Which head gasket for ZX Td

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gjb02
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Which head gasket for ZX Td

Post by gjb02 » 30 Jul 2002, 14:42

It looks like the condensation in the oil cap was just the start, I've now got bad idling lots of smoke on start and coolant loss, all of this in just a few weeks. But I digress. It looks like the head gasket is leaking around the no.3 cylinder, I cracked the fuel unions whist the engine was running to see which one was causing the misfire. And right enough no.3 stopped the smoke and the engine sounded great, tightened the union and the smoke and misfire returned.
What I would like to know from the more mechanically experienced forum members, and you know who you are..<img src=icon_smile_big.gif border=0 align=middle> is which type of gasket would be better, a 3 notch fibre, or 3 notch metal sandwich type. They both cost about the same, but what are the implications of using one instead of the other. The current gasket, which is blowing, is a ssandwich type. So I am tempted to use the alternative. Anyone<img src=icon_smile_sad.gif border=0 align=middle>
Gareth
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Dave Burns
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Post by Dave Burns » 31 Jul 2002, 04:33

Hiya Gareth, use the metal sandwich type that's already fitted even if it has failed, at what mileage by the way.
A fibre gasket may fail sooner on this engine and here's why, the head is cast aluminium and the block is cast iron, when they heat up they expand at different rate's which put's high shear force's on the gasket.
To cope with this the much stronger metal sandwich gasket is used, it has a fancy rubber coating to provide the seal and a compressive middle, the downside is it requires a very high quality surface finish to achieve a long service life.
A fiber gasket on the other hand is much less strong and need's a certain roughness of finish from the head and block to help hold it in place, that roughness is not there on these and other modern engine's which is why it may fail earlier.
A fiber gasket though might be a better choice where the head/block has been re-machined.
Dave
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gjb02
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Post by gjb02 » 31 Jul 2002, 04:53

Yet again another speedy reply!<img src=icon_smile.gif border=0 align=middle> Hello Dave, the car is currently on 163,000. I finally got the head off this afternoon, the No.3 cylinder had a small pond in it, and there were already signs of coolant crystallisation. The head itself looks like it has been previously delt with, there are new core plugs and the swirl chambers are relatively crack/burn free. The cylinder head face on the other hand is a dogs dinner. There is pitting in various places over the surface of the head, and considerable corrosion in and around the water galleries<img src=icon_smile_sad.gif border=0 align=middle>. I'm taking the head to my local engine specialists tommorrow, so I'll see if it can be rescued. As for the gasket, in light of what I have just told you, would the fibre one be the better choice?? And would you advocate the use of any additional gasket repair. Or is it simply not an option on a high compression such as this. On a completely seperate matter, how do you completely remove the RHS engine mount from the wing, rubber and all, its perished slightly and needs replacing. I think it's just a case of unscrewing it, but can't see an alternative to that. Cheers again Dave.
Gareth
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Dave Burns
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Post by Dave Burns » 31 Jul 2002, 05:23

If it had gone that distance on the original gasket I wouldn't be to upset at that for a turbo, Iv'e done one alot earlier than that.
If the head has grinding mark's rather than milling marks (swirls like mark's), then it has been down before.
May be wise to get it skimmed if it's still in tolerance.
Sound's like a fibre gasket could be the better choice but don't go shoving any hermetite or other gasket gunk on, it just don't work in these cases, just get it all as clean and smooth as possible.
If it does look bad I'd be tempted to give the bolt's an extra ten degrees when it goes back.
Never had to swap the engine mounting rubber so don't know how it comes out, can imagine having to knock up a special tool for it, I would only swap it if it started knocking or something.
Dave
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gjb02
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Post by gjb02 » 31 Jul 2002, 05:28

Don't you sleep either? <img src=icon_smile.gif border=0 align=middle> The marks ar like large sweeping circular scores in the face that almost travel the width of the face. Is that likelt to be milling mor than skimming? I'll avoid the Hermetite. What sort of mileage can I expect with the fibre gasket? Cheers again Dave.
Gareth
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Dave Burns
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Post by Dave Burns » 31 Jul 2002, 05:47

Thems original machining mark's and yes I need me beauty sleep, but it aint working<img src=icon_smile_sad.gif border=0 align=middle>
What mileage can you expect on a rebuild, well how long is a piece of string.
Dave (off to give it some zedz)<img src=icon_smile_sleepy.gif border=0 align=middle>
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