Mike P

Gurus:

My son's 2004 CLK 500 has developed an issue. Last week he noticed a slightly low coolant.....then a slight "hesitation" with shifting. Assuming the worst.....glycol contamination .......what parts need to be replaced???

Obviously the defective radiator( which in hindsight should has been switched) but does the transmission and/or torque converter also need to be replaced??

Suggestions for remanufactored transmissions??? Transmission Express offers a 5yr/100mile warranty.......

Thanks in advance.....what highly knowledgeable members!!!

Mike
SL65,SL600,560SL,560SL,E300D,240D 2015 SL65 on order

Rudeney

I am surprised a MY2004 would have the bad radiator. You can do a visual check using this as a guideline:

http://forums.mercedesclub.org.uk/sh...42&postcount=3

If you do have coolant in the transmission, it generally doesn't do any permanent damage, but you do need to make sure to get a full flush and fill with new fluid and filter.

Another thing to check is oil intrusion into the TCU. The pilot bushing where the electrical connector attaches to the transmission can leak and oil can "wick" int he the TCU, located under the carpet int he passenger footwell.

Mike P

Rodney:

You are one of the premier CLK gurus!!!! My son lives in Boston......his local indy wants to replace the tranny because of the glycol contamination.......mostly because of the torque converter. What's the downside to trying a COMPLETE flush including lines??? I will have him double check the radiator.

Thanks!!!! It's nice having independent experts assess a situation.

Best regards,
MAP

Rudeney

The main issue seems to be that if the transmission was run for a long time with antifreeze in it, it can be damaged. But if the symptoms have just been appearing, then I doubt that is your case. There is no downside to the full flush other than if the transmission does end up having top be replaced, then you're out the money paid for that flush. For me, I'd rather gamble on a few hundred dollars paying for the flush then gamble on spending thousands for a new transmission that might be just fine.

Glyn M Ruck

Most transmissions survive glycol contamination if caught early. The main damage, if any, is usually to the clutch pack friction materials. The 722.6 transmission is tough.

gaazmon

My 2004 E320 with an 02/04 build had the glycol radiator problem was very surprised when it happened. Luckily the whole thing was covered under CPO

Mike P

Much thanks to the expert advice....especially Rodney and Glyn. My son is off to his indy armed with additional knowledge derived from this forum.

He wants to have the TCU/pilot bushing checked along with what type of radiator. If the trans has glycol, will the radiator fluid appear contaminated also???

Updates to follow......thanks again for the sage advice.

Mike
SL65,SL600,560SL,560SL,E300D,240D
2015 SL65 on order for the CLK owner in Boston

Glyn M Ruck

Back contamination into the cooling system is usually limited due to pressurization but you can see come oiliness in the surge tank.

Mike P

Gurus:

Apparently no glycol contamination evidence. The indy did not even bother to check the TCU. They insist it's the torque converter.

My son's description: "Under linear acceleration, once 30mph is reached the car becomes somewhat jerky until more power is applied to get out of the jerking. Also when the jerking and stuttering happens there is a somewhat loud drone heard throughout the car."

Suggestions???? Just replace the often troublesome TCU part??

Much thanks in advance,
Mike

Glyn M Ruck

Please check the electrohydraulic bush.

This is what a TC failure sounds like. It should make a high pitched whine while stationary & rev dependent. TC bearings fail & then take out the seals & oil pump.


If it is a lock up clutch failure in the torque converter then it should show up on a Star.

Rudeney

My car has been making that noise for about three years. It's probably not "right", but I talked to one of the mechanics I trust at the dealership, and he said about half do this. He said it's the fluid pump on the torque converter, and while they do fail sometimes, plenty of them are just noisy.

As to Mike's problem, so there are no DTCs that indicate the problem? I am surprised. As Glyn said, if it's a problem with the lock-up function, there should be a code. And even if it's just a fluid flow problem, there should be a code, too.

Glyn M Ruck

I very much doubt your car makes that much noise. You could not tolerate it.

I know the noise you mean. Pump was redesigned on later 722.9's. Mine is silent.

Also early stages of TC failure usually give you a high whine at cold start up after standing which then shuts up as fluid pressure normalises in the transmission.

Many code readers are not capable of reading Benz transmission codes. You need a Star or something like a Snap-On Solus.

Rudeney

Let me put it this way - the transmission whine is loud enough that it drowns out the V8 exhaust note for anything below about 3K RPM. It is louder when cold (especially in cold ambient temps) but never goes away. It's louder in lower gears. I have heard this noise in about 1/3 of all 722.9's that I've been around.

Glyn M Ruck

Any correlation with early ones vs later ones in your experience? As they intruduced the pump upgrades? My C240 like yours with 722.6 was quiet. We had a W204 C350 (2008) in the family and that was quiet. My CLK is dead quiet but was one of the last built. A friend has an SLK55 that howls on startup but quietens as fluid pressure normalises.

As you can hear from the clip I posted the failing TC makes a really loud noise. I can't imagine driving a car making that racket.

Rudeney

As the 722.9 production continued, they made changes along the way that have made them more and more reliable. I've tried to find documentation on exactly what changes were made and when, maybe by unit serial number, but I haven't been able to do that. And unfortunately, as the time since I worked for MBUSI gets further in the past, I have fewer contacts that can get me that "insider" information.

My transmission does make the sounds in the video. It's just a "gear whine" sound. At idle, it's slightly noticeable, then gets louder as I rev the engine, but it's not quite louder than the engine. In other words, it's loud enough to hear, but not so loud as to drown out conversation. A guy that works in my office building has a MY2006 E350 that makes the exact same noise and we've talked about it. He said his as done it pretty much since it was two years old. Another car int he lot, a 2011/2012 GLK350 also does this. I've driven a few other that did, too and when I talked to one of the techs at my local dealership, he agreed that it's not uncommon. He said that a few customers have come in to have it fixed under warranty, and they haven't been able to do anything about it short of replacing the transmission. He said he suspects it's actually a problem with drive shaft misalignment where it mates into the transmission as opposed to the pump problem.

Glyn M Ruck

A failed TC would certainly interfere with with conversation.

Interesting. I have not heard it on any transmission later than maybe end 2007.

Mike P

My sincere thanks to forum gurus, especially Rodney and Glyn.

My last post indicated no glycol/transmission intermixing. The Boston indy wanted to replace the trans due to a "failed torque converter". Since the forum gurus had their doubts, while home for an Xmas visit my son had the CLK 500 looked at by my indy. The Pa. indy ran engine and trans codes.......nothing of significance. The Pa. indy suspected a defective EGR. Mobil 1 has been the oil of choice but it seemed pretty dark at the 3000 mile changes......another EGR hint??

The EGR was replaced and the car now runs fine. The Pa. indy also replaced the TCU interface with those notorious O rings along with a complete transmission/TC flush. The 10K mile old Bosch plugs were also changed as a precaution due to additional deposits from the faulty EGR.

$802 including MB trans fluid seems way better than a new trans unit which wouldn't have solved the problem.

Thanks again for the sage advice,
Mike

betrezra

Glad you got it fixed. I could not operate my mb's wo this place.

Rudeney

Good to hear all is well now!

Glyn M Ruck

Good news indeed! And thanks for letting us know. Your Pa Indy sounds sensible & methodical in his diagnosis.