How to read tranny dipstick
02-22-13, 03:22 AM
#16
Agreed, and the logic you set forth makes sense. But then shouldn't the markers for COLD on the dipstick be ABOVE the HOT markers?
02-22-13, 05:32 AM
#17
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Guys this is one of those common sense situations. The fluid should always be checked while the car is idling. If the fluid is still cold like 2 min after start up you use the cold marks. If it is hot like after you drove for an hour you use the hot marks. If you live in climates like Alaska or Arizona these times will obviously vary. Old cars had dip sticks stamped "check while hot idling in park". A mercedes I owned had no dip stick and never gave a bit of trouble. You can use sand paper on one side of the dip stick to break the glaze if you get those blotches that make the level hard to read.
Last edited by engine89; 02-22-13 at 06:21 AM.
02-22-13, 08:01 AM
#18
Moderator
There is no disagreement about when and how to check the hot mark.
The problem is we are trying to logically explain (or theorize) the position of the cold mark and their relative position.
Does the transmission fluid foam up when hot and in circulation?
Salim
The problem is we are trying to logically explain (or theorize) the position of the cold mark and their relative position.
Does the transmission fluid foam up when hot and in circulation?
Salim
02-22-13, 08:44 AM
#19
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I may be wrong but I have always understood that the fluid expands as it heats up to its normal operating temp. approx. 175F. The dipstick corresponds to this point with hot on the upper end and cold on the bottom of the stick. The same applies to the engine coolant and power steering fluid. I mentioned the procedure in my earlier reply because some of the posts seemed to indicate the fluid was being checked with the engine off thus the fluid appearing to be above the hot mark when cold.
Last edited by engine89; 02-22-13 at 11:07 AM.
02-22-13, 08:56 PM
#20
It sounds like you are checking the dip stick with the car turned off.
So is the car on or off when you are getting the readings?
02-22-13, 09:49 PM
#21
Moderator
Mostly material expands on heating up, but for transmission fluid to expand by the amount seems to boggle my mind. 2" in height with pan size ... is lot a volume that would expand into.
Salim
Salim
Last edited by salimshah; 02-22-13 at 09:58 PM.
02-23-13, 06:12 AM
#22
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I have not dropped the pan in the RX yet, but in some vehicles the trans dipstick terminates in a narrow channel, this enhanses the fluid rise on the stick with heat and pressure. Maybe someone noted the position of the stick with the pan off.
02-23-13, 09:58 AM
#23
Moderator
Google did find patent on maintaining capacity of circulating transmission fluid, so may be the fluid does expand by a large factor. (enough to boggle my mind).
Although I have a second set of questions based on this delta volume change ,,, people who increase the volume of fluid in a standard transmission. If the final (hot) level is kept the same as the un-modified (they use the same HOT mark to measure) then there COLD mark should not be valid.
Salim
02-23-13, 06:40 PM
#24
Dip stick pics with the pan removed are here: https://www.clublexus.com/forums/rx-...-change-6.html
I think you guys are over thinking it, it just expands some, it's a lot of fluid.
I think you guys are over thinking it, it just expands some, it's a lot of fluid.
09-27-18, 11:25 AM
#25
My RX's apparently are freaks of nature, defying physics altogether. Both cold, they read a little above the hot mark. When hot, the level DECREASES to right at the hot level. And the COLD markers would insinuate that the level should decrease significantly when cold. Not here...
Yes the car has been driven for 30 minutes, checking on a level surface after cycling through the gears, blah blah...never made sense to me so I settled for the hot level being where it was supposed to be and stopped fretting over it.
My 2 cents...
Yes the car has been driven for 30 minutes, checking on a level surface after cycling through the gears, blah blah...never made sense to me so I settled for the hot level being where it was supposed to be and stopped fretting over it.
My 2 cents...
09-27-18, 02:33 PM
#26
Lexus Test Driver
This measuring system has always puzzled me. I think it should be designed so that tranny fluid is checked like engine oil -- static, not running. Easy peasy, as they say. There probably is a reason it has to be checked running, but I have no idea what the reason is!
09-27-18, 02:41 PM
#27
its because of the torque converter. When running, it is full of atf, and the remainder has to be at the right level WHILE running for the parts in the trans body itself. If done while not running, the torque converter drains back down into the trans body and looks over full. If you try making the level "right" when not running, then run it, the torque converter would suck it all up and not leave enough in the trans body for functioning and lubrication.
09-27-18, 04:09 PM
#28
Moderator
Process is pretty clear, warmed up in Park engine running, vehicle flat.
BUT
In these years, I have never been able to read the level cleanly. There is always a smear of fluid which makes it impossible to read.
As a result, I always measure the volume of the fluid that was removed (after it had cooled down to room temp) and add the same amount of fresh fluid close to the same temperature.
Salim
BUT
In these years, I have never been able to read the level cleanly. There is always a smear of fluid which makes it impossible to read.
As a result, I always measure the volume of the fluid that was removed (after it had cooled down to room temp) and add the same amount of fresh fluid close to the same temperature.
Salim
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