The 2004 Monaco Coach Diplomat has 1 NHTSA recall campaign affecting an estimated 1,189 vehicles. Recall repairs are always free at any authorized dealer. Owners have filed 10 complaints with NHTSA, most often about the electrical system. Last updated July 5, 2026.
Recall campaigns
ENGINE AND ENGINE COOLING04V4410002004-09-131,189 affected
Defect
ON CERTAIN MOTORHOMES EQUIPPED WITH CUMMINS ENGINES, OIL CAN LEAK INTO THE ENGINE COMPARTMENT FROM A CRACK IN THE CUP PLUG.
Consequence
OIL LEAKAGE ON A HOT ENGINE CAN RESULT IN AN ENGINE COMPARTMENT FIRE, POSSIBLY RESULTING IN INJURIES.
Remedy
CUMMINS IS CONDUCTING THE OWNER NOTIFICATION AND REMEDY FOR THIS CAMPAIGN. CUMMINS WILL INSTALL A STEEL CUP PLUG BOSS CAP TO ALL AFFECTED ENGINES. OWNERS SHOULD CONTACT CUMMINS CUSTOMER ASSISTANCE CENTER AT 1-800-343-7357 OR MONACO AT 1-800-685-6545.
Verbatim reports filed with NHTSA, lightly edited for readability and with personal
information removed.
“Diplomat 40pdq 2004 motor home, the slide was off center and strips were not lined up properly. *bf the slide rides to high and causes so much wind noise that the consumer was unable to hear outside traffic. A gap under the window allowed water to coming into the coach. The captain driver seat…”
“Diplomat 40pdq 2004 motor home, the slide was off center and strips were not lined up properly. *bf the slide rides to high and causes so much wind noise that the consumer was unable to hear outside traffic. A gap under the window allowed water to coming into the coach. The captain driver seat…”
“Diplomat 40pdq 2004 motor home, the slide was off center and strips were not lined up properly. *bf the slide rides to high and causes so much wind noise that the consumer was unable to hear outside traffic. A gap under the window allowed water to coming into the coach. The captain driver seat…”
“Diplomat 40pdq 2004 motor home, the slide was off center and strips were not lined up properly. *bf the slide rides to high and causes so much wind noise that the consumer was unable to hear outside traffic. A gap under the window allowed water to coming into the coach. The captain driver seat…”
“Defroster not working windshieldd iced over when driving from snow. When stoped defroster will output enough heat to melt ice. Heater defroster is sub standard insufficient hot water flow from rear mounted diesel engine to heater core about 37ft.”
“Defroster not working windshield iced over when driving from snow and freezing rain.when stoped defroster will output enough heat to melt ice. Heater defroster is sub standard.”
“Dt: the caller has a problem with the front roadside slide on the motor home. They had it in for repair 8 different times, and it still is not fixed. To date the roadside slide is unstable. The slide is off center, and a person can put their hand in the bottom opening to the side. Therefore, the…”
“Dt: the caller has a problem with the front roadside slide on the motor home. They had it in for repair 8 different times, and it still is not fixed. To date the roadside slide is unstable. The slide is off center, and a person can put their hand in the bottom opening to the side. Therefore, the…”
Recall, complaint, and investigation records from official NHTSA datasets (FLAT_RCL,
FLAT_CMPL, FLAT_INV), synced weekly. Counts reflect NHTSA records for the 2004 Monaco Coach Diplomat as of
July 5, 2026. Complaint narratives are consumer-submitted and unverified. This page
contains ads and affiliate links. Full methodology.