How To Check Automatic Transmissions Leak

Some of the most common problems with automatic transmissions begin with leaks A transmission leak most often appears as small red fluid spots under a vehicle.  These spots are one early symptom of a transmission problem. Leaks never take care of themselves and normally get worse. Quick attention can help this problem remain small.  Left unattended, they may cause the transmission to fail. The fluid is literally the life-blood of an automatic transmission Most automatic transmissions hold eight to fourteen quarts of fluid.  The automatic transmission fluid lubricates, serves as a hydraulic fluid and helps clean and condition the seals of the transmission. When a leak develops, fluid is lost. With less fluid, the pump has trouble maintaining pressure and less protection is available to the transmission. Modern transmissions can sense a loss of fluid pressure. When this happens they may re-direct fluid from the lubrication circuits to the hydraulic circuits in order to keep the vehicle moving. This does keep the vehicle in motion, but can also cause severe damage. This is one reason why leaks are so dangerous. They can result in a burned up transmission. Pressurized leaks Diagnosing transmission leaks is easier with a bit of understanding. Some leaks will occur with the engine running.  These are normally pressure related leaks. Seals and connections that are pressurized when running are the first place to look.  This type leak may be less noticeable when the vehicle is parked and may not leave spots under the vehicle.  A physical inspection may be needed to learn there is a problem.  Examples might be, the front pump seal, the cooler lines, side covers and sensors. Cooler line leaks   Cooler lines and hoses connect the transmission to the cooler and are a common area for pressurized leaks. Leaks in these areas often show up after someone has tampered with the lines. When flushing a transmission, they often remove these lines and leaks may result. Replacing a radiator involves disconnecting the cooler lines and may also cause a leak. A front collision, even minor in nature, may bend the lines or move the mountings, causing transmission fluid leakage. Pressurized leaks will account for a significant loss of fluid, compared with gravity type leakage. Automatic Transmission and Transaxle Fluid Leaks - How to locate and repair!   The two most common ways people become aware that their automatic transmission or transaxle is leaking fluid is either noticing red colored stains on their driveway or garage floor and when checking their fluid level and seeing that it is low.  Regardless of how you become aware of a transmission/transaxle fluid leak, it is important to identify the source of the leak and get it repaired before the leak has a chance to cause more serious and costly problems. It is important to understand that automatic transmission fluid, (also referred to as automatic transmission oil and ATF), is not "used" or "burned" by the transmission in the same way engine oil is used and burned by the engine.  In other words, when your transmission oil dipstick reads low -- you have a leak. Automatic Transmission/Transaxle Fluid Leaks ATF Leaks can be classified as either pressure related or non-pressure related.  Both type leaks are explained in more detail below. Pressure Related ATF Leaks: Fluid leaks that only leak when the engine is running are typically classified as "pressure" related.  In other words, the leak only occurs when the engine is running and fluid pressure is built up inside the transmission or transaxle.  Common causes for pressure related leaks include: > a bad or damaged front pump seal> a leaking pump O-ring> a loose or damaged oil cooler line or fitting> a damaged or deteriorated side cover gasket Non-Pressure Related ATF Leaks: Leaks that are not caused by fluid pressure and that can leak anytime (engine running or not running and the vehicle parked or on the road) include: > a damaged or deteriorated transmission oil/fluid pan gasket > oil pan bolts overly tightened > damage to the transmission oil pan from being struck when traveling > a damaged or deteriorated transmission fluid dipstick tube seal/O-ring > a damaged or deteriorated shifter lever seal.    How to Locate and Repair a Transmission Fluid Leak THINGS YOU WILL NEED Jack and Jack Stands Flashlight or Droplight Shop Rags A can of brake cleaner or engine degreaser - for cleaning grease and grime from the underside of the engine and transmission. Note: In some instances, locating the source of a leak is not easy and may take more time than you are willing to spend.  If this case, you can purchase a dye which will make finding the leak much easier - it works great.  Here is where to find it - Transmission Fluid Leak Dye Detector  Screwdrivers Pliers Wrenches Socket and Ratchet Set with Extension Locating the Source of the Fluid Leak Normally, in order to locate the source of any leak you'll need to start with a clean undercarriage.  Use a degreaser or brake cleaner to clean the grease and grime from the bottom of the engine and transmission as well as other parts and components that are dirty and greasy.  The wipe everything dry.  A transmission fluid leak is usually red.  However, it can be dark red or brown if the fluid is old and dirty.  Be aware that other leaks that may show up in the same general area could be engine oil, power steering fluid, brake fluid and engine coolant. To distinguish transmission fluid from other leaks, look for these characteristics: Transmission fluid is normally a reddish color, has an oily/slippery feel and can smell sweet, or burnt if the transmission has overheated.  If you are having difficulty determining the color, place a piece of white paper directly underneath your vehicle where the fluid leaks on the floor and let the car sit overnight.  This will normally show the color more clearly. Once it is determined that the leak is transmission fluid, check all around the transmission oil pan closely as a leaking pan gasket is quite common.  Then check the pan itself for damage.  If it is dented or deeply scratched it could have a hairline crack that you cannot see. After ruling out the oil pan as being the source of the leak, check the fluid fill tube (or dipstick tube) where it enters the transmission.  If fluid is leaking from this area, the fill tube is either loose and/or not pushed down into the transmission completely or the O-ring is bad.  If no leak is found around the dipstick tube, check the area where the shifter linkage is mounted and bolted into the transmission/transaxle.  If you see a leak in this area you will need to un-bolt the linkage from the transmission and replace the gasket or O-ring.  Next, check around the sensors to see if any are leaking.  If you find a leaking sensor, remove the sensor and replace the O-ring. If no leak is found, you'll need to start the engine and move the the shifter through each of the gears before placing the shifter back into the Park position.  With the engine still running, look underneath the vehicle for the leak. Fluid level or gravity leaks  Other points may tend to leak when the vehicle is parked over night. Common examples are the pan gasket, the fill tube seal and the shifter lever seal. When the engine is running and for a while after stopping, fluid remains in the torque converter and various drums and clutches of the transmission. This has the effect of lowering the fluid level in the pan. When the engine stops running, gravity very slowly pushes these fluids back the pan of the transmission. It is normal for the fluid in the torque converter to drain back to the pan, when the vehicle is not driven.  This causes the fluid level to rise where it may reach higher points in the transmission. This is why some leaks only occur, or are much worse when the vehicle sits for a long time.  If the vehicle is driven every day, fluid is pushed back to the converter and the level stays lower.  Under these conditions, the leaks may not show or may be far less severe. Because the pan is usually the lowest point, many leaks appear to originate there. In reality, they may be leaking from higher up and running down to the pan. This type of mis-diagnosis results in many pan gaskets needlessly replaced and leaks that persist. Tightening the pan and side cover bolts is also a very bad idea. Over-tightening bolts will only crush the gasket and perhaps bend the pan. Not only will it not stop the leak, it may create a leak that did not previously exist. The threads in the aluminum transmission case can also be damaged by over tightening bolts. Front wheel drive transaxles Front wheel drive transmissions are prone to most leaks that rear wheel drive transmissions are. They usually also have axle seals and side covers that may leak. A front wheel drive transmission also includes the differential. This makes leaks even more critical, due to the high load on these components. A lack of lubrication will quickly damage the transmission and differential. In our experience, stop-leak never repairs a leak and very likely may create a much larger problem While it might seem inviting to add stop-leak to a leaking automatic transmission, this should never be done. Stop-leak may work by swelling the seals. Unfortunately internal seals may also swell and a complete rebuild may become necessary. The best way to prevent automatic transmission leaks is with a proper transmission service. New fluid contains seal conditioners that help keep seals pliable and prevents leaks. Having a professional perform the service also prevents additional damage from improper service. Many transmission leaks are very easy to repair, when properly diagnosed. Once the source of the leak is found a new gasket or seal is usually all that is needed. Best is to have a specialist that knows automatic transmissions advise you.