Citroen zx head gasket change

[Raul]

Hello


I am in the process of changing head gasket on my citroen zx 1.9 td. How do you prepare block surface for mls type head gasket? So far I have been using razor blades to get the old gasket off, but i was told that the suface finish has to be perfect to get the gasket to seal. I would like to use very fine grit sand paper, but everywhere I read about head gasket changing, they say that it is not allowed to use anything abrasive.



Raul

[addo]

If the remaining gasket material is something other than metal, you might try a methylene chloride type paint stripper. Lay it on thick and cover with a double layer of cling film to stop the solvents drying out too fast. After 30 minutes or so, see how readily you can scrape the residue away. It might take several applications. With products like this, be careful! They are bad for health and damage paint very fast.

[citronut]

hi and welcome

as long as there is no deep corrosion on the block surface i would just use scotch bright with duck oil/lubricant, then wash clean with petrol,

i wouldn't put anything corrosive on it as you don't want that to enter the oil or water ways,

also defendant on how much the head was skimmed you might have to have the valves sunk into there seats a bit,

as there are tolerance's as to how close to the head face they are, to close they will contact the pistons,

regards malcolm

[Raul]

Thanks for the replies. I use brake cleaner and some acetone based solvent. I would say that it is almost clean from the old gasket residue using razor blades but I am worried about the different coloured stains from old gasket( especially hard is to remove some copper coloured stain around the bores). I slipped my fingernail across the block surface and it seems ok, but it is not mirror like finish, it has different coloured areas. My main concern is that almost every source of information about using mls gaskets insist machining both block and head. What is your experience, can they be sealed without machining the block? This is my firts attempt to do such major job on the engine and tearing apart the block to get it decked is a little bit too much for me. The other option is to use fibre gasket, i would not mind to use it if I know it is very good quality.

[Xantidote]

mls?? Is that a multi-layer gasket?

In my limited car maintenance, I've never heard of machining the block, but I'm talking about cast iron blocks. The need to skim an aluminium head might arise if the engine had overheated, and the head had distorted. You could check this by putting a straight edge across it (especially check diagonally)

When I had to do the HG on my Xantia's 1.9TD engine, I did the final cleaning of the block and head faces with wet & dry, in white spirit, obviously being very careful not to get any particles/swarf in the bores etc. Followed this by cleaning with petrol soaked rag, and finally a wipe with acetone to remove any residual oil/grease/greasey fingermarks, prior to fitting the new head gasket.

[citronut]

as i said earlier as long as you clean any debry so the block feels smooth and there are no areas of corrosion into the block surface there should be no prob,
you don't need to get a bright shinny finish,

although i have not had experiance of those gaskets,
if you use a quality standard gasket the likes of Payen, Elring or Melior you wont go far wrong,


regards malcolm

[Chlorate]

It's always an idea to have the cylinder head skimmed even if the engine has never overheated. For example at university we recently pulled apart an engine for our Formula Student car, (Honda CBR 600) it had no history of engine trouble, but yet needed 8 thou skimmed off it before it was good to put back on the engine.
Simply torquing the head down is enough to deform the head a little, even when applying the torque in the correct pattern, the gasket will accommodate for this if the head was machined flat beforehand, it probably won't if it was already deformed.
The block is an "it depends" sort of thing. Generally simply cleaning the gasket surface is good enough, especially if it's a cast iron block. If it's an alloy block, having it machined would be ideal, but is seldom required.

[citronut]

it is always best to crack off the head bolts in the reverse order to torquing them down, so cracking off de/creasing circle from one end to the center,
and torquing down an increasing circle from the center outwards to the end,

regards malcolm

[Raul]

I got the head back from complete overhaul and when I inspected the surface closer at home, I was very suprised to find this small dent ( you can see it on the left from the pre chamber) :

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http://nagi.ee/photos/205d/20679971/" onclick="window.open(this.href);return false;

I took an old gasket and drew a line along the circle of the fire ring( the line is barely visible on the picture). So in conclusion this dent is somwhere in the middle of the fire ring. My question is: is it going to cause problem ? Everything else looks ok, but this small thing makes me worried.

[citronut]

if its in the coopers ring line yes it is a problem,
trouble is can you prove it was there before you took the head away from the company that did the work,

regards malcolm