan stayed at idle all the way till somewhere between the 150 and 165 then it went straight to high.

Not sure what you all think, but it sounds like a sensor that feeds the fan controller could be bad. I believe there is 3 sensors, air cooler temp, water coolant temp, and one for the A/C.

Not sure how to test these, but thinking I will just drive her over to CC to have them check it. As I am also in need of a alignment.

[BrianGlenn]

Here is a copy of the Sauer Danfoss Fan controller trouble shooting guide.

Hope this helps,
Brian