Does your engine seem to be running hotter than usual? Is the temperature gauge climbing higher than normal even after you’ve been driving for a while? These could be signs that your vehicle’s coolant isn’t circulating properly.
As a driver, it’s important to understand coolant circulation and know what to do if issues arise.
In this guide, we’ll explain the circulation process, common causes of coolant not circulating, symptoms to watch out for, and specific tests and fixes you can perform yourself to troubleshoot your cooling system.
Why is the coolant not circulating?
A common cause that your coolant is not circulating is the problem with the water pump, which is vital for pushing coolant through the radiator and block. The pump can fail due to normal wear, or if the belt driving it slips or breaks. A faulty thermostat may also prevent coolant from re-entering the engine as needed.
Additionally, the buildup of mineral deposits in the system from old coolant can clog radiator passages and restrict flow over time.
Addressing these issues helps ensure coolant moves freely to keep your car engine from overheating. But you need to confirm the cause behind this fault of coolant blocking.
11 Causes of coolant not circulating
Here are some common reasons of coolant is not circulating in your engine block.
Faulty radiator
A faulty radiator can likewise disrupt coolant flow through the system as one of the primary components responsible for transferring heat from the engine, damage or deterioration within the radiator itself can serve to impede circulation.
Cracked or warped radiator cores and end tanks may develop small leaks, preventing normal suction back into the engine.
Additionally, a buildup of mineral deposits or debris lodged inside radiator passages may restrict coolant flow.
Clogged radiator hose
Another possible cause of reduced coolant circulation stems from obstructed radiator hoses.
The rubber hoses that carry coolant to the radiator can sometimes get clogged. Over time, minerals and gunk from the coolant stick to the inside of the hoses.
If too much buildup happens, it makes the opening in the hose smaller. This makes it hard for the coolant to flow through easily.
The hoses can also get weak and crack from being old. Cracks and a smaller opening cause problems too.
When the hoses are clogged or damaged like this, less coolant can get to the radiator. That means less cooling for the engine. So it’s important to check the hoses sometimes and clean them out if they get icky inside.
Air in the System
Trapped air bubbles increase coolant viscosity and reduce its volume for heat transfer. Air pockets also cause cavitation as the temperature changes, undermining smooth flow. With air present, coolant cannot efficiently circulate.
Damaged Head Gasket
The head gasket seals the gap between the engine block and the cylinder head. When it blows, combustion gases and coolant can mix instead of remaining separate.
This violation of the cooling system boundary completely disrupts the dedicated coolant circuit. Coolant can no longer flow as intended, with sections allowing crossover between incompatible fluids.
Proper circulation is randomly interrupted. Without the head gasket maintaining circuit integrity, temperature regulation is compromised.
Plugged Water Jackets
The engine block and cylinder head feature a series of precisely machined internal channels called water jackets. Their intricate design is meant to ensure coolant washes directly against all hot internal surfaces.
Over many years, contaminants like sludge and scale accumulate in these narrow passages. The buildup can gradually restrict flow through the jackets.
In severe cases of complete blockage, nearby components are effectively isolated from the cooling loop. This stranded fluid is then useless for heat removal. The overall volumes and routing of coolant are disrupted.
Malfunctioning water pump
One of the most common reasons the coolant may stop moving is if the water pump isn’t working correctly. The water pump is a very important part that helps push the coolant around the cooling system. But with time, the pump can wear out or break down.
When this happens, it can’t efficiently move the coolant where it needs to go anymore.
Other issues like a bad belt that powers the pump can cause similar troubles. So checking that the water pump is in good condition is smart.
Replacing it if needed ensures the coolant continues circulating smoothly to keep the engine from overheating.
Thermostat failure
The thermostat also plays a key role in regulating coolant flow. It controls when the coolant circulates more rapidly to heat the engine or more slowly to maintain temperature.
Over time or due to mineral deposits, the thermostat may begin to stick open or closed. If open, it won’t restrict flow like intended, allowing coolant to bypass the radiator too easily without properly cooling down.
If stuck closed, it prevents coolant from reentering the engine block after warming up. Either issue disrupts the intended cycle. As such, checking that the thermostat opens and closes responsively is vital for proper circulation.
Replacing it can remedy thermostat-related circulation problems.
Leaking coolant
Another factor that can negatively impact coolant circulation is the presence of leaks within the system. When coolant gradually leaks out through cracks in hoses or radiator caps, seams around the water pump, or cracks in the radiator itself, less fluid remains in the engine to be circulated.
Over time, low coolant levels caused by leaks inhibit the water pump’s ability to efficiently move fluid. The engine also loses its cooling protection and is at higher risk of overheating.
Identifying any leaks through visual inspection or pressure testing allows leaks to be sealed before complete loss of coolant circulation arises from decreasing fluid volume within the system.
Timing Belt Issues
Timing belt issues can inhibit coolant circulation if the belt breaks or skips teeth. This causes the camshaft to lose synchrony with the crank, potentially bending valves. Damaged valves may then obstruct water jacket passages in the cylinder head, blocking coolant flow. Improper valve timing from a slipped belt can also allow combustion gases to track into the coolant circuit.
Damaged Fins
Damaged fins reduce the radiator’s ability to reject heat to the air. This causes higher radiator pressure and longer thermostat opening times. Both add strain to the water pump, undermining effective circulation.
Malfunctioning Passenger’s Heater
A malfunctioning passenger heater core can cause coolant circulation issues by increasing flow resistance if clogged with debris, allowing air into the system via leaks which compromises heat transfer ability, or disrupting balanced coolant loop flow if the heater control valve or thermostat fails. All of these effects strain the water pump and negatively influence total system circulation.
How to diagnose coolant circulation issues
Check the Water Pump
Remove any belts connecting to the water pump and spin the pump shaft by hand, looking for resistance or grinding that indicates wear. Vibration or noise while running could mean the bearing is going bad, reducing fluid movement.
Inspect the Thermostat
Remove the thermostat and place it in hot water, checking that it fully opens and closes at the proper temperatures. If stuck open or closed, it can prevent efficient circulation. Replace if not working correctly.
Flush the Cooling System
Draining and thoroughly flushing out the coolant system helps remove mineral deposits or contamination that causes internal clogging over time. This improves fluid flow throughout the engine and radiator.
Inspect Hoses and Connections
Examine all coolant hoses for cracks, bulging, stiffness, or leaks which can block, flow. Gentthatueeze each hose looking for obstructions. Hoses that are cracked or severely stiff should be replaced to allow proper circulation from the water pump to the radiator and back. Keeping the hoses flexible and intact is key to smooth circulation.
Bleed Air from the System
After filling the coolant reservoir and replacing any hoses or components, bleed any trapped air to ensure full circulation. With the radiator cap off, start the engine and have an assistant gently squeeze each hose sequentially as bubbles emerge.
Trapped air pockets can interfere with fluid flow, allowing hot spots to form. Repeating this process is important until only a steady stream of coolant flows from each hose with no bubbles. Run the engine for a few minutes with the radiator cap on to circulate any remaining small air bubbles
Air will compromise circulation if it compresses and blocks passages. Taking the time to properly bleed the system diagnosis any issues related to trapped air inhibiting an efficient cool flow from the pump to the radiator and back.the
How to fix coolant circulation issues?
Here are the most effective methods to solve coolant circulation problems:
Flush and refill the cooling system properly
Coolant circulation issues can be a sign that your vehicle needs a coolant system flush. Over time, mineral deposits and corrosion can build up in the radiator, engine blocks, and hoses. This residue clogs passages and reduces coolant flow through the entire system.
A depleted or contaminated coolant mixture also loses its ability to protect against corrosion and overheating. Poor circulation is one symptom that indicates it’s time for a cooling system service to remove these obstructions.
Here is our complete guide on the step-by-step method to do coolant flushing both by DIY and mechanic.
Performing a full cooling system flush is a very effective way to address poor circulation caused by internal contamination buildup over time. It returns-optimized heat returns-optimized flow throughout the entire cooling circuit.
Repair or replacement of a faulty radiator
Repair or replacement of a faulty radiator can be a necessary step to fix coolant circulation issues that may be causing overheating problems.
A radiator is a key component in the cooling system that allows coolant to efficiently transfer heat from the engine before recirculating. Over time, cracks, corrosion, or clogged radiator fins reduce its ability to dissipate heat from the fluid. When a radiator starts to fail, it inhibits proper coolant circulation through the entire system.
Some signs of a faulty radiator that can lead to coolant circulation issues and overheating include:
– Coolant leaks from cracks in the plastic end tanks or welds.
– Clogged or damaged fins restricting airflow through the core.
– Fluid overheating and boiling inside during engine use.
– Long warm-up times before the thermostat opens fully.
To repair the problem, the radiator often needs professional repair by welding cracks or complete replacement if damage is extensive. A new OEM radiator or high-quality aftermarket part restores the cooling system’s prime heat exchanger.
So radiator repair/replacement is an important potential fix for coolant flow and overheating vehicle issues related to the core cooling component’s performance degradation over time.
Cleaning or replacement of clogged radiator hoses
As radiator hoses age, they can deteriorate both internally and externally in ways that impact circulation. Over time, hoses become more brittle and inflexible.
Some signs that radiator hoses may be causing circulation problems include:
- Hoses that feel hard and stiff rather than pliable.
- Bulging/swelling of hoses under pressure.
- Leaks appear from cracks in the rubber.
- Coolant flow restrictions are noticeable during a flush
Installing new radiator hoses restores a clear, flexible pathway for coolant movement between components. This improves circulation capabilities by eliminating internal restrictions from aging original hoses.
Replacing clogged hoses as a cooling system service returns more efficient heat transfer throughout the entire circuit.
Repairing or replacing a malfunctioning water pump
The water pump is responsible for actively circulating coolant throughout the entire cooling system. If the pump is failing in any way, it directly inhibits proper flow.
Repair involves rebuilding the pump with new seals and bushings if wear is moderate. For severe damage, the best option is replacement with a new or remanufactured pump.
Installation requires proper belt tension and coolant refilling. Bleeding air from the system is critical.
An operating leak test before starting the engine verifies proper installation. Once running, the temperature should stabilize in the normal range.
Repairing or swapping out a faulty water pump restores the critical flow-inducing component. flow-inducing coolant is circulating efficiently through the entire cooling system.
Fixing or replacing a failed thermostat
Here are the steps to fix or replace a failed thermostat as a solution to coolant circulation issues:
- A thermostat controls coolant flow between the engine and the radiator. If it gets stuck open or closed, it affects circulation.
- Symptoms of a bad thermostat include slow war warm-overheating, and rough idling when cold.
- Replacements use the same housing size and opening temperature as the original. Remanufactured units provide OE quality.
- Drain some coolant and locate housing, typically between the radiator and engine. Remove housing bolts or clips.
- Extract the thermostat and inspect the condition. Replace if damaged, corroded, or parts broken off.
- Clean housing thoroughly before installing the new thermostat.
- Place stat in housing, ensuring it moves freely without binding.
- Reinstall housing with new gasket, tightening bolts evenly in a criss-cross pattern.
- Refill coolant and bleed air from the system burping lines and radiator.
- Monitor the temperature gauge for normal operation once warm to confirm the repair.
A new OE thermostat allows precise coolant flow control restoring optimal circulation for efficient engine temperature regulation.
Effects of coolant not circulating in the engine
Here are some potential risks of engine damage if coolant circulation doesn’t happen:
- Overheatingdoesn’tthout circulation to transfer heat away from the engine to the radiator, the engine will quickly overheat as hot coolant sits in the block. This can cause head gasket damage or warped/cracked heads.
- Hot spots – Areas of the engine like cylinders and valves may heat up unevenly if coolant isn’t flowing past them. This can cause warping, cracking, or failure of components.
- Corrosion – Deposits from non-circulating coolant will corrode internal passages and water jackets over time if left untreated.
- Cavitation – Air trapped in the coolant can cause cavitation pitting as it turns to steam in hot areas and implodes. This damages cylinder walls and heads.
- Coolant breakdown – Non-circulating coolant can rapidly break down its rust and scale inhibitors, reducing its ability to protect the metal cooling system.
- Preventative deposit buildup – Lack of coolant flow means it can’t wash away normal combustion byproducts that form deposits if left.
- Overheating damage – Components may seize or crack from sustained high operating temperatures without sufficient cooling. This can lead to a head gasket which can engine a replacement.
Proper coolant circulation is critical for efficient heat removal and extending engine life. Lack of flow needs to be addressed before overheating or corrosion damage occurs.
Conclusion
Common causes include damaged head gaskets, timing belt issues, clogged water jackets, failed water pumps, and damaged radiator fins. These inhibit proper coolant flow through the system.
Fixes involve repairs like head gasket replacement, timing component refresh, water jacket cleaning, pump swaps, and radiator repairs/replacement. Maintaining circulation prevents overheating and extends engine life.
Addressing root causes ensures heat is efficiently transferred away from critical parts through a balanced coolant flow.
Hi, Michael Williams here. I have always loved everything with an engine. After earning my degree in automotive engineering, I spent 5 years testing vehicles for a major manufacturer in Illinois. Now I am using my technical skills to review the latest models online and help others troubleshoot their engine problems with effective solutions.