Hino L6 - WTF with the coolant level sensor!

[LostDeere59]

We have two late model Hino L6's in rollback service, and both of them have had multiple coolant level sensor replacements, yet the problem continues to pop up at random times. And yes, we check the coolant level.

If you haven't had the wonderful experience of a late model Hino low coolant warning just find your local Bro Truck, lie down underneath in the back where his Horn Blasters horn rack is, and have him lay on the horn for about 4 minutes while you scream "DANGER WILL ROBINSON! DANGER!! DANGER!!! . . . .

Christ . . . .

Anyway, since my truck greeted me this morning with the low coolant warning, and this is the 4th sensor (including the factory install) I thought I would ask if anyone here has any information about this issue, especially something like an updated sensor that works, or a retrofit, or a software update to silence the ridiculous alarm . . .

As always, thank you in advance

Gregg

 

[LostDeere59]

So did some investigation of my own, first thing was getting my hands on the relevant Hino TSBs for this issue. The coolant sensor in my truck is supposedly the "correct" most recent sensor according to the production date and color coded marking on the sensor.

While inspecting the sensor I noted that there seemed to be a fair amount of tension on the harness at the connector to the sensor, with the wires folded over the back of the connector body. This can be an issue, especially with connectors in low voltage circuits, and also with connectors that have been repeatedly disconnected/connected.

If this was a BMW/Bosch sensor/connector I would have the terminals/parts necessary to do a pin drag test and replace the terminals if necessary, but I don't have ready access to the Hino components to do so. What I did do was pull the sensor harness gently through its securing points to relieve the tension on the connector, and carefully formed the wires into a U-bend so that the wires enter the connector body straight, or in-line with the connector. So far (about a week) I have not had any more intermittent warnings.

If you have a late model L6 with the Cummins and are having low coolant warnings even with the updated sensor you should definitely take a look at the harness. There is no slack in the harness from where it separates from the engine harness, I was only able to get about 1/4" of movement at the connector from all the way back to the engine harness (about 24") but I was able to relieve the strain on the sensor connector.

Gregg