High Coolant Temp Flashing

[odys996]

The last week the high coolant temp light has been flashing a couple of times. Engine temp has been normal. I have stopped the car and when I start up the problem is gone.

When the lights came on I had just been driving for 10 minutes and not hard at all. The level on the expansion tank has been normal.

I have checked for any trouble codes with Digimoto software but there is none.

What can cause this problem, what should I check?

[Loren]

Most likely the sensor in the tank has gone bad.

[number9ine]

The last week the high coolant temp light has been flashing a couple of times. Engine temp has been normal. I have stopped the car and when I start up the problem is gone.

When the lights came on I had just been driving for 10 minutes and not hard at all. The level on the expansion tank has been normal.

I have checked for any trouble codes with Digimoto software but there is none.

What can cause this problem, what should I check?

If you're checking your level after just a few minutes you may try removing, examining and re-seating the expansion tank cap. If there's a leak in the cap seal it could explain the flashing light (which is a low coolant level warning), and after a short drive the water level may return to normal before your visual inspection. Loren's probably right that the sensor in the tank is faulty, but there's the odd chance that it's a leak of some sort and a longer drive may result in an expansion tank overflow and overheat.

Mark

[odys996]

The last week the high coolant temp light has been flashing a couple of times. Engine temp has been normal. I have stopped the car and when I start up the problem is gone.

When the lights came on I had just been driving for 10 minutes and not hard at all. The level on the expansion tank has been normal.

I have checked for any trouble codes with Digimoto software but there is none.

What can cause this problem, what should I check?

If you're checking your level after just a few minutes you may try removing, examining and re-seating the expansion tank cap. If there's a leak in the cap seal it could explain the flashing light (which is a low coolant level warning), and after a short drive the water level may return to normal before your visual inspection. Loren's probably right that the sensor in the tank is faulty, but there's the odd chance that it's a leak of some sort and a longer drive may result in an expansion tank overflow and overheat.

Mark

The level in the tank is close to MAX when the engine is cold.

Both times when I have had the warning during driving, I have stopped the car immediately and checked the tank.

The level has then been low (under low level) but when I open the cap carefully (due to vacum in the system) it then raises up to MAX again. I have then started the engine and been driving for hours without any new warnings.

[judgejon]

The last week the high coolant temp light has been flashing a couple of times. Engine temp has been normal. I have stopped the car and when I start up the problem is gone.

When the lights came on I had just been driving for 10 minutes and not hard at all. The level on the expansion tank has been normal.

I have checked for any trouble codes with Digimoto software but there is none.

What can cause this problem, what should I check?

If you're checking your level after just a few minutes you may try removing, examining and re-seating the expansion tank cap. If there's a leak in the cap seal it could explain the flashing light (which is a low coolant level warning), and after a short drive the water level may return to normal before your visual inspection. Loren's probably right that the sensor in the tank is faulty, but there's the odd chance that it's a leak of some sort and a longer drive may result in an expansion tank overflow and overheat.

Mark

The level in the tank is close to MAX when the engine is cold.

Both times when I have had the warning during driving, I have stopped the car immediately and checked the tank.

The level has then been low (under low level) but when I open the cap carefully (due to vacum in the system) it then raises up to MAX again. I have then started the engine and been driving for hours without any new warnings.

were the radiators flushed recently? wonder if there is some air circulating in the system that might affect the sensor operation?

[scottiemac]

This happened to me about 2 years ago. I was driving it pretty hard on some mountain roads (followed very closely by a guy from my office in a Maserati Spyder). The light came on and stayed on (flashing) but the temperature never moved. I watched the gauge for a while and kept my eye in the mirror for any signs of a leak (i.e. the guy in the Maser turning on his wipers!). After a while I had a chance to pull over and stop. I shut the engine off and restarted it immediately. The light didn't come on and I haven't had a repeat of the incident.

My theory (as a sh*thouse engineer) is there may have been a bit of air in the system that got dislodged by the high rpm's and high cornering forces. It found its way back to the tank and caused the sensor to activate.

[juniinc]

by-pass the level sensor,,,easiest way to find out.

[odys996]

While I was driving a couple of days ago, the Check engine light came on. When I came home I ran a diagnostic and it turned out with DTC: P1123 and pending DTC: P1125.

I also monitored the sensors at idle speed, and to me it looks like the MAF is a bit high. One of the O2 sensor is also a bit low (?)

MAF = 6,65 g/s

RPM = 818

O2 sensor 1 bank 1 = 0.155V, bank 2 = 0.055V

O2 sensor 2 bank 1 = 0.440V, bank 2 = 0,435V

Today I disconnected the battery to reset the CEL, and I monitored the sensors at idle speed again. Now the MAF has normal readings and the car has been running for hours without the CEL (but I guess it`ll be back soner or later...)

MAF = 4,37 g/s

RPM = 695-720

O2 sensor 1 bank 1 = 0.765V, bank 2 = 0.075

O2 sensor 2 bank 1 = 0,625V, bank 2 = 0,625

For me it looks like O2 sensor 1 bank 2 voltage is a bit low, should I replace it?

I have also searched in the forum and there are a lot of pages regarding the CEL, and P1123/P1125. To me it looks like that in most of the cases replacing the MAF is the answer. Is this the solution for me as well?

Is MAF and O2 sensor just “plug and play”, or do I have to calibrate it/do it a service center?