[Nebster]

When taking delivery of 1234 last month, I started the engine on the second morning and saw a stop engine light right away.  The overhead silverleaf monitor showed "coolant extremely low" or some such.  We stopped the engine and filled the coolant reservoir in the rear and things were fine.

Fast forward 1,500 miles.  Made it home to Colorado last week, no issues along the way.  A couple days later I went out to start the engine to put out some slides, and same thing!  Reservoir seemed empty.

I see no sign of coolant anywhere on the ground or in the engine bay.  I also had the oil changed and analyzed halfway through my trip, and there was no sign of coolant in the oil (if that matters).  

I have an appointment at CAT next week to have them look at it, and I don't know very much about engines.  But...  does anyone have any ideas about what to check first?  I am concerned that the problem may be slow or intermittent enough that it is hard to tell if any particular change fixes things in the shop.  On the other hand, carrying some extra coolant is easy enough insurance for now.

Many thanks,

Ben

[HoosierDaddy]

No coolant in the oil sample is good. If it is losing significant coolant it is losing it from inside the engine or outside the engine. That is probably what CAT will check first. If the engine has been overheated prior to your purchase the head gasket could be compromised. That would allow coolant to leak into the crankcase( which should show up on the oil analysis if it is severe enough), outside the engine (which is not fatal but may not be visible if the leak is slow) or into a cylinder( which could be fatal if it fills a cylinder with coolant after shut-down).

[ccjohnson]

It could possibly be as simple as a bad radiator cap. We will keep our fingers crossed here. If it is getting into the exhaust side somewhere, ie a cracked head or bad head gasket, you should be able to smell it in the exhaust. Might also be a water pump leaking at a rate slow enough when driving that it drips and gets evaporated fast enough that it doesn't accumulate enough anywhere to make a puddle when you stop. Glad to hear you are taking it to CAT to get checked out. Coolant leak is not something you want to ignore.

[rheavn]

Ben,
On my coach there is a radiator fill tank and a expansion tank.  BOTH need to be filled.  On my coach the fill tank is high up on the left rear and accessed through a keyed door.  The expansion tank is in the engine compartment.

The expansion tank:      

[valento]

Ben,

Has the radiator coolant been changed recently?  CAT flushed my radiator system for I had a bad radiator hose and some other issues.  They apparently did not get all the air pockets out of the system for I ended up adding almost 3 gallons of coolant over a few thousand miles.  Now I am not having anymore problems for the system now seems to be full and the level is steady.  Hope your issue is this simple and not anything major.

[folivier]

Another thing to check is the overflow hose from the radiator to the overflow tank.

[Nebster]

Okay, fingers crossed indeed. Sounds like there are a lot of fairly benign reasons this could be happening. I don't have any documentation to know whether the coolant was recently flushed, but it's certainly possible. The radiator cap itself seems broken to me (retaining tab bent such that I needed pliers to remove the cap one time), so it could easily be the culprit. I have to go to CAT for a variety of other things, but this is my top priority. Will report back soon. Thank you!

[Nebster]

Okay, mystery solved, folks. The leak is in the radiator!

The good news is that it's not a mystery anymore and so it can be fixed. The bad news is that they need to pull the whole radiator and send it out to a specialist to get it rewelded (?). They are estimating three weeks for the whole process, which is okay since we are not using the coach this fall.

Probably cost about 4 AMUs. Are you guys familiar with AMUs? :-)

[Guy]

ok,  I'll bite. What the heck is an AMU? 

Do they eat much?

Are they housebroken?

[smagown]

Is that the big brother to an "IOU?"