Cat C9 overheating. HELP!

[Steve Glaser]

2005 Beaver Santiam with a Cat C9 rear radiator that keeps overheating.  I have cleaned the radiator, checked the coolant.  The records from the original owner (we're the 2nd) show he replaced the radiator and thermostats?  Are there 2?  We are on a month long trip out West and tired of running the heater!!  Any help is appreciated!

[Pat Long]

I believe you only have 1 thermostat.  I have heard about the water pump pulley slipping on the pump itself, or even the belt.  Have you checked those 2 areas?

[Steve Glaser]

I have not,I think it has a serpentine belt and a tension pulley I could be wrong,I have not crawled under there yet

[Dave Atherton]

Steve, you have a Caterpillar C-9 what is your engine serial number. Is the prefix start with
9DG, the engine serial number is ever so important to assist you with problem. Let’s first go
with prefix 9-DG . You indicated heating problem. Heating up running the flat roads or steep
long grades, are you losing coolant if so what are you adding, maybe this will get started with
taking a shot on guessing on serial number. Your engine has  ( 2 ) temperature regulators
that will start to open at 191 Deg F and Full open at 208 Deg F.  Next coolant loss looking at
Little rubber hose just under the radiator fill cap, than follow hose down to end of hose. What
you are looking for is the little wet on outside of hose about 1 to 2 inches, than tip hose so you
can see inside of hose ( is it dry and dusty inside or wet from coolant escaping) this is real
Important to determine your problem. This is a very common question I ask to determine
Stuck temperature regulator it faulty heat indicator bad connection or bad indicator. Last
question technical Cat information recommendations change out temperature regulators every
two years. Dave Atherton Retired Cat Mechanic

[Steve Glaser]

Hey Dave! 
My serial number 9DG02952.  I don't seem to be losing coolant.  The problem arises when climbing hills/mountains, especially long ones.  Are the regulators the same as a thermostats?  If so, they haven't been changed since we've had the coach for almost 3 years.  Would a CAT dealer have these and is this something we can do ourselves?  We are currently in Hurricane, Utah.  We had the stuck waste gate problem you looked at in Farmington with my wife, Cindy, and had the boost pressure sensor replaced in Peyton, Utah.  Hard to tell if it helped because we have only driven in 45 mph head/crosswinds and up mountains to get here.
Thanks for all your help, we're gettin' there!
Steve & Cindy Glaser

[Dave Atherton]

Good morning Steve, sorry I did not pick up on your motorhome but I handle several problems
daily and cannot remember or keep track who is who. Yes we need to change out the thermostats
and use only Caterpillar part replacement. Caterpillar recommended every two years before change.
One thing may be of interest as we talked at Farmington engine heat climbing long grades the engine
Shift to lower gear to keep engine rpms running higher, turn off AC just for long grade climb. At
Top of grade and descend down the other side the engine will cool down right away On heat indicator.
One of my questions we talked about no coolant loss but heat indicator reading very hot. If you
look back on the Cat ET diagnostic engine printout you want to look at engine temperature at that
time along with the intake temperature. If we had a problem present the intake temp would have been very high and engine temperature would have climb into the 175 deg f very short time. Going
Back on your C-9 intake manifold temperature calls for normal engine operation at 122 deg f. I
would suggest in running some more and give me more information on these two temperatures.
Running out on the rolling hills and flat road take note of the temperatures. I really do not feel a
problem is present and you are not in trouble. If you are blowing coolant out on the ground than
we have a problem . Have fun and do not worry, Dave Atherton Retired Cat Mechanic

[Steve Huber Co-Admin]

Steve,
Not sure what type of surge tank the C9 rear radiator employs, but if it is same as the side radiator version, there are 2 hose ports  on rear of the tank that can leak. Over time you can lose a significant amount of coolant and not see it as it doesn't run out the overflow hose.
Steve

[Doug Allman]

On our 2004 Marquis just exactly what Steve has mentioned happened. I was always adding some coolant but could not see where any was leaking, in my coach bay or in a campground site or along the highway in rest areas stopped. None showed up in the oil.
When I decided to do some other work on the coach which included changing all the hoses in 2014 I had to remove the coolant tank. Upon removing tank I noticed a wet spot on the frame rail. Looking closer then I found that the hose from the coolant tank leading down the frame rail was actually split along the bottom of the hose and leaking coolant. Because of it running along the inside of the frame rail and it going by the turbo where it gets very warm I suspected it evaporated before it could build up and leak onto the ground so you could see.
The plastic tank was fine but the hose was the problem and you could not see it due to the many items in that space when all items were in place. Hoses are not lifetime items.

[Joe DeWeese]

  We are having a similar problem with Cat C9 overheating on long uphill grades, especially at altitude over 6000 ft.  New problem since our transmission oil cooler split open and I had to temporarily remove it.  A new one is being made.  In the past year we have driven this ‘08 Monterey through lots of Colorado mountains with no issue. Yesterday the engine was so hot I pulled over at an off ramp.  I walked back to the rear of the coach to check the surge tank level.  Surge tank is full.  As I passed the side radiator I noticed that the radiator fan wasn’t even running.  It did come on after a minute but only ran a short time.  Is this normal?  What tells the fan to run?

[Steve Huber Co-Admin]

Joe,
The wax valve controls when the fan motor activates. See http://beaveramb.org/forum/index.php/topic,6482.msg47177.html#msg47177 
If you are running w/o a transmission cooler, I'd be very concerned about the temp the tranny got to when the engine overheated. IMHO I wouldn't drive the coach w/o the cooler.
BTW, your post said it was an 08, but I suspect a typo. Is the C9 a 350 or 400hp?
Steve

[Doug Allman]

I am sitting here with Dave Atherton and we have run into this problems before. I answered for you Steve event code 173-0 and 173-2 and codes indicate that there is extreme heat and there is no known fix as it is operator error. Clearly spelled on the CAT technical information on over heat on long grades.
You have to bring rpms above 1400 to maintain cooling. I think I provided information on ASK DAVE.
Any questions call Dave. Dave will provide technical information.

[Joe DeWeese]

I have replaced the leaking transmission cooler and it appears to be working without leaks.  However, I am continuing to have both transmission and engine overheats when going up grades, both long gradual and steep.  I am downshifting to keep the rpms up tp ~2000 but it doesn’t solve the problem. Both engine and trans temps drop down to normal soon after grade is past.  Also didn’t overheat when running with outside ambient in 40F range.  However, when outside temp is ~70F both engine and trans slowly heat up.  Interesting that when strong cross wind from drivers side both keep cool (side mounted radiators).  I have checked the trans fluid level and radiator surge tank multiple times both are okay.  I’m at a loss to figure what is going on.  Any suggestions?  Thanks

[Gerald Farris]

Joe,
Your description sounds like you have an underperforming radiator cooling fan. Have you had the fan checked?

Gerald

[Joe DeWeese]

Hi Gerald,
     The fan appears to me to be the prime possible cause.  Given the description I’ve read (hydraulically driven, wax valve controlled, etc.) it sounds to me like something requiring unique knowledge and experience to troubleshoot and repair.  I’m nervous about taking it to a run of the mill RV service shop here in N. Colorado.  Is this an accurate concern?  Is this type of fan installed widely in RVs and maybe large trucks?  I suppose I can just call a number of shops and ask if they have any experience.  What would you recommend?  Thanks, Gerald

[Gerald Farris]

Joe,
The hydraulic engine cooling fan in your coach is common on high end RVs with a side radiator and many rear engine school buses, but not on trucks. Most trucks drive the engine cooling fan with a belt and control the fan with a magnetic clutch like an A/C compressor uses. Therefore, many truck shops are not familiar with your cooling fan arrangement unless they also work on a lot of motorhomes like Massey Diesel here in Phoenix.

When it comes to an RV repair shop, many of them do not do extensive chassis work, they just work on the box that sets on the frame and send the chassis problems elsewhere unless they are a large dealership like BCS. Just make sure that they know what they doing when it comes to diagnosing the system because just throwing parts a the system is the most expensive way to fix it and can add $$$$ to the repair bill.

Gerald