Car Transmissions

Transmission Cooler Lines Leaking At Radiator: What You Need To Know?

Mike Cross
Updated Aug 25, 2021

One of the critical components of your car is the transmission. It is probably the second most important thing after the engine because if the transmission isn’t working right, then the vehicle can not be driven.

One problem that can happen with the transmission is that it might start leaking fluid, and this can occur in a few spots, but for transmission fluid cooler it will most likely happen at the radiator.

In this article, we will explain why your transmission might start leaking at the cooler lines, how to diagnose it, and also how to fix it. Read on to learn everything you need to know about your transmission cooler lines leaking at the radiator.

Transmission Cooler Lines Leaking At Radiator: What You Need To Know?

What is transmission cooler lines?

Before going into details, we will briefly cover what the transmission cooler lines and radiator are. That way you can locate them easier when looking at your car.

The transmission is responsible for switching the gears of your car, and the transmission fluid goes thru it to keep the gears and moving parts cool and lubricated.

The cooler lines are the tubes or hoses that come off the transmission and into the radiator. The radiator is the ruffle looking thing usually right behind the grill of your car and will have fans attached to it.

It is where the coolant goes into to get cooled off before going back into the different parts of your vehicle. The coolant has to be cool to cool the other components of your car.

How to know if coolant lines are leaking?

So, now that you have a better understanding of what the radiator and transmission so we can move onto diagnosing if you have a transmission cooler line leak.

The first thing that you might notice is that you have wet spots under your car when you move it. This could be a lot of different things though, and your transmission fluid leaking is only one of them.

It could also be oil, condensation, or another liquid. That is why it isn’t a surefire way to know that it is your transmission cooler lines leaking, but it is an important thing to pay attention to, so you can know if you need to look deeper or not.

If you do see liquid under your car, then you need to investigate and see where it is coming from.

One way to investigate is to open up the hood and look under it. Visually inspect all the hoses and see if you can see any liquid coming from any of the connections.

How to know if coolant lines are leaking
How to know if coolant lines are leaking?

Most of the time the problem or leak will happen at a connection, but sometimes the hose itself will get damaged. To see if it is transmission fluid leaking you can check all the tubes coming from the transmission.

You can also check the transmission fluid level on some vehicles with a dipstick. If your transmission fluid is low, then it is a sign that it might be leaking. Sometimes you won’t have a dipstick though, but can still look at the transmission fluid level in the reservoir and see if it is low there.

You might also be able to feel if your transmission fluid is getting low while driving the vehicle or hear if it is. This is because if your transmission coolant is getting low, then the transmission will most likely start shifting harder.

The lower it gets, the worse the shifting will get. If you drive the car regularly, then you should be able to feel or hear this. If you think your transmission is shifting funny, then it is a good idea to check the fluid.

The last thing that might help you know if your coolant lines are leaking is if the engine coolant is starting to get a reddish color. That is because the transmission fluid could be mixing with the engine coolant and that will lead to a color change. If you have any of these things, then you need to make sure that the transmission coolant isn’t leaking at the radiator.

How to fix Transmission Line Leak at radiator

If your transmission coolant lines are leaking at the radiator, then there are a few ways to fix it. If the lines are old, then you might need to replace the whole line. This is pretty simple. All you do is remove the old line and put the new one in.

This should solve the problem if the old line was leaking from damage. Another way to fix it is to put sealant on the end of the line where it connects. There are a variety of sealants on the market, but you want to make sure you get one specific to transmission coolant lines.

That is beaches you don’t want to damage more things by fixing the problem, and you need a sealant that can handle high heat.

If you don’t want to put a liquid sealant or can’t find one that is working for you, then you can also try adaptors. Some vehicles are prone to having transmission coolant lines that leak, and they have made adaptors to fix the problem.

You remove the line, put the adaptor on, and then put the hose back on. The adaptor is designed to fit the gap and seal it up. You can also use tape on the lines to help seal them up. A Teflon tape that can handle high heat is your best option if you want to go the tape route. There are a lot of ways to fix coolant line leaks at the radiator though, and most are pretty cost effective.

Just replaced the radiator.

One of the most common times to get a transmission coolant leak at the radiator is when you just replaced the radiator. This is because the hoses may not have gotten connected correctly.

When replacing the transmission coolant line or reattaching it make sure that you attach it right. Don’t cross thread it, which is easily done, because that will cause a leak. Also, if you have just reattached the hose and have a leak, then one last solution before anything else is to loosen it back up and jiggle it some and then tighten it back down again.

The problem might be something as simple as the hose not being seated right and the connection not being tight.

You just need replaced the radiator
You just need replaced the radiator


It is important to try not ever to drive your vehicle with low transmission fluid because it will cause significant damage to the transmission. That is why it is essential to stay on top of potential problems before they become more significant.

If you see liquid under your car, then you need to figure out what is causing it and fix the issue. If it is a transmission coolant leak at the radiator, then it is an easy fix. The way you can figure out if that is the issue is to check your transmissions fluid level, pay attention to the shifting, and check the coolant lines going into the radiator.

If you notice a leak, you can replace the line if it is damaged or add sealant or tape at the connection to tighten it up if the line is fine. Now you know how to find, and fix a transmission coolant line leak at the radiator.

Mike Cross
Life is too short to drive with stock audio

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2 comments on “Transmission Cooler Lines Leaking At Radiator: What You Need To Know?”

  1. I just replaced my radiator and the connection for the transmission line at the radiator is a little different so it doesn't tighten all the way down it's a 2002 Ford explorer where can I get an adapter that you speak of

  2. Hi,
    I just replaced the radiator and when I filled up coolant the coolant started leaking from transmission tube joint on radiator. I have been told by my friend that there leaks transmission oil usually. Can you give me an advice?

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