U-SEAL - discrete leaking. Replace or live with it

[BrazBenz]

I tought I may have a head gasket problem.
My mechanic finally diagnosed it as a leaking U-seal - far le$$ trouble...
The leak is extremely small. A little "drooling" and that's it.
I wonder what would happen if i just leave it that way.
Any risk?
Also, I was told that , given that I am replacing the U-seal I should replace the crankshaf gasket as well, taking advantage of the labor costs anyway incurred.
Any thoughts on this?
More on the topic here:

http://www.peachparts.com/shopforum/tech-help/233357-crankshaft-oil-seal-m104-repair-size.html#post1971037

Thanks, Jorge
C280 1997 50K miles (engine 104)

[G-Benz]

Originally Posted by BrazBenz

I tought I may have a head gasket problem.
My mechanic finally diagnosed it as a leaking U-seal - far le$$ trouble...
The leak is extremely small. A little "drooling" and that's it.
I wonder what would happen if i just leave it that way.
Any risk?
Also, I was told that , given that I am replacing the U-seal I should replace the crankshaf gasket as well, taking advantage of the labor costs anyway incurred.
Any thoughts on this?
More on the topic here:

http://www.peachparts.com/shopforum/showthread.php?p=1971037#post1971037

Thanks, Jorge
C280 1997 50K miles (engine 104)

The timing cover gasket seal is a common leak issue and is unrelated to the far-more-involved head gasket leak. I believe there is a top and bottom seal, and the trick is reinstalling the gasket properly...you can reintroduce the leak or make it worse if not done right.

I can't comment on the crankshaft gasket...not sure how that is considered a while-you-are-at-it type of fix without removal of a lot of ancillary components, but again, I'm not an expert.

As far as M104 head gasket leaks, they typically breach at the rear of the cylinder head (although mine failed near the front). The leak goes from a trickle to about a quart of oil every day, depending on how much you can live with! The major symptom is your engine temps climb uncomfortably high at every stop, even if the outside temperature is relatively cool.

[Arthur Dalton]

If the leak is very minor, let it go and watch the dip-stick..you never want to run a 104 on the Full oil level indicator mark ..1/2 way/hot is best and I have seen them actually stop leaking if one keeps the level on the low end of normal capacity.
Benz has TSB on that and recommended 1/2 quart less capacity on the earlier ones and a change in the Manuals to reflect the change.

[richard28]

Arthur, does that "1/2 way hot" also apply to the M103 engine, with or w/o the leak? Thanks.

[Arthur Dalton]

No .. That Campaigne Notice states only 104 HFM/SFI engine.

Camp. # 18/45 -00/134. Date 11/95
O/F Capacity changed from 7.5 ltr to 7 ltr.

Is also states not to excede the 1/2 way mark at 80C and customers should refrain from topping oil level off beyond that 1/2 way index mark on dip-stick. Level should be checked after a 2 min wait of stopped engine to assure all oil has reached the sump.

It also refer to 111 engine with the change being the 5.5 ltr revised to 5 ltr.

Effective Immediately..11/95

[richard28]

Thanks.

[Hirnbeiss]

The key to successful replacement of the lower front timing cover (Stirndeckel) gasket on the M104 is removing the dowel pins (and I think most mechanics include a heavy dose of RTV sealant as well). If you don't remove the dowels, you have a hard time keeping the gasket in place while you reinstall the cover.
It's a straightforward job, but a several hour job with removing the valve cover etc to get access, if my memory serves me correctly.

[Arthur Dalton]

Benz has a specific sealant that works best..

http://www.peachparts.com/Wikka/M104HeadGasket

[BrazBenz]

First of all thanks for the great guidance!
I definitely am at the top of the oil mark an will reduce it.
This will be the first and most obvious action.
Given that I will be in the States in October I will buy the U seal (1/10th of the price of Brazil) and the MB sealants. (002 989 47 20 10 and 001 989 61 20 10)
The main gasket of the valve cover has been replaced recently.
My remaining problem is to understand what really is the infamous U-Seal.
EPC shows a gasket ( A 104 015 02 20) under the name of "Gasket - Cover to the timing case". Is that the U-Seal?
Incidentally: I also head the U-seal replaced but I suspect they used the wrong sealant and - if the part is the above one - they may have used the P/N A 104 015 01 20 that was replaced (as per EPC) and specifficaly said NOT to be used anymore. (but I see sites offering it)
In summary, please help me confirming if I identified the U-Seal correctly.
Thanks again, Jorge

[Arthur Dalton]

http://catalog.peachparts.com/RenderScriptTemplate.epc?_cmd=epccat_VehicleAAA&cookieID=2GN17VPXQ2H30QZK67&yearid=1997%40%401997&makeid=MB%40%40MB%40%40X&modelid=C%2D280%2D001%40%40C+280+Sedan&catid=A%40%40Engine+Mechanical&mode=PA&subcatid=A5066@@Timing+Cover+Seal+Strip

The problem with re-occurence leaking of this seal after a proper replacement/install has 90% of the time been attributed to the incorrect/generic sealant being used. If you use the search feature , MBDOC has an article on this somewhere in there.... and he also has mentions one specific Lock-Tite product# replacement that has been working well..but your best bet by far is the Benz spec. sealant, even tho it is expensive, it is sure.

[NDP 2.6 190E]

Originally Posted by Arthur Dalton

No .. That Campaigne Notice states only 104 HFM/SFI engine.

Camp. # 18/45 -00/134. Date 11/95
O/F Capacity changed from 7.5 ltr to 7 ltr.

Is also states not to excede the 1/2 way mark at 80C and customers should refrain from topping oil level off beyond that 1/2 way index mark on dip-stick. Level should be checked after a 2 min wait of stopped engine to assure all oil has reached the sump.

It also refer to 111 engine with the change being the 5.5 ltr revised to 5 ltr.

Effective Immediately..11/95

I can vouch for this.

My recently acquired E320CA started leaking oil badly at the rear passenger side near the head gasket. Even though the PO had a receipt for previous head gasket replacement, I feared the worse

Turns out the main leak was caused by a faulty (or badly fitted) valve cover gasket. The rear two spark plug holes even had 1/4" of oil sloshing around. Since the paint on the valve cover was starting to flake, I had it powder coated before refitting with a new gasket kit.

But, the car still had a couple of small drips from the bellhousing area when parked overnight. The problem turned out to be an oil overfill by Jiffy Boob - where the PO had the last oil change done The oil was actually above the max-mark on the dipstick. They also managed to ruin the sump plug by using about 1000lbs or torque and rounding over the bolt-head

Anyway, I drained off excess oil to the dipstick half-way mark, and the leak has been totally eliminated. Hoorah

Cheers!

[Arthur Dalton]

Yeah, one of the few Benz screw-ups they would actually admit to....but at least they did send the info out and the remedy was simple enough.