How to: Change head gasket on M40 engine

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  1. How to: Change head gasket on M40 engine 
    #1
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    Gazdaman's Car Details
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    Ok, this project was done on a 1993 E36 318i but the engine is also fitted to E30s and I'd suspect the other 4 pot engines of a similar age are very similar.

    Tools you'll need:
    Decent socket set with extensions (various)
    Few screwdrivers (mainly to remove plastic trim bits)
    Spanners (the usual sizes plus an 11mm, stupid BMW)
    Mole grips come in useful.
    If you're doing it the proper way you need a viscous coupling locking tool and a crank and cam locking tool. I used neither.

    Parts needed:
    New gasket set, I paid £37 for the whole gasket kit off eBay
    New waterpump (may aswell change it while it's there, but you don't have to)
    New cam belt (same as the water pump)

    A Haynes manual is extremely useful, but hopefully this thread is detailed enough not to need one.

    Ok, first thing to do is bonnet up. Take the heat shield off from above the fan and radiator. Also the plastic scoop that's at the base of the windshield. They both just unscrew/unbolt. No tricks to removal.

    Next remove the top half of the inlet manifold. This first needs you to unhook the throttle cable. 2 Bolts and the plastic part just unhooks from the throttle body.

    Then there's a couple of tubes and a cable. Then a few bolts, 11mm iirc. Once they're all loose, the whole top half should just lift off, with the throttle body still attached.



    Then unbolt the lower manifold. Again it's a few bolts. You also have to take off the fuel hoses. There are 2. Ideally you need to depressurise the system by pulling the fuse. Personally I didn't, but I should have done because it sprayed a bit of petrol around.



    It's quite fiddly removing the lower manifold around the petrol hoses, but with a bit of maneuvring it can be done. Keep a record of the hoses and electrical connectors that get undone on this stage, because they can be a bit fiddly later.

    Next step I made was to undo the bolts that hold the rocker cover on. Think there are 8 bolts on the top of the cover. This bit comes off quite easily.

    In my case it was very obvious at this point that it was a head gasket failure



    You can also lift up the plastic cam cover to show the cam

    Don't remove the cam or cam caps! BMW cams are hollow and are extremely difficult to remove safely, you don't need to remove it, so leave it where it is.



    In this photo I've also removed the distributor cap and spark plug caps and HT leads. Dizzy cap is just 3 10mm bolts. Make a record of which HT lead is for which cylinder! There's also a plug that plugs in underneath where the inlet manifold was. Unplug that. There's one of the plug caps that plugs into the coil to the left of the engine.

    From here the job is made a lot easier if you remove the fan and housing. To remove the fan you need to unscrew it from the water pump which also spins. Requiring the locking tool. In my case I clamped a set of mole grips onto the pulley which as I spun it locked against the belt. Not professional, but it worked and was free. Note that the nut is left hand thread, so you turn to the right to undo it. It's a huge size aswell, think it was 37mm. While it's locked you may aswell remove the pulley from the water pump. There are 4 bolts. It's easier if you remove the belt first which is slackened by moving the alternator. Which is a 13mm locking nut on the back, then twist a mounting bolt on the front.



    Then you can remove the rotor from the dizzy cap, that's 3 bolts, believe it's a 3 or 4mm allen key. Can be renewed if you see fit. Then remove the various bolts that hold on the upper cam belt cover. Think they're 12mm and there are a few of them. Once you've got them all, the belt cover should just come off with no trouble.

    From there you can remove the water pump. 4 bolts hold it in. If it's a tight fit you can screw 2 M6 bolts at the top and bottom. There are threaded holes in the pump and they'll push against the block pushing the pump out. In my case the lugs on the waterpump just snapped off, but it should work in an ideal world!



    In order to remove the lower belt cover the crank pulley needs to be unbolted. There are 5 13mm bolts, but you can't really see them. There's also a 22mm bolt on the end of the crank, you may need to hold that still in order to remove the pulley bolts. Undo the 13mm bolts and then both pulleys can be pulled off. Note there's a locating pin so it goes back in the right place. The belt can be slackened and removed by adjusting the power steering pump (on my model anyway, it changes if you have air con).

    Now you should have something resembling this:


    A few more bolts on the lower belt cover and that can be removed too. Pay attention to the routing of the cable and where the cable clips are situated. Personally I label the bolts/nuts as I remove them so I know where they go.

    Now is the point where you can lock the crank and cam. You need to find TDC on piston 1 there's a section in Haynes on how to do it. You can then put cam locking tool on.



    It just sits over the cam and rests on the head. The next step is under the car, near the back right near where it joins the gearbox. There's a black rubber bung, take that out, and place in the other half of the tool. It should just slide into a hole in the flywheel like in this photo



    Personally I couldn't get them to work, when one locking tool was in, the other was in completely the wrong place. So I didn't use either.

    So I did it by eye. Not ideal but it worked for me. I would recommend locking.

    Next step is to loosen the 2 cam belt tensioners. Both are 13mm bolts. One on the left is an actual tensioner, loosen it and it pivots. There's also one on the right that's more of a runner. Loosen both and slide the cam belt off.

    Next up is the head bolts. There are 10! I only found 8 first time and wondered why the head didn't come off. You'll need a female torx socket, E32 or E35, I forget.

    Undo the head bolts and get under the car. There are 3 bolts that attach the exhaust manifold to the down section. Undo those, it can be fiddly.
    From there the head can be lifted off, it shouldn't need any wiggling or hammering. Mine just lifted clear off.



    Head off


    Bare block, just lift off the old gasket, and put the new one on.


    My gasket kit came with a new exhaust heat shield. It also came with valve stem seals but I didn't use them.
    At this point you should check the head for any visible warping. If the head is warped it needs to be skimmed by an engineering firm, it's not particularly expensive but if it needs it and you don't do it, it'll just ruin the new head gasket instantly.
    Any warping most likely won't be visible so may need to also be checked by an engineering firm.

    I gave it a visual check and decided not to bother, I ran a risk and so far it seems to have paid off.

    Pop the head back on, torque it down with new head bolts

    It's been suggested that you also check/clean out the head bolt holes as you can cause damage and/or get false torque readings. Personally I didn't bother, I just made sure I didn't get anything down the holes.

    Now to do a Haynes - the reassembly is the reverse of disassembly!

    Things to watch out for is the locating pin on the crank pulley, make sure that slots into the pulley otherwise it'll run off centre and the belt will come off and also hit the fan.

    Also the cables that run across the centre of upper and lower belt covers, make sure they're securely tied out of the way. New waterpump can be fitted, and everything back together. This is where it pays off by labelling cables/pipes because you can work out where they all go on reassembly.

    Job done, all back together, turn it over by hand a couple of turns to make sure the timing isn't so far out that valves will hit pistons.

    Then give it a go! Fire her up!

    Any questions I'm happy to help.
    Last edited by Gazdaman; 01-08-2009 at 21:46.
     
     

  2. The Following 4 Users Say Thank You to Gazdaman For This Useful Post:

    ask2firts (08-06-2012),Fels (09-10-2014),Ronnie (31-07-2009),steve23002 (31-07-2009)

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    #2
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    Cheers for the guide Gaz. It should help a few people out....
     
     

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    that is great man its really helpful i think i'm going to do the same with mine coz i have this problem to
     
     

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    i am asuming it would be a similar procedure for 6 cylinder
    dave,s got loads to do on his car :
     
     

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    I did my E30 325i and it was very similar procedure, just a longer head really.
     
     

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    That's a fantastic guide, I think even I could follow this.
     
     

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    Something that needs amending is where you put the flywheel locking pin in, it isn't put through the hole you show in the picture. It is put through a small hole in the engine block on the passenger side just under the starter motor. Hence why you couldn't get them to line up.
     
     

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    When removing the knackered head gasket, i would recommend using some sand paper to give the head a clean, you tend to get bits left behind when removing them.

    If there is any dust from doing this a quick blast with compressed air removes it.
    E39 M inspired
     
     

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    Bumping an old one.

    Can the photos be updated again? Ive found this quite helpful as I don't own a bentley or haynes manual. How tight did you torque the new H/bolts?
     
     


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