'99 E320 - Need help with transmission problem and preventative maintenance - Page 3 - Mercedes-Benz Forum
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post #21 of 26 (permalink) Old 04-05-2019, 09:10 AM
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Vehicle: 1999 C280 (sport), also 2001 SLK230
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I'm going to second @01blackhawk 's comment on URO parts. They are cheap Chinese, and will cause you heartbreak. As for the connector, it's a critical part, and I'd be inclined to go OEM also. You won't be paying much of a premium.

Also, you don't need to replace the lock pin on the dipstick tube. I've run my '99 C280 without the lock pin for 25,000 miles, and it has never come off, nor leaked, nor done anything untoward. And having the pin out lets me check the fluid level more easily.

As for your fluid, it looks bad to me. Yeah, the grit is what you say, but that oil should be pink-ish in color. So do the fluid change ASAP.

When I changed the fluid in my '99 C280, I had to disconnect the exhaust pipe which crosses just under the torque converter and then put a screwdriver into the joint. This deflected the exhaust tube just enough to allow me to get at the drain plug for the torque converter. I'd highly recommend draining everything, including the torque converter. That way you have the cleanest fluid possible going forward, and given how dirty your fluid looks, I'd consider that important if it were my car.

Finally, once you've drained the fluid, look at the bottom of the pan. Some clutch dust/residue is normal, but if you see shiny bits of metal, you've got a more serious problem. Post a photo or two, maybe one where you've dragged a finger through the thickest bit.

Finally, there's a terrific thread here on the 722.6 transmission. I'd read it, and also look up the Sonnax spring replacement kits. Here's a link to all their 722.6 transmission products. https://www.sonnax.com/units/211-722-6 The regulating pressure control valve spring is a common problem, and if you're in there, it might be wise to simply replace it. It's about a $10 part.

Good luck and let us know how it turns out!

Kim G
Redding, CA
Where we recently had a weird problem with our own transmission that appeared after sitting for 2 months, and then went away after being driven for a few days. I suspect it was the shift position sensor in the console.

P.S. My transmission (with the torque converter) took about 7.5 quarts of fluid, if I remember correctly.
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post #22 of 26 (permalink) Old 04-05-2019, 03:23 PM
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You only need 8 quarts. That's the capacity of your transmission. This is in the owners manual.

You don't need the red locking pin. The dipstick cap stays on fine without it. You won't need another drain plug either. I did the same thing thinking it's a good idea to have a backup but I realized it's very hard to strip or round out the drain plug head.

Also you need to get genuine Mercedes parts. The transmission adapter plug, the pan gasket and the transmission filter. Those other brands you got can't be trusted. Nor can any of the other aftermarket brands for the parts that you are getting.

And do not drain your torque converter, you will allow your K2 bushing to run dry which will increase your chances of failure. If you want to change your fluid you will need to just drain the pan and refill, and do that process a few times to get all the old fluid out. You can also disconnect your transmission cooling line and drain from there but that's more work.
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post #23 of 26 (permalink) Old 04-05-2019, 03:42 PM
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OP probably got confused now with all the different suggestions
I agree with the OEM parts, youd end up spending maybe $15 more but get the oem parts.
I also agree with not draining TC, but disconnecting the line is still easiest method as long as you have a second person. No lifting, no ramps nothing required just a wrench to disconnect the line and hoses and dipstick which you already have.
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post #24 of 26 (permalink) Old 04-08-2019, 09:29 AM
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Pardon my chiming in, but I'm confused now about the TC draining. I have a 99 and changed my fluid at 75k when I got it and again at 115k. Both times I specified to the shop to drain the TC to get max amt of old fluid out. Haven't had a problem yet. It has 139k on it now and I'm probably going to change it again at 145k (I only put about 6k/yr on it). So should I continue as previous or tell them not to bother draining the TC?

I agree about the OEM parts. As infrequent as AT service is there's no reason to try to save 15 bucks. The MB parts are quite reasonable even at the dealership.
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post #25 of 26 (permalink) Old 04-08-2019, 09:45 AM
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I'm in your camp: drain the torque converter. Yes, that means on startup you are running on the remaining oil film (which has a high propensity to literally stick around between tight-fitting parts). However, it's only for a minute or two at most, and only (if you're not an idiot) at idle speed with zero load. So I think fears of running the TC without fluid are akin to not changing the oil in the engine because when you restart it, you'll run it without oil for a moment.

The normal procedure would call for draining the transmission and the TC, then refilling the transmission until you hit the high point on the dipstick, then start the car and idle it for a minute or so. Then remeasure the fluid/oil and add. Reiterate until the car is at a normal fluid level. Then go out and drive it around until it's hot to get the fluid level exactly right. This should not damage anything.

Otherwise, if you don't drain the TC, you are doing iterative fills with very expensive fluid and/or leaving half the dirty fluid in place. Right? The TC contains roughly half the fluid in the system. Fill it, run it, drain it, refill (without draining the TC) and you still have 1/4 dirty fluid. Do it 3 times and you have 1/8th dirty fluid. Four times leaves you 1/16th dirty fluid, maybe acceptable, but I'd personally prefer that it be de minimis. But if you're using the recommended fluid at ~$15/quart, then you'd have to spend $480 in fluid to get to 1/16th dirty or 15/16ths clean. In my book this is not a good way to go. I will personally continue to drain the pan and the TC when I do my next fluid change.


Kim G
Redding, CA
Where we love converting torque.
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post #26 of 26 (permalink) Old 04-08-2019, 11:36 AM
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I’m a TC drainer but it’s hard to ignore the advice of an expert like MAVA.

On one hand draining the TC can’t be a different experience for the K2 bushing from installing a new TC. On the other hand, you don’t install a new TC every 50K miles... unless you’re MAVA

I drained the ‘98 wagon TC when I got it at 16xK miles, I’ll drain it again at 200K miles, then hope it lasts a couple of years after that. At the rate other things are starting to go, it’ll be retired before 250K miles. It’s barely worth $1000 today as it is. You folks with keepers have a more to consider.

Contrary to 01blackhawk’s claim, flushing is more work for me. I have to be under the car to change the filter so draining the TC is less work than flushing. I do enough flushing with the ‘02 wagon and non-MBs in the fleet.

Doesn’t the FSM say to drain the TC?

98 E320s sedan and wagon
02 C320 wagon
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