Radiator (gasket, idle, engine, BMW)

[jhall3131]

My antifreeze overflow tank falls slightly below the full level which causes my engine light to come on.

What could be the problem?

[texdav]

Doesn't sound like its the overflow take as slight below the full leavel is fine. What light are you talking abpout teh overheating light or check engine. I'd either get teh colling sysetm checked or a code reading if its the check engine light.

[charlesj]

I think some cars actually do have a sensor in the overflow since overflow is also a reserve. BMW may be one.

If that actually is the case, could be a leak, or could just be consumption of time. Over a long period of time, you will loose some, and it will sucks it out of the overflow. If its just once, fill it back up. If this happens regularly, you have an issue. I would look for a leak under the car where it sits, and if that does nothing have a pressure test done. A shop can pressurize your system when cool and see where its leaking and if it holds pressure. Can also be seeping head gasket.

First things first would be to make sure that light is actually the overflow level.

[SLCPUNK]

Is it the "Check Engine" light? Or is it a low fluid light? Those are different things.

Low coolant level is not going to throw a CEL. If it is CEL, get the codes pulled.

[jhall3131]

Following up on my first post concerning the CEL coming on while the coolant reserve was slightly less than full, I have another question. I did fill the reserve to full and two days later the CEL went off.

Today, Sunday, I had traveled close to 40 miles and the CEL came on again. The last time it came on, I had traveled about the same distance.

I am confused. When a mechanic checked the code he said I needed a tune-up.

Could it be the radiator fan or does this problem have nothing to do with the coolant or radiator?

[Deez Nuttz]

A few places the coolant could be going...

It could be leaking out of a hole in the hose....or a hole in the tank...

It could be leaking from the radiator....

It could be leaking into the engine's cylinder....due to a blown head gasket or a cracked head. Does the engine idle rough on start up? Does it emit a lot of white smoke? Does the oil have a milky color to it?

[jhall3131]

No to all three of your questions concerning the engine.

Would any of these leaks be obvious?

[johnfrisco]

Originally Posted by jhall3131

No to all three of your questions concerning the engine.

Would any of these leaks be obvious?

Could be leaking from the water pump, which is not all that common. If it is minor leak from a bad head gasket it can be difficult to detect an first.

You can bring it to a mechanic to pressurize the system to see where the leak is.

What make and model is your car?

[charlesj]

What is the actual code that comes up?

Also, you mentioned you filled the overflow and it came back on two days later. Does that mean you also checked the fluid level and it was low again? If you are loosing fluid from the overflow, the next step would be to wait for the car to be cool, open the radiator cap, and fill it right there. Once full, turn the car on with cap off. It will likely drop down so that you can fill it again. You can leave the cap off for at least a minute to get it full. If it starts coming back up consistently, cap it. Once you have done this, you can be pretty sure, the system is full or close to full. It may have been that it was down on fluid and just had not yet sucked enough from the overfill. If it goes away after that, you have a leak, either internal or external

[denise41]

i have a 1999 gmc yukon & the radiator leaks , i cant afford a new one ,please help