Engine fan

[mrwrenchman]

I have a 2006 Monaco with a 8.8L 400HP Cummins side radiator . Recently I noticed the engine fan is running full speed all the time . I know the fan is driven hydraulically and I think it thermostatically controlled . Is there a thermo. control valve somewhere that is possibly stuck in the wide open position , or some other condition .Any Ideas ? Thanks Don

[mrwrenchman]

Thanks guys , they don't make things easy do they . Don

[dons2346]

Couple of things could be wrong, start with the cheap stuff first.

Find the fan controller and take apart all the connectors on it and clean them with a contact cleaner. If that doesn't work then check all the sensors connected with it such as water temp, intake air temp. If you have the air conditioner on, it will also cause the fan to operate at a high RPM. It will do the same in vent mode also. Your controller could be activated by the ECM also.

A Sauer Danfoss controller can be had fromFluid Bernstein(sp) for about $500. You will need the actual part# because they come programed for your application..Wax valves also go bad but I don't know anything about them. You can get a replacement wax valve from Source Engineering but it is not a direct replacement.

[Waco_Kid]

I had the same issue, if you have a sauer danfoss fan drive control, it probably failed. There around $900. I replaced mine four years ago and it failed again, this time I replaced it with THIS. and it works great. Bruce

[JR45]

Fan controller
http://sourcerv.com/conversion
JR

[MPond]

mrwrenchman wrote:
I have a 2006 Monaco with a 8.8L 400HP Cummins side radiator . Recently I noticed the engine fan is running full speed all the time . I know the fan is driven hydraulically and I think it thermostatically controlled . Is there a thermo. control valve somewhere that is possibly stuck in the wide open position , or some other condition .Any Ideas ? Thanks Don

We had the same problem with our ISL 400, and it ended up being the hydraulic fan controller. I took it to Cummins Cal Pacific and described the same symptoms - Fan running at full speed all the time (tons of dust every time we pulled into an unpaved campground) and they found the failed part. I can't remember exactly what it was called, but it was a part that opened and closed a valve on the hydraulic lines that drive the fans. At least it was stuck open so we weren't overheating.

If you need more details I can call Cummins and ask them.

[crasster]

Agree completely. Those side rads can totally become clogged with junk after a nice trip. Especially if you happen to any offroading areas, dusty areas, or areas infested with bugs!

[Pogoil]

Just returned from a 2000 mile trip. Side radiator was flushed before trip on return I could have filled a coffee can with the debris that I washed out of the radiator and cac. Bottom inch had about 1 inch of new debris stuck to it.

I wash mine at least 4 times a year.

Remember to use the Simple Green formula that is aluminum friendly. The regular is hard on aluminum.

Pogoil.

[oldmattb]

I had a similar issue. My thermostat is a wax valve which is not electric. They often become clogged with a bit of junk.

In my case, the problem seems to have been a restrictor placed by the manufacturer, to reduce head pressure of the dash AC when the AC is on and the engine cold. I drilled out the restrictor to reduce cold fan speed.

Matt B

[moisheh]

Golden: He has a side rad. They do not normally plug like rear rads.

Moisheh

[smlranger]

Your coach may have the Sauer-Danfoss fan controller which reads info from several sensors (3 I believe) to control the fan. If the controller fails, it generally defaults to high speed.

Or you may have another set up. My 2007 425 HP ISL uses info from the engine ECM to control a little solenoid mounted on the hydraulic fan motor to control fan speed.

[Golden_HVAC]

It is probably dirty. Try using a garden hose to rinse the radiator, then spray with something like simple green. Let it soak for 1/2 hour, and then rinse with more water. ..

If you get off lots of dirt, that is your solution.

Some municipal bus lines have a full time mechanic to just wash radiators every day. One even went to the expense to make the fans reversible, and blow air the other direction for a few minutes each hour. This dislodges some of the dirt every hour.

Good luck!

Fred.