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for the details on crankcase ventilation on the 104.99x engine, see page 4 of this PDF, http://new.freescruz.com/.priv/W124/w124CD1/Program/Engine/104/01-0400.pdf



its fairly complicated and clever.


And It's very effective at keeping the engine clean as can be seen in my M104.995's like-new valve train with 228k miles on it.



Of course the previous owners' maintenance schedule and choice of oil and filter may have something to do with it as well.

PS. Here's another interesting article on the M104 crankcase ventilation and vacuum although it applies to the W210 body so the idle control valve and PCV valve doesn't apply. Also, there is no need to use an adhesive to glue the VC gasket into place.

http://www.pelicanparts.com/techarticles/Mercedes-Benz/09-ENGINE-Fixing_Common_Vacuum_Leaks/09-ENGINE-Fixing_Common_Vacuum_Leaks.htm




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Discussion Starter #22
Stripped threads inside the holes on the top head

tuttebenne, LeftCoastGeek, mercron, thanks for your latest posts.

Here is the latest update:

My Mercedes is still having burning smoke and smelling oil in the back of the rear engine area. I checked the valve cover bolts and four of the bolts were loose, two on the each side in the rear engine area. Tightened two bolts on the valve cover on the rear engine area on each side of the exhaust manifold and the intake manifold area.

However, another two of the bolts (one of each side of the intake side and the other bolt on the exhaust side) were still not able to be tighten. I feared the inside thread holes on top of the cylinder head inside threads are stripped. I thought the issue was resolved by putting in helicoils. When I removed the two bolts that were not tightened, I saw helicoills still attached on the end of each bolt below the bolt cover/sleeve. See the attached photo below. The 2 blue circles on the inside valve cover indicates the locations of the stripped threads on the top of the clyinder head.

It seems the helicoils are not doing its job. If I go ahead and retread again and using helicoils at a greater size hole, I believe it will crack the head since the top of the clyinder head thread hole is rather small on its width size.I have three options:

1. Take off the valve cover and using JR Weld and fill in the two holes using a syringe and dowel to push in the mixture to make it solid and tight. After 24 hours to dry, use a threaded drill bit and drill inside the hole. The trick is the drill have to be very straight going down on the new thread hole so the new rebuild thread will work on the valve cover bolts.

2. Someone wrote "Clean the holes out make sure they are clean and without any oil inside or the repair wont work. Fill the holes with plastic metal.Push the bolt in and let it set for a day.Then unscrew the bolt , Then ,clean the top of the hole flush.These are very low torque and if you over do it they will strip out in normal circumstances . I think 9nm to lock up . Put some hylomar blue on the gasket as well as you refit it. Also keep it all clean, or bits might get in to the oil"

Is plastic metal as described above referred to Bondo® Plastic Metal, 5 ounce, Plastic Metal seals?

3. The other option is I am trying to avoid (most costly and time consuming process) and that is to replace the head on top of the engine block with another head that have no issues on the inside threaded holes.

As for the three choices above, it seems that number 2 is the better choice. Any comments/feedback/advice is greatly appreciated.
 

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Discussion Starter #23
A better view/image of the head with red circles showed the stripped threads location

Mercron your picture of the head without the valve cover in your post #21 is excellent. My picture of the valve cover showing upside down with the blue circles showing the holes is rather crude. So I use your image and made red circles to show exactly where the female threads are stripped and probably caused the leaking oil and burning smoke. I hope you don't mind using the cropped picture to show the locations (in red circles)
 

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No problem. Hope it helps you. I thought that the cylinder head would be tougher to strip than the valve cover. But maybe someone over tightened the bolts due to a hardened rubber grommet. Out of your three choices, it looks like no 2 is the best for now.


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Discussion Starter #25
I also thinked that no. 2 is the best option of the three choices as well. I will go ahead and try this Bondo stuff and see how it goes. Stay tune.
 

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Discussion Starter #26
Right now I am putting on hold on this bondo thread stuff. I wanted to explore other options other than the ones mentioned earlier.


See attached photos below of the 2 bolts with helicoils that were removed. Notice the 2 bolts are the same size M6 x 65 with washer:

in regards to the type of form a thread inside the hole on top of the head. Should I use Loctite 442-28654 4.80ml Form-A-Thread Stripped Repair Kit or Bondo® Plastic Metal, 5 ounce, Plastic Metal seals? Does it make any difference? Any other brand of form a thread that would work on repairing these particular threaded holes on top of the head?

What about replacing with a longer Helicoils with the same size bolt M6 x 65 that will fit on the bolt?

How about using a longer bolt than the current size M6 x 65 to replace using a longer or shorter helicoils without fracturing the top head hole thread? Can that be done and if so how much longer of the bolt size M6 x 65 that could possibly work?

if using a form a thread, where should the application goes? Inside the hole? On the bolt? Would putting on form a thread on the outside or inside of helicoils would work?

How about using a longer bolt size to replace the current size bolt? Would that work without damaging/fracturing the area around the bottom/top hole of the thread? If a longer bolt is advisable, what length should it be? Would using a longer helicoils or the same helicoils that I have now would work better with a longer bolt size? Sorry about repeating myself. Just to explore what are my best options at this point.

Any comments/feedback/advice is greatly appreciated.
 

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Worst case scenario is that you may have to tap it and buy bolts of the same length but one size larger in diameter. Just use the existing washers and grommets.


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Discussion Starter #28
mercron, if going to tap it and buy bolts of the same length but one size larger in diameter, then the bolt sleeve or boot cover will not fit in the larger bolt size as shown above in the image/picture.
 

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True. You may have to not install the sleeve anymore. Just make sure that the grommet and grommet cover is installed.

That middle part of the valve cover is not to prone to leaks anyway unlike the corners.


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Discussion Starter #30
Permatex 81668 and LOCTITE 28654 Stripped Thread Repair Kit

Update:

I ordered Permatex 81668, a retread thread compound, online, since I have a hard time finding it in local stores. Also, I found another retread thread compound LOCTITE 28654 Stripped Thread Repair Kit, that does the same thing as well. Are there any other related retread thread repair kit that are similar to the ones like Permatex 81668 and LOCTITE 28654 Stripped Thread Repair Kit that are found in stores instead of ordering online?

I saw this youtube demonstration and from the looks of it, it appears to be a very good setup, less fussing, etc.




Check it for yourself and let me know what you guys think. The repair retread thread goes on the bolt and not the hole as demonstrated in the video. If that works, great.
Does this stuff really works to keep the valve cover bolts that goes inside the top cylinder head thread from stripping?

I am still waiting for the 3/8 socket torque wrench to show up so I can torque correctly on the bolts goes on the valve cover. This is why I have not been responding back lately, Stay tune.
 

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Discussion Starter #32
Mercron, thanks for your comments and the pdf file. The bolt torque is 10nm or closed to 7.4 feet per pounds. The 3/8 inch torque wrench I am waiting to arrive has a torque range of 5nm to 80 nm.

On page five of the pdf file, it also said:

Note:

Remove grease from sealing groove and existing reusuable gasket so that the gasket adheres better to the cylinder head cover.

What kind of grease is it referring to? RTV black sealer?

Since the valve cover gasket was new the first time I replaced the old one, I am going to reuse the valve cover gasket again. Before that happens, I will clear/clean the inside groove. The same thing applies to those two half moon gaskets on the rear/back of the cylinder head. After cleaning those areas, should I apply RTV black gasket sealer inside both the valve cover grooves and the half moon gaskets grooves as well? I did that before with the valve cover gasket, but not the half moon gasket grooves. This maybe explained the leaks coming from the rear cylinder half moon gaskets without putting the RTV sealer inside the groove in the first place.

Also, do I remove the helicoils on the two valve cover bolts when I apply the Permatex 81668 retread thread or just leave the helicoils on and apply the resistance compound prior to add the combo compound on the valve cover threaded bolt?
 

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The bolt torque is 10nm or closed to 7.4 feet per pounds. The 3/8 inch torque wrench I am waiting to arrive has a torque range of 5nm to 80 nm.
a torque wrench rated up to 80 Nm will not be very sensitive down at 10 Nm ... for small torques like that I prefer using a 1/4" wrench that has a max around 20-25 Nm. In general I try to stay above 25 or 30% of the wrenches maximum, so a max 80 Nm wrench, I'd use for torques above 20-25 Nm.
 

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I think it meant remaining oil. You shouldn't have to use sealant on the VC gaskets including the half moon ones. Just wipe the channel on the cover and the cylinder head surface dry of oil. Remove any existing sealant on the VC channel with a wooden stick (i.e. disposable chopsticks).

Check your work with a telescopic mirror especially in the back before you start bolting the cover.


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Mine will have sealant on it when i refit it .I never trust gaskets like these on their own ..Thats just me and not a guide .
And the rocker box is not fitted with force. 10 NM is the right settings . Its a job i do need to do myself asap, i to get a smell inside the car now and then .The rockerbox gasket is worn and weeping .. The days of 1/4 thick cork is no longer used .Shame realy as they are reusable.
 

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PS. You might want to pull up the coil pack ground spring (center of image) to make sure that it touches the cylinder head when you bolt the cover back on.

I had to do this on mine as that spring was not grounding my cylinder no 6 coil pack. And no, the magnesium alloy valve cover is not a good ground connection even if the coil pack is bolted onto it.

Check all three ground pins for the coil pack for ground when you have the valve cover on prior to bolting.




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Discussion Starter #37
Update: The torque wrench arrived yesterday and the Permatex 81668, a retread thread compound arrived today. The torque wrench is impressive, in my opinion. Heavy and firm grip on the handle. Solid steel all around. Will see how this torque wrench performs.

LeftCoastGeek, Mercron, and Trevor Hadlington, thanks for your latest comments/posts/tips. Tomorrow, I am going to work on this nasty oil leak issue. Stay tune.
 

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Discussion Starter #38
Update

After removing the top middle cover top on the valve cover, no oil is on inside the coil pack, wire sparks area, etc. See pictures 1 and 2. That is good news due to the fact when I first tried this job earlier, oil was everywhere before replacing with new valve cover gasket kit and replacing the fuel injector in the front facing on the driver's side, due to missing o ring.

While I removed the remaining 12 bolts on the valve cover, several of the bolts that goes on the valve cover, especially the front three bolts and the last two rear bolts, were not torque tight when reassembled the first time with new valve cover gasket kit. Then I remembered when I first put in the replacement valve cover gasket kit and after tightened the bolts, I droved the mercedes for a few miles. Afterwards, I did not checked the bolts again to the specific 10nm, since I did not have a torque wrench in the first place to re-tightened the bolts while the engine was still hot. Somewhere I missed/forgot to retorqued the bolts after the first time. Someone mentioned this somewhere. Always checked the torqued bolts first and second time after running the engine. Live and learn.

After removing the valve cover, I noticed a small opening on the valve cover gasket that was not set properly grooved inside the valve cover. See the pictures 4,5,6 and 7 below. The valve cover gasket loop facing on the passenger side rear engine. This could be the cause of the oil leaking dripping down on the exhaust manifold which resulted in burning and smoking oil. The gapped opening was big enough to cause a lot of oil to leak down along the side of the exhaust manifold and its pipe. Only after reassembled the valve cover gasket properly and set it in the groove will I know for sure that is the culpit.

Then it start to rain.... Stopped what I was doing until the weather is clear of rain. Mother Nature strikes again!!! Stay tune.
 

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Good. I think you've nailed it this time. Make sure to wipe the mating surfaces of the cylinder head clean of oil prior to reassembly. Bolt lightly and torque with a criss-cross pattern like you're stitching it closed or lacing your shoes including the center bolts.


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Discussion Starter #40
Mercron, thanks for your last post. I hope I nailed it this time, too!! The weather tomorrow should be better with clear skies enough for me to continue to finish this job once and for all. Stay tune.
 
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