piston crown cleaning ??????
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  1. #1
    Fellow Frogger! bazgti's Avatar
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    Default piston crown cleaning ??????

    in the haines it recomends to clean the crowns of the pistons when doing the headgasket.
    is this REALLY necessary?
    if not id rather skip it as we are in over our head already without complicating the process more.
    if its necesary ,ill do it.
    what is the best thing to clean them with ?
    also any tips on doing this job is much appreciated
    thank you from the uninitiated and slowly learning rebuild hobbiest.-BAZZ

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    Quote Originally Posted by bazgti
    in the haines it recomends to clean the crowns of the pistons when doing the headgasket.
    is this REALLY necessary?
    if not id rather skip it as we are in over our head already without complicating the process more.
    if its necesary ,ill do it.
    what is the best thing to clean them with ?
    also any tips on doing this job is much appreciated
    thank you from the uninitiated and slowly learning rebuild hobbiest.-BAZZ
    Use a scraper but don''t spread crap everywhere. Maybe best to leave alone.
    When are you working on the car next? I can come over sometime in the next day or so.
    Graham

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    Moderator Alan S's Avatar
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    Unless it's really bad, i doubt you'll achieve too much doing it.
    If you decide to, the things you need to worry about is getting the carbon down the cylinders and if there's any metal bits in there, scoring the bore or pistons.
    I did a decoke on a BX TZi engine a while back that worked fairly well by using instructions from some guys in Europe.
    I dropped about a teaspoonful of brake fluid down each plug hole, spun the engine a couple of times with the plugs out and left for a day or so. Replaced the plugs and took it for a run. Smoke everywhere but made a big difference with performance as we suspected the engine was pretty choked due to it being a "City" car all its life.
    That's an option worth looking at somewhere down the track. Incidentally, a spark plug that was taken out just after that we'd seen just before this treatment went from very grotty to shining and clean as a new pin, so it works, albeit a bit of a desperados way of doing it.


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

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    Contented Peugeot Driver addo's Avatar
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    The famous "Mexican Valve Grind" as one mechanic called it, to me.

    Yes, it will smoke running with brake fluid. Some people will feed this (in rather larger amounts) to a warm, idling motor and shut down; leaving to stew overnight. The idea there is it rips carbon off the valve backs also.

    If you look on American message boards, you'll see reference to a product called "Seafoam". This contains carbon-loosening agents and does a similar job. There are some modestly documented stories of the carbon removed (in any chemical manner) being inclined to temporarily foul valve sealing if the flakes are large enough to begin with.

    Methylene chloride paint stripper on the piston tops works with most deposits, as will ethanolamine based oven cleaners. Clean each piston at TDC, and then you can lower it after wiping, re-wipe, lower and repeat until almost every skerrick of grunge is gone. If crank position is important for resetting the cam belt, measure the piston depth in the bores before turning the motor and use these figures to "recover".

    Cheers, Adam.

  5. #5
    al
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    Quote Originally Posted by bazgti
    we are in over our head already without complicating the process more.
    Dude, i am in over my head... You told me you had done this a million times!!

    As for the pistons, surely they recieved a bath in the coolant?? If they don't need to be done i certainly don't want to disturb them...

    Graham, how is thursday looking? Your assistance would be greatly appreciated, as now i have the cam locked i am a bit terrified...

    Also, i sort of need it to go within three weeks... This maybe optimistic, but it may be sold for scrap if it is still immobile when my dad next sees it. (and the fuego in the same driveway)
    405 Mi16 - Sold - Now back
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    Fellow Frogger! bazgti's Avatar
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    Quote Originally Posted by GRAHAM WALLIS
    Use a scraper but don''t spread crap everywhere. Maybe best to leave alone.
    When are you working on the car next? I can come over sometime in the next day or so.
    Graham

    thursday by the looks of it about 2 or so.
    if possible ,could you bring a bit of pipe we can use on the breaker bar ive got .
    we are tackling the crank pulley to get the bottom cover off and then the head bolts.
    the crank pulley bolt is on at 109 nm torque so it will be fun getting it off.
    -BAZZ

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    Default Cleaning pistons

    Way I was taught was to bring pistons to top dead centre, smear some grease around the edges (stops carbon falling down the bore between piston and wall)

    Stuff material in the other open bores to stop carbon entering, lightly use a scraper to clean top of piston (s) then after cleaning off carbon scrapings use cloth to wipe up grease carefully around the edge of each piston taking care not to force grit into piston/wall gap, repeat process on other pistons.

    Less than five minute job in most cases.

    Ken

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    Fellow Frogger! bazgti's Avatar
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    Quote Originally Posted by Kenfuego
    Way I was taught was to bring pistons to top dead centre, smear some grease around the edges (stops carbon falling down the bore between piston and wall)

    Stuff material in the other open bores to stop carbon entering, lightly use a scraper to clean top of piston (s) then after cleaning off carbon scrapings use cloth to wipe up grease carefully around the edge of each piston taking care not to force grit into piston/wall gap, repeat process on other pistons.

    Less than five minute job in most cases.

    Ken

    thats the process thats also explained in the haines.
    i wanted to know if it was really necesarry as we have spent quite a bit of time already and we would like to get the thing back together as soon as possible.
    if its imperitive that it needs doing ,by all means we will do it but if not we wont.
    the general consensus so far is not to worry about it.
    -BAZZ

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    Moderator Alan S's Avatar
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    Remember: K. I. S. S.

    You start winding pistons up and down and the next project will entail liner seals if you don't lock them down.

    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

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    Quote Originally Posted by bazgti
    thursday by the looks of it about 2 or so.
    if possible ,could you bring a bit of pipe we can use on the breaker bar ive got .
    we are tackling the crank pulley to get the bottom cover off and then the head bolts.
    the crank pulley bolt is on at 109 nm torque so it will be fun getting it off.
    -BAZZ
    Do you guys need the torque wrench back? It's at Steve's but I can get it if nec.
    205gti

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    Brake fluid is also great for finding exhaust leaks. Hook up a small tube/bottle to a vacuum point and let the engine idle. White smoke soon shows up any leaks!

    '92 205 Mi16
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    Default Exactly

    Quote Originally Posted by Alan S
    Remember: K. I. S. S.

    You start winding pistons up and down and the next project will entail liner seals if you don't lock them down.

    Alan S
    Exactly - I would only scrape off very badly carbonised pistons to prevent pre ignition problems - never tried the brake fluid fix for decarbonizing insitu - you learn something all the time.

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    al
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    Quote Originally Posted by Alan S
    Remember: K. I. S. S.

    You start winding pistons up and down and the next project will entail liner seals if you don't lock them down.

    Alan S
    Believe me Alan, i am messing with the least possible things... I wasn't planning on touching the pistons, as i think the potential damage outweighs the benefits...

    When i have felt like playing around i have been using polish and plastic dye - not spanners...
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    Moderator Alan S's Avatar
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    Whenever I feel like "playing around", I usually end up getting a smack in the mouth for my trouble.


    Alan S
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

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    al
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    Quote Originally Posted by Alan S
    Whenever I feel like "playing around", I usually end up getting a smack in the mouth for my trouble.


    Alan S
    I must surround myself by more relaxed people then... lol

    I swear the 205 is mocking me now for being so incompetent... I can hear it saying that a headgasket shouldn't take six weeks... I think this must be a record though - most time spent on a headgasket change without actually getting the head off...
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    Moderator Alan S's Avatar
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    There's a difference between being incompetant and being inexperienced and you're doing the right thing taking it steady.
    In my younger days, I have ripped an engine and gearbox out, seperated, driven about 25 miles each way to collect and swap over an exchange short motor, refitted the head and all the bits and pieces, fitted the transmission, cleaned up the job, had a shower and shave, got changed and gone to the Exhibition Speedway in Brisbane (another 25 miles each way) in the car with the new engine and offsided in the pits at the Speedway.
    These days, I talk about doing a clutch job on a car for a month and still no closer to even starting, play about with valve stem seals off an Mi16 and complain about having to drive the owner of the two cars wherever he wants to go...............Mate; that's incompetance.


    Alan S
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  17. #17
    Fellow Frogger! Ren25's Avatar
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    Don't touch it!
    Back in the 1930's cars had to be decarbonised every 10,000 miles or so, due to- Low compression = low combustion camber temps = carbon build up
    Crap, low octane fuel
    Huge crearances, causing oil "suck up"
    Straight mineral oil that caused mucho deposito
    Relitavley (S?) modern engines, ie since the mid 60s, don't have any of these factors, the carbon on the top of those pistons amounts to nothing. You will cause many more problems by disturbing it than you will by simply leaving it be.
    Cheers
    Mike
    PS most of what you read in Haynes is C**p IMHO
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    1000+ Posts Gamma's Avatar
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    DE-COKE in a can.
    Add to the tank and drive.
    Most of the standard fuel additives and octane boosters will do the same job overtime.

    If the build-up of [email protected] on the piston crowns is that bad, then it might be worth taking them out and re-ringing the motor while you are at it.

    If you leave the motor out in the elements with the head off for a week or two the moisture gets under the crud and it will scrape off easier, (Holden 186 in a HT). You could stuff rags in the holes and take to the gasket-goo/concrete with a wire wheel on a drill, (202). Drizzle aircraft carby/landing gear cleaner, (yellow peril), down the throat with the revs up, (warning this stuff will take the skin off your hands in a jiffy and kills grass permanently ), like you would on a salad, (Morris 1100 , worked wonders).

    Note: all of the above measures were used and worked. I would not recommend them for any motor car which is beloved by the owner.
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    1000+ Posts Haakon's Avatar
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    I always clean the piston tops. Put it to TDC, and CAREFULLY scrape the carbon off. Dont scratch the piston top... Use a vacuam cleaner whilst doing this to grab the carbon bits that are scraped off.

    Use a little carby cleaner (wear gloves - nasty stuff) and a green kitchen scourer to clean it finally. Never had any problems with carbon bits beside the pistons. Smear oil on the bore to collect the little bits. These will be tossed out the exhaust on fire up.
    I tried to drown my sorrows in alcohol, but the bastards learnt how to swim

  20. #20
    1000+ Posts Dave's Avatar
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    I cleaned the ones on my GT when i last put my good head on it. They really need a clean after this many k's. See below:

    Before


    After:


    As you can see a lot less carbon after a bit of cleaning. I clamped the liners, put a bit of grease around the edge of the piston to catch grime there so it can be wiped off without getting between the liner and piston. Also an old headgasket is good for covering up the water galleries.

    As long as you have the liners clamped there is no reason you shouldn't clean them up a bit (if they are coked up badly).

    Dave


  21. #21
    Fellow Frogger! bazgti's Avatar
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    Quote Originally Posted by al
    I must surround myself by more relaxed people then... lol

    I swear the 205 is mocking me now for being so incompetent... I can hear it saying that a headgasket shouldn't take six weeks... I think this must be a record though - most time spent on a headgasket change without actually getting the head off...

    well if you count the actual hours we have spent it s been in 3-4 hr bursts once or twice a week ,it only seems like six weeks cause six weeks have passed since you got it.
    but i know,youre hangin out to drive it.
    but we are SLOWLY GETTIN THRU IT.
    i must say i agree with alan s about leaving the piston crowns,
    thank you to all the good meaning people with the tips on how to do this but the amount of time we have taken already just to do what we have is gettin a bit much.
    best to keep it simple and just do the head gasket properly,thoroughly .
    because the fun will start when we put it back together,[oh no what have i said]
    -BAZZ

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    Relatively high compression engines (from 9:1 & upwards), which have covered high kilometers, should have the piston crowns de-coked.

    All of the previous comments are valid re precautions, preparation etc. The situation with the high compression engines, which are in good condition, is that a layer or two of carbon on the piston crowns further increases the compression ratio.

    This will happen with any engine, of course, but at the higher end of the piston engine compression ratios, detonation becomes a problem. Even some premium fuels will have occasional problems under some operating conditions such as high load, hot temperatures, incorrect ignition advance etc, & thus the engine will ping.

    Typically, some operators will retard the ignition to prevent the 'pinging' problem. This, of course, means a power loss, increase in fuel consumption & higher operating temperatures.

    With 10 minutes of preparation of the engine block, I always remove the carbon from the piston crowns. You will be rewarded with improved performance when the car is returned to best operating specifications.

    Cheers,
    Kim.

  23. #23
    WLB
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    What they did back before WW1 was to pull out the spark plugs, drop a couple of bearing balls into each pot, put the plugs back in and go for a run.

    Can't remember how they said you should get the balls back out again.

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    Default Shot peening!

    Quote Originally Posted by WLB
    What they did back before WW1 was to pull out the spark plugs, drop a couple of bearing balls into each pot, put the plugs back in and go for a run.

    Can't remember how they said you should get the balls back out again.
    leave them in long enough and they would.

    (a) work themselves through the piston crown and intothe sump.

    (B) pass into the exhaust system with small bits of broken valve lip and piston peenings.

    Ken

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    Quote Originally Posted by WLB
    What they did back before WW1 was to pull out the spark plugs, drop a couple of bearing balls into each pot, put the plugs back in and go for a run.

    Can't remember how they said you should get the balls back out again.
    Another technique was to pull the plugs, go to TDC, stick a lighted oxy torch in the plug hole, heat things up pretty well and then turn of the acetylene, the pure oxygen would burn the carbon out.

    Terry

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