Oil Leak - Top front of Engine

[bpossel]

In the process of scanning old posts this morning (from this website and the Pagoda113.com website), I came across a post that has solved an oil seapage question that has puzzled me for some time.  I wanted to share with you as you may also have this issue...  Note: post came from the Pagoda113.com site from "Flips, dated Aug 2004"....

Here is a picture of my engine which shows the oil seapage issue.  I thought that it was coming from the valve cover gasket.  It turns out that it was coming from this screw hole, and the mystery solved with this old posting from the Pagoda113.com site... (read below).  Note: my bolt was installed, but w/o a seal as Dan C. mentions...



"...Here's something to watch out for...at the front of the head, there is a bracket that is supposed to bundle all the fuel injection lines together and attache them to the head. My car only has the part of the bracket that bundles the lines, and I only found out the hard way about the bolt that secures them to the head. This bolt serves a dual purpose. It also retains the shaft that the timing chain tensioner pivots on. The only thing holding the shaft in is......the bolt. I'm still not sure if the bolt was there and loose, or if it was never there, but eventually, apparently the shaft worked itself out of the hole. I had pretty much finished my "to do" list on the car, including fixing the leaky tachometer drive bushing, and was enjoying the fact that I no longer had to keep carboard under the car to catch leaks. I walked up to it in a parking lot one day, and saw a lot of oil under it. "Can't be from me" I thought, "my car doesn't leak anymore". Until I noticed the same puddle the next day. Oops. Like I said the shaft had come completely out, and now oil was squirting out the front of the head, apparently far enough to hit the fan at high rev's, because it's everywhere. Started to fix it last night, but of course dropped the little spring that keeps the tensioner bracket inline with the chain. Had to pull the cam sprocket off to find the spring, but I found it, and now have a plan for reassembly involving several wire ties (one holding the chain to the sprocket, one holding the woodruff key to the shaft, and one to hold the spring compressed), and hopefully I'll be OK. Just wanted to warn some folks about this, though, because I can see how someone wouldn't worry too much about this innocuous looking bolt. I'm just very very glad that the tensioner bracket stayed in place enough that camshaft didnt' get way out of time and destroy the whole engine..."

Dan C. replied with "You also need to place a seal on both sides of this bracket or oil will seep out..."


bpossel  (Memphis, TN.)
'71 280SL  /  '97 E320

[glennard]

Bob, Might have one back in the garage in Boston.

[jeffc280sl]

I was just working in this area.  This bolt is also used by the FrigKing A/C bracket.  Mine did not leak and had no seals that I could see.  I think I will go back over this item and install seals as per the recommendation.

Jeff C.
1970 280SL 4-speed

[jeffc280sl]

Had a look at the bolt Bob is talking about and discovered that it was not very tight.  I backed it out and found some aluminum threads pieces in the steel bolt threads.  Leads me to believe the threads in the head are stripped.  That's one issue.  

I have factory A/C and the A/C bracket is also secured by this bolt.  The bolt threads are 35mm long.  Is this bolt the correct length?  The pin appears to be about 50mm deep measuring from the outside of the A/C bracket.  Does this bolt thread to the aluminum head or the timing chain sprocket arm? Is the bolt supposed to but up against the pin.  I'm wondering if the bolt in my car is too short.  What does the end of the pin look like?

Thanks for the help.

Download Attachment: 20056434913_tensioner.jpg
62.06 KB

Jeff C.
1970 280SL 4-speed

[Naj ✝︎]

quote:Originally posted by jeffc280sl

Had a look at the bolt Bob is talking about and discovered that it was not very tight.  I backed it out and found some aluminum threads pieces in the steel bolt threads.  Leads me to believe the threads in the head are stripped.  That's one issue.  

I have factory A/C and the A/C bracket is also secured by this bolt.  The bolt threads are 35mm long.  Is this bolt the correct length?  The pin appears to be about 50mm deep measuring from the outside of the A/C bracket.  Does this bolt thread to the aluminum head or the timing chain sprocket arm? Is the bolt supposed to but up against the pin.  I'm wondering if the bolt in my car is too short.  What does the end of the pin look like?

Thanks for the help.

Download Attachment: 20056434913_tensioner.jpg
62.06 KB

Jeff C.
1970 280SL 4-speed

The tensioner pin is threaded so that it can be pulled out with a 6mm bolt:

Download Attachment: TensionerPin.jpg
40.95 KB

Without the A/C brkt,the original bolt is only about 15mm deep to keep the pin in place. It threads into the head.


Download Attachment: TensionerPin2.jpg
51.19 KB

naj

68 280SL

[jeffc280sl]

Thanks so much Naj.  

The A/C bracket and the fuel injector clamp bracket together are 20mm thick.  That means my 30mm bolt is threaded just 10mm into the head.  If the non A/C bolt has 15mm of thread than I suppose I could go with a slightly longer bolt.  Still means I need to repair the threads in the head.  Any ideas how to do that?  And I just put it all back together.  Oh well.

Jeff C.
1970 280SL 4-speed

[ja17]

Be careful, too long a bolt will go in and bottom out against the pin, tightening further can actually crack the head casting! Saw someone do it once!

Joe Alexander
Blacklick, Ohio

[jeffc280sl]

Thanks Joe,

Now that I've read some about heli-coil that may be what came out of the head with the bolt.  I have a feeling this was repaired once before.  Is heli-coil a one time application?  Must it be repaired each time the bolt is removed?  Been reading about timesert.  Sounds like the best solution.  I could always drill it out and tap it for the next size bolt.  Maybe next time I tear the front of the engine down I'll do one of these.  Leaning towards heli-coil right now.  Comments please?

Jeff C.
1970 280SL 4-speed

[ja17]

Hello Jeff,

Yes, you can re-install heli-coils as long as long as the threads for the coil are still intact. As I recall, this bolt is a less common thread. Damage usually occurs when someone uses the right diameter bolt but with the wrong threads.

There are other type of thread inserts on the market. A thread insert like heli-coil would be your best solution, since you would be able to use the original hardware.

Joe Alexander
Blacklick, Ohio

[jeffc280sl]

Thanks again Joe,

The bolt used in my car is an M12 x 1.5.  I wonder now if this is the correct/original bolt.  Can anyone confirm the bolt size?





Jeff C.
1970 280SL 4-speed

[Naj ✝︎]

quote:Originally posted by jeffc280sl

Thanks again Joe,

The bolt used in my car is an M12 x 1.5.  I wonder now if this is the correct/original bolt.  Can anyone confirm the bolt size?

Jeff C.
1970 280SL 4-speed

I think the thread is finer than 1.5. (Original bolt N 000961 012047). The bolt is 12 x 1.5 with 16mm shank.
I may have an old bolt but it will take some finding!!!
Anybody else have one handy?
naj

68 280SL

[jeffc280sl]

Thanks Naj.

Interesting info.  Maybe the PO used the wrong length and pitch bolt.   It would be nice to know the correct size.  Then I could tap it and see if there are any useable threads available.

Thanks for your help and Happy New Year!

Jeff C.
1970 280SL 4-speed

[jeffc280sl]

The more I read about helicoil and timesert to do this right the radiator has to come out, fan and alternator have to be removed and I have to remove the A/C bracket.  Now I have access to the stripped hole.

Options:

1) helicoil-need to drill out the hole, tap it and insert coil. Use correct M12 bolt
2) timesert- same as above with an added step of a counterbore for the collar of the insert
3) drill out the hole and tap it for a M14 bolt.  Drill out the A/C bracket to accept a larger diameter bolt.

Any thoughts on the trade offs?  I think timesert is superior to helicoil.  They both require drilling and tapping the head.  If I'm goint to drill and tap why not go to a M14 bolt and use the correct torque.  I do not intend to use the York compressor in the future and will opt for a rotary unit.  The York unit would stress the bracket the most so I don't think that is an issue.

Jeff C.
1970 280SL 4-speed

[Naj ✝︎]

Hello, Jeff,

Found the old bolt !  :oops:

It is 12 x 1.5 and the shank is 16mm long.

Sorry for the anxiety caused ! [!]

You'll have to be careful how deep you drill. Part of the head stock supports the tensioner pin as well.

naj

68 280SL

[jeffc280sl]

Thank you again Naj,

Looks like I have the correct bolt.  Closer measurement indicates it has a 35mm shank.  With a 20mm thick A/C bracket that would make the depth in the head 15mm which is close to your 16mm shank.  Thanks for your very important note on the head stock.  

My measurements indicate the A/C bracket is 20mm and the head thickness is 26mm.  The pin is located about 38mm deep, measuring from the outside of the A/C bracket. This leaves about 8mm of head stock to support the pin.  A 35mm shank bolt leaves a couple mm play between the bolt and pin.  Sound about right?

Jeff C.
1970 280SL 4-speed

[glennard]

Add another '64 missing that bolt!!   On the 111 coupes the hood opens on rear hinges-hence a missing said bolt is more obvious than on a 113.   The tensioner pin leaves about 15 or 16 mm of M12 1.5 threads in the head for the bolt.  Total bolt length needs, 14mm in the head plus what ever else it is holding.  Mine is just holding the fuel line support and washer so 20mm of thread does it.  JA pointed out the 'joy' of tightening up a too long a bolt.  Applies to removing the pins holding the chain rails.

aside  Bob Possel--  The pins are usually so tight there is no oil leakage.  Having trouble getting out the two pins in the head and the four in the block on a 127.982 engine.

[glennard]

quote:Originally posted by naj

quote:Originally posted by jeffc280sl

Had a look at the bolt Bob is talking about and discovered that it was not very tight.  I backed it out and found some aluminum threads pieces in the steel bolt threads.  Leads me to believe the threads in the head are stripped.  That's one issue.  

I have factory A/C and the A/C bracket is also secured by this bolt.  The bolt threads are 35mm long.  Is this bolt the correct length?  The pin appears to be about 50mm deep measuring from the outside of the A/C bracket.  Does this bolt thread to the aluminum head or the timing chain sprocket arm? Is the bolt supposed to but up against the pin.  I'm wondering if the bolt in my car is too short.  What does the end of the pin look like?

Thanks for the help.

Download Attachment: 20056434913_tensioner.jpg
62.06 KB

Jeff C.
1970 280SL 4-speed

The tensioner pin is threaded so that it can be pulled out with a 6mm bolt:
naj, That's easy for you to say!!!   Got a 127.982 head that I can't get either pin in the head out.  Ice on the pull bolt?


Download Attachment: TensionerPin.jpg
40.95 KB

Without the A/C brkt,the original bolt is only about 15mm deep to keep the pin in place. It threads into the head.


Download Attachment: TensionerPin2.jpg
51.19 KB

naj

68 280SL