Engine/Transmission (1998.5 - 2002) Engine Temp question

[Duluth Diesel]

I was towing a 2,000 pound single axle trailer up a 2 mile long hill. Not sure what percent grade, but enough to require truckers to check their brakes and gear down when coming down the hill.

I was running about 60 mph in 5th gear, about 2500 RPM, and leaning in to the throttle a little. My temp guage (all factory guages) went higher than I've ever seen it rise. Normally, I can only get my guage to read 190 when running her hard and it usually drops down right away. But while climbing this hill, I had temps at about 220 and they stayed there for the entire climb, and didn't drop off real fast.

Is my clutch fan not engaging? I THINK I heard it, but I'm not sure.

Should I have the dealership replace the thermostat?

I'm still under full warranty.



Is getting a little toasty when towing a light little trailer normal?

Engine is stock 24 Valve HO with 6-speed. :--)

 

[RustyJC]

We tow a 36' 13,500 lb 5th wheel RV, and the hottest I've ever seen our HO on a long 6% grade is with the needle just on top of the right side of the "0" on the "190" marking on the gauge - the ambient temps were around 95 degF. That's with the accelerator pedal floored in 6th gear, 1100 degF pre-turbo EGT and 30 PSIG boost. By this time, the thermostat should be full open and the fan clutch should be engaging - you'll know it if it does!



Rusty

 

[kkreigh]

I have had similar experience with my 01. I don't think it is anything abnormal. It is just that you are loading the engine beyond normal and the increased temp dissipates into the oil and coolant. I have an oil temp gauge on my truck and I see fluctuation to about 230 degrees from 206 degrees (normal running conditions) during heavy loads , long grades and most particularly with ambient air temps above 90.

 

[B.G. Smith]

Temp

You have reason for concern, at the speed you were going I don't think the fan would make much difference. Could be the thermostat though or the gauge but they seem to be pretty reliable. I would try the dealer for the thermostat. bg

 

[Loren]

Duluth,



I don't think you have a problem, although it's possible that your fan clutch is not engaging. It makes quite a roar when the clutch engages and the fan spins at full speed. You should be able to hear it.



If you didn't hear it, it could be that:

1- You just didn't notice it, or there was enough other noise in the cab that you couldn't hear it.

or

2- The temperature wasn't high enough for the fan clutch to engage.

or

3- The radiator is partially clogged. If the radiator is not flowing enough air, not only will your engine water temperature be high, but your fan clutch will not engage. This is because the fan clutch senses the temperature of the air exiting the rear of the radiator. When that air is hot enough the clutch engages. If the radiator is clogged, the air exiting the rear of the radiator is insufficient to cause the clutch to engage.



The first thing I would check is the radiator fins. Blow them out with water and/or compressed air.



The next thing to check would be the fan clutch, although I can't find any test procedure for this in the service manual for my 2000 truck.



Last, I would test the thermostat. Except for the rare occasion when a piece of foreign matter makes its way into the thermostat (and holds it open), thermostat problems are relatively rare.



It seems that lots of drivers who post here change their thermostats at the first sign of high temperatures, ususually replacing the factory one with a 180 degree thermostat. If the factory 190 degree thermostat is working properly, changing to a 180 degree thermostat will not solve any overheating problems. It will just cause the engine to run 10 degrees cooler during normal operation. Cooler is not necessarily better. These engines are designed to operate at a given temperature, and I generally assume that Cummins knows more about what's best for my engine than I do.



You can test a thermostat by placing it on a stove in a pot of water with a thermometer. It should start to open at 181 degrees and be fully open at 203 degrees.



Happy troubleshooting.



Loren

 

[dblake]

This is direct from Cummins.

Summary: ram isb temp cycl characteristic



Solution:

Thank you for your email. What you are seeing is normal, though we admit it seems a bit unusual compared to passenger car (and previous) experience. The change is omitting the "bleed hole" in the tstat and having a tight seal, both of which serve to allow the coolant to come up to temp; with the previous tstat there is always some flow, and the robust cooling system heat-rejection capacity would delay the engine coming up to temp - hence the reason for the change.



Here's what we usually say on the subject: This is to address cycling of the coolant temperature in your Dodge Ram 24-valve Cummins ISB. We have discussed this and have seen it before, and what you are likely experiencing is a normal phenomenon. A brief explanation, but first we will include the caveat that exact temperatures are subject to the sensor and gauge that Chrysler provides; they may be accurate or they may not be - but what you are seeing is relatively normal, especially if you are talking about running at light loads.



A little history; In the earlier 12-valve engines, the thermostats had solid metal contact and some "pins" - the result was that sometimes they would not close completely and coolant would sometimes bypass so that under light loads the engine would not come up to full temperature. With the 24-valve, the thermostat design was changed so that the valve part does not seat against metal but against rubber, so that a tight seal is obtained; the thermostat remains closed and the engine reaches temperature.



With a heavy-duty (high capacity) cooling system in place - which is needed for higher load applications - when the engine reaches temperature, the thermostat (tstat) opens, the coolant enters a large capacity (from volume and heat transfer perspective) radiator, and the coolant immediately drops way off in temperature, the tstat closes and the cycle starts all over. If any appreciable load is applied the tstat will stay open enough to not cycle in this manner.



If you are driving easy and it's cold out you may see this cycling phenomenon; it is not a problem - alternatively, if it's warm and you're running at moderate speeds you may have a sticking tstat and you should have the dealer take a look at it.



As far as sensor/gauge accuracy is concerned, the only way to check that is with a thermometer or calibrated sensor/gauge - the dealer can do that for you too if required.



We thank you for your interest in Cummins products. Please let us know if you need assistance in locating the nearest Cummins-authorized Dealer or Distributor Service Provider. For assistance in locating a Service Provider, feel free to use Cummins North America Dealer Locator, which can be found on Cummins website:

http://www.cummins.com/service_locator/index.cfm



Please let us know if you have other questions and if away from your computer or have a time-critical request that needs more urgent attention, feel free to call us toll-free (from North America) at 1-800-DIESELS (343-7357). Customers may also call Cummins switchboard 1-812-377-5000 (worldwide toll call) and ask for the 800-DIESELS Call Center for assistance.



Email direct: -- email address removed --



Regards,

--

Powermaster

Customer Assistance Center

Cummins, Inc.

Columbus, Indiana, USA











Details:

Hi,

I just installed a new dealer purchased cummins thermostat in my

2001 dodge HO diesel. I immediately noticed that my temperature now wanders

between 160 and 195 where with my old thermostat it would pretty much stay

rock steady at 195. Both the dealer and a local cummins shop have verified

it's the correct part #. I did notice that it looked a little different from

my old thermostat(kind of a larger black body on it. I wish I had kept my old

one for troubleshooting.

Have you guys changed these lately?Will this cause any

problems?Quite a few other people have noticed the same thing on the TDR

site and other webrings. It seems like this thermostat is either wide open or

fully closed. Any clarification would be greatly appreciated. Thank you.

 

[klaybus]

Fan Testing

Theres a procedure in the 99 Service Manual for testing fan operation. In short, block off the front of the radiator, run at 2000-2400 rpm & when the ambient temperature gets around 190 degrees the fan should engage & while parking running at those RPM"s you WILL hear the fan! (I just watched my water temp since I didn't have any means of measuring the air temp on the back side of the radiator. ) I was experiencing warmer than normal temps too while towing our #6500 5er over Snoqualmie Pass & it was dirt & debris on the front side of the radiator blocking the flow of air to the radiator. I took compressed air & blew all the crap off & immediately noticed a difference in water temps. I also flushed, changed the coolant, & replaced the t-stat... . But ultimately it was the front side of the radiator having crap on it that was the problem.

The other items I did because they needed to be done any how. Good luck, over-heating problems SUCK!



Clay