Coolant fluid top-off?

[Beetlebug62]

Mine is empty as well. Have you tried checking it when the Coolant is hot?

No, but that's a good idea.

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[JCERRN]

I'm pretty sure there is a low coolant warning. The reservoir has the "Max" fill line, and then I assume the seam is the minimum line.

If its not giving you a low coolant warning, id leave it be, as even opening the reservoir can void the warranty according to what @mongo posted

 

[syburtruck]

Might be worth talking to service. Here's what Grok said. Nice call-out to this group at the bottom by Grok...

Based on reports from Cybertruck owners and Tesla service discussions, an apparently empty coolant reservoir (visible in the frunk after removing the access panel) without any cooling system alerts or errors in service mode is **not fully "working as intended"**, but it's a relatively common observation in early-production vehicles and doesn't always signal an immediate problem. Here's a breakdown of what's happening and what to do:

### Why This Might Occur
- **Reservoir Design and Function**: The coolant reservoir primarily acts as an expansion/overflow tank rather than the main holding area. Most of the coolant circulates in sealed loops through the battery pack, drive units, and other components. If the reservoir looks empty, it could be due to:
- Air pockets or incomplete "burping" of the system during factory filling, causing the level to appear low until the vehicle runs and circulates fluid (especially when hot).
- Minor evaporative loss over time, as Tesla's systems aren't 100% airtight (similar to older models like the Model S).
- Incomplete initial fill at assembly—some owners report service centers finding and correcting this without evidence of leaks.
- **No Alerts Triggered**: Tesla's sensors monitor pressure, flow, and temperature in the active cooling loops, not just the reservoir level. If the system detects adequate circulation (e.g., no overheating or pressure drops), it won't throw a customer-facing warning or service mode error, even if the visual level is low. This threshold-based detection is by design to avoid false positives, but it can lead to situations like this where a visual check reveals an issue before sensors do.
- **Owner Experiences**: Multiple Cybertruck owners have reported the same thing (e.g., at 4,700 miles with no leaks or codes). In one case, the tank was empty but the system ran fine; service topped it off with no further issues. However, a small subset of early deliveries (e.g., under 100 miles) have had actual leaks, sometimes denied warranty coverage by Tesla.

This isn't unique to Cybertruck—similar reports exist for other Teslas, where gradual drops go unalerted until they hit a critical point.

### Is It Safe to Drive?
- Yes, in the short term, if there are truly no alerts, unusual noises (e.g., whining pumps), overheating (e.g., high battery temps on the screen), or performance drops. The system prioritizes battery cooling automatically, even pulling from the low-voltage battery if needed.
- But don't ignore it long-term: Low coolant can eventually stress the battery pack or components, leading to reduced range, inefficient charging, or (rarely) thermal issues.

### What to Do Next
1. **Schedule Tesla Service Immediately**: Use the app to book a thermal system inspection (free under warranty). Techs can perform a vacuum refill, pressure test for leaks, and burp the system—often resolving it without cost. Mention the empty reservoir and lack of alerts for context. Avoid driving far until checked, especially in hot weather or during heavy use.
2. **Do Not Top Off Yourself**: Tesla's Cybertruck Owner's Manual explicitly warns against opening the coolant cap or adding fluid, as it can introduce air/contaminants, void warranty, or cause damage. Only use Tesla-approved coolant (orange OAT/HTF-LS) if directed by service.
3. **Monitor in the Meantime**:
- Check service mode periodically (Controls > Software > Service Mode) for any thermal errors.
- Watch battery temp (via app or screen) during drives/charges—anything consistently over 50°C (122°F) is a red flag.
- Inspect under the vehicle for blue/green puddles after parking (coolant residue).

If it's a factory fill issue (common in new EVs), service should fix it quickly. For peace of mind, join forums like Cybertruck Owners Club to compare notes with others who've seen this. If you have photos of the reservoir or service mode screen, that could help Tesla diagnose remotely.

 

[melb7425]

Got my coolant and battery checked. Turned out my level was underfilled.
Technician Notes:
No issues were found with the vehicle's thermal systems. The diagnosis confirmed the vehicle's systems are functioning correctly.
However fluid level was found to be underfilled, performed vacuum fill of system to top off coolant

 

[hemiarch]

Got my coolant and battery checked. Turned out my level was underfilled.
Technician Notes:
No issues were found with the vehicle's thermal systems. The diagnosis confirmed the vehicle's systems are functioning correctly.
However fluid level was found to be underfilled, performed vacuum fill of system to top off coolant

So where is this tank if I want to check mine? What’s the easiest way to visualize it?

 

[melb7425]

So where is this tank if I want to check mine? What’s the easiest way to visualize it?

There’s no real way to check since the reservoir doesn’t show the true level. Just ask the Service Center.

 

[hemiarch]

There’s no real way to check since the reservoir doesn’t show the true level. Just ask the Service Center.

What should I ask for? Check battery coolant level?

 

[melb7425]

What should I ask for? Check battery coolant level?

What I asked for was a battery check because there was dripping from underneath the truck, which they said it was more likely the AC, but they did a coolant check anyway. You probably get a AC drip too, and just mention your concern.

 

[hemiarch]

What I asked for was a battery check because there was dripping from underneath the truck, which they said it was more likely the AC, but they did a coolant check anyway. You probably get a AC drip too, and just mention your concern.

Very good sneakiness. I like it.

 

[RoboTaxi]

Cool….another thing to look out for

 

[mongo]

Cool….another thing to look out for

The truck will alert you if it is low enough to matter.

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