Mysteriously missing coolant - Round II

richard5933 · May 06, 2018, 09:34:11 AM

We just completed our shakedown cruise after completing the updates on our 4108. We drove about an hour north to visit friends and spent the night boondocking at Walmart. Things went well and other than a couple of minor issues we're pleased. The battery bank did great, with more than 75% remaining after running the furnace and fridge overnight and using the inverter to watch a movie.

However, this morning when I started the low-coolant light was lit on the dash. I shut down and checked, and sure enough I had to add 2-1/2 gallons to bring the level to the bottom of the filler cap opening.

Total time running the engine since checking coolant last was the hour or so yesterday and the 45 minutes coming home from the shop, with another hour in between running the engine to work on various systems. Not a lot of time time on the engine to go through 2-1/2 gallons of coolant.

The circulating pump was repaired and is dry. The engine bay shows no signs of coolant anywhere. I see absolutely no sign of coolant in the oil - it still looks nearly new and fresh. No white smoke from the exhaust. There are not any signs of coolant leaks in the tunnel (no coolant dripping down into the bays).

My thoughts are either I've got a pin-hole that leaks when the system is under pressure, or once again there were air pockets and the system was not fully filled after the coolant circulating pump was repaired.

I've exhausted my knowledge base on this, and other than asking the shop to pressure test the system I have no clue what to do.

Any thoughts where my coolant is going?

chessie4905 · May 06, 2018, 09:45:34 AM

Since you recently had the system apart, I wouldn't worry right now. Run it as usual keeping an eye on level. Good chance it was an air pocket. Great to have a low coolant warning system.

eagle19952 · May 06, 2018, 12:59:21 PM

My money goes on air in the system.

Especially if your PAX heat is still intact.

richard5933 · May 06, 2018, 01:05:54 PM

Quote from: eagle19952 on May 06, 2018, 12:59:21 PM
My money goes on air in the system.

Especially if your PAX heat is still intact.

PAX heat? Never seen that abbreviation before. Are you referring to the over-the-road passenger heat? If so, yup - it's still there and working well.

eagle19952 · May 06, 2018, 05:03:19 PM

Quote from: richard5933 on May 06, 2018, 01:05:54 PM
PAX heat? Never seen that abbreviation before. Are you referring to the over-the-road passenger heat? If so, yup - it's still there and working well.

oh. found here, i was acquainted with the acronym at an airport..

https://www.quora.com/Why-are-passengers-called-pax

The reason being that from a bus company's point of view it's crucial to distinguish between Passengers (who pay the fare when boarding), and Passes (using a Season Ticket, or some other pre-paid authorization to travel)....

lostagain · May 06, 2018, 06:23:24 PM

We always have used that pax abbreviation in the bus business as long as I can remember.

JC

Iceni John · May 06, 2018, 07:41:34 PM

If you have a coolant surge tank and you feel like making/adapting/modifying something (and what true busnuts don't ever want to do that?), you can add a Schrader valve to its upper hose. And why, you ask? You can then easily pressure-test the entire cooling system without running the engine, useful if you need to find any leaks. It's certainly not a major project, but it could help you at times like this.

John

luvrbus · May 06, 2018, 08:05:36 PM

He needs a oil sample test to be sure the old Detroit's can be sneaky devils

brmax · May 06, 2018, 08:13:02 PM

Thats a great idea
I've had an old regulator, to use as you mention. This helped me stay under the factory radiator cap pressure during test.

Good day

Floyd