RV Repair: overheating, winnebago chieftan, fan clutch

Question
Hi, I recently purchased a 93 Winnebago Chieftan with a 460 which was running great. After having a fluid change(tran oil, engine oil, diff fluid and radiator) it seems to get hot a lot quicker, to the point where the check engine light frequently comes on, which engages the fan and seems to cool it temporarily. Is this normal? Also, what is the proper function and use of the overdrive? When should it be engaged and what damage could be caused by not engaging it? it seems to have a substantial effect on the temp. Thanks in advance for your help and for offering this wonderful service.

Answer
If all is ok after the fan clutch engages, you may need to replace the fan clutch.  The engine should never get close the being that hot before the fan comes on.  Over drive should be used when on fairly flat ground or better description, if the transmission is down shifting a lot due to load or grade, turn off the over drive.

Garry