cstevenson

About two weeks ago this problem developed: the car tends to jerk a couple of times when I accelerate, and it's very uncomfortable. It happens at different gears, and different speeds, but usually not highway speeds.

Coupled with this issue (I couple them because they developed at the same time) is that when I give it gas to climb a hill (however slight), the RPMs get stuck at around 1,000 and the car rumbles exactly like if you try to climb a hill without downshifting. The car will continue to rumble, and keep the rpms at 1,000 rpm until I floor it (or basically give it A Lot of gas, then they shoot up and I actually start accelerating.

I originally thought it was a wheel bearing I knew was worn, so i replaced that one and checked the other three, but to no avail. There are no error codes.

Would STAR diagnostics tell me anything about transmission issues?

Any thoughts would be appreciated!!

Rudeney

This does sound like it could be a transmission issue. If so, a scan of the ECU with a generic OBDII reader won't tell you anything. You would need it scanned with SDS (a.k.a. Star, Xentry) or something like iCarsoft that can read the TCU. Even then, you may not get any codes if it is a hydraulic issue (low fluid) or the torque converter is failing. You might want to invest in a transmission fluid dipstick and IR thermometer to check the level. If it's low, get it changed and refilled, then see how it does.

cstevenson

Thanks Rodney!

This car has a "sealed for life" transmission, is it still worth checking the fluid level? Am I even able to add fluid to it through that dipstick tube under the hood?

gaazmon

Do not believe that sealed for life statement from MB. That is definitely not true and I have no idea as to why MB marketed the vehicles that way. The tranny fluid should be changed ever 40k miles according to regular maintenance standards. The 2003 and some 2004 5 speed autos did suffer from the dreaded glycol contamination issue (my 04 e320 did) so it could be contaminated fluid as well.

cstevenson

well I have a dipstick on order from amazon, I'll update on Monday when It arrives and I check the levels. It definitely feels and sounds like something's binding in the powertrain, and if that's the case, I can't imagine the damage I'm doing to my transmission

gaazmon

It may just be low fluid as I have had that happen to me on my current vehicle once and it did have rougher shifts and so I just had a flush and new fluid done and all was fine.

The problem with waiting too long to change the fluid is that the transmission adapts to the thicker fluid over time and the metals inside react differently. So sometimes, if a fluid change is done very late, the transmission may experience slipping and other issues due to the new fluid being much thinner without all those other contaminants now in it.

The 5 speed in your car is a very solid and durable transmission so hopefully its nothing serious.

cstevenson

would a throttle reset help with those issues? The reset where you hold the accelerator pedal down for a few seconds and it supposedly clears the car's memory of your driving habits.

Rudeney

Gaazmon is right - the 722.6 5-speed was sold as "sealed for life". That's fine unless you expect "life" to last more than maybe 150K-200K miles. Around 1999 or 2000, they even deleted the torque converter drain. Why would you need a drain plug on something that never needs to have the fluid removed for a change, right?

The newer 722.9 7-speed was also originally sold as sealed for life, and with no torque converter drain. After some early failures due to bad torque converters and fluid pumps severely contaminating the fluid, a one-time 40K mile change was indicated. They also added back the torque converter drain. Sometime later, they officially recommended regular fluid and filter changes every 40K miles.

The 722.6 does not have the contamination problems from its pump and torque converter, but it will still benefit from a fluid/filter change. It may not need to be very 40K, but I'd say a change and flush every 70K. Here are instructions for fluid and filter change:


http://benzbits.com/722_6/FluidFilterChange.pdf

And here's the flush:

http://benzbits.com/722_6/TransmissionFlush.pdf

What you probably want to do is a flush, then follow with the filter change and refill. This means you'll need 14 quarts for the flush plus another 4 for a refill after dropping the pan.

Gaazmon is also smart to mention the possible coolant contaminant due to the Valeo radiator failure. If you have the Valeo, I'd replace it and then do a full flush and filter change. Here is a good guide to visual identification:

http://benzbits.com/w203/radiator/list.php

gaazmon

Ah yes I forgot to mention the 40k standard is for the 722.9 7-speed model. The 722.6 can definitely handle a lot more in many senses. I can tell with my current vehicle compared to my previous that the 7-speed is much more sensitive, but I wouldn't worry much with regular fluid changes and if the car is an 08 and up model. The 722.6 was definitely quite an engineering marvel for back in its time. I wonder how often the new 9-speed fluid should be changed

Regarding the glycol for the OP, my transmission on my 04 E320 failed from glycol at around 54-55k miles (the fluid had not been changed previously from my knowledge as I bought it CPO). Some have their failure rates happen at much higher mile ranges. It all depends on the leak I would assume. The CPO saved me in this instance.

Rudeney

The gears, clutches and hydraulics of the 722.6 and 722.9 are the same except for the additional ratios on the 722.9. The 722.9 uses a different torque converter and fluid pump. The clutch material in its torque converted wears more quickly and thus deposits more particulate into the fluid. The bell housing on the 722.9 is magnesium, which is a soft metal. Both use basically the same fluid pump with a sleeve bearing driven via the torque converter shaft. The elliptical orbit gear on both fluid pumps rides against the inner surface of the bell housing. The 722.9, however, uses a magnesium bell housing which is softer. The sleeve bearing is subject to more wear, which can cause the pump gear to "wobble" and chew into the bell housing and deposit more particulate into the fluid on the 722.9. This is why the 722.9 really needs more frequent fluid changes. Sometime later in the 722.9's life, the torque converter was changed to use less "dirty" clutches, and the sleeve bearing in the pump was replaced with a needle/roller bearing version for a longer, quieter operation with less wobble and less deterioration of the bell housing surface.

If you want to maximize your transmission's lifespan, change its fluid (all of it) and replace the filter. If yours is a 722.9 prior to about 2009, then I'd do it every 40K miles. Later versions, and the 722.6, are probably OK with longer intervals. If you are so skilled and DIY, it will cost you about $100 for fluid and parts.

Regarding the mixing of coolant and transmission oil, the rubber seals used int he original Valeo radiators WILL fail. It's not like the balance shaft failure where it's rare - the rubber they used will deteriorate and allow these fluids to mix. Coolant in the transmission fluid will cause a change in hydraulic properties that will result in bad shifts and poor torque converter performance. Contrary to popular belief, coolant will not rust out your transmission. But it can deteriorate the clutch surfaces over time. Most of the time, a good flush of the fluid and a new filter (and a new radiator) will solve the problem.

cstevenson

Wow, thank you for all of this information, you're making me (and my wallet) feel a bit better about this problem haha!

I forgot to mention, but I drive a 2004 CLK 320, with 206,000 miles. I will definitely do a transmission fluid change now, it certainly couldn't hurt.

Thanks again, you guys are the best!

Rudeney

Note that there are some schools of thought that will say not to change transmission fluid that hasn't been changed in a high-mileage car. Her'es why:

Your transmission contains various gear sets that are manipulated to select the various ratios. They use sets of "sun gears" and "planetary gears" that rotate within and against various drums. Allowing a particular drum to rotate, but locking another in place means one set of gears rotates against another and they all add up to a given ratio. Changing which drums are able to rotate and which are locked thus changes which gears rotate (and even in which direction).. This gives you the various ratios, plus reverse (even two ratios in reverse). Clutch plates are used to lock the drums. There are ducts within the transmission housing and the drums that allow fluid to flow into the clutch plates. Pressure from fluid locks the clutches, thus stopping that particular drum. The valve body contains servos that are engaged to direct the flow of fluid into these various ducts. The conductor plate is the electronic part that energizes those servos based on instructions from the TCU. The conductor plate also contains a few speed sensors that detect and validate which drums are rotating. The torque converter is basically a set of clutches separated by fluid that will engage as the converter spins faster, thus building up more pressure.

The idea is that new fluid can cause a failure because the clutch plates have become worn, but are still able to grip due to the particulate in the fluid. Cleaning out that particulate makes the fluid thinner more slippery and thus gives worn clutches less grip. Personally, I do not subscribe to that theory. I believe that failures occurring after such a fluid change were going to happen sooner or later anyhow. Clutches operating in dirty fluid for 200K miles will be weak. But moreover, thicker fluid filled with more particulate does a poorer job of lubricating the gears and also makes it harder to be pumped through the tiny ducts. The gears in the transmission can only benefit form fresh fluid.

If there is a concern about changing such old fluid, you might consider only the 4-quart pan drop and filter change and not the full flush. Then, do another pan-drop and filter a few more times every 5K-10K.

Oh, one more thing - if you have the Valeo radiator, you MUST replace it and do a full flush to clean out the coolant.

shadenfroh

Rudeney, I just read yesterday that the Valeo radiator problem is present in the 208 too (previously I thought they only started fitting the problematic ones with the 209). Can you clarify how to check the brand of the radiator? I looked all around mine, couldn't find a label, also couldn't identify if mine has the straight or the wavy metal from the photo that's floating around.

Thanks.

xsever

Look at the metal crimps where they meet the plastic.

cstevenson

So I checked the ATF level yesterday and it was fine. The color was green, is that normal?

I'll do a fluid flush this weekend (hopefully) and report back.

xsever

ATF is red. Green is the color of coolant so make sure the car is not driven a single km until the full flush and radiator and filter replacement are carried out.

This happened to my car as it had the Valeo radiator and I caught it early and did the above right away. The transmission was starting to make weird noises and vibrations and we saved it in time.

sailorben

Was it a mucky brown-green or was it fresh and clean. I only ask because I've a slight recollection of some non spec fluids being used as atf, which are green. If it is fresh and clean then it could be that the fluid was changed already but with an incorrect spec fluid. It would still need flushing out either way, however this would help determine whether it is a coolant issue or not.

cstevenson

I'd say it was pretty green, definitely greener than I expected for 200k miles.If I remember right, there was a Fuchs ATF for this car that was green, so I'm just guessing that that's what is in there. I also checked and it's a Behr radiator.

I'll do an ATF flush this Saturday and hope that fixes it, seeing as this is probably the last of my cheap repair options lol.

xsever

A Behr radiator could technically still fail and leak coolant to the ATF; just not as likely as a Valeo which was flawed from the beginning.

Yeah like you said a full fluid flush along with the filter and gasket are your best cheap option for now. Do it and keep us posted. Good luck!

sailorben

Fuchs are the OEM fill for our transmissions, the one meeting MB specs is not green. I'd be surprised if an MB spec fluid was green rather than red. A full flush will correct this anyhow.

cstevenson

so I did a full transmission flush, and though it does seem smoother in general, all of the old problems remain, unfortunately. The car jerks while accelerating and is very slow to downshift. It's quite annoying, I'll be driving up a slight hill and it will upshift and start rumbling like it doesn't have power (because it's trying to climb a hill in fifth gear lol).

I guess my question is what sort of diagnostics can I do now that the ATF flush didn't do anything for the problem? The fact that it didn't affect the symptoms at all makes me wonder if its not the transmission...

How much do dealers usually charge for STAR diagnostics? and can anyone recommend other DIY diagnostics or tests I could do to try and isolate the problem?

Rudeney

Most dealers charge n hour's labor ($100-$150) for a diagnosis. For about that, you can buy your own iCarsoft i980 that can scan and reset codes on all the car's proprietary systems (ECU, TCU, SRS, ESP, ACC, etc.)

sailorben

Alternatively, try hunting down someone local with a scanner.. my local Mercedes specialist only charged me £20 to produce some codes.

cstevenson

welp, my AC compressor seized up and left me broken down at the side of the road on the way to work on Tuesday. So I'm gonna fix that and then get back to this transmission issue haha. Thanks for everyone's help for now, I'll be back in this thread soon lol

xsever

Are you talking about the same car? Are you still driving it?