Primary Radiator Fan

[Larry Dedrick]

Larry would like to know on a CAT C12 what drives the primary radiator fan.  Also what drives the smaller cooling fan?  Also if the primary radiator fan is not functioning properly what would be the temperature indications?  Would the temps fluctuate?  

We are running in the highway today at 70 MPH and the temp is running from 192 to 201.  The 201 is when we are going up a steep grade.  The temp did reach as high as 206 when we first hit the road but then dropped to 176.

Is there a way to tell if the fan is running?

Thanks,
Laura

[Gerald Farris]

Laura,
There is only one radiator fan on your coach, and it is driven hydraulically by the same pump that powers your power steering system. If the radiator cooling fan is not functioning, the coach will overheat to the point of derating within a few miles. However, if the fan is operating marginally, overheating would be noticed under heavy loads.

I do not know what you are talking about when you refer to the small fan, unless you are referring to the electric fan motor that is attached to the engine bay door on some coaches. If so that fan plays no part in cooling the engine. It is simply to purge the hot air from the engine compartment to reduce the heat-soak problem in the bedroom.

If the engine temperature went from cold directly to 206 degrees before it started to drop, I would suspect a malfunctioning engine thermostat if the cooling system is full of coolant.

Gerald    

[Edward Buker]

Larry and Laura,

The 192 to 201 is a normal range. If you are climbing a hill and the temp is rising you can downshift to 5th or 4th depending on speed and grade and by keeping the RPMs high (1800-1900RPM range would be reasonable) the hydraulic driven fan will have more available hydraulic pump flow volume and the engine water pump should have more coolant flow. Along with this the engine will not be working as hard. As a result the climbing engine temperatures should be better managed.

The main fan is hydraulically driven from a pump that resides on the Cat C12. There is a valve arrangement that is driven by antifreeze temperature which enables the hydraulic flow volume to the fan hydraulic motor. That regulates the spin speed of the fan and when it operates. If the fan was not running you would be overheated beyond the temps you are seeing. The temp reaching 206 starting out and then dropping to 176 is abnormal in my mind. The temps will usually climb slowly to 180 or 190 depending on the thermostat you have and then remain quite stable unless you are involved with a climb. Any time there is quick dropping of a temp or wide range like what you indicated I would want to be sure that the block and expansion tank are indeed at the proper coolant level.

I'm not sure what smaller cooling fan you are referring to, let us know on that one.

Later Ed

[Joel Ashley]

Because this condition seems to be only exhibited at idle and low load, I'd think like Gerald that the thermostat would be the most likely suspect.  The higher number on grades is not abnormal, and ditto on your other numbers except idle, so everything to me points at thermostat.

I'm not familiar with your coach model, and Gerald may have clued into the compartment cooling fan that some rigs have, otherwise the only other fan around the engine might be the one outside the air conditioning radiator like is on mine.

Joel

[Larry Dedrick]

We are dead on the road!  Managed to find a thermostat and while I was driving to pick up the part Larry checked the coolant once again and it was almost empty.  We obviously have a leak somewhere.  Luckily I had not left the parts dept so could pick up coolant.  Now to figure out where it is leaking.  Waiting on a mobile repairmN that was due here 20 minutes ago.

[Jeremy Parrett]

Check under bedroom access to front top driver side of engine. There is a 3/4 inch hose comes off the manifold to a T that is down beside the transmission.  My hose had chafed thru where it passes the transmission support strut.
This hose is the supply of coolant to the dash heater system.   This hose must have been leaking for some time before it finally split at 4.00pm in rush hour traffic center of Ensenada .Baha Mexico.
All the symptoms you have were present on our drive across from Florida to San Diego.   Hope this helps.  Bon voyage.

[Keith Moffett Co-Admin]

Darn fan just wont come on and the temp still only reached 192 even at high idle while standing on the RV pad.  I did just clean the radiators real well so the air flow is much improved but not enough to run for over an hour without the fan comming on at all.

Is there a way to trick the system and make the fan kick on?

Keith

[Tom and Pam Brown]

Keith, you can turn on dash A/C and it should cycle.

[Gerald Farris]

Keith,
The dash A/C system on your coach will have no effect on the engine cooling fan. The dash A/C will only cause the A/C condenser fan that is located behind your front bumper to turn on. The engine cooling fan is temperature controlled, so if your coach only reached 192 degrees, you were probably below the set point for fan engagement.

An experienced diesel mechanic should be able to show you how to make the engine cooling fan fully engage, but that fan takes a lot of horsepower to run, so you do not want to leave it running continually.

Gerald

[Tom and Pam Brown]

I stand corrected by the wizard! Forgot the condensor was not part of the cooling pack.

[Tom and Pam Brown]

Gerald,

Out of curiosity I went to the coach today, when the a/c is off the fan disengages when I turn it on it engages.  If you are right and you probably are why does this happen?

[Edward Buker]

Tom,

When you run the air there is a transition that has to be made from a gas to a liquid and from a liquid to a gas for a Freon blend. The job of the condenser is to take a gas and condense it back to a liquid and give up heat (think of steam). The fan runs to move air over the fins to aid in extracting the heat so that condensation can occur.

later Ed

[Tom and Pam Brown]

Thanks Ed, I am familiar of how a system works, I was speaking of the radiator fan turning on and off with the operation of the A/C.

Thanks

[Gerald Farris]

Tom,
Keith was asking about the hydraulically driven engine cooling fan, and the A/C system has nothing to do with it on his 2002 Marquis. The electric condenser fan on his 2002 is located under the front of the coach, just behind the front bumper, and it is the only fan that turns on when the A/C system is turned on with the exception of the dash blower motor.

Some coaches have the A/C condenser located with the engine radiator, and in those cases there is an electric fan for the condenser that turns on to blow air across the condenser. Since the condenser is stacked in front of the radiator, some air goes through the radiator also, but the air flow is not enough to cool the engine.

Gerald

[LaMonte Monnell]

I just traveled to Iowa to the HWH factory and had coolant temps range from 186 all the way up to 205 at climbing hill times, but as soon as I leveled out the temps went down to 186-192 range.
The transmission temps ranged from 185-202 and stayed there the whole 2800 mile trip!






LaMonte

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
2001 Contessa