How to Check Engine Coolant Level and Condition
Check the level in the reservoir, read the freeze point with a gauge, and pressure-check the system for leaks.
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The reservoir sits low on a cold morning and the temperature gauge has been climbing further than usual, and the first thing to check is the coolant, not the thermostat. How to check engine coolant comes down to the level in the reservoir and the condition of the fluid, and the tools in this guide cover the checks that follow.
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Block Tester Head Gasket Combustion Leak Test Kit
A combustion leak check kit with fluid that turns from blue to yellow when a leak is present, with enough fluid for 16 checks.
Pros
- Fluid turns blue to yellow when a combustion leak is present
- Enough fluid for 16 checks
- Limited lifetime warranty
- Made in USA for over 45 years
Cons
- Checks combustion leaks only: it does not read the freeze point
- No pressure-check function for finding coolant leaks
- No battery or freeze point scale is stated
- Fluid is spent after 16 checks, with no refill stated
OMT Master Coolant Pressure Tester Kit
A 34 pc coolant pressure-check kit with 23 adapters, a vacuum pump and hose clamp pliers for finding leaks and air-free refills.
Pros
- 34 pcs with 23 adapters for wide coverage
- Vacuum pump and purge and refill tool included
- Aluminum alloy, nylon, rubber and brass build
- 1 year warranty, per the spec table
Cons
- No freeze point reading: it pressure-checks only
- No combustion leak check function
- No battery check function
- No coolant condition reading beyond leak checks
HyVisTek 5-in-1 Antifreeze Refractometer for DEF
A 5-in-1 refractometer that reads glycol freeze point, DEF urea, battery specific gravity and washer fluid, with automatic temperature compensation.
Pros
- Reads freeze point from -60°F to 32°F
- 5-in-1: coolant, DEF, battery and washer fluid
- Automatic temperature compensation
- DEF scale from 30% to 35% with 0.2% accuracy
Cons
- No warranty term is stated
- No storage case is stated in the listing
- Reads fluid samples only: no level or pressure check
- Specific gravity scale is for rechargeable batteries only
Antifreeze Tester, Coolant Test Strips
A dial-type antifreeze gauge that reads the freeze point from -45°F to 13°F, with a hose that draws fluid from the reservoir.
Pros
- Dial reads from -45°F to 13°F in Fahrenheit and Celsius
- Pocket-sized: 3.9 in body with a 5.3 in hose
- One-hand operation with no professional tools needed
- Silicone bulb and hose with a rugged PC body
Cons
- No warranty term is stated
- Title mentions strips for checking coolant, but the bullets describe a dial gauge
- Spec table lists the color as Volkswagen
- No combustion leak or pressure check function
How to check engine coolant: start with the level
Look at the reservoir first. The level shows whether the system has lost coolant, and a low level points to a leak somewhere in the system. The OMT kit pressure-checks the radiator, expansion tank, head gasket, heater core, water pump and hoses, so a leak shows up before it strands the car. Check the manual for the right coolant for the car.
Check the freeze point with a gauge
The level is only half the check. The freeze point shows whether the coolant still protects the engine in the cold, and a gauge reads it from a small sample. The TAVWILLANG dial gauge reads from -45°F to 13°F: insert the hose into the coolant reservoir, draw fluid to the marked line, and read the freezing point directly from the dial. The HyVisTek refractometer reads the freezing point of glycol-based coolants from -60°F to 32°F, and it also reads DEF urea, battery fluid specific gravity and washer fluid.
Pressure-check the system for leaks
The OMT kit is a 34 pc set with 23 adapters, a vacuum pump, hose clamp pliers, a purge and refill tool, a probe thermometer, a wrench, EU and US air joints, O-rings and hoses. It spots leaks in the radiator, expansion tank, head gasket, heater core, water pump and hoses, and the vacuum refill leaves the system free of air pockets. The adapters are color-coded, and everything packs into a molded case.
Check for a combustion leak
A combustion leak lets exhaust gas into the coolant, and the Block kit catches it with a color change. The fluid turns from blue to yellow when a combustion leak is present, and the kit gives a result in seconds for leaks caused by a blown head gasket, cracked head or block, pulled bolts or studs, and warped sealing surfaces. It works with gasoline, diesel, propane, natural gas and alternative fuel engines with closed cooling systems, and it includes enough fluid for 16 checks.
Engine coolant tools for the job: the gear in this guide
The tools below cover the checks in this guide, from the freeze point reading to the pressure check and the combustion leak check.
Use rated jack stands on solid ground, wear eye protection with power and air tools, keep fuel-burning equipment out of a closed garage, and follow the manual for every tool. Read our Safety Disclaimer.
FAQ: garage tools
How do I check the coolant level?
Look at the reservoir: the level shows whether the system has lost coolant. A low level points to a leak, and the OMT kit pressure-checks the radiator, expansion tank, head gasket, heater core, water pump and hoses.
How do I check the coolant freeze point?
Draw a small sample and read it with a gauge. The TAVWILLANG dial gauge reads from -45°F to 13°F, and the HyVisTek refractometer reads glycol coolants from -60°F to 32°F.
What does a combustion leak check show?
It shows whether combustion gas is leaking into the coolant. The Block fluid turns from blue to yellow when a combustion leak is present, and the kit gives a result in seconds.
Can one tool check the battery and the coolant?
The TAVWILLANG listing describes a battery hydrometer for 6V, 12V and 24V systems, and the HyVisTek refractometer has a specific gravity scale from 1.10 to 1.40 for rechargeable batteries.
How many combustion leak checks does one kit do?
The Block listing includes enough fluid for 16 checks.
Related: the best engine coolant gauge picks, the refractometer vs coolant gauge comparison, our best coolant vacuum refill kit picks, the how to drain engine coolant guide and our engine and shop equipment hub.
