Coolant Reservoir Does not Drain Back into Radiator (WHY?)

Coolant Reservoir Does not Drain Back into Radiator

The reason why coolant reservoir does not drain back into radiator could be because of a damaged or loose radiator cap, coolant not at a good level, a bad radiator, a hole in the radiator hose, or a cracked or blown head gasket.

The engine cooling system is a vital part of a vehicle; it ensures excessive heat is removed from the engine, maintaining the engine’s temperature so it can work efficiently.

In case you have your reservoir filled but don’t drain back into the radiator, it means there is a problem with some parts of the engine cooling system. Knowing the main reason why yours isn’t draining back into the radiator will help you know how to fix the problem.

Where Is The Coolant Reservoir In My Car?

The coolant reservoir can be found close to the engine compartment, which is on the upper-hand side. It helps the car engine to stay cool. It is essential to have a functioning reservoir to ensure the car doesn’t overheat.

As a car owner, you must be able to identify which is the coolant reservoir and the radiator to detect any errors if there are any.

Does Coolant Overflow Go Back Into Radiator?

Yes, coolant is expected to flow from the reservoir directly into the radiator to ensure the vehicle’s engine works efficiently.

A damaged radiator cap or a clog can cause the coolant from overflowing back into the radiator. The coolant by nature of design is expected to get filled to ensure a cooling process takes place.

While that is done, the radiators’ reservoir takes the overflow contents and houses it until the engine’s temperature cools off.

Reason Why Coolant Reservoir Does not Drain Back into Radiator

The reason why the coolant reservoir does not drain back  into the radiator is because of:

1. A Damaged Radiator Cap

Your coolant reservoir not draining back into the radiator can be a minor problem that wouldn’t need you to get a mechanic to fix it for you.

The problem might simply be loose in the radiator cap or sometimes it can be damaged or broken, which prevents it from its usual function.

A radiator/coolant cap ensures there is access to fluid in a closed system. If the radiator cap is faulty, it is cheap to get, take a picture of it and visit a store to get one.

2. Problem from the Coolant Level

Overflowing sometimes is likely a “YOU” problem. It is important you have the required and proper level of coolant in your vehicle before calling a mechanic to check-in.

This simple trick is likely to get you worked up if you don’t pay attention to it. Ensure you always check to know you have the proper level of coolant in your vehicle.

3. A Radiator Problem

In case you have checked through every petty problem and you can’t find why your coolant reservoir doesn’t drain into a radiator, it can also be that the radiator is faulty and it needs to be replaced. If there is a leak, patch it if possible, but if it is a bigger problem, get it replaced.

4. A Hole in the Hose

If there is some sort of air leak on the coolant overflow hose, will prevent the vacuum to occur thereby preventing your coolant reservoir from draining back into the radiator.

Moreover, you need to ensure that the coolant overflow tube actually reaches the bottom of the coolant overflow tank.

Even if the hose is not leaking, ensure that it is where it is supposed to be. If the hose collapses when the car is shut off, it may cause the reservoir not to drain back to the radiator.

5. A Blown or Cracked Head Gasket

A cracked or blown head gasket can be the reason why the coolant reservoir does not drain back into the radiator. To be check if it is a blown head gasket, follow the steps below:

  • You need to, first of all, fill up the radiator
  • After it is filled, install a cooling system pressure tester
  • Now, pump the cooling system tester up to around 10 psi
  • Start the engine and rev it up and down
  • While revving your engine, you should watch the pressure gauge carefully
  • If the gauge jumps up a little every time you rev the engine, you have a blown or cracked head gasket.

What To Do When Coolant Reservoir Does not drain Back into Radiator?

Fixing this problem is easy if you pay close attention to each detail. As explained earlier, solving an overflowing problem will require you to know what the problem is. The problem explained earlier is the easy to relate to problems that can affect your radiator.

Here are a few solutions to consider.

  • Get a New Radiator Cap: If after investigating and you realize the problem is a leaking radiator cap or a broken cap, you will need to patch it or get it replaced before your coolant can drain back into the radiator. Before you change the cap or have it patched, ensure your engine is cooled down already and you have the best radiator cap fit for your car.
  • Get a Mechanic: When it is a radiator problem, it can be delicate and it will require you to have professional hands to get it all fixed.

It can be a total damaged radiator or a worn-out hose. To get it fixed will require changing a few components of the vehicle and to do that, it will require you to know more than just the basics. Allow your engine to cool off and get a mechanic to check it for you.

Depending on what the problem is, it can be expensive or cheaper than whatever you think of. Get yourself to do it if you can, but if you can, drive your car into a mechanic shop.

Symptoms of a Bad Coolant Reservoir

You should be able to recognize a bad coolant reservoir when you see one. Being able to detect the problem will help you know if a replacement is needed or not.

Here are a few symptoms you should consider.

Car Exhausts Producing White Smoke

When you notice your car is producing white smoke exhaust, see a mechanic quickly because it might be the coolant reservoir is already in an inferior position.

A bad coolant because of the white smoke exhaust can mostly be related to buying a used car. If you are getting a used car, spend more time checking through to ensure you have a good one. I would suggest having a mechanic check the vehicle before you buy it.

Coolant Reservoir Tank Getting Filled

Expected from every coolant reservoir is to have its contents drain back into the reservoir. If it doesn’t drain, it might be a problem you need to pay attention to.

Your coolant reservoir, above all odds, needs to be at a certain level when the engine is hot or cold to ensure the car functions well.

If the overflow isn’t treated, it can cause a blow in the reservoir cap because of a developing pressure inside the cooling system.

How to Identify a Bad Radiator Cap

Being able to detect a problem before it gets too heavy to control is a good thing. There are a few things you need to know to identify this problem, which include:

A Leaking Coolant

There is a break in the hose of a radiator when the radiator cap is stuck. A stuck radiator cap cannot allow fluid to circulate to the expected position in the engine.

This causes a developing pressure in the radiator, which thereafter leads to a leak. To be more cautioned, always do a frequent check to notice any wear and tear or hole in the radiator cap. If you notice any, ensure you have it replaced.

Air in the Cooling System

Imagine having your radiator cap not properly closed or not tight enough. It gives the air a free will to parade around it. We can always find air in the cooling system of an engine when the radiator cap is not properly tightened.

Air in the cooling system isn’t an advantage; in fact, it causes the engine to overheat because of being unable to sustain a constant temperature flow.

Your Engine Overheats

A bad radiator cap can cause your engine to overheat. A bad radiator cap is likely to be punctured or has a few loose ends; it can’t prevent air from having access to the cooling system.

It is important that you have your engine turned off. Allow it to cool before replacing the radiator cap so as not to get you burnt.

Final Thoughts

Coolant reservoir not draining back as it is supposed to be a problem to a car owner. When you notice this is happening, ensure you see a mechanic before it affects the engine completely.

A common symptom is when you have your car overheating. If this happens, ensure your car engine is turned off, allow it to cool, inspect your radiator cap and then have it replaced if it is damaged. Don’t get burnt while doing that.