How long should the Low Coolant light stay on.

[rdm]

Our low coolant light stays on for 3 to 5 minutes after starting the engine.
When the motor is idling this has occured the last 4 times I have started the engine.
Could this be an indicator of future water pump problems
There is xtra coolant in the resevoir prior starting and after starting
when the light goes out and we drive down the road the engine temp is normal and the light stays off.

Hope everyone is having a great weekend
Thanks
Ray

[jimmickle]

The first step is to check the level in the radiator when cold. It is probably low. The coolant light goes out after a few minutes when the coolant gets hot and expands. Your problem is likely the seal in the radiator cap. If not, there may be a leak in the hose to the resevoir. The system is designed to pull coolant back from the resevoir when the radiator cools. If there is an air leak anywhere, it won't pull the coolant back. Try a new cap first if inspection doesn't reveal any other problems. It's NOT a water pump problem.

Jim Mickle

[87MH]

Originally Posted by rdm

Our low coolant light stays on for 3 to 5 minutes after starting the engine.

Could this be an indicator of future water pump problems
There is xtra coolant in the resevoir prior starting and after starting
when the light goes out and we drive down the road the engine temp is normal and the light stays off.

Ray:

On the '87 Xeppelin, I just assume that the "low coolant" and "water in fuel" lights are just a couple of lifes mysteries, and we mortals shall never truely know the real reason for their vagaries.

The "water in fuel" light is a diesel specific install, yet the dash light keeps appearing - and I have isolated the engine compartment connections! Of course, if that light really bothered me, I could always just remove the dash lamp.

Now, the "low coolant" gremlin is another matter. My radiator system is in good shape, no leaks, and is "breathing" as it should during the heat and cooling cycles, yet, for no apparent reason, the light mysteriously comes on, and, just as mysteriously, goes off.

Keeps me occupied, wondering why it does it - sort of like the vaccuum Thermos bottle -- How do it know?

I gotta get a life.

If either of the lights REALLY bother you, a Craftsman wire cutter is under ten bucks -- problem solved.

[JanP]

The low collant light means exactly that! There are a pair of contacts about 2" from the bottom of the external coolant tank, if coolant is above this set of contacts the low coolant will not be on. If the coolant level is just below the contacts the light will be "on" until the coolant expands due to temp. increase until the contacts are covered again. If the coolant light does not go off you may need a new engine in the future. Just add a little coolant to the reservoir to cover the contacts when the engine is cold. Light should then not come on at all.


Ernie and Jan

[swebster]

rdm - I agree with Jim on this one. My 86 has the same wires and when the coolant is low the light comes on. You could be just below the level until the thermostat comes on and possibly changes the level of the resevoir. I would add some coolant and see if it changes the behaivior.

One note...this light saved my skin (not to mention my motor) once on a trip. I blew a heater hose to the aux heater under the couch and was dumping coolant on the highway (in the summer). The light came on and I was able to exit the interstate quickly and perform some roadside repairs.

I too have the glow plugs & water in fuel lights which I can only assume were a cost saving measure from AS when making both gs an diesel versions of the classic MH.

[swebster]

another thought on this. My light came on unexpectedly once on a long trip. I pulled over, checked the coolant level and it was fine. A few more miles and the light went off...then on then off. It turned out to be a loose connection on one of the wires to the coolant resevior. A quick re-crimp and it works fine now.

[87MH]

Originally Posted by swebster@myrvadvanta

another thought on this. My light came on unexpectedly once on a long trip. I pulled over, checked the coolant level and it was fine. A few more miles and the light went off...then on then off. It turned out to be a loose connection on one of the wires to the coolant resevior. A quick re-crimp and it works fine now.

Steven:

I have to agree with you on this one, but I still think there are a couple of holes in this "low fluid" argument.

You stated earlier that your "low coolant" light came on when your aux heater line blew. If the engine was loosing coolant, I can't conceive a scenario that would explain how the external coolant reservoir was "sucked dry" while the engine was running. I would imagine that as the engine lost coolant, and continued to heat up, it (the hot engine) would continue to "boil" the coolant, causing even more pressure, and eventually emptying the active system of fluid, but maintaining pressure until the very end, which would preclude the external reservoir from being sucked "dry". The engine and radiator would have to be in a "vaccuum" situation to pull the coolant into the active system from the external reservoir.

Now, my external reservoir does not have electrical contacts, the windshield washer fluid reservoir does, but not the coolant reservoir. Of course, my expansion reservoir could very well not be stock.

I had always assumed that there was a "float" with contacts near the top of the radiator that would indicate actual fluid level in the radiator itself (I thought I had heard this in an old thread). I searched my radiator, and the only electrical contact on the radiator that I can find is near the bottom back, curbside, between the radiator drain and the transmission fluid inlet line, and I believe that that electric contact is a thermostatic switch for the electric air fans.

So, to summize, my radiator does not appear to be equipped with a "float" switch to indicate low radiator coolant level. And, if the contacts in the external expansion tank activate the "low coolant" light, how did your aux heater leak empty the expansion tank while the engine was running (and maintaining a positive pressure in the cooing system).

One good thing, this thread precipitated a thorough inspection of the front section of the engine compartment. I found the #2 electric cable from the charge splitter to the battery compartment partially severed by the Air Conditioner Compressor drive pulley. One minor catastrophy averted.

Any other thoughts on how the "low coolant" light is activated?

[swebster]

Dennis,
No idea why either. I guess I always thought that the expansion tank stored a median amount of "reserve" coolant when needed by the engine and provided a place for overflow to go when the engine was hot. Mine does not appear to part of the "pressurized" system as I can open it when the engine is hot but on this last trip the level of the expansion tank was indeed higher with the engine running between 190 and 200 degrees.

What I am sure of is when my light came on (last summer) it was closely followed by an increase in temp and the smell of coolant from the ruptured heater hose. When I pulled off I checked the coolant level in the reservoir was lower than the two contacts. I guess I just asumed it had been "pulled" into the main cooling system which was loosing coolant.

See...now you're going to make me read up on coolant systems.

As far as a float switch. I have that same lead on the driver side bottom of my radiator. It is a single lead on what appears to be a temp sending unit. When I had the radiator out I did not find anything else electrical in there.

One footnote: Right before this recent trip I had a new small leak in my tired old radiator. I successfully (and likely temporarily) stopped it using a bottle of Prestone's leak stuff (not the brand name ) but I think a new radiator (or recore) needs to get on the Q2 AS budget.

Will this ever end?