So ever since my AC compressor was changed I’ve had coolant low warning light issues. First time after about 20mins the expansion tank was empty. That happened again next day so I took it in for a pressure test. No leakage under pressure but they swapped the cap (and replaced the coolant as I requested)

This time 2 days of trouble free driving and then the low coolant warning light again. Nursed it to the shop expecting another empty expansion tank who said there was hardly any coolant loss and probably caused when they removed the cap. Shop suggested faulty coolant level sensor but would have to replace the complete “bottle” as they called it as the sensor is inside. I asked if the sensor could be tested and they said no. So my question is can the sensor be electrically tested say with a multimeter?
Thanks
Alan

 

Maybe. Yes, you could check the resistance values with and without fluid in the tank, but what are the correct values? If the values (with and without) are the same, then it’s a a bad sensor.
But you seem to have an intermittent failure, and that would be hard to test. Is it temperature, operating time, a combination?
The shop’s perspective is that swapping in a known good ‘bottle’ is the easiest solution (if that sensor is really the problem).

 

So it just got weird again. When the warning light came on and I nursed it to the shop they said hardly any fluid was missing. So I just drove home from the shop (about 20 mins urban driving) and no warning light but just checked under the hood and the fluid has dropped a significant amount! I can see the exposed plastic parts inside the expansion tank now! See pics

 

Seems to be airlocks, faulty pressure caps and leaking fluid season.

Have you read the Engine Cooling section of the workshop manual:
"The expansion tank provides the following functions: Service fill.
 Coolant expansion during warm-up.
 Air separation during operation.
 System pressurization by the filler cap.

The expansion tank has an air space of approximately 0.5 liter (1.06 US pints), above the MAX level, to allow for coolant expansion."

I think there's a simple explanation for this... the system was checked at your garage while the engine was warm.
If you overfill it and go for a run (as per the workshop manual, engine rpm above 2000 for 8 minutes), with the heater on, does the level eventually come to equilibrium at the full mark? If you loosen the bleed screw and allow some air out while the engine is warm that may allow some fluid to enter some vacancies.

Please do not misinterpret me!! This is not a way to circumvent the proper procedure of filling the coolant using the vacuum system or the raising of the reservoir approach. But I have had success with this manner on the LR.

And fwiw, there are 2 reservoirs that periodically get changed on my vehicle; the coolant reservoir and the power steering reservoir.

 

Doesn’t look like the sensor is your problem.

 

LOL, @kj07xk , we are playing tag.

@alanroberts50 , some shops are not aware of the fact that the reservoir on your car needs to be raised 50mm during the proper fill process. My process above takes this into account but you will need to perform this a couple of times.

 

But! And thanks for all the suggestions, why would the low coolant warning come on while driving if the coolant wasn’t low when I drove it into the shop? It’s a big LR shop and some Jags too. It’s mid summer here so I’m guessing they didn’t have the heater running when filling so I will tell them to do that. But I’m still wondering about that sensor. Do I just run the AC at max heat or is there a way to operate heater without using the AC?

 

The coolant is red if I can get it locally here in SA what brand and is it already diluted to correct strength?

 

I don't understand. Are you not in LA?

Richard

 

1. Did you read the filling instructions post.
2. Yes, run your system at a high internal temperature. "Econo" mode switches off the airco... but why would you do that? It also acts as a dehumidifier.
3. Switches wear out. But the container is marginally opaque for a reason...
4. Any WSS M97B44-D compliant fluid. Mixed to 50%. (Check out the local ford dealer)

 

South Africa

 

Thanks for the Forf tip I do have one close by

 

I think I’m making progress hopefully. I’m pretty sure each time the shop refilled or topped off the coolant they did it with the heater off! The AC was set to max cold each time I took it in and was the same when I got it back. So either they didn’t have the heat on when they drained and refilled it or they are incredibly service oriented and reset the AC when they returned it.

i found the correct coolant, parked on a decent slope, put heater on max and slightly overfilled using about 1ltr total Drove for 8 mins at 2k rpm and so far so good. It’s been so unpredictable lately so I will need a couple of weeks to begin to trust it again.

 

Glad you’re finally on the right path.

Things left to do one last time;
1. when the engine is cold, top it off again, marginally above full.
2. when the engine is warm/hot, slightly loosen the air bleed screw and lightly release “some” air. Don’t forget to retighten.
3. do that drive again, with the heat on for a short bit.
4. after the drive and with the engine cold, check the level.

As for your comment of trust… you are driving a 12 y.o. GT. It is necessary to check about the car for wear and tear more frequently.