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Premium Member
1983 380 SL
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2,468 Posts
Discussion Starter #1
Quick two questions... I've read the horror stories about stripped threads when removing the heads on alloy blocks. I was wondering if that problem is related to time or mileage? The reason I ask is that my timing chain went twice... once at about 30K miles (or thereabouts) and again at around 80K miles. Both times there was valve damage requiring the removal of the heads. The second time is when I had the conversion to dual row done.

I currently have about 116K miles on the car but it's been about 25 years since the heads were last pulled... so my question is... due to the fact that the heads have been removed twice before, is the likelihood of stripped threads greater, less or about the same for when I pull the heads in the fall?

Is the likelihood of stripped threads greater, less or about the same if I use an impact wrench or a breaker bar to remove the head bolts?

Thanks
 

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1986 560 SL
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7,303 Posts
I think torquing the bolts back in is where the risk lies. And I guess the more often that's done, the greater the risk.
 

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Premium Member
1983 380 SL
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2,468 Posts
Discussion Starter #4
Do you know if timeserts were installed?
I thought of that after I made the original post. Wouldn't it be great if either timeserts or heli-coils were installed during one of the head removals. Am I that lucky? Probably not, but I'll have my answer this fall. :thumbsup:
 

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75, 280Sl /5speed
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1,303 Posts
Don't know if the V8's are the same as the M110 but it uses steel pins in the block to locate
the head when replacing. Real, real easy when trying to place a fully assembled head on the pins,
by yourself, while leaning over the engine, to gouge it. Definitely a 2 man job if possible. Learned the hard way.
 

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Registered
1967 250 S (sold) 1986 560 SEC 1987 560 SL
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1,285 Posts
I have heard, though I've never done this before, that you should just budget to have timeserts/helicoils installed, even if there is no obvious thread damage. Seems like it would be frustrating to get the valves all sorted and then upon reinstall discover the bolts aren't torquing properly. Just my .02.

Please keep us apprised of your progress. This will be a closely watched thread for me! Thanks @Jyuma!
 

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Premium Member
1983 380 SL
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2,468 Posts
Discussion Starter #7
I have heard, though I've never done this before, that you should just budget to have timeserts/helicoils installed, even if there is no obvious thread damage. Seems like it would be frustrating to get the valves all sorted and then upon reinstall discover the bolts aren't torquing properly. Just my .02.

Please keep us apprised of your progress. This will be a closely watched thread for me! Thanks @Jyuma!
The engine tear down may come sooner than I thought. Today I took the 107 to work and by the time I got there the tapping had become a full blown clacking. And here's the kicker... it no longer sounds like a rocker tick... I listened from under the car and the tapping (now clacking) is much louder when listening from below and it sounds like it's coming from the timing chain cover. :confused:

I'll post a video when I get home later this afternoon.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
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9,862 Posts
The engine tear down may come sooner than I thought. Today I took the 107 to work and by the time I got there the tapping had become a full blown clacking. And here's the kicker... it no longer sounds like a rocker tick... I listened from under the car and the tapping (now clacking) is much louder when listening from below and it sounds like it's coming from the timing chain cover. :confused:

I'll post a video when I get home later this afternoon.
Not convinced that pulling the head is going to fix this.

I did my head gasket without installing inserts and I lived, 65K mile and still going, but as far as I know it was the first time it as pulled.

For another data point I used to install head gaskets on Briggs and Stratton lawn mower engines repeatedly using a 3/8" drive impact gun.

There really is no reason for a properly designed AL thread to fail over a steel one. The thread engagement length is increased for Aluminium to make up for reduced shear strength. At least that's the theory.:D
 

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1984 380SL
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2,363 Posts
I'd be impressed if they were able to remove the head without damaging the threads.

When my engine was rebuilt, the invoice mentions timeserts as a line item .
 

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Premium Member
1983 380 SL
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2,468 Posts
Discussion Starter #11
This must be trying your patience! Do you mean like "chain tensioner died" kinda noise? :eek
No, not a chain tensioner noise... more like a very loud rocker tapping. Besides, the chain tensioner is new... not that it's impossible for a new tensioner to go bad, just unlikely.
 

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Premium Member
1983 380 SL
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2,468 Posts
Discussion Starter #12
As promised I made a video when I got home from work. Unfortunately by that time the clacking had returned to just a ticking but it is fairly pronounced. I can't tell where the tic is coming from but it definitely is loudest at the front of the engine. Maybe one of you can identify a likely source.

I was wondering about the condition of the AC but the compressor clutch isn't engaged so the compressor isn't turning... there's no R12 in the system, hasn't been for many many years. Everything else that spins in the front is new except the Aux air pump but that shuts off within a few minutes of starting. I did notice that the power steering belts need tightening but that would make more of a squeak than a tic.

I've had the rocker covers off a dozen times... there is no indication that the chain is hitting the cover and none of the rockers are loose.

Eight of the rockers are new, but that was just throwing parts at the problem... none of the rockers I replaced look worn at all. I also changed 4 of the thrust washers but this noise isn't being cause by a .35mm difference in thrust washer thickness.

The video makes it sound like the loudest point is right at cylinder #1 but that might be due to the proximity of the mic in the phone. By ear it sounds like the tic is coming almost directly from the center of the engine at the front.

Any ides. :confused:
 

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Premium Member
2007 ML320CDI, 1959 220SE, 1971 280SL, 1982 380SL
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598 Posts
Here is something else I have done to diagnose valve noises that are hard to find. I don’t like it because it is messy, but if you have tried other means, it might be something to consider. - - -

I remove one valve cover, wrap the cam oil squirt hole tubes with foil so they don’t squirt all over. I have also removed the entire squirt tube assembly and placed a piece of tin over the oil feed hole to direct the oil back down into the head.

Place a piece of tin (or even broiler duty foil) over the cam gear to reduce splash. Cover fenders and what you can with towels.

Work with a second person. The second person starts the car and only lets it run for 5 or 6 seconds. In the meantime, you use the stethoscope and your ear to move quickly alone the lifters to I.D. the noisy culprit.
 

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Premium Member
1983 380 SL
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2,468 Posts
Discussion Starter #15
It does sound valve train related. Maybe a flat lifter? Could a flat lobe be developing on the cam? I have had some luck using one of these to isolate where these sounds come from-

https://www.harborfreight.com/Mechanics-Stethoscope-63691.html
I already tried the the HF stethoscope... it didn't help. I also checked every cam lobe with a vernier caliper... all measure exactly the same.

I agree... it sounds like valve train but I've had all the rockers out and all the compensators out... I even replaced all 4 exhaust compensators on the right side with new ones, but it made no difference. I then replaced all the intake compensators with the ones I removed from the exhaust and it also made no difference. I then repeated the process on the left side and still there was no difference.

I'll keep checking but it's getting to the point of being absurd... :(
 

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Premium Member
1983 380 SL
Joined
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2,468 Posts
Discussion Starter #16
Here is something else I have done to diagnose valve noises that are hard to find. I don’t like it because it is messy, but if you have tried other means, it might be something to consider. - - -

I remove one valve cover, wrap the cam oil squirt hole tubes with foil so they don’t squirt all over. I have also removed the entire squirt tube assembly and placed a piece of tin over the oil feed hole to direct the oil back down into the head.

Place a piece of tin (or even broiler duty foil) over the cam gear to reduce splash. Cover fenders and what you can with towels.

Work with a second person. The second person starts the car and only lets it run for 5 or 6 seconds. In the meantime, you use the stethoscope and your ear to move quickly alone the lifters to I.D. the noisy culprit.
I did something similar (kinda)... I cut the top off of a spare rocker cover, bolted it on and started the engine. Oil went everywhere so I shut it off. Messy is an understatement. :laugh
 

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Premium Member
1985 380SL
Joined
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131 Posts
For the hell of it unplug your cruise control actuator. I've read that when the diaphram goes bad in these things they can make a ticking sound as well. You could check the actuator with your stethoscope as well.
 

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Premium Member
1985 380SL
Joined
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131 Posts
Trying to think outside of the box since you've had the valve covers off 200 times and went through every component in the valve train 50 times. You could also remove your belts to confirm the tick sound is not a belt driven component.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
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9,862 Posts
As promised I made a video when I got home from work. Unfortunately by that time the clacking had returned to just a ticking but it is fairly pronounced. I can't tell where the tic is coming from but it definitely is loudest at the front of the engine. Maybe one of you can identify a likely source. https://www.youtube.com/watch?v=0LFVs7fNeK0

I was wondering about the condition of the AC but the compressor clutch isn't engaged so the compressor isn't turning... there's no R12 in the system, hasn't been for many many years. Everything else that spins in the front is new except the Aux air pump but that shuts off within a few minutes of starting. I did notice that the power steering belts need tightening but that would make more of a squeak than a tic.

I've had the rocker covers off a dozen times... there is no indication that the chain is hitting the cover and none of the rockers are loose.

Eight of the rockers are new, but that was just throwing parts at the problem... none of the rockers I replaced look worn at all. I also changed 4 of the thrust washers but this noise isn't being cause by a .35mm difference in thrust washer thickness.

The video makes it sound like the loudest point is right at cylinder #1 but that might be due to the proximity of the mic in the phone. By ear it sounds like the tic is coming almost directly from the center of the engine at the front.

Any ides. :confused:
Dose sound a bit on the mechanical side but I wouldn't rule out exhaust manifold too quickly. They can sound somewhat similar.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
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9,862 Posts
You have done everything else so you might as well pull the belts and verify the noise isn't coming from the alternator or something.
 
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