After a recent head rebuild on my 1989 560SEL a couple of the lifters on the passenger side (my car is a RHD) seem to leak down and clatter after the car has sat for a reasonable period, say a day.

On a cold start the lifters take about 30 seconds to go quiet and then the motor is silent. The local dealer who performed the head rebuild recommends replacing all the lifters as diagnosing the noisy ones is quiet difficult and the extra labour to do the whole motor is not significant.

My questions are, does anyone just do one bank of cylinders? After having the head milled/planed during the rebuild will the shims need to be altered when I install new hydraulic compensators?

Cheers
Matt.

If the job was done correctly, the mechanic should have checked lash on each valve with a special MB tool and installed the proper lash pad according to the gauge reading. You shouldn't need to change lash pads when you change lifters.

Peter

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Auto Zentral Ltd.

Thanks for your reply.

The lash wasn't checked when the heads were refitted hence my question.

Does anyone have any feel for the likely hood of this being needed to be done?

Cheers
Matt.

It is a very good idea to check the installed height of the valves and fit the correct shim-otherwise the lifter may be forced to the end of its adjustment capability--resulting in either noisy valves (clearance on valve closed), or a valve not closing all the way or too late in the cycle. Either way its not good. When the heads were 'milled', its extremely important the cam towers be shimmed to the correct height individually--unless both sides of the head were milled and the head surfaces are true parallel. (unlikely since valve guides and casting plugs have to be removed and reinstalled, and head thickness carefully measured all around to ensure against non-parallel finished surfaces. If this cam tower shimming is not done properly, the cam is under bending load because the bearing centers are not the same height, and the cam will fail.

Kebowers,
Where are you geographicallly located? Your answer has merit, but I question the shimming. In this case there was no over heating as far as I know so there would be no need for shims, but there would be a need for an offset key. What is your background? I'm not challenging you; I just want to know if I'm dealing with a fellow professional or an autodidact which is ok either way.

Peter

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Auto Zentral Ltd.

According to the service CD, if the HLC is replaced, you need to check the basic position with the guage and install the correct shim. The basic position must be checked and corrected, if the rocker or cam is changed also. All 4: the valve, rocker, cam and HLC; work together to achieve proper opening and closing of the valves.

And yes, you can do just one bank of cyclinders. In fact, you could just replace the failing HLCs. The only reason I can think of that you would replace the entire side is to avoid going at it, a little later if another one fails. It is not a big job replace one. The overhead is quite light, just opening the valve cover, plus maybe a new valve cover gasket will be required if the existing is older than 1 year and the valve cover bolts were not over torqued.

Keep the old HLCs, since some them sound like they are still good.

Also, when you get a valve job, it is normal practise to test the HLCs, before replacing them. I presume they were removed from the head prior to the head going to the machine shop?

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1989 420 SEL

To piggy-back on this post... I'm going through a rebuild in my 560 and I'm about to be putting my lifters back in. I bagged all the lifters, rockers, plates (between the rocker and the spring) so that I can put them back where they were. I've kepts the lifters separate and upright, yet organized. How can I test them to make sure they're good before I put them back in?

I ask becuase I had .05" to .1" of black cakelike sludge below each one of them when I removed them from the head. The heads have been cleaned/machined and look like new now.

I live in Houston, am an engineer, and have been intimately involved in maintaining fine auto engines for over 30 years. 2 sibblings and Father were also. So here goes.

IF you have a MBZ aluminum head resurfaced because it was warped--first question is--how much was it warped? These heads are flexible and will easily pull down tight if they are within or near warpage specs (0.030"). THe cams run in precision bearings in towers mounted to the top of the heads. If you remove metal from the bottom surface only to remove the 'warpage' --you end up with a head whose thickness now varies--and the TOP surface., when tightened down, now has the mirror image of the warpage that was removed.

MBZ supplies shims in peel apart stacks to fit UNDER the cam towers to bring the bearings back into perfect alignment. You can easily tell when its right because the bare cam will turn easily in its bearings with all the head bolts torqued down. If the cam does not turn easily--it will overheat the out of line bearing(s) and will eventually break from bending as it rotates--if it does not seize, break the drive chain and destroy the engine before it breaks and destroys the enbgine. Either way it is not a pretty result. It WILL happen if the head has been resurfaced and the cam towers are not shimmed back into perfect alignment. I have never seen a U.S. shop that can resurface the head properly (grind both sides at the same time to ensure absolute parallel surfaces.) This is because it requires removal of the guides and core casting plugs so the top surface can be ground as well.

I KNOW a lot of times the cam towers are not properly shimmed, and the engine runs--and many times the cams do not seize or break--but for how long? When I head about cams breaking, or timing chains breaking, I am pretty confident that a large majority, if not al, of these failures are caused by out of line cam bearings and the resulting bending and increased drag.

LOTS of heads are resurfaced unnecessarily when all they need is a good dressing with a flat edge wrapped with 100 grit wet or dry abrasive paper to uniformly clean up the sealing surface. It may take an hour in a bad case (and you do have to use a good straight bar to span the head crosswise) But its faster to throw the headback and forth on a blanchard grinder and presto-- in 2 minutes you have a nice pretty and clean 'flat' head that will cause your camshafts to break.

Thanks for all the replies everyone.

The motor was never overheated so the heads weren't milled to correct any warping therefore shimming the cam towers shouldn't be needed.

I guess what I was really asking was if anyone had insight as to how necessary the shims are for the compensators, I certainly fully understand the theory behind the shims but often practically speaking things are different.

The dealer is recommending doing the whole motor to save having to go back in but as the noisy lifters are all on one side I was thinking about just doing one side.

Cheers
Matt.

Before you go to all the trouble, you might try a flush like Auto-rx or an additive like Rizalone. hbofinger cured a "ticker" in his 560 with the latter.

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

Mattman, your original post states: "...After having the head milled/planed during the rebuild will the shims need to be altered when I install new hydraulic compensators?". Next we hear that "...The motor was never overheated so the heads weren't milled...". (Italics mine). I think we'd all like clarification on whether the heads were milled or not before proceeding. What exactly was 'rebuilt' during the rebuild?

As to your other question, re. doing all or just the offending lifter/HLC replacement, I'm voting for locating the bad one(s) and replacing them only. Get a mechanic's stethescope and listen to all 8 (on your passenger side, as you posted) through the valve cover while the engine is running to aproximate the cylinder/valve that is ticking. Then pull the valve cover and remove the rocker arm on the suspect valve.

The procedure, as I recall, is to push down on the lifter with something like a wood hammer handle and check the resistance compared to a known 'good' lifter filled with oil. A bad one will collapse easily when you push down on it.

I also think your dealer is full of it...if they replace all of the lifters, you're going to need all new rockers too, and each one is going to require a shim check with the guage as described by the other posters. Big $$, both labour and parts.

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1986 560SL
2002 Toyota Camry
1993 Lexus

Kebowers,
It sounds like you did your homework. By the way you probably know the difference between mechanical engineers and structural engineers. Mechanical engineers buil weapons, and structural engineers build targets. I think too many things like cylinder heads and rotors get machined for no reason in this country, because most mechanics don't know how to check tolerances. Everytime a job is done on a domestic piece of doo doo that involves stretch bolts, it gets new stretctbolts, because there are no specs available for domestic stretch bolts nor does anyone know how to measure them. I always reuse stretch bolts after I have measured them with a mic and checked the TDM. As you say, a slight warp can be tolerated especially when you see that each head uses 18 bolts. I didn't suface the heads on the 560SEC and 380SEL that I did in the last few years. I'm doing a valve job on a 380SEC right now, because it jumped timing andnot doing the heads, because they checked out with a straight edge and feeler gauge. The 560SEC I did came in months later with a tick in the left bank. I used a stethoscope to isolate the lifter and changed only the one lifter. You made a good point about the cam turning free. A good mechanic always checks the turning ease of things before finishing the job.

Peter

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Auto Zentral Ltd.

Thanks again to all those who have replied.

As I said the head wasn't planed to correct any warpage however the head was resurfaced, the car had a blown head gasket and there was some minor marking around cylinder #1. In addition new guides and seals were fitted and a vavle grind was done.

I have run a bottle of lifter free through it already and after having done 1000km's they are much better but still clatter for 30 seconds or so on startup after the motor has been sitting for a while.

I wasn't aware that the rockers had to be changed at the same time as changing the compensators, I can understand if the rocker face is worn or ensuring the compensators stay paired with the original rocker but do they need to be replaced when fitting new compensators?

Cheers
Matt.

Well, strictly speaking 'on principle' and from the MB manual, yes. If it were me, no, I'd locate and replace the collapsed compensator(s) and re-use the rocker(s) and associated shim(s), assuming the rockers are in good condition. My MB-trained friend has advised me in the past that the rocker can usually be re-used as well.

I guess it's a judgement call, so I'll not say any more since I'm not a mechanic...my experience is limited to a complete 2 camshaft swap, with all compensators and rockers, from a used 116 engine to another ('76 450SE), a gruelling 32 hour job that involved the whole 9 yards, including measuring the shim clearance with the special tool. Previous to that, I tried to save the old worn camshaft by installing new compensators and/or rockers on just the worn lobes, but it didn't work because the lobes just kept digging into the rocker faces and ruining them.

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1986 560SL
2002 Toyota Camry
1993 Lexus