Low coolant but no code?

[Raroia]

Recently replaced the HEPA filter on my 2017 75D, took a look at the brake fluid reservoir and coolant reservoir while I was in there.

Coolant appears to be below the "MIN" line, but I checked in service mode and there is no warning for low coolant.
Is it normal for this level to be low through evaporative loss over nearly a decade? I realize this is a sealed system and not normally topped up.

I would estimate probably 1 to 2 litres low. No signs of leaks on underbody panels or floor, although I know the 3 way and 4 way valves are a common failure point.

 

[DerbyDave]

It looks like you are at the bottom of the MIN line. I would expect a warning to go off when the coolant is below the MIN line, which isn't very far away. It may be a bit excessive, but normal, and I would consider having Tesla change the coolant if you are going to keep the car. It may be a slow leak in one of the motors (or elsewhere). I wouldn't expect the labor to be more than 1 1/2 hours, and the coolant probably is fairly expensive because there are 11 liters. . Tesla can check if you get the coolant changed.

 

[Raroia]

Thanks for the input. Are motor coolant leaks a common issue in the small drive unit model S? I have never heard of this happening. Not sure if it’s worth replacing all the coolant but probably not a bad idea after such a long time…

 

[DerbyDave]

Leaks in the motor are not a common failure, particularly on the non-performance versions. Usually happens with the large rear motor, if at all. There could just be a very slow leak somewhere like the chiller or some other part the coolant goes through. I don't think it is normal for the coolant to be as low as yours, so I would just keep an eye on it if it continues to drop and the warning appears in the next 6 months or so. Opening the cap will void any warranty, but you may already be beyond that. Link to checking the rear motor for leaks:

 

[ucmndd]

Just top it up and don’t think twice unless it runs low again in short order. Coolant has water in it - some will evaporate over 7 years. That reservoir certainly isn’t 100% air tight.

 

[livesmith]

Thanks for the input. Are motor coolant leaks a common issue in the small drive unit model S? I have never heard of this happening. Not sure if it’s worth replacing all the coolant but probably not a bad idea after such a long time…

Shouldn't be any coolant leaks in the motors of a dual, non performance model since the small drive units don't have coolant lines...

 

[DerbyDave]

Shouldn't be any coolant leaks in the motors of a dual, non performance model since the small drive units don't have coolant lines...

I have never looked, but according to this removal procedure from Fix Your Tesla for the small motor, it says to disconnect coolant hoses.

 

[livesmith]

That's interesting. I find the same mention in Tesla's online service manuals.
I specifically picked a non-p, D model because of the SDU's. Everything I've read says the LDU's have coolant running through the motor and a seal on the shaft inevitably goes bad then you just just to fix and wait till next time.
And that the SDU only uses oil so even if the seal leaks it's not a big deal.

So I'm wondering if the SDU does still have coolant but only running to the inverter or maybe outside of the motor itself?

 

[PCMc]

Your car is not too dissimilar vintage to my mid-2016 (June 2016) build MS90D. about 18 months ago I noticed one day a very small stain on my garage floor under the front of the car. Kept an eye open and never saw a lot. Now for most of the past few years I was on international assignment and my car would sit for 3ish months at a time, then get driven for about 3-4 weeks when I'd be back in US. So not a typical daily driving like most. But about 6 months later, I came back home to find I had a low coolant warning.

Now I never had checked the reservoir myself, so I can't tell you where my coolant level was at in relationship to yours.

I had debated just refilling it, and letting it go, but given I was about to head off for a few long range trips (1,000+ miles over a few days) decided not worth pressing my luck, was able to quickly get it into my local service center, and ended up being the 3-way coolant radiator bypass valve that needed to be replaced.

I know you said you checked under the car for any signs of wetness. From my experience I think any leak at the 3-way valve may start as very small leak and depending upon your operating profile there may not be a lot of obvious signs for a bit. If I was in your shoes I'd probably take the monitor route, which sounds likely the road you're headed down from the other comments.

Enjoy your car.

 

[PaulF2020]

Leaks in the motor are not a common failure, particularly on the non-performance versions. Usually happens with the large rear motor, if at all. There could just be a very slow leak somewhere like the chiller or some other part the coolant goes through. I don't think it is normal for the coolant to be as low as yours, so I would just keep an eye on it if it continues to drop and the warning appears in the next 6 months or so. Opening the cap will void any warranty, but you may already be beyond that. Link to checking the rear motor for leaks:

How's opening a coolant cap voiding the warranty? Any links ?

 

[DerbyDave]

Excerpts from Manual:
"Caution: The Battery requires no owner maintenance. Do not remove the coolant filler cap and do not add fluid. If the instrument panel warns you that the fluid level is low, contact Tesla immediately.

Note: Any damage caused by opening the Battery coolant reservoir is excluded from the warranty.

BUT DO NOT REMOVE THE FILLER CAP AND DO NOT ADD FLUID. Doing so can result in damage not covered by the warranty.

Under no circumstances should you remove the filler cap and/or add coolant."

 

[PaulF2020]

Excerpts from Manual:
"Caution: The Battery requires no owner maintenance. Do not remove the coolant filler cap and do not add fluid. If the instrument panel warns you that the fluid level is low, contact Tesla immediately.

Note: Any damage caused by opening the Battery coolant reservoir is excluded from the warranty.

BUT DO NOT REMOVE THE FILLER CAP AND DO NOT ADD FLUID. Doing so can result in damage not covered by the warranty.

Under no circumstances should you remove the filler cap and/or add coolant."

Interesting, how do they know coolant is being added ?

 

[DerbyDave]

Interesting, how do they know coolant is being added ?

I assume they have the history of the coolant level reporting low. If it reported it was low, and the coolant is not low anymore when at Tesla Service, they will know.

 

[Raroia]

Update on this, still no low coolant code in service mode. Have not added any.

 

[ClipperS]

I just got this code. Anybody know what the costs is before I schedule a service? I probably need to replace the filters too.

2016.5 Model S

 

[PCMc]

I just got this code. Anybody know what the costs is before I schedule a service? I probably need to replace the filters too.

2016.5 Model S
View attachment 994698

It's impossible to accurately estimate the cost without knowing the source of the leak. I went through this about a year ago. My initial estimate on my mid-2016 build MS90D was about $930 but was based upon needing to replace multiple multi-way valves in the system which could all be source for a leak. Now it turned out that my issue was with the 3-way radiator by-pass valve, none of the other possible sources, and total repair cost was right at $455 ($165 in parts, $280 in labor, and about $10 is local sales tax).

Now if the leak was due to actually the radiator being damaged/leaking, I could envision it being much more expensive, but without diagnosing why you are low on coolant it is a total guess.

 

[ClipperS]

It's impossible to accurately estimate the cost without knowing the source of the leak. I went through this about a year ago. My initial estimate on my mid-2016 build MS90D was about $930 but was based upon needing to replace multiple multi-way valves in the system which could all be source for a leak. Now it turned out that my issue was with the 3-way radiator by-pass valve, none of the other possible sources, and total repair cost was right at $455 ($165 in parts, $280 in labor, and about $10 is local sales tax).

Now if the leak was due to actually the radiator being damaged/leaking, I could envision it being much more expensive, but without diagnosing why you are low on coolant it is a total guess.

Thanks. Will open a service request. I checked the garage floor and no leaks that I can see. Hopefully it's nothing big.

 

[PCMc]

Thanks. Will open a service request. I checked the garage floor and no leaks that I can see. Hopefully it's nothing big.

Mine was very minor. I notice really small spot on the floor under the front center of the car a time or two, but them much of the rest of the time if I looked really closely, was more a dried up stain. Almost like what you might have from say AC condensate on occassion. I actually had noticed that a few months ahead of when I got the low coolant warning, so either it was a really small, really slow leak over time, or the 3-way bypass valve would leak more while I was driving and not so much while parked. You're case may be totally different, but that's some of my experience.

 

[ClipperS]

Update: took it in and no leaks were found. Coolant level was slightly below minimum. They topped it off. Costs $223

 

[Raroia]

I guess this supports the theory of slow evaporation over time, obviously they may have missed the leak, but I think it is a valid assumption