Attempting to change the head gasket on a W202

Discussion in 'Engine' started by Nasco12, Mar 29, 2017.

  1. Nasco12

    Nasco12 Active Member

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    The engine in question is a 111.945 (2l)

    Here goes:
    [​IMG]

    Undertray removed. The grime may well be the result of the oil escaping past the head gasket.

    [​IMG]

    And we’re stuck. I can’t get the exhaust manifold bolts out. According to the Haynes manual it does have to come off because the manifold stretches all the way down to the transmission. I have tried a nut splitter and a chisel (both subsequent to taking this photo).

    [​IMG]

    The solution as I understand it is usually heat. As the car is currently parked at the side of the road I am rather reluctant to get out a blow torch. Even if managed to avoid setting passers-by alight it might be alarming for some. Access for a hacksaw is poor.

    The one bit of good news is that I have been able to locate the block coolant drain plug. I was beginning to think it was something of a myth.
     
    Last edited: Mar 29, 2017
  2. toolman1954

    toolman1954 MB Enthusiast

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    Hi,
    So you are playing " Kerbside Autos " and are you near your own/ friends house, and have you got electricity?
    The way I would tackle this would be to use a nice sharp drill bit and drill 2 or 3 holes across each nut and split the nuts off with a nice sharp ( preferably English ) cold chisel.
    Centre pop the nut first before you drill it and if you wrap a bit of masking tape around the drill you wont drill too far into the nut.
    Sometimes just the heat from drilling and the vibration is enough to crack the seal on the nut and they will come off with a socket / spanner. Also try to tighten the nut a tiny bit before slackening it off, that also helps to crack the seal.Penetrating oil on the nut overnight often helps.
    Only the lower nuts on the manifold are going to make you cry. Hammer on an old socket and get a big bar, and if the stud snaps just deal with it later.
    Real last resort is to jack the car up, gt a ramp under the front wheel and try to get at the exhaust to manifold bolts and undo them.They will also be tight but, not so cooked as the manifold to head bolts.
    Best of luck.

    Steve.
     
    Last edited: Mar 29, 2017
    1 person likes this.
  3. Will

    Will Hardcore MB Enthusiast

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    I'd have thought with a decent socket and leverage one of three things would happen:

    1) the nuts would come off
    2) the nut and stud would come out together
    3) the stud would snap - but you'd still be able to remove the manifold and extract the broken stud afterwards.

    What happened when you tried to undo them, and what tools are you using?

    I hate to say it but I think you're going to struggle with this job. Have you got the tools to remove the headbolts? What about the tensioner etc? :)
     
  4. OP
    OP
    Nasco12

    Nasco12 Active Member

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    Wouldn't shift. I am using sockets and wrenches from Halfords. More leverage you think?

    You're probably right. The point is that I have little to lose and even if I don't succeed there is much to learn.
     
  5. Will

    Will Hardcore MB Enthusiast

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    You want a decent quality six sided socket and a breaker bar, or a very decent ratchet at least.

    If you can't remove those nuts on the exhaust with the tools you have got you've got no chance with the head bolts! :(
     
  6. neilrr

    neilrr MB Enthusiast

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    Nasco,

    Before you tear this thing apart or scrap it why don't you try https://www.kseal.com/uk/

    Seems to me you've got nothing to lose.

    HTH.
     
    1 person likes this.
  7. OP
    OP
    Nasco12

    Nasco12 Active Member

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    Exhaust manifold nuts are now off. I had one last go at using my sockets not expecting much and... hey presto! everything came off.

    I think this is because I gave everything a dab of PlusGas last night. If this is the reason then this is the first time PlusGas has ever worked for me.

    Having said that, even when I did manage to loosen the nuts it still took an age to unscrew them - access being so limited. I am not looking forward to re-assembly. And some cannot be tightened with a torque wrench - so there'll be some guesswork involved.
     
  8. Auto-mobile

    Auto-mobile MB Enthusiast

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    That won't stop a oil leak.

    I recommend steam cleaning the engine and monitoring the leak.
     
  9. toolman1954

    toolman1954 MB Enthusiast

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    Hi,
    I had a think on your problem whilst walking the dog this morning. What makes you think that oil is seeping out of the head? Finding oil on the drip trays is not a conclusion I would make of oil coming out of the head. So without being patronising, what other things have you checked to narrow down your own diagnosis.?
    Oil only gets chucked out of an engine "generally" while its under pressure, then it finds the easiest way out. Pistons go up and down creating pressure which is normally vented out through breather valves and pipes. The cylinder head is bolted down to some extreme pressure and the head gasket is probably the most least likely place for it to come out.
    So working downwards, check the cam cover and the oil filter (is it loose ) then check all the breather pipes for blockages. No one ever seems to clean them, even when you have a service they never seem to get cleaned. You may need to look at a manual to find out where the breather pipes are. Front oil seal behind the pulley wheel is a possibility. My old 508D van leaked there and the centre nut was a right pig to release. If you are really unlucky then it could be the rear oil seal but unlikely. Has someone been careless in filling the engine with oil? or of course is the engine over filled.?
    Have you wiped a finger on the drip tray and had a sniff of the oil? Is it oil, is it ATF from power steering pump, is it ATF from the gearbox.
    Best option now is to put things back together and do as AUTO- Mobile suggests... that is, to steam clean or Gunk and pressure wash the whole of the engine ( including the drip tray) run the engine for a week or so and then inspect everything thoroughly. My 50 bob would be on a blocked breather valve or pipe somewhere, which is easier to sort out than taking the head off.

    Steve
     
  10. Will

    Will Hardcore MB Enthusiast

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    I think the OP has been having other issues aside from just the oil leak - repeated coolant loss, rough running etc. The header tank looks suspect to me and reading another of the OPs threads he seems to indicate that an MB specialist has also confirmed the cylinder head gasket to be at fault.
     
  11. toolman1954

    toolman1954 MB Enthusiast

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    Ahhh..... 1/2 a story, I didn't know about the other issues. Oh well I hope he gets it sorted. My mindless ramblings may benefit someone?

    Steve
     
  12. Tuercas viejas

    Tuercas viejas Active Member

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    My remedy for these nuts as an oxy torch with a #5 tip and a few pounds of acetylene and oxygen.

    Heat the nut 'til its red then bust it loose with a socket and extension.
    Works every time.
    Tuercas Viejas
     
  13. OP
    OP
    Nasco12

    Nasco12 Active Member

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    Steve, Your ramblings are far from mindless. Please keep them coming.
     
  14. OP
    OP
    Nasco12

    Nasco12 Active Member

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    I may have got the nuts off but exhaust manifold still won’t come off the head because it is connected to the exhaust front pipe.

    [​IMG]

    I really don’t fancy my chances with this. There appears to be no gap underneath those bolt heads (A) which implies they are either welded on or part of the casting. So any unbolting will have to be done at the nut at the top (B). And there also appears to be a mounting (C). Presumably this also has to come off. And look at the state of that nut! (D) And access is poor. And it’s underneath the car.

    “What if” I thought, “I removed the studs from the exhaust manifold?” As it turned out this proved much easier than I had anticipated.

    [​IMG]

    I presume there’s a way of getting them back in.
     
  15. toolman1954

    toolman1954 MB Enthusiast

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    Hi,
    " Refitting Studs ".....well that's an easy one, just lock 2 nuts onto the stud, by back tightening one against the other, then screw in the stud as you would a bolt and then undo the nuts and the stud is fitted.
    If the threads are stuffed, then using a hacksaw, cut a cross in the the bottom of the stud, drill a small concave hole where the + is. Get a small ball bearing and locate this in the bottom of the hole and screw in the stud. The ball bearing then spreads out the the bottom of the stud and locks it in the threads.

    Steve
     
  16. Auto-mobile

    Auto-mobile MB Enthusiast

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    Exhaust bolts are not welded to the exhaust flange (only by rust!) loads of wd40 should help, if they snap Mercedes can supply new ones, they screw into a square copper "nut" if you like, this sits in the flange exhaust side.

    Hope that makes sense.
     
  17. OP
    OP
    Nasco12

    Nasco12 Active Member

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    Looking ahead it would appear that the cylinder head bolts will have a 12-point head. Can I get away with using something other than the proper socket? If not, does anyone know where I can get the proper socket? Will it be expensive?
     
  18. Will

    Will Hardcore MB Enthusiast

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    Woah!

    Absolutely not.

    100% you need the proper tool. DO NOT try and use anything else.

    The bit will be a an XZN type, otherwise known as triple-square.

    You'll also need a decent (ie 2ft) breaker bar.

    Also you will new a torque wrench for re-assembly and an angle gauge (or posh torque wrench that does degrees).

    The bolts need to be measured and often replaced upon refitting.

    Also be certain you understand how the chain tensioner works and how to remove/reassemble it before re-assembly :)

    If you get really stuck getting hold of the correct tool PM me and I may be able to help.

    Will
     
    1 person likes this.
  19. OP
    OP
    Nasco12

    Nasco12 Active Member

    Messages:
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    Some progress to report. The inlet manifold is off. As are the cam cover, thermostat housing, front cover and timing chain tensioner.

    The inlet manifold was a bit of chore due to inaccessible bolts. But we got there in the end.

    Should the cam cover be that dirty? Would it benefit from a clean?

    [​IMG]From Flickr

    Signs of an oil leak. I was expecting to find an O-ring when I removed the (variable valve timing control?) but there was nothing there. Should there have been? Also, the Haynes manual talks about recovering an O-ring when the front cover is removed. There was none to be found.

    [​IMG]

    Getting the engine to 20˚ ATDC was amusing. The pulley had to be cleaned to reveal the markings. I presume 0|T means TDC and what I am looking for is for the 2|0 after TDC (cranking clockwise). And to align that with the mark on the engine. Like so:

    [​IMG]

    It was possible to insert allen keys through the bearing caps and into holes in the sprockets. So, I guess I was doing something right.

    I am now attempting to remove the exhaust cam sprocket. But this is proving far harder than I had imagined. I don’t happen to have a spanner big enough for the flats and for the bit for the Torx on the sprocket only ends up with a 1/4” ratchet. I think it’s going to be a case of new tools, vicar.
     
  20. horatio

    horatio Active Member

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    Please keep the updates going... I have a W202 with (I suspect) a HG leaking oil everywhere.

    It's a solid non rusty car and would make a nice runaround so I'm tempted to give it a go. Just not worth paying a specialist £100+ p/hr to do it.
     

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