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Can I Use Rubber Hose for Transmission Cooling Lines?

Vehicles are one of the most useful objects that we use in our daily lives. Some regard cars as a second home since they commute to far away places on a frequent basis. 

As these vehicles are of such utmost importance to us, it is vital to take proper care and know how to keep them in shape. You can learn some relevant information regarding a vehicle’s transmission cooling line down below.

Can I use a rubber hose for transmission cooling lines?

Rubber hose can be used for transmission cooling lines if the hose is rated for transmission cooler lines. Avoid placing it near the exhaust because usually rubber hoses are susceptible to higher temperatures. Do not use regular rubber hoses because they will break down and clog the valve body.

A vehicle has many intricate parts embedded within it that allows it to run for miles after miles without having any significant performance drop and has a high durability as well. 

One of the reasons behind such maintenance of the vehicle is its transmission line which connects the vehicle’s transmission to the vehicle’s radiator.

Transmission cooling lines, or transmission lines are responsible to keep the transmission from overheating as they take away the hot fluid away from the transmission, and pump it back when the fluid has cooled down. 

This way the car gets rid of the excess heat and maintains its durability.

However, its placement in the vehicle’s underside causes it to be exposed to hard debris off road. Repetitive damage to the transmission line could cause it to get ruptured and leak out.

The most common way to diagnose a leak is to look for pools of red fluid beneath the spot you parked your vehicle.

But the good news is – transmission lines are easy to repair since you have to just remove the old line and replace it with a new one. 

If you are not experienced with repairing your vehicle yourself – then the location of the transmission line can make the replacement a bit of a challenge.

To fix the leak, you could use a rubber hose as a replacement for the transmission cooling line since the fluid pressure is not too high. However, since the hose will be transferring hot fluid – you should purchase a hose that is rated for transmission cooling lines.

What kind of rubber hose for transmission line?

If your transmission line has been ruptured or rotted in several places throughout the line, then you should repair it as soon as possible. The best repair for such parts is a replacement but you might be thinking of replacing the line yourself with easily obtainable and cheap rubber hoses. Below are listed the types of rubber hoses that you should use for a durable performance:

Transmission rated hose:

There are several types of rubber hoses available in the hardware store but not all hoses are built equal. There are specific rubber hoses that have the word “Transmission” inscribed into their body – which signifies that those rubber hoses can be used as transmission cooler lines.

Unlike other rubber hoses, these “transmission” rubber hoses are around 300 psi and designed to carry oil. However, they are still made of rubber and have the same weakness all rubber hoses have – heat. 

Since these rubber hoses have no additional protection to them, you could cover the rubber hose with some heater hose especially around the engine.

Hydraulic fluid hose:

Hydraulic hoses can serve the purpose of a transmission line even though its specifications are built for a completely different function. Hydraulic hoses have a very high psi rating – thus they are stiff and can withstand high pressures of fluid passing through them. 

They also have similar weakness to transmission rated hoses and must be provided with heat protection.

What size are transmission cooler lines?

If you are repairing your vehicle’s transmission cooler line yourself, you might be tempted to overlook the size specifications of the hose and end up grabbing whatever hose is available to you nearby in your garage. 

Carelessness towards these tiny details and specifications of the hoses could end up in a leaky installation of the hose.

Most cooler lines are available in the range of sizes between 5/16 to 5/8 inches, therefore you should take note of your old transmission line before you use the new one. 

However it is recommended to use a 3/8 inches Inside Diameter hose which can withstand high temperatures, not pressure.

Transmission cooler lines do not generate much pressure in of itself other than the pressure induced by the volume of fluid flowing – which generates about 200psi pressure when active. 

But the temperature of the transmission fluid is about 190 to 220 degrees Fahrenheit, ideally getting a size that can withstand high temperature and light pressure.

How much pressure is in a transmission cooling line?

There is very low pressure in the transmission cooling line and that pressure is not due to the fluid flow itself but due to the volume it takes up in the cooling line. 

When the vehicle is on standby, the transmission cooling line is expected to experience pressures up to 100 psi maximum. Most vehicles have their standby pressures much lower to be around 50 psi as well.

When the vehicle is up and running and the fluid is actively running through the transmission cooling line, the pressure will build up inside as high as 200psi or slightly higher. But most hoses are built to withstand such pressures with no issues.

Can you repair the transmission line with a rubber hose?

When you travel off road or into the countryside or drive along an out of shape road, many exposed parts of your vehicle could get severely damaged from the rocks and debris hitting them and could even cause the transmission line to rupture. 

In such cases, you could use rubber hoses to repair a section or the complete transmission line.

Although it is possible to repair a transmission line of a vehicle with rubber hose, it should be duly noted that not all rubber hoses should be used to repair the line. Some rubber hoses are not even built to withstand the conditions of the transmission fluid.

But the good news is that there are different rubber hoses with the “transmission” label in them – which means they are suitable to be used to repair transmission lines. However, since they are made of rubber, they still need protection from heat.

Can you use a fuel hose for transmission cooling lines?

Transmission lines have high temperatures and a bit of pressure which transmission lines and rubber hoses can withstand but not all lines can withstand these conditions. 

Fuel line is a nitrile tubing that is specifically made to carry petroleum and is protected against weathering as well as heat – which would make people believe that fuel lines can be used for transmission cooling lines.

And fuel lines could be used for transmission lines if not for some conditions it fails to meet. Fuel lines can withstand a maximum of 50 psi, whereas transmission lines exceed in pressure way beyond that. 

Apart from that, fuel lines are not ATF resistant so the transmission fluid will eat up the fuel hose.

How to repair a transmission line with a rubber hose?

The repairing procedure is detailed as follows:

Diagnose the area of leak:

The first thing you should do after you notice a red puddle beneath your parking area is to identify where the leak is coming from and make sure that the leak is from the transmission line. Usually transmission line leaks occur due to rusting in the clamp area where moisture and dirt gets trapped.

Check the size of leak:

If the leak size is too big or there are multiple leaks in different places, get a replacement transmission line. If there is one leak, cut off that segment to isolate the two lines.

Attach the rubber hose and clamp:

Attach a rubber hose with both ends of the transmission line and tightly secure two or more screw clamps on both ends of the connection.

Check again for leakage:

Afterwards, park your car to a clean spot and let the engine run for a few minutes to see if there is any more leakage.

Can I drive with transmission fluid leak?

Whether you can drive or not with the leak depends on the size of the leak. The fluid is responsible for holding the gear as well as preventing overheating. If the fluid levels drop too much, you will not be able to drive.

Final Thoughts

Rubber hose can be used for transmission cooling lines if the hose is rated for transmission cooler lines. Avoid placing it near the exhaust because usually rubber hoses are susceptible to higher temperatures. Do not use regular rubber hoses because they will break down and clog the valve body.