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Low Coolant Question
I had something unusual happen today. I started the bus in south Mississippi and the outside temperature was over 70. My outside tasks were completed except for hooking up the car so I sat in the driver’s seat and messed with my GPS and log book while the bus was warming up.
It had been running 15 minutes when I pulled up about 10 feet to make room to attach the car. As I started to get up the coolant light came on and the Detroit Diesel monitor showed low coolant. I have had this happen a few times on extremely cold days and it always goes off in 2-3 minutes. This always causes me to check the coolant level the next day and it is never very low if at all. I know the extremely low temps play a big part in that.
I have never had this warning come on when the outside temp is any where near warm. I jumped up and ran outside expecting to find a coolant leak but found nothing. I was parked on blacktop and had been there for a week and there was no sign of coolant on the ground. I went back inside and the light was off and the warning was gone. I was not out of the driver’s seat much more than a minute if that long.
Prevost Nashville drained and refilled the coolant to put on my new compressor in February but I have driven 7 days and 800 miles since then. If it was not full when I left there I would have known by now.
I only traveled 25 miles today but with traffic, parking and idling I ran about 2 hours and the engine temp came up to normal and I had no more warnings. When I arrived at my destination it was pouring the rain and has rained all evening so I could not look for leaks.
Was it a fluke? Could a sensor be about to kick the bucket? Any ideas?
Thanks,
DKO
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8 Replies
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check ALL connections! Vibration could cause an intermittent warning. Also on mine I changed the sensor but it continued. It turned out to be a low coolant “module”.
Be very careful with the low coolant warning as it CAN cause the engine to shut down at the most inoportune times! Don’t ask how I figured that out but it DOES happen!
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DKO
Ace gave good advice. I don’t want to scare you but I will repeat that low coolant is one of the conditions that will shut down your coach.
If I was sure I had no leaks and the engine had no internal issues that affected coolant level (there are ways coolant can get into the engine, none of them good) I would add some coolant to insure the header tank had an adequate amount. I suggest no more than half a header tank of coolant when cold.
The sensors can fail so if you know the coolant level is OK yet you get the warning you can put a jumper (paper clip) between the two terminals on the sensor plug to keep you going. Just be aware you have no coolant level warning when you do that. If the sensor is lying to you, just replace it.
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Order a coolant level sensor now, you will be needing one.
JIM
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Thanks for the help, guys. I appreciate it. Where is the sensor? Is it up on the tank? Also, where is the “module” that Ace mentioned?
Do I need to order the sensor from Prevost parts or is that something I can buy locally. I am in the Mobile area and I will be driving down to the Fairhope and Foley area Monday.
Thanks again.
DKO
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the sensor should be located at the bottom of your surge tank! That’s the tank that has the sight glass in to be able to check level and also where you add coolant. Look for a fitting resembling an automobile spark plug with a wire attached to the end and possibly a ground wire off the side of it.
As for the module? I was told to replace them in pairs. On my H3-40 model ( different than a 45) it was located in the electrical bay drivers side rear and mounted on the roof of that bay! A simple plug into the harness and its installed!
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The sensor is where ACE said in the preceding post. Buy it from Prevost, free shipping and not expensive.
For anyone: If the alarm light comes on, you can disconnect the wire at the sensor and let it hang until a new sensor is installed. The light will be light on the dash….just keep on driving. Replace the sensor as soon as possible/convenient.
JIM
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I cranked up and traveled less than 50 miles yesterday. Before I did I uplugged this and cleaned boths sides of the connection and plugged it back in. I am assuming that is the sensor that may be going bad, on the side of the tank underneath the sight glass. Right?
Here is a picture of the whole side of the tank
This hose attached to the bottom of the tank leads over to this on the side of the engine.
This is where it goes on the driver’s side of the engine up high.
DKO
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Yes that is the sensor. On an unrelated, but related note those small hoses (there should be three of them) are likely original and if you so much as breathe on them they are likely to fail.
A while back one owner gave us a heads up that those hoses look perfect but they are so brittle that even touching them could cause them to snap in two. Any local hose shop canmake new ones up for replacements. Very important you check and replace them.
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