Community Forums

Thom Rose · 01-28-2025, 04:54 PM

The idiot light for low coolant is on. I recently replaced a leaky water pump, then refilled the coolant through the expansion tank. The level in the expansion tank is at the max, but the low coolant light still comes on. Is there another place to add coolant? Is there a place where a pocket of air could prevent a full refill of the coolant? Could the low water sensor have gone bad, and where is the sensor located, anyway? The coach has been driven about 60 miles since the pump repair, and the water temp is remaining in the safe zone.

SafariBen · 01-28-2025, 09:28 PM

It should be on the expansion tank, unless it's not a pressurized expansion tank, then it could possibly on the radiator itself.

In 94 it should be a simple switch. Once you find the low level sender, disconnect the wire from the sender and see if the light goes out, or ground it if the light doesn't go out when disconnected. Very possible that the wire got disturbed in the process.

jacwjames · 01-29-2025, 07:43 AM

If you have the original surge tank it may be mounted in the top.

Mine had a long probe that was in the top of the surge tank, actually held in place with a large rubber grommet. It was a one wire probe that would act like a ground when in contact with the coolant. This worked in conjunction with a Kysor Low coolant alarm. If the coolant got low it broke ground and the Kysor low coolant alarm triggered the light and the audible alarm.

The original probe was know to have a problem with "stuff" coating it and the light coming on. Remedy was to remove the probe and clean with a scotch brite pad.

I replaced my surge tank in ~2012 due to cracking, the new one is made of a similar material and suppose to resist cracking and the new low coolant sensor is mounted on the side near the bottom. It is a one wire sensor that does the same thing.

New tanks are now metal.

Here is the original parts page for my surge tank

8.3Oilbuner · 01-29-2025, 11:59 PM

Hi ThomRose. Do you have what they call, the Volvo football expansion tank? Has a green cap on the end and a radiator cap on the top of the tank along with a one wire connection to the low coolant sensor probe on top of the tank. My 2000 Monaco Windsor with the 330 hp Cummins's had that style of expansion tank. It was plastic or nylon. For parts you might have to check with a Volvo truck parts dealer. Not sure if any of those parts are around anymore.

Argosy · 02-05-2025, 07:50 AM

Do you have a coolant sensor in the radiator? Have you looked in the radiator at the coolant level?

Thom Rose · 02-11-2025, 02:36 PM

Thanks for all the advice. I do have the Volvo "football" style expansion tank, and the sensor is located on the top. Unfortunately, the tank is mounted at the top of the engine compartment, almost right up against the ceiling. Because of that the only way to extract the sensor is to unfasten the tank and lower it. I did that, extracted the sensor, and used a scotch brite pad to clean it up. Put it all back in with a new machine screw to attach the sensor wire (since the old screw got mangled in the extraction process). Everything works well since that was done.

Thom Rose · 02-17-2025, 01:42 PM

But the problem is not solved. After cleaning up the sensor, took a little 20 mile trip in the coach without the light coming on, but now the problem has reoccurred. Would like to just replace the sensor. However, I have not been able to find the replacement part online. Will try a truck parts shop, but in the meantime, if anyone can direct me to the part online, that would be great. The expansion tank it goes on is the Volvo football style tank with the sensor threaded into a hole in the top of the tank. The engine is a c8.3 Cummins.

jacwjames · 02-17-2025, 06:30 PM

You might try contacting

https://www.veurinksrv.com/monaco-factory-direct-part

8.3Oilbuner · 02-17-2025, 09:19 PM

Hello Thom Rose; I have the original Monaco part number for that sensor as I replaced it once in our previous 2000 Monaco Windsor. The part number is (2317). As Jacwjames mentioned, you might try contacting Veurinks RV as I also understand they have access to a lot of older parts. As I mentioned that number was a Monaco part number. That sensor was installed in a Volvo expansion tank. In your area do you have a Volvo heavy duty truck dealer or a heavy-duty truck parts supplier? Take some pictures to the dealer and see if a good person behind the parts counter can match anything up. I think those tanks were used in medium duty Volvo box delivery trucks as I remember seeing one. They were mounted low behind the cab in plain view. Let us know if you have any luck and good luck on your search! I see you are in the Medford area. Been there many times over the years and remembering seeing some heavy-duty truck repair shop in the north part of town right off of I-5.