6.9 removal of heads

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Styria

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I must have liked carrying out this work previously on Gleaming Beauty, because I am knee deep into exactly the same thing as previously with my Astral Silver 6.9. Whereas this work on GB was one of absolute necessity on account of a very badly blown head gasket, the work on the Astral Silver car was more or less dictated by slight valve seating problems, and not water/oil issues.

As is my wont, I have some pics to show various facets of the work, but more importantly it is my intention to point out some of the pitfalls one may encounter and some aspects of the job that can lead to considerable frustration.

Initially, it is fair to state that this task is NOT for the handyman that can wield a spanner, nor is it possible to do in your home garage unless you have a compressor, and a varied selection of quite special assemblies of tools. Disassembly initially is quite straight forward - just a matter of removing some wiring, fuel lines etc. The fun, and skill factor, begins with the removal of the inlet manifold. Some of the bolts are in contact with water, and they can be a 'sod' to remove. You don't get many opportunities to 'crack' them, and it is easy to round out the Allen headed bolts. Good tools are needed here, and count on at least one or two broken bolts that will have to be removed from the head(s) when the Engineering Shop services them.

This next item refers to right hand drive cars only. On Gleaming Beauty, we left the Master Cylinder and power brake unit in place, rendering removal of the head bolts at the back very, very awkward. Also, exhaust manifold nuts/studs are quite awkward to get to. I was going to remove the booster unit by undoing the securing nuts BEHIND the dash, and had in fact removed them. The unit, however, did not budge so I left it in place and just removed the master cylinder. That helped considerably with access to nuts and bolts. Just an observation - the fact is that studs and nuts secure the exhaust manifolds to the heads. It really makes for an awkward removal as you have to pull the manifold away from the head(s) and you do not have a lot of space.

Next in line, of course, are the timing chain and chain wheels and tensioner. I decided to 'plastic tie' the chain to the wheels initially, but knocked the wheels off the camshaft(s). I also took photographs of the positioning of the camshaft lobes, with the engine at TDC. Once it is on that setting, I do not turn the engine again. Also, you need to ensure that the chain does not fall into the engine - secure it any way you like - just don't let it disappear down the 'gurgler'. You are now ready to remove the camshaft(s). Mind you, we're still on the driver's side. Here the point to pay attention to is the fact that, with the brake booster in place, you will NOT be able to remove one of the bolts securing the rear camshaft bearing. The bolt and bearing need to be removed together with the head as one unit. Also, forget any notion that the exhaust manifold and head can be removed/replaced as one unit. It just doesn't happen unless, perhaps, the steering box is removed. Not sure, but not otherwise.

So, let's go to the passenger side. Again, same problems with exhaust manifold studs/nuts. This time, however, you also have to battle with the EGR (?) valve that's fitted to the manifold. That's a real sod of an item. You can remove it all right, but the long studs are still sticking out and it's touch and go on account of space to remove the manifold. On Gleaming Beauty, you don't have that valve fitted to the manifold. There is also another issue one has to contend with on both sides - removal of the head bolts close to the exhaust manifolds - about four of them, on both sides, you just cannot remove unless the manifolds are out of the way. Hmm....There are some real skill factors that need to come into play - both now, and later when re-assembly commences. Anything else to report - no, not really, except for cleaning etc. and I'll cover that later. Could I put an estimate on the time required for removal - yep, I'd think you'd need at least twelve hours and a few choice swear words. Regards Styria
 

TJ 450

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Nice post, Styria. ;)

IMHO, you can get away with just two special tools, the "bent" allen key and the valve spring compressor. The LH exhaust manifold on cars with EGR can be removed by simply jacking up the engine, but I found it easier to remove the power steering pump as well, for extra room. Timing chain guide rails and such can be removed with M6 bolts and a selection of nuts and sockets and the like for packing.

I have just removed the cylinder heads from my 380SE for reconditioning, it must be the flavour of the month, or year. Mind you, removing heads from the smaller engines is the proverbial piece of cake in comparison. ;)

Tim
 
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Styria

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Hi TJ450, thanks for your favourable response. One item I failed to mention was a head bolt spacer used at the very front on the left hand head. This is quite curious as really MB could have used a shorter head bolt and therefore done away with the spacer. I remember it from the job on Gleaming Beauty - I had a bit of a job finding a spot for it at the time of reassembly.

I have to admit that it was a bit of touch and go as far as lifting the engine was concerned in order to remove the left hand side. Mind you, it was really the last thing I wanted to do - it was yet just another job on top of all the others and I was glad that I didn't have to lift the engine.

In fact, a friend of mine with a 6.9 is of the opinion that he'd prefer to remove the engine from the car to carry out a valve grind and decoke. In his opinion, it'd be so much easier to remove components. Well, again I wanted to avoid that scenario if I could help it - it would have put another slant on the whole job, what with separating the gearbox from the engine, removing the three oil hoses etc. etc. No, just too much for my liking. Regards Styria
 

TJ 450

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Thanks Styria,

You raise an interesting point with the spacer. On my car, some time during its previous life, someone failed to install that spacer and the bolt was just sitting in there. I'll have to see if I can source a suitable replacement for the job.

Tim
 

WGB

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Thanks for all the detail - priceless information.

A couple of personal observations -

1) Removing the whole motor will allow replacement of all seals including the rear main seal.

2) Valve spring compressors simplify all valve work immensely.

Bill
 
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Styria

Styria

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Thanks Styria,

You raise an interesting point with the spacer. On my car, some time during its previous life, someone failed to install that spacer and the bolt was just sitting in there. I'll have to see if I can source a suitable replacement for the job.

Tim

Hi TJ450, there is nothing special about the spacer. If you're interested, I can easily rustle up a spare unit and send it to you FOC. BTW, both you and WGB raise the subject of valve spring compressor - I decided a long time ago that the heads would go to an engineering shop to get overhauled. I know for a fact that, at 220k.'s the exhaust valve guides can be in need of replacement. Thus, it is best to get this sort of work carried out by specialists. Plus, I could never hope to match the cleanliness aspect of the whole job, including the heads. Regards Styria

N. B. That just reminds me of something I need to do - I will need to tell the engineering shop 'to go easy' on the grinding of the valves. It is easy to be heavy handed with this job.
 
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Well, news has come through from the Engineering Shop that I could have done without and, frankly, I am quite disappointed. I have been advised that they need one new exhaust valve (ouch !) and new inlet and exhaust valve guides - staggering news and very much surprising......and I won't say ouch again. Regards Styria
 

TJ 450

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I think it's safe to say that guides usually require replacement, but a new exhaust valve... that is surprising.

Tim
 

WGB

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At least you'll know that all will be in good working order when you are finished and compared to what you get at a dealer with a new Benz - a "B" service and a set of brake pads would probably cost about the same.

Bill
 
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Styria

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At least you'll know that all will be in good working order when you are finished and compared to what you get at a dealer with a new Benz - a "B" service and a set of brake pads would probably cost about the same.

Bill

Hi Bill, you're probably quite right, although I am not familiar with the cost of dealer services and charges. Mind you, though, Engineering Shops are not always the cheapest either, but at least you pay for "REAL" knowledge and skill. As well, as you pointed out, it is of vital importance that the work be right - you don't want any hang-ups after it's all assembled. Regards Styria
 

TJ 450

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Regarding the tightening of head bolts, do you have a dog-leg allen socket, or did you get around the camshafts in some other way? I haven't seen a 10mm dog-leg socket anywhere, only the 8mm version for M116/117 engines.

Tim
 

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I have purchased a pair of 8mm and a pair of 10mm high quality US allen Keys which I will attempt to bend using oxy-acetylene and then quenching in oil to retain the temper.

I was going to make an 8mm and a 10mm curved allen key brazed into 1/2 inch sockets and also make a pair of the "U" shaped sockets that are designed to go around the camshaft and are pictured in the Chilton's manual.

HexKeysforHead.jpg

When I torque the heads on my 6.9 and potentially my 4.5 I would appreciate the experienced telling me whether they think the "u" shaped socket is required as it is obviously more difficult to fabricate.

Bill
 
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Styria

Styria

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Hi Bill,

As such, there were no special tools required - not even for the headbolts that are situated below the camshaft - I am just trying to recall how we overcame that particular 'obstacle'. The lifters were set up on the bench prior to the heads being refitted - so the necessary lifter clearances were well within the specified static setting limits.

The 'special' tools I refer to are 'hand built' units - I have four sets of Allen headed tools, with both half inch and three eights socket heads. In addition, I have made up about eight or nine Allen keys of non standard lengths with sockets welded to them. In addition, I have also shortened socket Allen keys for specific jobs.

The main head bolt 'culprits' are the ones right on the sides next to the exhaust manifolds some of which cannot be removed with the manifolds in place. They are causing quite a bit of grief unless, as TJ450 has suggested, you lift the engine and possibly remove the power steering pump. Neither of the two I wanted to get involved with. At the moment, I am toying with the idea of refitting the exhaust manifolds with bolts, rather than the studs and copper nuts that normally hold the manifolds in place. Some studs actually screwed out with the exhaust nuts. I would also suspect that a 12mm copper lock nut is the largest size you can use on account of restricted space that could actually prevent sockets being used to tighten those manifolds.

This is probably all pretty mundane and boring stuff, but nevertheless part of the work and deciding if there are better and more convenient ways of doing it , is of some importance. Regards Styria
 

TJ 450

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That's very useful information.

I noticed in the manual, that they don't mention any bent allen keys either... just a long 10mm (150mm +) and a selection of other fairly standard items including a long 6mm allen key.

I had a look on my car last night... it seems a 10mm allen key will clear the camshaft, as long as the 1/2" attachment is above the camshaft.

So, it seems that this is yet another advantage the M-100 has over M-116/7 engines.

Tim
 
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Styria

Styria

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That's very useful information.

I noticed in the manual, that they don't mention any bent allen keys either... just a long 10mm (150mm +) and a selection of other fairly standard items including a long 6mm allen key.

I had a look on my car last night... it seems a 10mm allen key will clear the camshaft, as long as the 1/2" attachment is above the camshaft.

So, it seems that this is yet another advantage the M-100 has over M-116/7 engines.

Tim

Hi TJ450, I am glad that, in a round about sort of way, you corroborate and confirm the accuracy of my previous post. We certainly did not need any specially bent Allen keys, and I really didn't have the opportunity in the meantime to check on the headbolts under the camshafts to determine which 'special' socket type Allen key had been used on Gleaming Beauty's work.

The offending exhaust valve has a crack in the 'seat' area, so is obviously no longer useable. Presently, I am busy finding a replacement for it. Have not checked on the price of a new unit - probably not game enough. If 6.3s are any guide, at least $250.00 to $280.00 per valve. That was about four years ago. New inlet and exhaust guides have been bought, but I haven't received a firm price at this stage. Will keep you posted on that. Regards Styria
 
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One aspect to emanate from this particular work relates to water passage corrosion in heads. Despite the fact that a good quality inhibitor has been used during my ownership, there was corrosion evident once the heads were removed.

The 'critical' areas are right at the back of both heads where you have two small water holes (each head) situated very close to the combustion chamber. Invariably, they need to be welded during any servicing of the heads. Gleaming Beauty had precisely that problem, and this Astral Silver was heading in a similar direction. It was just a matter of time. If I get a chance, some pics will follow. Regards Styria
 
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One of the many "benefits" of heads removal relates to the rubber drains - both located on the firewall and designed clear dirt and debris that accumulates in the fresh air chamber (where the windscreen motor is located).

The one on the left hand side looking towards the front of the car is easy enough to get to. The one on the right - just a tad more difficult. Well, it must be, as evidenced by the picture hereunder..

ChrisPearsonAstralSilver69044.jpg

So, with tongue in cheek, it's a great idea to remove the head on that side just to clean out that dirty little puppy. :D Well, it's not easy to get to or remove - just try it. Regards Styria....and yes, I have been hanging onto this pile of dirt for two weeks now - all nicely wrapped up.
 

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ChrisPearsonAstralSilver69044.jpg
So, with tongue in cheek, it's a great idea to remove the head on that side just to clean out that dirty little puppy. :D Well, it's not easy to get to or remove - just try it. Regards Styria....and yes, I have been hanging onto this pile of dirt for two weeks now - all nicely wrapped up.

What do you plan doing with that stuff Godfather?
Keep it for posterity? :p
 
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