Hi Sheep, did you ever get round to writing up the rebuild process? I have a 2010 polo 1.2 with damage to the pistons. I am weighing up my options at the moment. Thanks
Knowlsey
No, not enough interest at the time. The pistons are replaceable though, these engines were fitted to the skoda fabia, seat as well as the polo. This is what i wrote for some one else Who had already taken the engine apart, and it might as well be public
Ok so you have stripped the engine down, i don't know your reasons for this but as far as rebuild goes i will try my best .
If you are tempted to buy a second hand unit DON'T! the main culprits of failure are valve stem guides, burnt out valves and piston rings (shows up as really good compression, but caused by oil blowing back past oil control ring).
To make these engines work effectively again as a bear minimum you will need to replace the valve guides the timing chain and most importantly piston rings (doesn't matter how good they look or how much compression you think you have they are the main cause of problems, oil seeps past into bore and causes artificial reading when in fact the opposite is true), and obviously a full gasket set. the shell bearings for the big ends and condos is going to be a question of how worn they are. mine were completely serviceable so they went back in.
1 depending on how you separated the bottom halves will determine if you have distorted the block or not. due to its fragile nature it needs to be treated like a cylinder head undoing the bolts in sequence.(From memory i think there was about 16 or 18 bolts and they are tight. 8 of these are are slightly larger and act as the main bearing carrier bolts. Start at one corner, then opposite working your way back towards the centre, just as you would on a cylinder head. undo all the bolts a quarter turn at a time to avoid uneven pressure across the block.
2you are now looking at the crankshaft with the connecting rods, remove these and the pistons you also have a balance shaft with a cogged wheel with matches up to the crank.
3 I'm going to skip cylinder head just about completely as the information is all in haynes book.
4 THE FOLLOWING IS HOW I DID THE REBUID THIS MAY OR MAY NOT WORK FOR YOU. (Sorry **** covering bit)
5 starting with the main block the first is to hone all three cylinder bore (
)
6 Refit pistons and conrods back in to cylinder bore just flush with surface of block.
7 The next bit is to fit the crankshaft, THIS BIT IS IMPORTANT on the crank shaft and the counter balance shat are aligning marks, a single dot similar to a centre punch mark. IT IS 100% IMPERATIVE THAT THESE ARE ALIGNED, otherwise the balance shaft WILL jam against the conrods when it turns. As the bottom halve forms the main bearing caps and leaves little to no room to tighten the con rods to the shaft you have no choice but to do them first. Turn the crank so that when the pistons are inserted they will be half way down the bores, you may have to wiggle the con rods a little to achieve this, start with the centre piston, push it down the bore and connect the end cap just to the point where you need to apply force, now move on to the 1st and 3rd piston, doesn't matter which.
8 As torque settings for this engine have never been released it now becomes total guess work. My initial thought was to look at the settings for the 1.4 engine and go from there. However they would be used with a secured crankshaft! I worked up in steps of 10NM starting on the centre piston and working out to the other two. My thoughts being this would cause less chance of any damage or distortion to the block. being honest i can't remember what the finish torque was, but if you are applying force and it feels to much stop.
9 At the time i rebuilt the engine i used a standard silicone sealant between the two halves (it didn't leak), on other engines I've done since with a machined face i use stag wellseal (if you use this make sure you follow the instructions or it will not seal). Carefully lower the bottom casing on to main block, make sure that the shell bearings stay where they should. As you will possibly have noticed when you stripped the engine, there are two different sizes of bolts, the larger centre ones are basically the bearing bolts and the smaller ones being the casing bolts. starting with the two centre cap bolts gently tighten till you feel resistance then move outwards to left or right, (again doesn't matter much as there are no instructions or settings for this engine) then go back to the other end, similar to tightening a head. now with all the larger bolts done move out to the smaller ones working out from the centre in a diagonal pattern to minimise any undue stress.
10 Again i tightened everything down in 10Nm stages starting at 20 Nm until i was happy with it, the smaller bolts will not need the same torque as the larger ones or you will end up snapping them. The second point to note is they will not feel anywhere near as tight as when you tried to undo them. Another thing I did at each tightening stage was to ensure that the crankshaft turned, two reasons one to make sure the balance shaft was in the right place on the first turn and subsequent turns to make sure it was free running and not wrapped the block. Trying to remember i don't think much above 45Nm for the main bolts and about 10 less for the smaller.
11 All the original bolts were reused with the exception of the centre crankshaft pully bolt.
12 Torque the bolts down, don't be tempted to angle tighten on these little delicate engines.
13
IMPORTANT The cam chain tensioner relies on oil pressure, before you try and start the engine properly crank it over with the spark plugs OUT, this will ensure no resistance from combustion and fill oil passages. The reason is if the chain is not under pressure there is the possibility of the chain jumping, removing resistance reduces that possibility. I also removed the spark plugs on all subsequent oil changes.
14 If you don't have access to a press for replacing the valve guides it is possible to tap them out with a small drift and a hammer, A cheap kit can be brought of eBay to refit them , but make sure they go in straight, any doubt on these get help. Only other point about cylinder head is make sure you lap all the valves back in, time consuming and boring but worth it.
15 the only way you are going to find out if there is any distortion to the block is when you put it back together, chances are though that if you can put a flat edge across the main cylinder head and its still within spec probably ok.
16 I can't think of anything else of the top of my head, but any questions i will try to answer. My boy ran it for about two years before he sold it on and upgraded to a golf.
Other points i forgot to put on the rebuild, take the flywheel off before you try and separate the two halves, its extra weight and stress that could lead to distortion, second on reassembling make sure the bearings are lubricated and after the second tightening put the crankshaft pulley bolt in and make sure the crank rotates, then wind it on so all three pistons are level again and continue with tightening sequence.
as a big part is the cost of parts, just for the 6 valve AWY engine you are looking at £200 to £300, (also will depend on 6 or 12valve engine, the bottom half is pretty standard though) depending on whether you need to replace the pistons (PISTON RINGS NEED TO BE DONE REGARDLESS THOUGH). the engine is pretty simple lump though even if it is a bit delicate. The pistons are replaceable, as are the big end and main bearings. NOW THE DOWNSIDE, AS OF TO THE BEST OF MY KNOWLEDGE THERE ARE AS YET NO AVAILABLE TORQUE SETTINGS FOR THE BOTTOM HALF OF THE ENGINE, the only reason there are settings for the top is due to the amount of valve stems and burnt out valves that occurred early on.
Good Luck
Useful Links
1198cc 2002-ON AWY BMD CHFA CHFB BBM 6 VALVE. REBUILD KIT VOLKSWAGEN POLO 1200 3 cyl engines VW. ENGINE REBUILD KIT TO FIT THE FOLLOWNG VOLKSWAGEN ENGINES. AS FITTED IN VOLKSWAGEN POLO ENGINES WITH THE FOLLOWING ENGINE CODES.
www.ebay.co.uk
AUDI/VW 03D100031JX. Das Reparaturkit bestehend aus •1x Distanzscheiben / Anlaufscheiben für Kurbelwelle. Preis inkl. SKODA FABIA I Praktik (6Y5) 1.2 2001.07 - 2007.12 40 54 1198 null. SKODA FABIA II (542) 1.2 2006.12 - 2014.12 44 60 1198 8004-AFG.
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