Coolant symbol came on although everything seems fine

4063 Views 22 Replies 4 Participants Last post by alpac, Oct 5, 2017

alpac

Discussion Starter · May 20, 2017

Hi Folks,
Today was a pretty hot day over here, 94 degree. My wife took the 1999 E320 to go downtown. After about 25mns of driving in stop and go traffic the engine coolant symbol came on. She said the car never overheated, the temperature gauge went close to 90 but not more. The engine coolant symbol stayed on until she came back home. As soon as she was home I checked the car and could see that indeed the coolant symbol was on but no engine light. I stoped the car, checked if there was any error code in memory with my OBD2 reader but there was nothing. When I started the car again after only a couple of minutes not running the coolant symbol was gone and never came back even after letting the car iddle for 15mns in hot weather. There is plenty of coolant in the reservoir so it is not a low coolant problem. The fan seems to run fine so I am wondering if there is a sensor somewhere that is sending a wrong message. Any idea?

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alpac

Discussion Starter · #21 · Oct 5, 2017

Here is an update. after my last post I checked the pressure of the AC and I was expecting it to be low since it only blew hot air. To my surprise the pressure was very high, close to 200psi! when the normal should be between 30 and 45psi. I have no idea how it got to that level. Anyway, I pushed on the AC valve to release the pressure until I got to the normal range. I then took the car which was already warm for a 20mns test drive. The AC worked wonderfully, it blew nice cold air and today the outside temp over here in Raleigh is close to 90F. The engine temp remained in between the 80 and 90 mark. The engine fan message never showed during my test drive while as I explained before it would show everytime the AC was turned on. So it looks like there is some kind of correlation between the engine fan message and the AC pressure. I checked the AC pressure after my test drive and it was OK.
The engine did not stall on me during the test drive although I turned it off and on several times, one time after 5mns waiting. Should the CPS not trigger and error code? Anyway I will drive the car all the week-end and see if the problems reoccur.

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mrboca

· #22 · Oct 5, 2017

200 psi is a lot for the low side. works out almost 14 bars which is typically what you see at the HIGH side. That is what happens when the compressor is turned off due to overfilling and when the expansion valve is fully open.

Check your sensor values through the hidden menu on the a/c controller. especially for the refrigerant pressure when the a/c is running (#7). How to do it should be in the stickies (press and hold REST button).

When the high side is so high due to overfilling, the a/c controller asks for maximum cooling to remove heat from the condenser, and to reduce the high side pressure. That is why when you turn on the a/c, you get the maximum airflow demand, which generated the fan fault. When you reduced the pressure, the airflow demand wendt lower, so the fan message did not show up. I guess you can still get the fan message by pressing the AUTO buttons simultaneously to demand highest fan speed, for testing and confirmation.

So, the demand from the refr. overfill is more likely the symptom, rather than the cause, if the fan test action confirms it.

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alpac

Discussion Starter · #23 · Oct 5, 2017

mrboca said:
200 psi is a lot for the low side. works out almost 14 bars which is typically what you see at the HIGH side. That is what happens when the compressor is turned off due to overfilling and when the expansion valve is fully open.

Check your sensor values through the hidden menu on the a/c controller. especially for the refrigerant pressure when the a/c is running (#7). How to do it should be in the stickies (press and hold REST button).

When the high side is so high due to overfilling, the a/c controller asks for maximum cooling to remove heat from the condenser, and to reduce the high side pressure. That is why when you turn on the a/c, you get the maximum airflow demand, which generated the fan fault. When you reduced the pressure, the airflow demand wendt lower, so the fan message did not show up. I guess you can still get the fan message by pressing the AUTO buttons simultaneously to demand highest fan speed, for testing and confirmation.

So, the demand from the refr. overfill is more likely the symptom, rather than the cause, if the fan test action confirms it.

Thanks again mrboca for your always detailled responses and logical explanation

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