Irregular transmission leak? -- Toyota RAV4

[535678]

My mother's 2004 Toyota RAV4 2WD has a leak of some sort that accumulates on the bottom of the transmission. I first noticed this a few years ago when changing her oil. At the time, I checked all of the fluids and found them at their maximum levels, so I degreased the entire area and decided to keep an eye on it. About 500 miles later it was dry. Again at 1000 miles it was dry. When I changed her oil 5000 miles later, it was wet again, but all the fluids looked great without any noticeable drop. I degreased again, took some pictures, and asked some mechanic friends. They were stumped.

Fast forward to the next oil change about 5000 miles later and it was completely dry and clean! There's been an irregular pattern ever since -- dry for 5K to 10K miles -- and then it starts leaking again, but never enough to drip onto the driveway.

Besides being suspicious of the transmission pan gasket, the brake fluid reservoir is directly above this area. In the past I never detected a drop in brake fluid, but today it is down about 1/4" from the MAX line where it was 6 months ago after I bled the brake lines and refilled. Pin hole leak, perhaps?

Unlike motor oil leaks which turn into a paste and retain a little bit of the brownish color, this stuff is much lighter consistency, always wet, always 100% black, and never forms a paste when mixed with road grime.

Any ideas?

 

[HTSS_TR]

Brake fluid in reservoir downs by 1/4" in 6 months is a little much, when brake pad wears off brake fluid in reservoir will go down a little, may be 1/8" in 6 months.

I would re-torque the bolts on the transmission pan, the leak seems to be very little no need to replace pan gasket.

 

[535678]

I said a 1/4" drop in the brake fluid reservoir. Could be more like 1/6" but certainly more than I'm used to seeing in a such a short period of time.

The transmission pan has never been removed and it's due for a 100,000 mile drain and refill. This is a good time to replace the gasket anyway.

I don't understand though why the gasket -- if that's the problem here -- is fine for such long periods of time, then leaky again.

 

[shDK]

Perhaps the breatherhose/pipe in the transmission is clogged or out of funktion so when it gets real hot it makes overpressure in the sump.

 

[LeakySeals]

Originally Posted By: 535678
The transmission pan has never been removed and it's due for a 100,000 mile drain and refill. This is a good time to replace the gasket anyway.

I don't understand though why the gasket -- if that's the problem here -- is fine for such long periods of time, then leaky again.

Assume you know all this.. A drain and fill will come from that 10mm hex bolt, no pan removal required. Its a screen filter, no need to open up and replace it. A drain and fill (vs exchange or "flush) only gets 40-50% on that transmission, so it should be performed every 30-40k. T-IV is not a 100k or lifetime fluid no matter what the dealer says. Check the stick, if its red its good, purple-grey on the way out, grey its mostly gone, grey black completely gone.

It doesn't look like the pan gasket to me. From your description overflow is possible. When was the last time the fluid was changed? Were there any topoffs? If it is transmission fluid T-IV has a distinct smell. Sniff the stick and compare.

 

[JTK]

That looks like some very minute rear main seal leakage to me. My Honda has done that since new. Always greasy at the bottom of the bellhousing at oil changes. Never enough to drip, notice a loss or make additional mess.

 

[GSCJR]

Perhaps, if any brake service was done within that period, you could have some brake fluid residue that was not cleaned up well. Do not lose any sleep over this.

 

[Doog]

Originally Posted By: LeakySeals

Assume you know all this.. A drain and fill will come from that 10mm hex bolt, no pan removal required. Its a screen filter, no need to open up and replace it. A drain and fill (vs exchange or "flush) only gets 40-50% on that transmission, so it should be performed every 30-40k. T-IV is not a 100k or lifetime fluid no matter what the dealer says. Check the stick, if its red its good, purple-grey on the way out, grey its mostly gone, grey black completely gone.

It doesn't look like the pan gasket to me. From your description overflow is possible. When was the last time the fluid was changed? Were there any topoffs? If it is transmission fluid T-IV has a distinct smell. Sniff the stick and compare.


This is your best advice. I would do 3 drain fills with 2-3 miles of driving in between. Make sure you get a new crush washer and only use Toyota ATF.

 

[535678]

Originally Posted By: Doog

This is your best advice. I would do 3 drain fills with 2-3 miles of driving in between. Make sure you get a new crush washer and only use Toyota ATF.


Any reason I couldn't use Mobil 3309?

 

[threeputtpar]

No thought on the possible transmission fluid leak, but the drop in the brake fluid level is probably due to the stuck caliper on the brakes in the pic. Look at all of that brake dust! The pads are probably toast on that side and the caliper piston is probably at the end of its travel, lowering the brake fluid level in the resivoir.

Feel free to use JWS3309 trans fluid, it's the same as the T-IV from Toyota.

 

[535678]

How can you tell the brake caliper is stuck looking at that photo?

What am I missing?

 

[dishdude]

Originally Posted By: 535678
How can you tell the brake caliper is stuck looking at that photo?

What am I missing?


Looks normal to me - since it never rains in CA, every hub is covered in brake dust like that.

 

[threeputtpar]

Originally Posted By: 535678
How can you tell the brake caliper is stuck looking at that photo?

What am I missing?


The amount of brake dust on the inside of the wheel and all over the steering knuckle was my clue. To check it out, pull the wheels in the front and measure the thickness of the remaining brake pads on both sides. If one or more of the pads is significantly less than the others, something isn't functioning as it should be.

Also, if you remove the pads and reinstall the caliper empty you can try to slide the caliper by hand to see how much resistance you get. That would be another way to tell if it is binding on the slider bolts.

Even if it almost never rains where you're located, I'd think that the car would see the car wash occasionally so any accumulated brake dust would be washed off periodically. If the car never gets washed, then maybe that could be normal accumulation over many years of driving and it would be perfectly normal. Personally, I've only seen that amount of accumulation when there was a problem with the piston inside of the caliper or it was stuck on the slides.

 

[535678]

Originally Posted By: threeputtpar
Originally Posted By: 535678
How can you tell the brake caliper is stuck looking at that photo?

What am I missing?


The amount of brake dust on the inside of the wheel and all over the steering knuckle was my clue. To check it out, pull the wheels in the front and measure the thickness of the remaining brake pads on both sides. If one or more of the pads is significantly less than the others, something isn't functioning as it should be.

Also, if you remove the pads and reinstall the caliper empty you can try to slide the caliper by hand to see how much resistance you get. That would be another way to tell if it is binding on the slider bolts.

Even if it almost never rains where you're located, I'd think that the car would see the car wash occasionally so any accumulated brake dust would be washed off periodically. If the car never gets washed, then maybe that could be normal accumulation over many years of driving and it would be perfectly normal. Personally, I've only seen that amount of accumulation when there was a problem with the piston inside of the caliper or it was stuck on the slides.


Yeah, this is somewhat normal here. We've haven't had meaningful precipitation with puddles on the road since January or February -- at least not during the commute hours.

I sprayed brake cleaner on the areas pictured and very little came off. From the outside it looks nasty because the only areas that clean up are small patches where water is able to move through the wheel. I crudely measured the front pads through the wheel with a depth gauge and the front pads were .015" apart left vs. right, which could simply be measuring error.

By the way, it's neat to see you're from Appleton. We have lots and lots of family in the Appleton area.

 

[535678]

Back to the original topic, since the transmission pan has never been dropped before, I plan to do so when doing the drain & refill.

Should I use an OEM pan gasket?