5 Critical Volvo D13 Coolant Level Sensor Problems & Solutions!

Seeing a low coolant warning on your Volvo D13—but the tank’s full? You’re not alone. Let’s fix this common sensor glitch for good.

If you drive a Volvo D13, you’ve likely seen a low coolant warning pop up for no reason. It’s a common issue. The tank is full, but the dash says otherwise.

This often points to Volvo D13 coolant level sensor problems. A bad sensor, float, or wiring glitch can trigger these alerts. And when that happens, it’s both confusing and annoying.

These coolant sensor failures can hit different model years—like 2013, 2016, 2017, and 2018 Volvo D13s. I’ve seen this a lot while working on trucks.

In this guide, I’ll explain what’s really going on. You’ll learn what causes the problem, how to fix it, and even how to try a Volvo D13 coolant level sensor bypass if needed.

If you’re tired of chasing false alarms, you’re in the right place. Let’s get to the bottom of your Volvo D13 coolant issues—once and for all.

What Is a Volvo D13 Coolant Level Sensor Problem?

This issue shows up when your dash says “Low Coolant” but your tank is full.

I’ve run into this many times on Volvo D13 trucks. The coolant level sensor sends bad info, and it tricks the system. It thinks there’s not enough coolant, even when the tank is topped off.

Here’s what usually causes the problem:

• Bad sensor: The part itself fails. It happens with age or heat.
• Stuck float: The float inside the tank gets stuck. The sensor reads it wrong.
• Wiring issue: A loose plug or broken wire sends false signals.
• Dirty sensor: Gunk builds up inside the tank and messes with the reading.

The warning light on your dash pops up and stays there. It’s annoying, and it can cause shutdowns if the truck thinks coolant is really low.

Some years—like 2013, 2016, 2017, and 2018 Volvo D13s—seem to get this more than others. I’ve seen the most sensor issues on those in the shop.

This kind of false alert is more than just a small glitch. If you ignore it too long, it can lead to bigger problems, like an engine derate or a roadside breakdown.

How Does the Volvo D13 Coolant Level Sensor Work?

The coolant level sensor checks how full your coolant tank is. If the level drops, it tells your dash to light up a warning.

On a Volvo D13, the sensor is inside the surge tank. It reads a small float inside. When the tank is full, the float sits high. If the coolant drops, the float drops too.

That’s when the sensor sends a “low coolant” signal.

But here’s the catch—this part doesn’t read the fluid. It tracks the float. If the float sticks, or the sensor fails, you’ll get false alerts. Key facts of Volvo D13 Coolant Level Sensor Problems:

• Type: Magnetic or reed switch
• Reads: Float position
• Talks to: The truck’s ECM
• Fails when: The float sticks or the sensor wears out

When that happens, your dash might show a warning even if the tank is full. I’ve seen this issue a lot. It’s a small thing, but it causes big headaches.

5 Most Common Volvo D13 Coolant Level Sensor Problems & Solutions

Over the years working on Volvo D13 engines, I’ve run into coolant level sensor issues more times than I can count.

Whether you’re a truck owner trying to avoid a roadside breakdown or a fleet manager juggling maintenance schedules, these sensor hiccups can be a real pain.

Let’s break down the five most common problems I’ve seen, why they happen, and—most importantly—how to fix them without wasting time or money.

1. False Low Coolant Warning – Even When Full

There’s nothing more frustrating than seeing a low coolant alert when you just topped it off. I’ve had this pop up on the dash of more than one 2016 Volvo D13, and it’s usually the same culprit—a faulty magnetic float inside the coolant reservoir.

Reason:
The magnetic float inside the tank gets stuck or loses magnetism over time, tricking the sensor into thinking levels are low.

Solution:

• First, recalibrate the tank using diagnostic software if available.
• If recalibration doesn’t work, you’ll likely need to replace the tank altogether.
• I recommend checking the float before ordering any parts.

2. Intermittent Warnings During Wet Weather

I’ve seen this issue spike in rainy seasons. Drivers get intermittent coolant warnings when driving in wet conditions, especially on older 2013 and 2017 models.

Reason:
Moisture sneaks into the wiring harness or connectors, shorting out the signal intermittently.

Solution:

• Unplug the connector and inspect for any signs of water or corrosion.
• Dry the contacts carefully. Use electrical contact cleaner if needed.
• Apply dielectric grease and seal with waterproof heat-shrink tubing to keep future moisture out.

3. Sensor Warning After Replacement or Repairs

Funny enough, I’ve had sensors throw warnings after they were replaced. You’d think putting in a new part would fix the problem—but not always.

Reason:
The ECM (Engine Control Module) might not sync up properly with the new sensor. Sometimes the probe gets damaged during install too.

Solution:

• Double-check the wiring continuity using a multimeter.
• If wiring checks out, have the ECM scanned for any pending errors or mismatched sensor inputs.
• Re-learn procedures may be needed using Volvo’s diagnostic tool.

4. Complete Sensor Failure (No Signal)

When the sensor just stops responding completely, it’s usually a sign it’s lived out its useful life. I’ve pulled out sensors with cracked housings and soaked probes more times than I care to admit.

Reason:
Over time, the sensor gets worn out or the internal probe cracks due to heat cycles and vibration.

Solution:

• Replace the sensor with a genuine or high-quality aftermarket option.
• If it’s built into the coolant tank unit, you’ll need to replace the whole tank.
• Don’t forget to bleed the coolant system after replacement.

5. Sensor Stuck or Sluggish Response

Ever had a sensor that seems to lag or get “stuck” reading one level? I’ve cracked open coolant tanks and found the float caked in grime, coolant sludge, or even bits of gasket.

Reason:
Debris inside the tank gums up the sensor float or track.

Solution:

• Drain the coolant and remove the tank if possible.
• Clean the interior thoroughly and check the sensor track for damage.
• Run a coolant flush to prevent future buildup.

Year-by-Year Breakdown of Volvo D13 Coolant Sensor Issues

Over the years, I’ve noticed a pattern when it comes to coolant sensor problems on Volvo D13 engines. Certain model years seem to have their own quirks, and I’ve seen these same issues echoed in service bulletins, repair forums, and even among drivers at truck stops.

If you’re troubleshooting a problem on your D13, this breakdown can help you pinpoint what’s most likely going wrong—based on the year your truck rolled off the line.

2013 Volvo D13

This was a big year for sensor complaints—especially during wet weather.

• Rain-related wiring issues were common. I’ve seen warnings triggered just from moisture under the hood.
• The main issue? Weak insulation and unsealed plugs on the harness near the coolant tank.
• I’ve even seen forum threads where techs had to redo the entire harness section just to keep the signal stable.

Tip: If your 2013 model throws codes during rainy days, check for moisture ingress near the tank connector.

2016 Volvo D13

Ah, the year of mystery warnings. I’ve had customers replace sensors—only to still get the low coolant alert.

• Persistent false alerts even after putting in a new sensor or tank.
• In most cases, the root cause turned out to be ECM communication failures.
• The ECM either couldn’t “see” the sensor or was reading it incorrectly.

Real Talk: I once spent half a day chasing a sensor issue that turned out to be a pinched wire upstream from the ECM. Lesson learned—don’t skip a full continuity check.

2017 Volvo D13

This one’s sneaky. At first glance, everything works fine… until the engine cools overnight.

• Cold-start coolant reading errors were a thing. In the morning, trucks would alert for low coolant—then be fine by noon.
• Turned out to be sensor location issues or the float sticking slightly during warmup.
• I’ve had to clean the tank or shift the sensor mount slightly to fix it.

Note: If your truck cries wolf on cold mornings, look at the float movement or check if the tank is partially sludged up.

2018 Volvo D13

This year, one issue topped the list—and I saw it a lot.

• The faulty magnetic float inside the tank was hands-down the most common failure point.
• Replacing the sensor alone didn’t cut it. In most cases, the best fix was swapping out the full tank.

Pro Tip: If you’re chasing warning lights on a 2018 model and the coolant level is fine, don’t waste time—just replace the tank with a new float unit.

Volvo D13 Coolant Level Sensor Location

So, where exactly is the coolant level sensor on a Volvo D13? I get this question all the time—especially when folks want to check it without tearing into the engine.

The sensor sits inside the coolant reservoir, usually mounted on the side of the surge tank. It’s a slim probe that sticks into the tank. Most of the time, it’s held in place by a clip or threaded mount.

To access it:

• Let the engine cool. Never open a hot coolant tank.
• Locate the coolant reservoir on the passenger side, near the firewall.
• Look for a small wire harness going into the tank—that’s your sensor lead.
• Gently unplug it before inspecting the sensor itself.

Tip: If you’re planning to test or replace it, always disconnect the battery first to avoid shorting anything.

How Long Does the Volvo D13 Coolant Level Sensor Last?

I get asked this a lot—“How long does the sensor actually last?” And honestly, it depends. But here’s the general rule I go by:

• Typical lifespan: Somewhere between 50,000 to 100,000 miles.
• Some sensors hold out longer, but I’ve seen many go bad before 75k if the conditions are rough.

Now, let’s talk about what affects that lifespan.

What Wears It Out?

There are a few main things that beat these sensors down over time:

• Vibration: All that shaking under the hood? Yeah, it can loosen connections and cause the sensor to misread.
• Heat cycles: The constant heating and cooling weakens the internals and the float inside the tank.
• Coolant quality: Dirty or wrong-type coolant can gum up the float or corrode the sensor tips.

I’ve pulled tanks before where the coolant was so sludgy the float couldn’t even move. No wonder the sensor kept screaming “low coolant.”

How to Help It Last Longer

If you want to stretch the life of your sensor (and your sanity), here’s what I recommend:

• Use OEM coolant that meets Volvo’s spec. Don’t cheap out—it matters.
• Keep the coolant tank clean. Flush it every time you swap coolant. Gunk buildup is a silent killer.
• Check for signs of leaks or moisture near the harness plug. If you see green crusty residue—clean it and seal it.

Quick Resources:

Here are a few links you might find handy:

Note: If you go aftermarket, make sure it’s SAE J2099 and ISO 22241 compliant. Otherwise, you’re asking for more trouble.

Preventive Maintenance Tips

Now here’s the part that saves you money before things go wrong.

I’ve seen too many trucks come in just because of something that could’ve been fixed with a $2 hose clamp or 5 minutes of preventive care. So here’s what I always tell my customers:

Quick Weekly & Biweekly Checks

• Look inside the coolant tank every 2 weeks. Just a quick glance can catch issues early—discoloration, low levels, or floating debris.
• Check for oily buildup. If you see it, flush and refill with the right coolant ASAP.

Keep It Clean and Sealed

• Use a funnel when topping off to avoid spills or contamination.
• Make sure the tank cap seals properly. A loose or cracked cap can cause slow leaks or let in dirt.

Protect the Wiring

This one’s huge. Exposed or frayed wires can cause sensor failures even if the sensor is fine.

• Wrap wires in convoluted tubing to shield from heat and rubbing.
• Apply dielectric grease to the connector pins. It keeps out moisture and improves contact.

Use Quality Parts

I’ve had better luck sticking to OEM sensors. Some aftermarket ones are decent, but I always look for brands that match OEM specs and have solid reviews.

Cost of Repairs or Replacement

Let’s talk dollars—because that low coolant warning light can quickly turn into a high-dollar repair if you’re not careful. I’ve helped out on more than a few Volvo D13 coolant sensor replacements, and here’s what you can expect when it comes to cost.

How Much Does a Coolant Level Sensor Cost?

The coolant sensor itself for a Volvo D13 engine usually runs between $40 and $120, depending on where you buy it. If you go OEM (which I recommend if you want fewer headaches later), expect to be closer to the higher end. Aftermarket sensors are cheaper, but they can be hit or miss in quality.

Labor and Diagnostic Fees

Now, if you’re not doing the job yourself, you’ll need to factor in labor costs and possibly a diagnostic fee. Here’s a rough idea of what that looks like:

• Labor: $100 to $180, depending on shop rates and how buried the sensor is in your setup.
• Diagnostic scan: $75 to $150, if they need to pull codes or confirm the sensor is the real issue.

Some shops will waive the diagnostic fee if you have them do the repair. Others won’t. Always ask.

Cost-Saving Tips if You’re Going DIY

If you’re comfortable turning a wrench—and you’ve got a bit of patience—you can save a lot by tackling the job yourself. Here’s how I’ve cut costs for myself and others:

• Buy the part online from a trusted seller. Look for verified OEM numbers and reviews from other Volvo owners.
• Use a scan tool to confirm the sensor is the problem before replacing it. You don’t want to chase a false lead.
• Follow a repair video or step-by-step guide if you’re unsure. YouTube has some great walkthroughs for the Volvo D13.

Also, always inspect the wiring harness. Sometimes it’s not the sensor—it’s just a loose or corroded connector. Cleaning that up might save you the cost of a new part altogether.

Frequently Asked Questions (FAQ)

Can I drive with a bad coolant level sensor on my Volvo D13?

Yes, you can usually drive with a faulty coolant level sensor, but I wouldn’t recommend it for long. The sensor’s job is to warn you about low coolant levels, which can lead to serious engine damage from overheating. If the sensor is giving false readings, you might ignore a genuinely low coolant level. It’s best to get it checked and fixed as soon as possible to avoid potential problems down the road.

How do I know if my coolant level sensor is bad?

Common signs of a bad coolant level sensor include getting frequent low coolant warnings even when the coolant level is fine, or the warning light not coming on even when the coolant is clearly low. Sometimes, the light might flicker or come on intermittently. A proper diagnostic check can confirm if the sensor is the culprit.

Is bypassing the coolant level sensor safe long term?

Absolutely not. Bypassing the coolant level sensor might seem like a quick fix for a persistent warning light, but it completely eliminates the safety net it provides. You’ll lose the ability to get an early warning about low coolant, which could result in severe engine damage. It’s always better to address the underlying issue and replace the faulty sensor.

What does a magnetic float do in the coolant tank?

In many coolant tanks, including those in Volvo D13 systems, the coolant level sensor often uses a magnetic float. This float sits on top of the coolant. As the coolant level drops, the float goes down with it. When it reaches a certain low point, the magnet inside the float triggers the sensor, which then sends a signal to your truck’s dashboard to warn you about the low coolant level.

How much does it cost to replace a Volvo D13 coolant sensor?

The cost to replace a Volvo D13 coolant level sensor can vary depending on several factors, such as the specific model year of your truck, where you get the work done (dealership vs. independent shop), and the cost of the sensor itself. Generally, you can expect to pay somewhere in the range of $[Estimate Price Range – e.g., $100-$300] for the part and labor. It’s always a good idea to get quotes from a few different places to compare.

Final Thoughts

From my experience wrenching on these Volvo D13 engines, I’ve seen my fair share of coolant level sensor issues. More often than not, those pesky false low coolant warnings boil down to a simple problem with the magnetic float getting stuck or some moisture creeping into the sensor’s electrical connections.

Remember, keeping up with regular maintenance on your Volvo truck is the best way to avoid these kinds of headaches in the first place. Checking your coolant level regularly and ensuring the system is properly sealed can go a long way.

I hope this guide has been helpful. If you’ve experienced coolant level sensor problems with your Volvo D13, or if you have any questions specific to your truck’s model year, feel free to leave a comment below. I’m always happy to share what I’ve learned over the years.