Thrust washer deviation - Mercedes-Benz Forum
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post #1 of 84 (permalink) Old 06-05-2019, 07:24 PM Thread Starter
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Thrust washer deviation

I finally couldn't take the infernal rocker tic in my 380 anymore, so today I torn it apart. Much to my dismay I found nothing wrong. I did however determine that if you don't crank the engine for at least 30 seconds (fuel & ignition off) between each check with the go no-go gauge, you're results will be useless.

How do I know? I had one valve that showed a slight minus deviation indicating that I needed a thicker thrust washer. The thrust washer that was on that valve was a 5.10mm so I replaced it with a 5.45mm thrust washer expecting the go no-go gauge to either show no deviation or even a small + deviation. Instead, the go no-go gauge indicated that the minus deviation was now worse with the thicker thrust washer. What??? A minus deviation indicates the need for a thicker thrust washer but when I replaced a 5.10mm thrust washer with a 5.45mm thrust washer the minus deviation became greater. Impossible right? Wrong... not if you don't crank the engine for several revolutions after changing the thrust washer.

Then I had another valve that only moments before had measured perfectly on the go no-go gauge suddenly develop a minus deviation that was so severe I could wiggle the rocker back and forth with little effort, only to have the deviation return to nominal after a few cranks of the starter motor. Proving that cranking by hand just doesn't cut it... you gotta crank with the starter motor.

I'm beginning to think that agonizing over getting the go no-go gauge to read nominal is a waste of time and effort. If you've got a noisy lifter, it ain't gunna get fixed by adding .35mm to the thrust washer thickness... hell, the oil in the compensator can make up for way more deviation than .35mm.

bTw... I measured every cam lobe and they're all within .05mm of each other. I measured with a vernier caliper which is not as accurate as a micrometer, so my measurements could be off a little, but not enough to have missed if I had a worn cam lobe.

Tomorrow I'm putting this thing back together and if it still has a loud rocker tic I'll put a couple of quarts of Sea Foam in the crankcase and run it until it blows up or the tic goes away... whichever comes first.
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post #2 of 84 (permalink) Old 06-06-2019, 06:11 AM
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That's going to make a hell of a mess with the cam covers off.


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post #3 of 84 (permalink) Old 06-06-2019, 08:53 AM Thread Starter
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That's going to make a hell of a mess with the cam covers off.
Yup... but that's what they make paper towels for.

I was impressed with how much oil flowed to the top on just the starter motor but the cover off cranking proved to be very effective. I found one compensator that appeared to be intermittent... it would work fine for a few cranks with the starter motor and then suddenly go limp. By limp I mean the compensator would compress when the valve was opening but on occasion it would stay compressed and not return to full (preload) height.

I replaced the compensator and matched the appropriate thrust washer. I also re-checked all the remaining valves with the go no-go gauge. Most of them showed a very sleight minus deviation but not enough to justify going one size thicker. I put everything back together and fired her up... tic, tic, tic, tic,... damn. I have to say though... the tic is not nearly as loud and almost went completely away after a short drive. I'll give it a few days to settle down and retest.

One good thing came of all of this... while I had the fan off (for hand rotating the engine) I put the old (original) fan clutch back in (took out the brand new Behr fan clutch I got from AutoHaus) and now my roaring problem is gone. The difference is very noticeable... no more roaring fan as I pull away for a stop... and the temp gauge reads the same as it did with the new fan clutch. I wonder if I could get my money back on the Behr fan clutch from Autohaus... it is obviously not working properly.

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post #4 of 84 (permalink) Old 06-06-2019, 09:31 AM
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I wonder if I could get my money back on the Behr fan clutch from Autohaus... it is obviously not working properly.
Ping the Autohaus guy who is a frequent poster on this board. He/She should be able to make this right.

Contact info here: https://www.benzworld.org/forums/28671-autohausaz.html
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post #5 of 84 (permalink) Old 06-06-2019, 02:28 PM Thread Starter
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Ping the Autohaus guy who is a frequent poster on this board. He/She should be able to make this right.

Contact info here: https://www.benzworld.org/forums/28671-autohausaz.html
Thanks.

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post #6 of 84 (permalink) Old 06-06-2019, 05:29 PM Thread Starter
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Playing trial and error with thrust washers that cost $22 bucks a piece can get expensive in a hurry. To remedy that, I just ordered hardened steel disks from McMaster that are 1/2" OD and .01" thick (.26mm). Using 1 on top of the valve stem (under the thrust washer) is roughly equivalent to using the next size up thrust washer (.26 increase in overall thickness versus a .35 increase). Using 2 on top of the valve stem (under the thrust washer) is roughly equivalent to going 2 sizes up on the thrust washer. By using the shims I can determine exactly what size thrust washers to order and thereby avoid buying a bunch or $22 dollar thrust washers in sizes I don't need.

I'm even thinking it might be OK to just go with the shims instead of new thrust washers. The shims are hardened steel so the worst that will happen to them is they may flatten out a little over time. Should I care?

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post #7 of 84 (permalink) Old 06-07-2019, 04:30 AM
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I finally couldn't take the infernal rocker tic in my 380 anymore,
Whatever you do....don't get a 280SL.

LOL
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post #8 of 84 (permalink) Old 06-07-2019, 06:29 AM Thread Starter
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Whatever you do....don't get a 280SL.

LOL
The plot thickens.

Yesterday after I put everything back together and started the engine , the tic was there but much quieter. After about 10 minutes of driving the tic was almost all gone... that and the lack of fan roar made driving a pleasure again. Later that night, I went for a nice top down drive. The tic was almost completely gone and life was good. Then on the way back home the tic came back with a vengeance... just as loud as before. WTF!

When I had the covers off I took measurements of all the thrust washer thicknesses, the deviation of each valve and the cam lobe height. All the cam lobes were almost exactly the same so the cam is off the table. That leaves compensators, rockers and shims (and the valve itself).

It has always sounded to me like the tic is coming from the drivers side but I can't be 100% certain, but based on my measurements, the drivers side thrust washers are almost all 5.1mm but the passenger side has mostly 5.45mm thrust washers. And again... most of the valves on the drivers side show a sleight minus deviation. When the .01"mm steel disks arrive on Monday I'll shim all the 5.1mm thrust washers on the drivers side to eliminate the minus deviation and I may even favor a sleight plus deviation. If that doesn't work I'll do the same to the passenger side and if that doesn't work I have on last desperation move to try. Read on...

Last year I bought a used drivers side rocker cover. If I'm out of options, I'll cut the top of the rocker cover off so I can see the rockers in action with the engine running and without spilling oil all over the place. I have run the engine with the oil fill off and watched the oil stream down on the cam but I didn't ever see much oil splashing. Even if it does splash all over when I cut the top of the cover off, the cleanup chore will be well worth it if it isolates the offending valve. With the top of the rocker cover cut off I should be able to isolate the problem to a specific rocker and take remedial action on that specific rocker/thrust washer/cam lobe combination. It that fails... maybe I'll try a 280.

p.s. I read somewhere (I don't remember where) that at some point, Mercedes modified the go no-go gauge sizing to produce additional preload. Maybe my gauge is the old style and I'm not giving the valves enough preload. Just wondering.

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post #9 of 84 (permalink) Old 06-08-2019, 04:43 AM
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Jyuma,Sorry to hear you are still chasing this tic. You have probably covered this before, but what weight oil are you running.? Also, how about some Lucas???I had a noisy tic at the end of last season. I found one badly worn rocker.I can only assume the oil tube got plugged up. Anyway,replaced rocker and made sure tube was cleaned out. I decided to not mess with compensators and just see how it went. Running quiet so far...Hope you get it sorted, enjoy the good weather finally!!
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post #10 of 84 (permalink) Old 06-08-2019, 05:24 AM Thread Starter
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Jyuma,Sorry to hear you are still chasing this tic. You have probably covered this before, but what weight oil are you running.? Also, how about some Lucas???I had a noisy tic at the end of last season. I found one badly worn rocker.I can only assume the oil tube got plugged up. Anyway,replaced rocker and made sure tube was cleaned out. I decided to not mess with compensators and just see how it went. Running quiet so far...Hope you get it sorted, enjoy the good weather finally!!
Just last week I changed the oil and filter... I went with 20W/50 for the summer. I also poured a quart of Lucas in at that time but my understanding now is that 1 qt is the recommended amount for a 5 quart system. Our 107's take closer to 10 quarts so I might pour in another quart of Lucas.

I've been thinking about this problem for the past 2 days... (no doubt overthinking the problem)... I wondering why the suspect rocker quieted down so much after I put everything back together only to return as loud as ever after a short drive. I'm thinking maybe dirt in the engine broke loose and found it's way to the tiny oil hole in a compensator.

Let me explain... when I had everything apart (3 days ago) I removed every compensator, measured their nominal height (with compensator in hand) and then using a wadded up paper towel soaked in carburetor cleaner (and clamped in a hemostat), I cleaned out the mounting hole in the head where the compensator lives... they were all quite dirty. I also shot carburetor cleaner into the hole that supplies the oil to the compensator as well as the oil hole in the compensator itself. I had performed this same procedure last summer and all the compensator mounting holes were cleaned in the same manner at that time, so it's a bit worrying that they got so dirty so quickly, which leads me to believe that there must be crud deep in the bowels of the engine that accumulated over 36 years that may be slowly breaking loose and gumming up the compensators.

I don't know if I should have done the next thing I did or not, but here goes... the ball on the top of the compensator is not hard connected to anything inside and is free to rotate (although I don't know what would cause it to rotate). On a few of the compensators (which, by the way, were all 20 years old but brand new as I had replaced them all just before I parked the car for it's 20 year nap) the ball would not rotate freely. I clamped the ball in the rubber jaws of one of my wood clamps and broke it free. I rotated the ball several times in both directions until the ball would spin without noticeable binding. That only occurred on 2 or 3 of the compensators, all the rest spun without binding at first attempt.

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