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#1
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Valve cover bolts will not tighten on the head.
On my 1994 Mercedes E320 wagon, I replaced the valve cover gasket with a new one. When I put in the 12 bolts on the valve cover and goes on top of the head, all but two of the bolts went through ok and tightened. The other two bolts did not tightened and upon looking at the threads of those two bolts, it appears to be some form of liquid on the bolts threads. The 2 bolt threads themselves are fine, no thread stripping on the bolts. It seems that the 2 inside threads on the top head are stripped and the bolts will not tightened. Here is the location of the two holes on the valve cover that the 2 bolts will not tighten on the head. (blue circle):
Is there some kind of thread repair that can be apply to the two holes on the head and be able to tighten the bolts? I believe there is something like liquid thread that can be apply on the bolts. I appreciate some comments/feedback on this issue. Thanks for reading. |
#2
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Are all 12 bolts the same length? If so then your best bet is to install new threads with a Heli-coil or a Time-sert replacement.
Band-aid approaches are a short term repair at best and on valve covers they are almost futile.
__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.” ― Brian P. Cleary, You Oughta Know By Now |
#3
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Mike D. Thanks for responding. No, 8 bolts same size, 4 bolts same size just a little shorter than the other 8 bolts. In my case, 1 bolt is longer, 1 bolt is shorter, that are not tightened. Also, I did some checking out where using Loctite® Threadlocker Red 271™ Nut and Bolt Locker on the bolts will tightened on the head (through valve cover)
Will this Loctite Threadlocker Red work? |
#4
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Already answered the question.
You might try using a SLIGHTLY longer bolt on the two stripped threads. Be careful, it is easy to crack aluminium by installing a bolt longer than the existing hole depth. Do yourself a favor and replace those threads. I'm a lazy mechanic, I just like to fix things ONCE.
__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.” ― Brian P. Cleary, You Oughta Know By Now |
#5
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Mike D. I have never done this replacing threads. Also, I was doing some checking on this issue. I came across this Loctite® Threadlocker Red 271™ Nut and Bolt Locker. Will this work? Also, I remember someone using some white tape (thread sealer?) on the bolt thread and shows through the groves of the bolt thread. Don't remember the name of this white tape. Also, will the m6 x 1.5 Helicoil repair kit will work on 1 m6 x 50 bolt and 1 m6 x 65 bolt? Both bolts go on inside the top of the valve cover and threaded to the top head, two different lengths.
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#6
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The thread repair kit will work on both length bolts.
__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer |
#7
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Sugar Bear, thanks for your above message. I found Helicoil 5546-6 M6 x 1 Metric Coarse Thread Repair Kit on Amazon. Is that the correct size and length for both m6 x 50 bolt and m6 x 65 bolts?
I can't see to find Helicoil m6 x 1.5 Helicoil repair kit will work on 1 m6 x 50 bolt and 1 m6 x 65 bolt? or does that matter? What would be correct Helicoil thread repair kit based on the bolts size as mentioned above? |
#8
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dmorgan, measure 1) the thread projection of the two bolts past the end of their respective spacer sleeves, and 2) the depth of the blind holes in the head. Those dimensions will determine which length Helicoil to install. Now you know why oil accumulated in the spark plug holes. It's likely a tech stripped the female threads in the head using an air tool, and did not want to take the time to repair his mistake.
The Loctite Threadlocker keeps bolts from loosening due to vibration. It does not repair stripped threads.
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Fred Hoelzle |
#9
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Clean the holes out make sure they are clean and without any oil ,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
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#10
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Put in helicoils after tapping the holes. Tightening with valve cover bolts. Bolts tight and job done.
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#11
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Good deal. Keep the inserts handy for the next time you change the gasket.
__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.” ― Brian P. Cleary, You Oughta Know By Now |
#12
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Mike D. Thanks for your latest response. I appreciated it.
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#13
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Sugar Bear, optimusprime, and Ferdman. Thanks for the coments and I appreciated it.
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#14
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Thread Repair
I much prefer the time-sert if you have not already purchased the Helicoil, its a much stronger repair.
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#15
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I prefer the Time-sert also. The one draw back to using the Time-sert is the fact you need to drill a larger hole for installation. This is not always possible in some areas and in fact can cause a fracture.
If you have adequate material and the need for the extra clamping force then the Time-sert is the choice. For the application in question, a Heli-coil is sufficient.
__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.” ― Brian P. Cleary, You Oughta Know By Now |
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