Transmission fluid loss?

Hi, my car lost transmission fluid . My son checked it out, could not find a leak. I took it to my mechanic, he put it up on the rack. He washed the underneath of the car, could not find a leak. He said that the only thing that could have caused this, is that while the car was hot, while driving it blow out some how. There are zero issues when it changes gears, so there is no transmission damage. Any ideas. Thanks. :blush::roll_eyes:

How did you determine that you lost fluid? For many folks the first sign of low fluid is slipping or transmission noise. How did you get the car to the mechanic, did you add fluid?

The check transmission light came on, so i checked the fluid level. It was none on the dip stick. So, as it idled, I added a little at a time until it showed on the stick. There were never any issues when changing gears, no slipping, no sounds. It is puzzling, even my mechanic was puzzled. Immediately after I added some , the check transmission light went off and never came back on. Yes, I drove it there, and back home, 25 miles one way. Checked it when I got home, it is full.

Did you follow the procedure described in the owner’s manual to check the tranny fluid?
Different cars use different procedures. Mine says to get the tranny warmed up with a good drive, then (with the engine running) move the shifter up and down through the positions, and only then (with the engine still running) check the dipstick. Failure to follow the manufacturer procedure will give you an erroneous reading.

If you truly are losing fluid, it’ll most likely be via the tranny input seal or output seal(s). But be sure you really are before messing with anything.

Yes, I did follow the car manual.

Has anyone checked the radiator?

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My mechanic did.

That’s a good question. I never even thought of it. And I amend my answer to “it’ll most likely be via the radiator”.

Some cars build both the engine coolant and the transmission cooler into separate portions of the same radiator. Sometimes a breech between the sections will allow passage of the tranny coolant into the engine coolant section and visa-versa. You may want to monitor your coolant for evidence of cross contamination.

Ok. I thought of that, so I will watch it.

I will contact my mechanic tomorrow concerning a breech between these. My son had suggested the same thing. Thanks, I have to get to bed, have to get to get up at 3:15am orr work.

If your Sable’s transmission has a Vacuum Modulator this could be the culprit. Had one leak on a 91 Mustang, vacuum line drew fluid into engine.

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fyi, my truck’s automatic transmission lost fluid last summer when street repair work meant I had to park it at a really extreme angle. Something like 30 degrees pointed uphill. Somehow that angle allowed some the transmission fluid to leak out. But it never leaked a drop when parked where it is usually parked, on level or mostly level ground. So I never noticed the fluid leak. It didn’t develop any symptoms at first. Then it started to exhibit balky shifting, but only when cold. At which point I noticed the fluid level was low. I added about 3/4 quart which brought it back to the proper fill point. The shifting was still balky though. So I did a routine service, drop the pan, replace the filter, refill with new, and that fixed the balky shifting. We’ve been having unusually cold weather here in San Jose this week, and just the other morning I drove the truck in probably the upper 30’s temperature, and all the shifts were perfect. Given what you say, I doubt you’ll have any ongoing problems.