Transmission oil leaking into motor. 06 toyota Corolla. It makes no sense. How could this be happening?
The only way transmission fluid is leaking into the “engine” would be through the radiator and mixing with the coolant making what looks like a Strawberry Milkshake… That in turn if ignored for a long time would be overheating and blew a head gasket… possible but not probable…
Again sounds like you have a leaking transmission cooler (the cooler is internal in the rad) in the radiator…
Coincidentally I’ve noticed a little transmission oil gets on the back-side of my 30 year old Corolla’s engine as well, in the area where transmission and engine meet. Most of it puddles on the top of the transmission, just a little gets on the engine. I have never figured out how it happens. Manual transmission in my case. Not enough of a leak to be worth spending time to investigate further in my case, but I’ve been thinking maybe it involves the speedo cable.
If OP has an automatic trans rather than manual, my first guess would be a transmission cooler tubing connection is leaking. Look carefully at the radiator. You should see two metal tubes running between the radiator and the transmission. Look for signs of leakage along the length of both tubes. (Those tubes connect to tubes inside the radiator. If the inside-the-radiator tubes leak, that’s a very big problem, b/c it can allow coolant to flow into the transmission, which will quickly damage its innards. Unlikely in a 2006 though. Esp if coolant has been replaced on a regular basis.)
Common sense says OP should make sure to monitor transmission fluid level regularly.
The OP stated the fluid was leaking into the motor not on the motor, I take that at face value…
As a rule of thump ALL automatic transmission radiators have an internal transmission cooler built into them, it is not only to cool the fluid but also bring it up to operating temp faster… Any internal cooler can rupture and mix the transmission fluid with the coolant, and yes even newer vehicles can do this, my sons 09 did it a few years ago…
I am assuming (yes I know) that the OP was talking about seeing the trans fluid in the rad…
But until they respond we don’t know for sure…
Oops, good point, I didn’t read OP’s post carefully enough. Perhaps OP can identify with more clarity where exactly inside the engine the transmission fluid is going? Is it being noticed in the coolant? In the engine oil? Into the cylinders and coming out the tailpipe? Where ?
Some older transmission designs use engine vacuum for certain functions, so there is a tube(s) from intake manifold to transmission. If a diaphragm fails, tha can cause transmission fluid to be sucked into intake manifold. Probably doesn’t apply to a 2006 Corolla.
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The transmission would have to have a vacuum modulator on it for that to happen… Those went away with the electronic controlled transmission… 2006 Corolla has a fully electronic controlled transmission…
But yes we need to know exactly were they saw the trans fluid leaking into at…
The original post is on the “one and done” section, AKA “ask someone”. Unlikely we will get any further information.
BTW George, my common sense says fix it, not monitor it.
Much like 30 years ago, while in military service, we were require to implement a “quality assurance” program in which we monitored and charted a high volume procedure for 60 days, made a note if it got better or worse, then filed the report without doing anything.
Whereas “quality control”, a problem developed, you stop and correct the problem before proceeding with the task.
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The transmission likely has a vent at the top which is connected to the intake plenum sharing a low vacuum manifold with an engine vent.
Ummm No, Any thing hydraulic has to be able to breath needing it to have a vent in the system so it can breath… you have to have air behind fluid (yes even your master cylinder cap is vented)… The vent does not require vacuum and if it did it would just suck the fluid out…
Plus a vent will puke out any unwanted fluid…
I base my post on observations of various makes and models over the years and hope that occasionally the OP can find some benefit from my memory. Many might be surprised to know that a 1953 Jeep and vented the differentials, gear box, bell housing(sealed), and crankcase through a common manifold attached to the air intake to the carburetor.
No, they don’t. Using the term “rule of thumb” by its very nature means “most” not ALL.
My '13 Mustang does not have a trans cooler in the radiator. It is separate from the radiator and uses a thermostat in the trans to warm up the fluid faster and regulate temperature.
Rule of thump and most mean there are exceptions to every rule… Your external transmission cooler (not in rad or run in series) is an exception to the rule and the t-stat probably stops (by passes) the cooler until it reaches a predetermined temp to warm the fluid up before it allows it to start flowing through the cooler…
A rule of thump is that internal combustion engines run on gas or diesel, but we know some run on LP, Hydrogen etc etc, but for most know them as only gas/diesel…
Most of my local gas stations don’t carry french fry oil, LP, Hydrogen etc so I would call that most or as a rule of thump…
I may have used rule of thump loosely but I guess if I would of said most ALL you would have corrected me on that also… Sorry I’m not an English major, and different parts of the country say things differently then others, right or wrong…
Point taken and much respect to you and Mustangman for your experience…
They did a lot of strange things way back then by todays standards… I am better versed from late 60’s and up, but have worked on many older vehicles also… lol