Coolant Warning Light

jmcgarity · 07-24-2011, 12:33 PM

I have a 2007 Fleetwood Discovery 39V. Last week while checking on it in storage a warning light came on "Low coolant". I suspect there may be an air pocket in the coolant system.
Today I added about a third a gallon of 50/50 coolant to the expansion tank, started the engine and let it idle for a minute, then ran the engine for @ another minute at 1000 rpm. The light did not go off but neither did my coolant level go back down in the tank.
I repeated the start-up and ran it another minute at 1000 rpm - the light remained on.
I then let the engine idle normally and the guage never climbed out of the lower third of the dial, so it does not appear to be over heating.
No apparent sign of coolant leakge.
My manual also refers to "petcocks" (upper and lower) that should be opened and closed if purging the system of coolant. Would that be part of the equation? Where would they be locate on a pusher engine?
My last annual Freightliner service was two months and 3k miles ago.

Skip426 · 07-24-2011, 01:17 PM

The engine coolant would not develop an air pocket without the system leaking. The level sensor in my coach is in the expansion tank, and visible below the add coolant line. If your coolant resivoir was always above the add line I would suspect electrical issues , rather than air pocket in the system the sensor would not detect that, until the coolant is down. If the level was low and you have added ; if I read your info correctly; the sensor may have developed scum on the contacts or float, depending on the type of sensor, and need cleaning or replacement.
Petcocks are most often used during , flush and complete draining of the coolant. location varies; greatly!

Crabby Mike · 07-24-2011, 08:05 PM

I have gotten a "check cooling system" warning several times (Cummins ISL 425 on 2008 FL chassis), and have found that adding some coolant to the surge tank (even though it already appeared to be up to the line) stops the warning from re-occurring. I have been told by FL techs that that the level sensor in the tank, due to its position, can be oversensitive when the level is borderline, but this is easily solved by raising the level slightly.