stripped thread help

[CzarFC]

Why should anything go right today I ask myself as I strip out aluminum threads from the block.

I just re-installed my passenger's side head on my 560SEL. After torquing all my 8mm bolts I was installing the three 6mm bolts which are forward of the timing chain. One is internal to the engine, the other two are external. The long one (the one on the top) stripped out.

My question is what do I do? Do I:
a) remove the head and time-sert the hole and try again
b) drill it all out and use some sort of insert
c) FIDO - Fudge It, Drive On.
d) something else?

Also if I pull the head again, do I need to get a freash gasket to replace the new one I just put on?


Thanks in advance!


Scott

[stevebfl]

Real hard to tell without seeing it.

I would try and install an insert from the current position if possible. If removing the head is the answer, I might do it at my leisure. The bolts in question only seal the timing cover from oil leakage. It is conceivable it won't leak and if it does the head doesn't get any harder to do with time. A new gasket should be used. This is all based on it being your problem and your decision. Selling it in such a condition would be fraud in my eyes, so it always is something that will be there, until it is fixed.

[dmorrison]

Stripped out a drilled/taped hole in my sons alluminum transmission.
To fix it I got a Helicoil

With the helicoil, you will drill out the hole with their drill and tap it with their tap. Then insert the helicoil and install the bolt.

http://shop.store.yahoo.com/toolsplus/hel-threading-tools-helicoils.html

http://www.emhart.com/products/helicoil.html


You should use a new gasket. When you torgue the head you partially crush the gasket. So pullling the head and using the old gasket sort of sets you up for a leak.

With my sons 65 mustang I had to pull the left head 3 times in one month. Gasket leak problem twice dropped valve once. Boy what a pain getting that straightened out.

Dave

[CzarFC]

Well, heres more of the story to answer some questions. I just had the heads done. I purchased the car in July and have no intentions of selling it. I'm hoping to find a fix that does not involve pulling the head again as that is such a joy to do solo, especially since I have the cam towers and cam installed already.

If anyone knows a way to do this without pulling the head I'm all ears otherwise I suppose I'll be ordering a thread repair kit and head gasket this week and I know what I'll be doing next weekend.

Thanks for the advice!


Scott

[samiam4]

If your careful- you can do it in-place.

When tapping for the heli-coil or timesert, use grease to retain the chips. After it starts, I'd go forward 1/2 turn then backward to break the chips. Remove the tap a few times to clean the grease/chips. Not hard, just not a place to make mistakes.

Yes, new headgasket and measure the headbolts. They are stretch bolts and are generally only reused once.


Michael

[CzarFC]

Thanks for the heads-up sam!

I went back out to the garage and did some looking and my fingers (with dental tool) saw something I didn't make out at first with my eyes due to the light (hard to get light down a 3 inch hole where I can still see) anyway, what I felt, then saw was about a 1mm radius difference between the blind hole in the block and the channel though the head. It looks to me as if I can do this in-situ perhaps scarring the channel with the new tap, but nothing which would cause permanent harm. I'll get the kit and if it doesn't fit through the channel, then I'll pull the head and order a new set of bolts & gasket. (I'd just like to avoid the hasstle!)

Thanks for the advice, I appreciate it alot!

Scott

[myarmar]

Scott, when you said the 6mm bolt you probably ment allen head size? Is so the thread is M8. Now if it is fine thread M8x1, the helicoil insert outside diameter before insertion would be 10.25mm. The tap for it would have a major diameter 9.422mm. If it is coarse thread M8x1.25 (unlikely) you need even more clearance in the head hole. Check this hole to make sure you have clearance!
Reg. Mike

[CzarFC]

Mike- yes, I was refering to the hex-bit size of 6mm. Thanks for the tip, you saved me a bit of research I was planning on doing tomorrow!

[pmckechnie]

Something I have found works in some cases is measure the depth of the hole. Then subtract the length of the bolt. Hopefully you will find the hole has room for a longer bolt.
Lets say that you find the hole is 3 1/2 inches deep and the bolt is 3 inches then go to the hardware store and get a bolt 3 1/2 inches long with the same threads. If it won't go quite all the way in you can use a washer or 2. The threads in the very bottom of the hole have never been used and usually are strong enought to get the job done.

[CzarFC]

I picked up a helicoil kit today. I got it home and looks like I dodged a big bullet as the tap just fits through the channel to rest on the head with just enough of the shaft exposed to tap deep enough into the block!

Now if I can avoid screwing this up! LOL!

...only if my luck changes! Can ya'll tell I'm a pessimist?

[CzarFC]

Thanks everyone for the advice! I was able to drill out the old threads and install a helicoil without pulling the head. It took a couple of times and a couple of dead heli-coils (which I was fortunatly able to extract) before I got it right. The bolt is now in and holding good torque. Since I didn't know what the torque spec on this bolt is I set it 20Nm and let it go. Hopefully thats not too tight.

for the record, the bolt is M8x1.25

Again, thanks all for the suggestions and to the next guy who does this, it sucks, but it's fixable!



Scott

[recruiting]

Help please, I have a 1995 C280 and 2 of the bolts securing the valve cover are stripped. They hold a bit but it looks like they are damaged down in there and do not give a unifide hold to the valve cover thus I have some oil seepage on one side.

I want to fix this issue with a Helicoil kit but do not know what to order, can anyone help me out with this...

Thx,
Bill

[gerryvz]

This SAME exact thing happened to me with the same bolt even ! This thread really saved my bacon. Thanks for documenting your fix.

Cheers,
Gerry