M156 head bolt problems
and they did it. All they told me was they had to lower the coolant level.
No studs, just new MB OE bolts.
Need a mb tool to hold the one adjuster and a 4mm bolt to hold the other cam adjuster. Also need a mb tool to hold both cams in the proper position so they can be bolted back down.
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also putting marks on cam gears to make sure they go back in the right spot.
once the engine is rotated to 40degrees. The cams have 2 parallel sections machined flat where you put the other MB tool that holds both cams perpendicular to the head. This allows you to remove and install the cams in the right position. I dont see how it would be possible to install them incorrectly with this tool on them as they are held at 90degrees off the head.
Without the tool you could install them back if you made markings, but good lucky because you are trying to bolt the cams down against the valve spring pressure and some lobes are hitting the tappet at an angle. So as you bolt the cam down without the tool, the cam will start to flop around.
Here is a pic with the tool on the cams. Its just a black piece that holds them both and bolts to the head.

When you remove the cams, you dont need to remove the adjusters.. Just lock them in place and remove cam with adjuster. The tool to install the adjusters isnt needed since you arent removing them.
Just looking at these pics now I found and I see you posting there.. That is very disheartening to see that tappet and cam damage, something else to worry about now LOL. I dont think the suggested oil change intervals is helping hah.
https://mbworld.org/forums/w211-amg/...y-lifters.html
Last edited by Merc63; Nov 5, 2013 at 02:57 AM.
Here is a PDF that shows how the cam adjusters work. The bolt holds the rotor. The rotor holds the adjuster that floats on the cam. As oil is shot in, the rotor either moves CW or CCW as the cam spins to retard or advance the timing and change duration between the intake and exhaust.
Please stay with us on the cam lobe vs lifter pressure during assembly. In another life I tore down 1600 Lotus engines which had cast (brittle) cam shafts. It was possible ( and happened once) to snap the cam during the tightening of the bearing caps. Are the C63 cams strong (billets)? Are the valve spring pressures high?
Do I hear the readership strong on trying the one-at-a-time replacement method? Any such engines with successful high mileage? thanks
when I first install them I torque to 80 ftlbs. After all the studs are in at 80 ill go over them and torque to 110ftlbs as per the spec.
the numbers I list previous were wrong. I couldnt remember exactly what we did that time. I just went over the weistec arp stud instructions and thought I should correct that.
I took the TSB along with my Data Card (to show I was in the bad head bolt range) to the dealer. My MB dealer is a regional sales and service rep and therefore, had to make a call to the dealership’s national “home office” for more clarification. Since the TSB is a “LIxxx.xxx.xxx” version, learned it was recognized to be a “Local” version; vice a “GExxx.xxx.xxx,” which would mean a “Global”distributed TSB. It was further explained to me that there is no recall over the head bolts for the M156.
I now have an appointment to have the car checked under warranty on the head bolt issue, now that the dealership acknowledged the “LI” TSB. If I didn’t have the TSB, it would’ve been a hard sell. So, definitely thank you B. Wilkinson. It helped me get the ball rolling in what I think is the right direction.
Here’s my recommendation for anyone who is concerned of an engine block leak for those M156 engines that are in “the range.” They may not be catch all indicators, but may help. Check the coolant reservoir with a dab of white paper. If oil has made its way into the coolant system, dabbing the white paper in the reservoir will reveal the oil as it should eventually rise to the top in the reservoir. You could also check for a mix of coolant into the oil with a thorough oil dipstick check. Even if you haven’t received the warning and your engine is in the range of the faulty bolts, do these checks periodically or closely monitor your coolant level as preventative maintenance. You may also want to press the issue with your MB dealership, using the TSB as a justification, rather than waiting for the failure or the failure occurring just when you’ve hit the point of being outside your warranty.
Luckily, I’m still within my warranty and if the check-up is revealing, the service should be cost-free to me. I did ask about getting the SLS lifters/tappets if the head bolts are replaced during the engine rebuild. The SA was unsure, noting they would have to use whatever MB dictated by part number.
Does anyone know if the SLS lifters are automatically used; previous M156 lifters precluded? Part number for the new ones?
Thanks...
The dealer would have needed me to put the engine back together and add fluids back before I were to bring it back anyway. Cost of putting it back together and bringing it to dealer would not be cost effective.
So, my error, brought it to my trusted local indy shop first, HOWEVER, my opinion, I would have "potentially" received up to 15% discount (best case scenario) off of high dealer repair costs, possibly not even saving me any out-of-pocket expense. Additionally, my opinion is that my indy shop will do higher quality work than dealer.
So this is what I keep telling myself to make me feel better about the whole situation.
Disappointed in MBUSA for lack of support of their engineering failure.
No total cost of repair yet. Still in shop. Expecting to get it back next week.
Last edited by Mgsafety; Nov 8, 2013 at 02:25 AM. Reason: misspelling







