Losing Coolant But No Visible Leaks? (Here’s What to Do)

Last Updated on July 12, 2021

While you should check your fluid levels every time you fill-up the gas tank, most people leave it to the mechanics. It’s a huge mistake. Just because you don’t see any fluids on the ground doesn’t mean that everything is working as it should. 

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There are multiple places your coolant could be ending up, and if you aren’t keeping an eye out for the symptoms, you might end up with an engine that is constantly overheating

But where is that coolant going, and what can you do about it? Keep reading, and we’ll break it all down for you. 

Common Causes of Losing Coolant (But Don’t See a Leak)

Whether you drive a Subaru or a Lexus, your car needs antifreeze. So, when your coolant is disappearing, you need to track down the cause, and you need to do it quickly.

Below are the three most common reasons your coolant reservoir is empty time and time again.

#1 – Head Gasket

bad head gasket

It’s likely the first thing a mechanic will tell you the problem is. Head gaskets are notorious for leaking, but it leaks everything right into the combustion chamber instead of the ground. While this won’t leave any visible signs on the ground, it will be pretty straightforward if you take a quick look at the exhaust.

If you have a blown head gasket, you’ll have a ton of white smoke coming from the exhaust. This is because unlike gas, which leaves mostly clear or black exhaust fumes, coolant burns white, no matter what color of coolant your car uses.

#2 – Radiator Cap

bad radiator cap symptoms

If you’ve ruled out an internal leak, that means your engine is burning the coolant somewhere else. The most common place is the radiator cap. Radiator caps hold the pressure inside the system, but if it’s not sealing properly, then some hyper pressurized coolant will escape in the form of steam.

Once your engine is warmed up, you’ll be able to tell if steam is escaping from your radiator cap by merely taking a quick look at it. You shouldn’t see any steam or smoke coming from the cap, and if you do, then you’ll need to replace it.

See Also: Can You Put Water in a Radiator in an Emergency? (It Depends on the Type)

#3 – Leak Onto the Engine Block

engine block damage

While a leak onto the engine block will typically leave a puddle under your vehicle at some point, if it’s leaking directly onto the top of your engine and puddling up until the engine warms up, it might burn the coolant off before it can reach the ground.

While it’s rare, it can happen, and just like a bad radiator cap, a tell-tale sign is a cloud of white smoke coming from the engine bay while the engine is running.

Step-By-Step Troubleshooting Guide

When it comes to disappearing coolant, finding the culprit is often the easy part. If you follow our step-by-step guide below, you should be able to identify the problem without ever needing to take it to a shop!

#1 – Check the Exhaust

white smoke blowing from exhaust

It’s the most common reason that coolant burns off. It’s also one of the most straightforward problems to spot. All you need to do is look at the exhaust smoke while the engine is running. If there is excessive white smoke, then you have a blown head gasket.

However, just because there is some white smoke doesn’t mean that it’s a head gasket. It needs to be an excessive amount.

During colder weather, your vehicle will have more smoke coming out of the exhaust then during the warmer months. This is entirely normal.

#2 – Check the Oil

check engine oil

If you’ve looked at the exhaust smoke and still can’t tell if you have a blown head gasket or not, then take a look at the oil. Simply pull the dipstick and see if the oil level is rising over time.

When you get coolant in the combustion chamber, it doesn’t always get completely burned off. If it’s left in there, it’s only a matter of time before it works past the O-rings and finds its way into the oil pan.

If you’re an experienced mechanic, you can tell by merely smelling and feeling the oil, but novices often have to keep an eye on the level to see if it’s rising.  

If you do have coolant in your oil, you likely have a blown head gasket, and you need to have a mechanic take a look at your engine.

#3 – Check for Engine Smoke

smoke from car engine

If your engine is smoking, that’s a sign of a problem. Try and track down the smoke, but if it’s white, then it’s coolant.

If you don’t have a visible leak underneath your engine, then you should take a look at your radiator cap or anywhere along the top or sides of your engine. If you find any antifreeze, then you’ve located your problem!

 

12 thoughts on “Losing Coolant But No Visible Leaks? (Here’s What to Do)”

    • Yes, this is definitely possible. I actually had to look this term up because I know a welch plug as a “freeze plug”. Both names refer to the same part.

      Reply
  1. Just checked radiator cap and hose no leak cap is on properly, put coolint in 2 days later all gone can’t seem to find the problem
    Help

    Reply
    • Try performing a leak down test. You may be losing coolant internally, through a head gasket leak for instance.

      Sometimes coolant leaks are hard to find. They make dye you can put in your coolant that shows up under UV light to make detecting leaks easier.

      Reply
  2. Any ideas plz I have had problem with overheating for a while now and can’t find why. Have had head skimmed gasket replaced water pump timing belt thermostat housing replaced new rad cap within last month n went on 40 mile journey n lost all water gone on small runs n no problems never had so much trouble or work done on a car as this one don’t no what to do next

    Reply
    • Can you tell if the coolant is leaking internally or externally? When you say you had the head skimmed, do you mean it was decked as part of a head gasket replacement?

      What is the year, make, and model?

      Reply
  3. I have a 2007 Jeep Commando had the water pump done new radiator new thermostat in my cooling system still be running out and don’t see kno leak underneath

    Reply
  4. I have a Jeep Wrangler 4.0. It apparently has a very small coolant leak. I can smell it but cannot find it even with a pressure tester. The coolant level stays the same. With the engine off the smell is strongest around the radiator. No visible leaks. Any ideas? Should I try the UV leak detector fluid?

    Reply
    • UV leak detector might not be a bad idea. Did you check the coolant level in the radiator and the overflow reservoir?

      If you smell coolant and the level doesn’t change, perhaps you had a leak in the past and you’re smelling the leftover spill? You might be able to see some white streaks coming off of some of the cooling components. This may indicate the presence of a current or past leak in that area.

      Reply

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