Using HHT to Measure W210 ATF Level
 

I was playing around with Xentry on the W210 this afternoon. It brings up HHT. I found the place where it measures ATF level. It gave the temp which, in and of itself, is a great benefit...no more guesswork!

But for the level, it says it has to be 80C. As mine only read 67C, there was no level reading. Does it actually have to reach 80C and not a degree less to give a level reading? The temp starts to drop quickly, so I of course wonder if I could get everything hooked up in time after a drive to get an 80C reading.

That being said it may be simplest just to interpolate the correct level based on whatever temp reading I get.

I'm having to keep an eye on things because of a slow leak.

Thanks.

Near as I can tell the 722.6 never got electronic level reading, just a temp reading for transmission over load and accurate dip stick readings. My 97 has the temp sensor and the HHT can access trans temp.

The temp sensor is not active when in park / neutral from what I recall as it is part of the neutral safety SW circuit. To build temp, apply the parking brake, press service brake , select drive, then bring engine up to 1500 RPM or so. This will build heat in the torque converter.

Yes to all the above. I just did a fluid/filter change on my E300 this weekend.

You do need the special dipstick tool to read the fluid level. There is no internal level sensor in this transmission. According to the FSM you have to be at 80C but I did not see any +/- tolerance on that requirement.

Also I forgot that the NSS and temperature sensor were the same wire, and I thought I had an off scale sensor until I remembered it has to be in a driving range to work. The HHT emulator display has a line below the temperature that says RD4321 and it's trying to remind you that the sensor is open circuit in P or N.

One other thing you want to make sure to do is go into the fluid life screen and reset that. For bonus points reset your adaptations and get the transmission to re-learn how you drive. With the new fluid the transmission will behave differently. I noticed a marked improvement in the smoothness of the shifts after doing this.

My fluid had about 90 k miles on it, so it was definitely due for a change. However the pan looked great, there was very little wear material in the bottom of the pan.

If you drain the torque converter you will need about 8 liters +/- to totally refill.

Also another tip. The Xentry will think this is a later 722.6 and will try to talk to it via a method not supported in the E300. You have to cancel out after it gives you the communications timeout message. At that point you will be presented with a choice for 722.6 with HHT. You want that selection, which brings up the HHT emulator.