986 coolant light blinking, temp at bottom of scale

[garyman42]

My 2001 Boxster S just started blinking the coolant light, and the temp gauge reads bottom of scale, and the coolant indicator light is on.

I checked the coolant level in the rear trunk, and it is fine.

What's up?

[pk2]

You probably have a bad connection or disconnected wire from your sensor (on the cap I think ) or the float is stuck. pk

[N41EF]

The blinking light is a low coolant level. If the level is fine it's a level sender issue. It isn't on the cap, it's on the bottom of the resevoir. The parts diagram show what it looks like, and the fact that most carry it, makes it seem that they fail. I'd check the wiring to it, then the sensor itself.

[1schoir]

Here is a photo of the coolant level sensor switch, located under the coolant reservoir:

Also, keep in mind that the same warning light can also flash to indicate a fault in the engine compartment blower fan.

Regards, Maurice.

[garyman42]

Thanks for the responses. I'll look into the sensor connection this evening.

I noticed the blinking coolant indicator when I started the car to head home from work.

The engine should have been cool, and I should not have needed the fans.

TEMPERATURE INDICATOR:

So... any idea about the temp indicator reading at the bottom of the scale? That is definitely

not right. Also, the amber coolant idiot light is on.

I am still hoping this is a minor concern!

Cheers.

Edited November 9, 2010 by garyman42

[Richard Hamilton]

Four functions of the coolant warning light:

1. Engine coolant level too low

— light flashes slowly (0.5 Hz)

2. Engine compartment temperature too high

— light flashes slowly (0.5 Hz) (engine compartment blower might be faulty)

3. Engine coolant temperature too high

— light is lit; pointer on the right

4. Temperature sensor at water outlet faulty

— light flashes rapidly (1 Hz); pointer on the right

Note

The temperature warning in point three is indicated if the conditions "engine coolant temperature too high" and "engine coolant level too low" are present simultaneously 

(1Hz = 1 flash per second.  0.5Hz = 2 seconds per flash)

So it might be the temperature sensor is faulty (if the light is rapid flashing).

[garyman42]

Four functions of the coolant warning light:

1. Engine coolant level too low

— light flashes slowly (0.5 Hz)

2. Engine compartment temperature too high

— light flashes slowly (0.5 Hz) (engine compartment blower might be faulty)

3. Engine coolant temperature too high

— light is lit; pointer on the right

4. Temperature sensor at water outlet faulty

— light flashes rapidly (1 Hz); pointer on the right

Note

The temperature warning in point three is indicated if the conditions "engine coolant temperature too high" and "engine coolant level too low" are present simultaneously

(1Hz = 1 flash per second. 0.5Hz = 2 seconds per flash)

So it might be the temperature sensor is faulty (if the light is rapid flashing).

Hi Richard,

From my memory, the flash speed was about 1 Hz. That would be consistent with the faulty water outlet temp sensor. Seems

that would also be consistent with temp indicator at bottom of scale.

Would that also be consistent with amber coolant idiot light on the row of indicators below instrument cluster illuminated?

Thanks,

--Gary

[Richard Hamilton]

I think it would. A diagnostic check should show what's wrong if it is the temperature sensor which has failed.

[garyman42]

I think it would. A diagnostic check should show what's wrong if it is the temperature sensor which has failed.

Thanks Richard. It makes sense that a faulty sensor would drive the behavior of all three symptoms.

Is this a shop fix, or is this something I can do? Any instructions and illustrations on how to

replace the sensor?

Thanks,

--Gary

[Richard Hamilton]

The workshop manual makes it sound easy enough:

19 78 19 Removing and installing coolant temperature sensor

The place of installation is at the left front in the direction of travel, in the area of cylinder 4.

Removal

1. Remove rear underside panel.

2. Pull off electrical plug connection. Undo temperature sensor (wrench size 22).

Installation

1. Check sealing ring and use a KD (service) sealing ring if necessary.

Note

As standard, the temperature sensor has a captive sealing ring.

Tightening torque 25 ± 5 Nm (18 ± 3.5 ftlb.)

I would be tempted to get a diagnostic check done first though. Don't want to be barking up the wrong tree.

Edited November 10, 2010 by Richard Hamilton

[garyman42]

The workshop manual makes it sound easy enough:

19 78 19 Removing and installing coolant temperature sensor

The place of installation is at the left front in the direction of travel, in the area of cylinder 4.

Removal

1. Remove rear underside panel.

2. Pull off electrical plug connection. Undo temperature sensor (wrench size 22).

Installation

1. Check sealing ring and use a KD (service) sealing ring if necessary.

Note

As standard, the temperature sensor has a captive sealing ring.

Tightening torque 25 ± 5 Nm (18 ± 3.5 ftlb.)

I would be tempted to get a diagnostic check done first though. Don't want to be barking up the wrong tree.

Thanks again, Richard. I started it up again last night. Confirmed 1Hz blink rate on the temp indicator.

The amber light on the cluster I thought was a coolant indicator is the check engine light.

I'll get her checked out at a shop.

Cheers,

--Gary

[garyman42]

Final analysis - Broken wire at the coolant temperature sensor. All is well after the wire break was repaired. :)

Thanks for your help.

[Richard Hamilton]

Good result! Must be worth a contribution! <_<

[AlanOulette]

My coolant light on my '99 Boxster started flashing last fall. Turning the car off and back on alleviated the problem. I check the coolant level, and it appeared to be just a smidge above Min level.

This spring, I added about 3 cups of coolant (mixed 60-40), to bring the reservoir level to about mid level. The light hasn't flashed since.

I'll have to keep an eye on it...not sure why that small amount of coolant is missing. It's almost due for a coolant flush anyway.

[ReyGabriel]

check again at broad daylight your coolant level...its "hard" to see the level...the max should only be about half an inch to the top...if you can see the arrow pointing upward as the max..then see the line.....if this dont work. ...you have to check the temp sensor underneath the coolant container..

[budcamp1]

Anyone know if you have to drain the coolant and remove the coolant reservoir to be able to replace the coolant level sensor?

Step by step on replacing this sensor would be more helpful.

[JFP in PA]

Anyone know if you have to drain the coolant and remove the coolant reservoir to be able to replace the coolant level sensor?

Step by step on replacing this sensor would be more helpful

Depending upon your year and model, you may not have to drain anything to change the level sensor (it is on the outside of the tank, yellow arrow):

[budcamp1]

Thank you for the reply. That's what I was thinking but last thing I want is Coolant all over the trunk. 98 Boxster - is the year.

Drain or not to Drain that is the question?

[JFP in PA]

Thank you for the reply. That's what I was thinking but last thing I want is Coolant all over the trunk. 98 Boxster - is the year.

Drain or not to Drain that is the question?

If all you are going to do is change the level sensor, no, you do not need to drain it..............