1.2 3 cylinder petrol rebuild

i hate 1.2 awy

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This is going to be my first post on the subject of this pain in the backside throw away engine! first don't through it away it can be rebuilt and run afterwards! i brought one of these for my son thinking vw 68000 miles should do him for a couple of years, err wrong answer! after going through the same as everyone else who has had one of these and that has not been regularly serviced (THIS IS THE BIG KILLER, NOT SERVICED ON TIME AND DECENT OIL) we performed all the usual checks engine compression timing checks (we had replaced the timing chain as a matter of course as you would a belt) add oil to bores recheck everything! in the end the option suggested to us was scrap the car or get a replacement engine, well the rest of the car was to good to scrap, unfortunately trying to source a decent second hand engine proved almost impossible without paying £400 - £500! Having rebuilt engines before i decide to give it a go despite what the manual says you can't dismantle the bottom half of the crank case, (you can, just need to be careful). all the parts are available to rebuild it, rings, bearing shells, valves and valve guides. the main thing to note is that even though we originally had good compression and even better when oil was added to the cylinder bores, the main cause of our engine problem was the oil control rings allowing oil past and burning it in the combustion chamber this affected the emissions and the computer then tried to compensate causing more fuel to be burnt along with large amounts of oil. anyway back to the rebuild separating the the two halves of the crankcase if done in a similar manor to the cylinder head (diagonally and working in) undoing each bolt a small amount at a time then repeating until they are all loose, lift away the bottom half and now you can get at the end caps for the pistons (a bit at a time again). the main thing now is to examine all the dismantled parts check what needs replacing and what can be reused, best advise you've got it apart replace the lot IE bearings and piston rings. initially i thought the whole thing was shot as the play in the crank end float and piston lateral movement in the bores was a lot more than what i was used to seeing in engines (even a totally worn out engine), on first inspection the piston rings don't even appear worn and are not stuck to the piston or gummed up but believe me they are shot! Don't forget to deglaze th cylinder bores pay particular attention to the cylinder head, the hydraulic tappets were pretty much all stuck. after all the valves were removed the whole head and block were taken to a local garage for a dip in the cleaner (not 100% needed but makes life easier) all the valve guides were replaced (again this wasn't 100% needed ) but what the hell i didn't want to do it again, so in went new valves. reassembly took time as there are no specifications availably for this engine (beg and plead with vw as much as you like it ain't going to happen) so with patience and gentle use of a torque wrench it has been resembled. bear in mind this engine uses oil pressure to tension the chain, THIS IS IMPORTANT! TAKE OUT SPARK PLUGS (THIS MEANS NO COMPRESSION OR STRESS ON ENGINE AND TIMING CHAIN SHOULD NOT JUMP), DISCONNECT FUEL INJECTORS (THIS STOPS NEAT PETROL GOING IN TO THE CAT AND RUINING IT). CRANCK ENGINE FOR AT LEAST A MINUTE TO GET OIL ROUND. now reattach everything and give it a try. 500 miles on and we have just done oil change after running engine in!

I am in the process of writing the rebuild process fully ( it may take some time as i do't have a lot of it!) if any one is interested please let me know.

The Sheep
 

Crasher

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I know of some people who have tried and not been able to get the crank to turn, it just locks up when torqued down. The other problem is the main and rods bolts, they are TTY one time only.
 

i hate 1.2 awy

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Yeah that was one of the problems i had heard about being encountered, maybe i just got lucky or didn't apply as much torque. i offset the crank so all three pistons were at approximately the same level to try and minimise any distortion to the block. as i said you have to tighten the bolts gently and evenly, to avoid distortion i did the main bearing cap ones first then worked my way to the outer bolts. The bolts were all the originals with a light coating of thread lock, why? because it never crossed my mind to change them and after speaking to a real mechanic (Not the book says no! one), he was telling me a lot of the bolts are replaced needlessly as most are thread locked originally and the only real problem occurs with worn threads in the softer aluminium castings when bolts are overtightened and stretch or strip the thread, allegedly !. also as regards the crank don't forget the balance shaft needs to be in the right location otherwise the the crank gets jammed against it! i know cause i did it! the whole engine was a learning curve.


PS
once all the bolts were hand tight on the rods they were tightened to very small torque setting and crankshaft rotation checked before next stage of tightening, then recheck rotation etc. then the same process applied to the main bearings. One thing to bear in mind is make sure the flywheel is not on the crank as the weight of it will very defiently distort the block and any chance of getting an even torque setting.

The Sheep
 

Knowlsey

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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
 

Crasher

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With damaged pistons the only viable option is to replace the entire engine as in the normal parts supply chain, the pistons are not replaceable.
 

i hate 1.2 awy

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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

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Crasher

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VW don’t list BMD pistons and those in the German eBay advert are in genuine looking plain brown boxes so they must be using the piston from something else.
 

i hate 1.2 awy

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VW don’t list BMD pistons and those in the German eBay advert are in genuine looking plain brown boxes so they must be using the piston from something else.
VW don't list anything for the bottom of that engine, be it a BMD, BBM or anAWY its all aftermarket and sometimes its try it and see! Both Skoda and Seat use the same engine. failing that its probably someones back shed in a corner of China producing pistons😂



BORN AND BRED IN STABBO, GET OVER IT!
 

Crasher

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They have long gone past the age where professional repairs to that engine for anything beyond a timing chain doesn't add up against the value. Doing for yourself or buying and selling can still work, at the moment.
 

i hate 1.2 awy

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They have long gone past the age where professional repairs to that engine for anything beyond a timing chain doesn't add up against the value. Doing for yourself or buying and selling can still work, at the moment.
Totally agree, recon 1.2 engine prices are silly money (engine parts and labour, probably £800 to £1000and then you still have to have it fitted, say another £300 plus), second hand engines are going to have the same issues. so you can do one of two things, go out and get a recon or if you want to try it for yourself rebuild it. so yes unless you doing it for yourself not worth doing on a £600 car.
 

i hate 1.2 awy

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I don't trust ANYONE who rebuilds engines, they are all charlatans...
you obviously been to sneinton and colwick as well then. Thats why i do mine myself for me, at least i know whats in it! one day i might get a car with a good engine! or maybe not😂
 

Crasher

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Mother of Crasher was a teacher in Sneinton for decades near the windmill and still only lives straight upt road through lower Calcutta. Same here though, either genuine VW or my own.
 
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