A transmission cooler operates similar to a regular radiator found in any vehicle. But instead of engine oil, it cools down hydraulic fluid pumped from an automatic transmission pan through a metal line. The transmission fluid circulates throughout the cooler, which absorbs its heat and then releases it to the outside air before the fluid returns to the transition through another metal line. Depending on the design of the transmission cooler, it can be integrated in a radiator or come as a separate unit.
While most regular passenger vehicles equipped with a manual transmission do not have a cooler, every car or truck with an automatic transmission features a cooler of either type mentioned above. If you’re not sure whether your car comes with a transmission cooler, you can get in touch with your nearest dealer or check your owner’s manual. If you do have it, the following signs of a faulty transmission cooler might come in handy for you.
You have to top up the fluid level on a regular basis
If this is the case for you, you might have a leaking cooler or line. Check your transmission cooler and all lines for leaks. If a leak is found, it must be fixed as soon as possible to prevent transmission overheating.
There are fluid leaks on the ground under the vehicle
If you notice red or reddish-brown leaks, which smell like petroleum and are thicker than engine oil, under your transmission cooler or somewhere between it and the transmission, most likely you deal with a leaking cooler or one of its lines. This problem should be addressed immediately to prevent damage to the cooler and the transmission.
Abnormal noises coming from your transmission
A lack of fluid caused by a leaking cooler or line can lead to a low fluid level in the transmission. This will increase the friction between its moving parts, resulting in grinding or clunking noises when shifting.
You smell burning fluid
This may happen due to a low fluid level caused by a leaking cooler. The transmission will get overheated, and, in some cases, you’ll notice the smell of burning fluid.
Your engine runs hotter than it should
A malfunctioning cooler or overheating transmission can cause the engine to deal with extra heat inside the engine bay. As a result, it can get overheated and damaged.
Illuminated check engine light
Abnormal cooler and transmission temperatures can cause your engine control unit or powertrain control unit to turn on the check engine light on your dashboard.
You should avoid driving a vehicle with a clogged or leaking transmission cooler. This may lead to transmission overheating and its serious damage, and, therefore, unplanned expenses for its rebuild or replacement.
Can I fix a bad transmission cooler?
To answer this question your transmission cooler should be subjected to a thorough diagnosis. In some cases a faulty transmission cooler can be repaired by fixing the damage and leaks. If your cooler is not repairable, your mechanic or repair shop will offer you to replace it with a brand-new unit. You might need to replace the whole radiator if your transmission cooler is a built-in one.
While at first glance replacing a transmission cooler seems to be an easy job, especially, if it is a separate unit, we would not recommend you to do the trick yourself. It is a part of a very complex system, which requires a certain knowledge and experience. Besides, the transmission and the cooler are operated under high pressure, which may involve special tools and equipment to deal with. Plus, on some vehicles you may need to disassemble a lot of other parts under the hood to access the transmission cooler.