Coolant Replenishing Tank

[Glennman]

On my 2002 MCI I have a small tank at the very rear passenger side in the engine compartment that apparently replenishes the larger main tank that is above the rear fans behind the upper rear cap.

During my fluid checks in anticipation of our first bus outing next weekend, one task on my list is to check and replenish my coolant. I've only driven the bus about 100-200 miles since getting it. The system was about 2 gallons low. When I got the bus, the flip door on the upper tank was rusted shut and didn't work correctly so I replaced it. The little flip door on the lower tank works fine. That tells me that the previous owners probably used the tank with the pump to replenish the upper tank.

All that being said, does that pump come on when needed automatically? Or does it need to be turned on manually whenever the upper tank is low?

Thanks you guys for all the help you provide. 

[epretot]

There is a manual switch in the engine compartment. At least on my dl3...

With the engine start and stop switch.

[Jim Blackwood]

My '96 also has a manual switch. Fill the lower tank, flip the switch and watch the upper sight glass.

Jim

[Sebulba]

My '96 also has a manual switch. Fill the lower tank, flip the switch and watch the upper sight glass.

Jim

Ditto on my '97

Seb

[Glennman]

Thanks everyone. I'll look for the switch.

[Jim Blackwood]

Could be around the lower coolant tank, or on the yellow box. I forget which.

Jim

[luvrbus]

Follow the wire from the pump it will lead to the switch. Mine was in the corner on the right side when you opened the door where the tank was

[mqbus767]

It's manual on my 2001 DL3 and the switch is located on the same yellow box in the engine bay (driver's side, top) as the switches for rear start and fast idle.

[Glennman]

Thanks mq, I have one of those yellow boxes too. I should have thought of that. I'll check it out.

[havinatime]

The maintenance manual for my 2007 MCI instructs to leave the radiator cap on the upper "surge tank" open while filling. The lower "recovery tank" should fill the upper tank automatically during normal use, if my sensors were working correctly. So far I've had to replenish my system manually. There's a sight glass on my upper tank to show when the level is optimal. I have to reach up and take pictures of it with my phone since there's no room to fit my head up there, then use the yellow service box to fill at 2-5 second intervals, or until it starts overflowing out of the open cap from the upper surge tank.