Transmission Stop Leak | Good or Bad?


Ignoring a leak could be a dangerous and expensive mistake. A faulty transmission can even cause an engine to overheat or rattle and not distribute its energy correctly.

A transmission stop leak could help you seal a minor fluid escape depending on why and where it’s leaking. In some cases, it can be like placing a band-aid on a bullet wound. Using a stop leak product could save you from an immediate repair, but you may also be postponing a matter that you shouldn’t ignore.

In this article, I will clarify several of your questions related to the transmission stop leak and how this system could help the performance of your vehicle.

Is Transmission Stop Leak Safe?

Transmission stop leak is safe to use. However, it cannot help your transmission when there is considerable damage in its many different parts. It can work if applied in moderation and understanding that it is not a permanent solution. It will rely on the size and location of the gap in the transmission.

The key is moderation because even the best transmission seal product cannot target the source of the issue separately, meaning that it runs through all system areas. The seal will cover all the places, broken or not, with a material that stops the leakage but can swell other regions. The swelling is a particular guarantee after repeated, unsuccessful uses.

As a consequence, excellent seals can lose their levels and begin overflowing and causing leakage. No matter if you happen to know precisely where your transmission is leaking from and to what degree. Overusing this product can have serious side effects on the other components of your gearbox that do not need any mending.

Some transmission stop seal products claim they can go as far as sealing your busted pan gasket, while others claim to work better on smaller fissures.

Is Stop Leak Bad For The Cooling System?

In some cases, a stop leak may cause damage to the cooling system. Excessive use of this tool can clog the fluid system from the radiator to the water pump, engine, and thermostat. This clogging can also damage the engine as it may not achieve the proper level of cooling.

For all these reasons, experts do not recommend using the stop leak continuously as it directly affects the operating capacity of the cooling system.

Does Stop Leak Work?

To get the maximum possible benefit from stop leaks and to say that they work, we must take into account the following:

  • A leak in the radiator, no matter how small, is always an indication of a significant problem.
  • A stop leak is only a temporary solution, not a definitive one.
  • To get the best performance from the stop leak, we must follow the manufacturer’s instructions to the letter,
  • The effectiveness of the stop leak will also depend on the size of the leak. The smaller the leak, the more successful the use of this additive will be.

How Long Does Stop Leak Take To Work?

It depends on the brand of the stop leak. You must let the stop seal circulate your vehicle on its way to its transmission, and the time it takes to work differs effectively. Some of the best brands suggest up to two days of driving to allow the product to operate correctly. Others state that only 30 minutes would suffice for the product to bid before recommending multiple applications.

We must stay away from products that require multiple and repeated applications. By then, you’ve possibly wasted the additive along with transmission fluid. Not to mention that you may have seriously compromised the lifespan of your transmission and its parts.

You need to find a stop leak that will work faster requiring the least amount of miles, before seeing results.

Look for the fastest working stop seal product you can find at the store. We should not overuse this product nor have sure-fire expectations from it. It all depends on your vehicle’s reaction, which is directly proportional to its received damage.

What Is A Good Transmission Stop Leak?

The best transmission stop leaks are:

Nevertheless, if you have a more severe issue at hand, you might be speeding up your gearbox’s demise, all the while thinking you’ve solved the problem. A minor gap could be sealed and perhaps never repaired, but it could also disintegrate a month later and send you into the body shop once and for all.

You must be alert on how your vehicle reacts to the leak stop because assuming it will just work could have terrible consequences.

Will Stop Leak Fix A Blown Head Gasket?

Stop leak will not fix a blown head gasket. It could seal a minor fissure in your pan gasket, but this is different when dealing with a blown head gasket. It will likely need to be replaced. Have it looked at by a certified mechanic to find out for sure.

There is some anecdotal evidence that stop leak can fix the issue, at least for a while. However, there is only one way to find out, and that is by trying it. Many brands claim they can tackle this issue for you permanently, which could be the case.

As I said before, stop leaks cover all transmission areas, so your blown gasket will surely get a dose. Still, you may be damaging other areas that do not need sealing with repeated uses.

Where Is The Leak?

Engine Transmission

Four consequent seals compose our car transmission: the valve body seal, transmission pan seal, drive shaft seal, and input shaft seal. But, there is also a fifth band member, if you will, and that is the pan gasket, which sits between the entire transmission housing and the transmission pan. It is there to block any leakage from the latter.

The transmission pan is the part that is subject to the most wear and tear because it has a significant exposition to debris, poorly built roads, and high temperatures. Time itself is racing against this little fellow here. It can require maintenance somewhere between every 30,000 to 60,000 miles despite being used with extreme care.

Road conditions and driving affect it, so if a rock on the road were to loosen up a screw or puncture the pan itself, it would create a gap that would allow the fluid to exit. Losing fluid causes a domino effect throughout the other components.

Let us also add that transmissions are not unlike your brakes and coolant. They also have lines that transport the fluid around to keep everything properly lubricated.

Every vein system like this one also requires a pump to maintain the pressure and propel the fluid where it needs to be so the pump could also be behind the leakage. It is also known as the torque pump or torque converter. These are the types of components where your stop leak product could become even less effective.

What Other Ways Can I Check My Transmission Fluid Level?

Start by checking the transmission fluid dipstick, ensuring your fluid is on the level and its color is not brown yet. We are looking for a pink and nearly clear complexion in the liquid oil. If we see it be below level, we can add some but be cautious of overfilling it and triggering a different set of unfortunate events.

Finding that dreaded puddle beneath your car is the easiest symptom to notice, but it is far from the only one. If you hear clunking sounds from your vehicle, grinding gears, feel vibrations from the engine, or a burning smell creeps up on you, then the transmission could be low in fluids. Noises in neutral, delayed acceleration, and extreme heat from the transmission often accompany these symptoms.

Some older cars don’t have dipsticks. In the case of such transmissions, servicing would be the only option since you would have no way to access the gearbox to supply it or check its oil level.

Final Thoughts

Stop leak can fix your issue, but that could come at the expense of other parts. It is important that we use a brand that acts rapidly. For that purpose, I recommend Blue Devil Transmission Sealer.

Check your fluid levels periodically to detect these issues early and have a chance to act effectively. In the case of a large leak, this product may not do all that much to help you. It is best to take it into the shop and save yourself the stress of waiting to see if the car will stop leaking.

I hope this article has been helpful. Thanks for reading!

For more, check out What Makes My Engine Skip or Misfire When Cold?.

Jim James

Hey, I'm Jim and the author of this website. I have always been interested in survival, fishing, camping, and anything in nature. In fact, while growing up I spent more time on the water than on land! I am also a best-selling author and have a degree in History, Anthropology, and Music. I hope you find value in the articles on this website. Feel free to contact me if you have any questions or input!

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