That large leak stain coming from under your car might be what most car owners would mistakenly assume is a motor oil leak. One Acura owner, however, recently discovered what his similar-looking motor oil-like stain really is and why no one should ever attempt to drive their car after seeing it.
According to a Reddit r/MechanicAdvice forum, the OP told his story:
"We took our Acura to the dealer because the A/C stopped working on the driver's side. Worked great everywhere else. After removing and replacing the freon, they said it was a mixer motor, covered under warranty."
For clarification: The "mixer motor" in an Acura (also known as a blend door actuator) controls the air temperature and airflow direction within the cabin's climate control system by regulating the movement of blend doors, and it was presumably one of the causes of the A/C repair request.
"We also did A136 service: oil change, replace transmission fluid, rear differential fluid, and transfer case fluid."
For clarification, Acura uses alphanumeric codes and subcodes as part of their Maintenance Minder system to monitor the health of your car model and provide recommended service suggestions.
In the OP's case, an A136 signifies:
A= Oil change
1= Rotate tires
3= Replace the transmission and transfer case fluid
6= Replace rear differential fluid (if equipped)
All appeared fine afterward until the next day when the Acura owner noticed this:
"I noticed a funky smell in the garage on Saturday, and I wondered if we had a propane leak, but we have no propane near the garage. We pulled the car out today so we could search for a dead animal somewhere and saw this big puddle of fluid that is kind of sticky and slippery, smells odd, and is right under the engine."
"The service department is closed now....any ideas?"
Stain Smells Can Be a Diagnostic Clue
Automotive fluid stains are a good indication of what kind of problem your car has or is developing. Understanding fluid stains is a crucial aspect of maintenance and repair.
Three fluid stains you should be able to discern and identify by its texture and color include:
- Engine oil―typically ranging from amber to dark brown/black and is slippery to the touch. Motor oil can also have a gasoline-like smell due to cylinder washing.
- Coolant―is usually green, orange, or pink, and sweet-smelling, which is why dogs have been known to lap it up and become very sick and/or die.
- Transmission or gear oil―Usually a dark brown color and has a thicker feel to it than motor oil (depending on its viscosity and age). However, there is one key feature that easily distinguishes gear oil from motor oil — a strong sulfurous odor, sometimes described as heavily pungent, like rotten eggs, burnt garlic, or a dead animal nearby.
Why Sulfur Is Used in Gear Oil
Gear (and differential) oil formulations often contain sulfur due to additives consisting of sulfur-phosphorus compounds, which form a protective coating on parts that become very hot under pressure.
Gear systems, especially in transfer cases, differentials, and manual transmissions, where very high pressure and metal-to-metal contact promotes premature wear, would not last long without these additives.
Thread Responses to the OP's Questions
Fortunately, the OP sought help before deciding to drive his car back to the garage with a complaint.
Several post replies identified the likely source of the stain by its distinctive smell as originating from the transfer case — a gearbox that receives power from the transmission and then distributes it to both the front and rear axles.
Very likely it's differential fluid. Not sure what it is like on your vehicle but it looks like it either isn't sealed properly or the Fill plug got left off. This is from the internet, and I could be very wrong, but that's either engine oil, brake fluid, or Differential/gear oil. And based off of the funky smell alone, I'm leaning towards the Differential Fluid." ―Exotic_Climate5072
If it smells like propane, that's probably the gear oil, which has kind of a sulfur smell. Check the plugs on the differential and everywhere else, too." ―TheGuyInRooM420-1
Several other posts also correctly warned the OP not to drive his car back to the service department, as a leak in the transfer case, resulting in a low level of gear oil, would cause the gears to quickly deteriorate, even with just a short, quick drive.
The best advice provided was the shared theme of contacting the garage and asking them to tow the car back to the service department for an analysis of the fluid leak, to determine why it occurred, and to assess whether any harm had resulted.
The OP leaves us with this final post:
Final Thoughts: The key takeaway is that car owners need to be aware of fluid differences so as to be able to assess a leaking fluid problem.
In short, knowing your automotive fluids is knowing how to avoid a catastrophe.
For additional fluid-related automotive articles, here are a few for your consideration and enlightenment:
- The Truth About Motor Oil Additives
- The Truth About Oil Change Intervals and Analysis from Experts in the Field
- DIY Toyota Camry Hybrid Transaxle Fluid Change Demo
COMING UP NEXT: While Driving My Cyberbeast, I Gave My First Thumbs Down To A Model 3 Owner
Timothy Boyer is an automotive reporter based in Cincinnati who currently researches and restores older vehicles with engine modifications for improved performance. He also reports on modern cars (including EVs) with a focus on DIY mechanics, buying and using tools, and other related topical automotive repair news. Follow Tim on Twitter at @TimBoyerWrites as well as on Facebook and his automotive blog "Zen and the Art of DIY Car Repair" for useful daily news and topics related to new and used cars and trucks.
Image Source: Deposit Photos
