Cummins 400 ISL Overheating

[richmargroup]

2007 45’ Monaco Dynasty; ISL400; Allison transmission; custom chassis built by Roadmaster; side radiator; 60K miles;

Since we overheated 2 years ago, we have had a constant overheating problem when the ambient temp is over 80 degrees and engine underloaded. I've learned to downshift and have become very aware of the timing of heating and fan starting. It seems to me that the fan doesn’t come full on at the right times. Downshifting helps only to an extent. When I run the rpms above 2200, the temp will hold. I’ve tried both automatic and manual shifting and found that it makes no difference.

Multiple times the coach has been checked and “repaired” in Albuquerque, Los Angeles, Sacramento, El Paso, and Coberg. The following things have been done: Silverleaf twice showing overheating, but no correction; thoroughly cleaned radiator; checked for blockages; replaced engine water thermostat multiple times; set radiator fan to full speed and checked to assure that fan speed is correct; flushed radiator; and replaced control valve associated with the hydraulic fan pump. I’ve been to Cummins, Freightliner, a Sacramento truck repair and also a reputable RV repair, and key RV places in Coberg. It was checked by the engineer who designed the Monaco system and now works independently.

I do not know whether the CAC has been cleaned or whether the cap was changed. Will have that done next week. What are other areas to check? Any thoughts on qualified repair places in the Sacramento area?

thanks! Thanks for the suggestions on Forum topics. We've done them except for the CAC and cap.

[tbutler]

You have a 2007 45' Dynasty with the same engine as my 2004 40' Windsor, same radiator configuration. It sounds to me as if the engine is, dare I say it, too small for the weight of your coach? We tow a car and have never had a temperature over 190 to 192 in any ambient temperature. What is the GVW with your tow? Ours runs between 39,000 and 41,000, loaded with the tow. We have 150,000 miles on the coach and never have had an overheating problem.

[jleamont]

richmargroup,

Depending on the amount of miles you travel, could dirt be a factor again. I have a few questions:

1, "radiator flushed" did that mean internally or externally?

2, "cap" not replaced, assuming radiator cap, was it ever tested? If your radiator cap is releasing pressure to soon it will cause the coolant to boil prematurely.

3, what temp is the Silverleaf displaying, or are you boiling over?

4, coolant tested recently, proper ratio?

You may have an issue with the CAC being blocked with dirt between the radiator and CAC.

I have the same model engine (non emission version) my combination is 35,000 lbs towing, I have pulled 9% for a few miles at 40mph around 2100 rpms and my "Scan Gauge" never went over 189 degrees (dash gauge was buried at 230, none of my gauges are very accurate).

[chp007kd40]

I wrote about my experience a few years ago and the conclusion I have is that the radiator is barely able to keep the motor cool. We travel a lot in the mountain areas in the West and desert areas where there are considerable grades. We do exactly as you do by downshifting prior to it getting hot and slowing down to moderate the rpm's in lower gears.

Here is what we found and fixed Took the radiator out (not easy) and it was literally clogged with very small particles of volcanic crushed rock ( light and sharp) we could not pull it out with picks without ruining the radiator so we replaced it at around $900.00 dollars. The well equipped shop said we did not have a very large radiator for a 540 cu in diesel motor in our Itasca Horizon 40kd at 32k lbs with 400hp ISl so we needed to keep it in good shape. They also commented on the design and how close to the ground the radiator was to all that dirt, dust, weeds and mowed fields we often find at events.

My maintenance man and myself did notice that the factory tried to seal the outside of all those coolers that are in front of the radiator so as not to let air come up vertically between them, but did a poor job with inexpensive materials. The idea was have all air come horizontally through the side radiator. Makes sense, but I have since noticed a lot a side radiators with that issue. Brett brought up a good point in that discussion about radiator screens and how much they restrict air flow and they really do!!

We do not tow, but carry a BMW 650 GS. We never have problems on any of the major highways or freeways. It is usually when the curves start to slow us down is when I start being careful.

I AM ALSO CAREFUL NOT TO GO TO CAMPING WORLD FOR ANYTHING!!!!!!!!!!!!!!!!!!!!!! Send rain to Calif...

[richmargroup]

Thanks for your ideas. Since posted, we have gone to Sac Truck where they couldn't find a problem. Then to Superior in Newcastle where they took the radiator out and showed us the road junk that clogged the bottom third of the radiator. Makes us wonder what the previous repair folks didn't see and did/didn/t do. They also noted the corrosion inside the radiator caused by plain old water being used rather than antifreeze in the radiator. So, that being said, our weather is still cold and we won't be testing the new radiator in hot weather for a couple of months.

But, a big thanks to your suggestions as well as those other forum and blogs. Had we not traveled so many miles before this overheating began, we would have possibly thought the engine was too small also.

[wolfe10]

Like most larger diesels, the Cummins ISL is a LINERED ENGINE.

The correct coolant, which is discussed in your Cummins owners manual is critical for protecting the cylinder liners.

Basically two types of coolant are approved:

Low silicate coolant for diesels with added SCA-- SCA (Supplemental Coolant Additive must be tested for and replenished)

The new-generation OAT-based coolants. Put it in and forget about it for 6 years.

BTW, will be discussing this in the Caterpillar Engine Maintenance Seminar I present in Perry and at the Diesel RV Club Rally two weeks prior to Perry.

[garyreed]

Thanks for giving me the opportunity to join the discussion.

Having read your first post in October, it sounds like you may not be the original owner, if so were there any service records with the purchase? It seems highly unlikely that so many service professionals could miss the problem, although it may be more than one issue and they may be quitting after finding one fault.

Will the engine shut down after it reaches a certain temp?

Do you rely on a dash gauge or warning light for the temp? Have they calibrated the gauge with the computer scan tools to determine if there is a difference?

They should be able to tell you the max temps, the number of times it was reached, and the hours at which they occurred.

How much coolant do you have to add if any?

Does it lose water gradually and get hot or get hot and blow the water out?

Is the water level in the expansion tank above the normal line when hot or below the cold line when cold?

Where does the transmission cool? Most are through a heat exchanger either in the radiator, or external still using the coolant to cool the trans. fluid.

Are there any issues with transmission function mainly slipping or what may seem like soft shifting?

In your last post you mentioned the corrosion from using plain water, Have you ever put straight water in, if so how long did you run it? It will usually take quite a while to do damage.

When the unit has been checked and/or repaired, does the new anti-freeze remain clear or does it get cloudy or rusty fairly quick?

Has the water pump been removed and inspected or replaced?

These are just a few questions that has come to mind. My biggest concern is the corrosion.

At the least, the water pump impeller could be eaten up or spinning on the shaft. This is very common on class eight over the road trucks and heavy equipment regardless of the engine make or model.

As far as the radiator being undersized, it has been my experience over the years that the engine manufacturer has minimum specifications on cooling capacity and Rv's usually exceed those requirements. It is when power upgrades and alterations occur that may change the cooling requirements so that when an issue does happen it makes it worse.

Gary