Transmission oil temperature - PeachParts Mercedes-Benz Forum

JeffreyP · #1 10-12-2006, 02:09 PM

Not another ATF thread, I just want to see if this would work for measuring ATF temperature without spending money on the infrared thermometer or the like.
According to the ATF DIY article and recommendations, the ATF level measurement (in my case a 98-E320) must be done at 80Celsius. Here are my questions:

1. Doesn't the transmission line go through the radiator for cooling? If yes, then
2. should the ATF be at the same temperature as the engine coolant? So measure the coolant temp should be quite simple

I believe there is also a procedure using the "REST BUTTON" to see the coolant temperature? Does any one have the link?
Please let me know what your thought on this - Gilly, MBDoc and other informed mechanics?

Regards,
JeffreyP

Matt L · #2 10-12-2006, 02:23 PM

The fluid is cooled by the engine coolant in the radiator, but this does in no way imply that they will be at the same temperature.

Gilly · #3 10-12-2006, 06:54 PM

Not the same temp, the ATF wil typically be hotter, all depending on the ambient temp, how hard the tranny is working (if at all) and how hard the engine is working.
Gilly

uberwgn · #4 10-12-2006, 07:28 PM

Quote:

Originally Posted by JeffreyP

Not another ATF thread, I just want to see if this would work for measuring ATF temperature without spending money on the infrared thermometer or the like.
According to the ATF DIY article and recommendations, the ATF level measurement (in my case a 98-E320) must be done at 80Celsius. Here are my questions:

1. Doesn't the transmission line go through the radiator for cooling? If yes, then
2. should the ATF be at the same temperature as the engine coolant? So measure the coolant temp should be quite simple

I believe there is also a procedure using the "REST BUTTON" to see the coolant temperature? Does any one have the link?
Please let me know what your thought on this - Gilly, MBDoc and other informed mechanics?

Regards,
JeffreyP

Jeff, there are two reference points on the dipstick tool: 25C and 80C. It's much easier to gage the level at the lower temp. It can be challenging to get the temp up to 80C.

sokoloff · #5 10-12-2006, 10:06 PM

I thought Mercedes came out with a service bulletin saying to not use the lower mark and only check the fluid using the 80 degree mark.

Len

Gilly · #6 10-12-2006, 10:07 PM

Yeah they sure did, get tired of posting same things over and over.
Gilly

uberwgn · #7 10-13-2006, 08:40 AM

I have not heard that. OTOH, I have checked my car at 25C and 80C and get FULL indications at both reference points.

BTW, the MB tech that posts here says they only use the 25C indicator, FWIW.

JeffreyP · #8 10-13-2006, 09:54 AM

Thanks guys,

I guess there goes my theory. I suppose I can always spend 60 bucks for an infrared thermometer.
I am ,however, supprise that we couldn't use the "Rest Button" to get to the transmission temp sensor as we could access other (cabin, coil, vac etc..) temp.
sensors

Regards,
Jeffrey

Gilly · #9 10-13-2006, 10:36 AM

That temp comes through the ETC, trans control unit, so wouldn't ba able to get it through another module.
Gilly

uberwgn · #10 10-13-2006, 10:55 AM

I've seen the IR thermometers as low as $10 (Harbor Freight has numerous models). I bought a Sears/Crafts. for around $30 on Fleabay. It was new, IIRC, regular retail was around $55 or so. It's a handy tool for lots of other things around the house.

JeffreyP · #11 10-13-2006, 04:54 PM

Thanks, I am going to give Harbor Freight a shot.

Now last question, will pinging the transmission pan (DYI post) gets the same temperature as ATF fluid temp. inside? If not how else can you get it?

Regards,
JeffreyP

Gilly · #12 10-13-2006, 08:13 PM

You can get it from the shop computer. There is a sensor inside the transmission that's used for this purpose.
Gilly

royaiii · #13 10-16-2006, 12:45 AM

Gilly do you recommend topping off the transmission. I have a 97 e320 w/ 81 k miles never have had the fluid changed and was wondering if I should add 100-200 mL of tranny fluid to account for the past 10 years.

forp · #14 10-16-2006, 01:46 AM

royaiii,
No fair thread-jacking

. JefferyP started this one concerning transmission fluid temperature. You'll get more/better info from everyone if you start a new thread concerning whether or not to add fluid to your tranny. OK, having said that, and I hope Gilly agrees with me on this, I think if you read the many threads here about the 722.6 "filled for life" transmissions, the consensus would be to change the fluid, not add, at 9 years and 81K miles. I changed mine at 60K miles. Fresh fluid, new filter, happy tranny.

Gilly · #15 10-16-2006, 05:20 AM

After this much passage of time, I really think the owner will have to decide, to a certain point, when "enough is enough". My experience has been the one E300D that I know went 350,000+ without a change, and I've lost contact with that car. To me it isn't unusual for an older style MB trans, say a 733.3 to require a rebuild in that many miles. Not saying it was correct to push it that far, I'd opt for maybe 10 years 200,000 or so, but hey, it's YOUR baby, I'd use that for a guideline. I certainly don't buy into 30,000, 60,000, or even 100,000. Not me personally. If it's going to fail in that low of a mileage, it'll fail if you change it every time you change the oil, IMHO. Something besides MB service intervals are wrong with that trans, maintenance won't fix ALL problems, believe it or not. It was put together wrong or "someone" is beating the hell out of it.
Royaiii, the fluid either stays or it goes, if there is no leak I'd leave it alone or if you're really curious have it properly checked.
Gilly