M104 Head gasket

Martyn_n

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I'm about to bite the bullet and replace the head gasket on my E320. What I want to know is this; exactly what gaskets will I need to have ready to do the job. I know I need the timing cover gasket(s) head gasket (obviously) and the green U-shaped one but what else do I need (and do you know the part numbers?). The method recommended by MB has you leave the exhaust and inlet manifolds attached to the head when you remove it so the gaskets associated with those won't be needed (but are included in the kit from MB). I don't want to buy the whole gasket set just to throw most of the parts in a drawer if all I will use from it is the head-gasket.
 

GP801

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I would just get the whole kit. Its not that pricey. I think there are different kits depending on whether the head needs skimming or not and by how much.
 
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Martyn_n

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I can only find one listed, and the difference in price is £38ish over and above just the HG. If it included the timing cover gaskets I wouldn't hesitate, but I don't believe it does. As I already know I won't be using the inlet and exhaust gaskets I don't think that £38 looks good value.
I think there may be some air-injection / emmissions connections that may need an o-ring or two but they should just be pennies surely!?

Mercedes Benz | Euro Car Parts UK

This shows what is included (I'd buy it from a main dealer though) and it's the six parts in the bottom right I need I think.
 

BlackC55

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Get a genuine kit ONLY. The aftermarket HG kits are crap.

Disconnect the inlet manifold and leave the exhaust manifold on. Do you know how to re-load the tensioner?
 

Ian B Walker

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£38 is cheap. Personally I would sooner pay a bit extra and get a Merc one (£58 if memory serves me right)


beat me to it Olly
 
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Martyn_n

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As I said, I'd get it from the dealer. This was the only pic I could find. Agree it is very cheap, but I only want to do this once.

Just to confirm, head gasket only is £46, kit is £85 (Both main dealer prices) I'm committed to buying the u-shaped gasket and head gasket, and taking on-board the advice so far will now be replacing the six inlet manifold to head gaskets (£20). Therefore it looks as though there is only about £15 in it, will just get the kit and put the exhaust gaskets to one side.

As for re-loading the tensioner, I've read about how to do it and seen pictures of it being done. Never done it myself though so cannot honestly say I "know" how to do it. Any tricks of the trade are always welcome.
 
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Martyn_n

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Olly (BlackC55) did mine. Do whatever he says.
A pro like Olly (would probably be a poor substitute but unfortunately I'm too far away to use the real thing) would be doing mine if I wasn't skint, I need to keep some (read "lots of") money by for when the loom falls apart during the process!!
 

GP801

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A pro like Olly (would probably be a poor substitute but unfortunately I'm too far away to use the real thing) would be doing mine if I wasn't skint, I need to keep some (read "lots of") money by for when the loom falls apart during the process!!

Very wise. The loom will fail at some point. Fortunately ours was done by the previous owner but unfortunately in addition to the head gasket ours also needed a new ECU a few months ago. Very painful.
 

w124nut

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If the engine wiring harness is original (I don't know how you can tell), for peace of mind, factor in the cost of a new loom and replace the old after you finish replacing the head gasket.

My loom went soon after a head gasket replacement and I was lucky that nothing else under the bonnet needed attention.
 

kth286

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in comparison to replacing a head gasket, the job of replacing a loom is
not long at all.

Do consider unplugging the loom from the ECU and remove the loom completely.

It will make the job of gasket replacement easier anyway, by having those wires out of the way, and you avoid the risk of trapping a wire.
 

grober

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Here's how to do the loom swap. Notice the poster advocates laying the new one beside the old when doing it using the old one as a template/guide. PeachPartsWiki: W124 Engine Wiring Harness Replacement
There's also a guide on CHG replacement PeachPartsWiki: Head Gasket Replacement
Personally its a job for the pros imho as you may need to get the head planed flat if it is warped? If you don't the CHG will fail again fairly rapidly 6months -1year not worth risking it.
 
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Martyn_n

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I bought the car with the sole intention of doing work on it myself, it's a hobby not an essential form of transport for me. I'm pretty confident at doing the work, and have pretty much resigned myself to doing the loom at the same time.
With regard to whether the head needs skimming, is there any way of actually knowing if this is the case? I would assume that you need a thicker gasket if this needs to be done, don't want to dive in and buy a standard one before starting just to have a skim and need to get a thicker one.

Have any of the pros on here who have done a few any idea what percentage need skimming?
 

Will

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You can check the head for trueness using a engineer's 'straight edge' and feeler gauges. Off the top of my head, max deviation from trueness is something like 0.05mm across and 0.10mm lengthways (although I'm not sure I'd be happy with that much!)

In reality, worth taking it to an engineering shop if in any doubt, you could have it lightly 'faced', removing such a minimal amount to ensure the mating surface is 100% true and cleaned from old gasket deposits/burnt oil/carbon etc. A few hundredths of a millimetre won't cause you any issues with head gasket thickness or compression etc IMHO.

Will
 
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