I have a 93 T/A A4. I bought her over the summer and when i drove her home I noticed the low coolant sing was on....put some in didn't do anything. And took it to the local Mechanic he said the sensor was bad. Well Last Thursay night i was going home the light came on again...and I was by a Target to pulled in and put some fluid in. The light went away. So i was like ok maybe it was little low. Today comin to college it off again. Pulled into a gas station everything was fine. There's was more then enough fuild there. And drove to college the Engine temp stay where it always does and as it went past 210, the fans came on. So could it be the sensor again. Please help me out thanx. Any help or suggestions will be appreciated, Thank you in advance.

 

If the light keeps coming on and the coolant isn't low, the sensor is still bad. Maybe your mechanic simply tried to clean it rather than replace it.

If you are asking if the low coolant level light could cause the fans to come on, the answer is "no, not directly".... the coolant level sensor is only connected to the dash light. It isn't connected to the PCM, so there's no way for the PCM to even know the low coolant sensor light is on. The fans will come on if your temperature goes past 210degF.... specifically, the first fan comes on at 226degF and the second one at 235degF. Remember, your PCM does not use the same coolant temp sensor as the gauge, so there can be some difference in the readings.

Have you tried "bleeding" the coolant system to insure there are noo air bubbles causing the problems?

 

It seems to be common for these sensors to stop working properly. Sometimes they're just dirty and can be cleaned.

Their only function is to turn on the idiot light on the dash; open corresponds to "enough coolant", so one solution is to just unplug the sensor and call it a day. Only drawback is you don't have a low coolant warning light anymore...some people care, some don't...

 

Mine did this, so I flushed the cooling sensor and got a new sensor and have had no problems at all.

 

if it does it and the fluids still full its the sensor bad. i had problems like you did, but unfortunately mine was a head gasket and the coolant was getting low. never overheated but it was a slow leak. im going to hope im wrong but you might have a head gasket out. itd be atleast something important to eliminate before your bearings go shot from the coolant in the oil. hope im wrong

 

Well if there's a head gasket blown then should there me at least something on the floor from the car. Like you said you coolant went low. So it was leaking. I am going to check and make sure how the coolant level stays. If it goes low or there's something on the floor. Or how else can i find out?

 

The coolant would go down if it was leaking through the head right? Any more suggestions?

 

Mine did the same crap.... no coolant was missing so I decided to clean the sensor... I was very carefull at it and it hasnt worked ever again since I cleaned it... I just disconected it and plan to buy a new unit but then It seems that there are two types for my same vehicle..

When I figure whats what I will replace it if only to have fully functional as it was when I first bought it.

Marvin

 

you may also have a small air bubble in the system but if your engine temp never seems to jump up and down you should be ok...the next thing i would do is do a system flush...go ahead and replace the sensor then bleed the system properly and you should be ok

 

Well I took the car out for a drive this morning. And after getting one of the replies about the possible head gasket i looked around the engine to see if there was any wet spots or anything like that. The driver side was dry and clean checked the passenger side best i would and it seemed pretty dry. At firs the car was started to warm up and the low coolant light wasn't on. So I was like ok...maybe it's gone. The car was on about good 1o mins. I let it warme up than take it out. Everything was fine. So took it for a drive and about 5 mins into the driving the light came on again. I like great. Turned around came back to the college parking lot. Checked the fluids and everything was there. I still put little bit in and started it up again and the excessive fluid seemed to drain out of the reserve coolants cap. I don't know if this reply will help but I am trying to shed some light on the matter. All the replies are greatly appreciated and keep them coming guys thank you.

 

If you loose a head gasket, it isn't likely that you will find coolant leaking out the sides between the head and the block. The exhuast/combustion gasses will be forced into the coolant, causing bubbles. These bubble will generally cause the coolant in the radiator to blow out the overflow hose, and then blow the coolant out the vent on the reservoir. There is a test kit to test for oil and/or other hydrocarbons in the coolant.

Yours seems to be showing signs of blowing coolant out the reservoir. Not a good sign. Could still be a bubble in the system, so a good venting should be the first step. But if it continues to blow coolant out the reservoir vent, I'd have the coolant checked for hydrocarbons.

 

When I get bored at work ..(like right now) I love to go through threads and
just read them because they are interesting to me...well anyways...to answer your question. Recently I read a Thread that had to do with coolant
and I read that the PCM records the signal when the coolant light is on so after you top it off properly and after you bleed the coolant system the car
must go through a certain number of cycles during open loop and then the PCM will shut the light off. It is very possible that your car just did that since your light will not come on anymore. But also, it is a very common problem and a lot of people end up removing the light bulb from the dash instead of
replacing the sensor. Hope this helps!

 

Ok me again... My car did blow out coolant out of the reservois *randomly* with no white smoke out of the tail pipes. Only steam out of the reservoir. It turned out to be the Radiator Cap... it has a coolang return valve that is spring loaded and the spring got toasted... the valve was just there floating around and somehow it would close up and work ok and sometimes remain open and let the car do a fog show.

My Coolant temp sensor was still bad though. After I replaced the radiator cap the system held full pressure and it was all nice again. I still have to replace the coolant level sensor though.

Check the Radiator Cap first thing... Maybe its best to just buy a new one. They are cheap. Dont drive the car after it gets too hot for now... Hopefully it wont be your head gasket.


Good luck and hope you fix your car.

Marvin

 

Where did you read that? The "low coolant" sensor is NOT connected to the PCM in any way, shape or form.

 

Hey BoobSter-lt1-z,

Please shorten your sig to 5 lines or less... yours is a bit excessive. Thanks!!!