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Blown Piston after crankshaft and piston replacement
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Old 24 Nov 2010, 03:23 AM   #31 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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Originally Posted by stiimpreza1984 View Post

what a piston looks like after detonation is the engine stripped yet?
Well, almost but not quite. The piston was damaged on the side. I'll pass by the garage today and take a picture of it.
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Old 24 Nov 2010, 03:27 AM   #32 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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just premium he says what ever rating that is there..?? i dont think it did detonate from whats said..just started knocking but at those rpm's after that work i with no proper running in period its inevitable some things going to go wrong..,but by the sound s of it the crank has survived as there has been no mention of that..so thats very lucky
The crank survived thankfullly. I agree with you carwisperer that it could have been the aggressive driving soon after the rebuild. I know a couple of guys with STIs who use the same fuel and they've not had problems with their engines.
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Old 24 Nov 2010, 09:24 AM   #33 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

Did a bit of searching myself on the net and the petrol is between 91 and 95 octane. 91 is for inland Africa and 95 for coastal areas. Does your car have a recommendation inside the fuel flap door. I would check. If it's 98 like ours you definately need octane booster and I would think this lead to your original problem
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Old 24 Nov 2010, 11:01 AM   #34 (permalink)
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Unhappy Re: Blown Piston after crankshaft and piston replacement

Just passed by the garage and its not good news. The mech took it out for a test drive and after about 50km it started making the same knocking sound that it did the first time, which was diagnosed as a rod knock. That is frustrating. Earlier in the day I had told him about keeping it under 3000rpm like you guys had suggested and he says that he had done about 500km under 3000rpm by the time I picked it up (that is the first time it was in the garage). He tells me also that today he was driving under 3000rpm when the engine lost power and the knocking sound started. So now they have to strip down the engine again to see whats wrong this time.
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Old 24 Nov 2010, 11:18 AM   #35 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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Originally Posted by shambles View Post
Did a bit of searching myself on the net and the petrol is between 91 and 95 octane. 91 is for inland Africa and 95 for coastal areas. Does your car have a recommendation inside the fuel flap door. I would check. If it's 98 like ours you definately need octane booster and I would think this lead to your original problem
I checked the inside of the fuel flap and surrounding areas of the filler cap but could see no indication of the fuel rating. The manual says that one should use fuel that is at least 91 AKI.
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Old 24 Nov 2010, 12:40 PM   #36 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

Aki is the average mixture of mon and ron and is usually about 4 - 5 units less than the ron so you should be aiming for at least 95ron. Just trying to help what caused the problem in te first place. Need to find out now exactly what you are being sold to determine if you need octane booster. Regarding your engine I'm glad he driving it when it started to knock again. Sounds to me like he rebuilt it poorly. Sorry for your bad luck!
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Old 24 Nov 2010, 12:54 PM   #37 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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Originally Posted by shambles View Post
Aki is the average mixture of mon and ron and is usually about 4 - 5 units less than the ron so you should be aiming for at least 95ron. Just trying to help what caused the problem in te first place. Need to find out now exactly what you are being sold to determine if you need octane booster. Regarding your engine I'm glad he driving it when it started to knock again. Sounds to me like he rebuilt it poorly. Sorry for your bad luck!
Yeah, looks like the rebuild was not done well. Its kind of frustrating. Thanks shambles for the information. I'll endeavor to find out the exact RON.
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Old 24 Nov 2010, 01:58 PM   #38 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

It is very strange that its started knocking again just after the second rebuild..for the knocking to start again there must be damage to the crank or some thing(possibly oil pump)but something is not being picked up on and repaired mate you had another set of bearings this time round again didnt you?its very hard for you in this situation as you cant be sure what he is saying or doing i spose..,but there need to be found this time round for sure mate,possibly the crank though.. :/ sorry to hear of the bad luck your having.
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Old 24 Nov 2010, 02:18 PM   #39 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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It is very strange that its started knocking again just after the second rebuild..for the knocking to start again there must be damage to the crank or some thing(possibly oil pump)but something is not being picked up on and repaired mate you had another set of bearings this time round again didnt you?its very hard for you in this situation as you cant be sure what he is saying or doing i spose..,but there need to be found this time round for sure mate,possibly the crank though.. :/ sorry to hear of the bad luck your having.
Thanks. The mech told me he put in a new set of bearings and piston rings. You could be right, I'm starting to think also that the crank is no good.
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Old 24 Nov 2010, 02:41 PM   #40 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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Thanks. The mech told me he put in a new set of bearings and piston rings. You could be right, I'm starting to think also that the crank is no good.
ID be getting the oil pump off as well and clean or replace that just incase there is a lack of oil feed to the crank bearing theres little holes under the shell bearings that feed the oil to the crank lubricating the shell bearings in the rods around the crank possible they may not be clear enough to feed sufficient oil the the bearings or even blocked so it would only get the oil being thrown around in the oil sump and slowly finding its way around and thats would cause it,ive had these rod shells go before and the little notch in them that helps hold them in the correct position breaks off and can get stuck in these oil ways in the crank,he would have seen it im sure but with things the way they are it may be worth you checking this your self if you can..see what state the crank bearing faces are any scores etc,some thing just isnt right is it?
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Old 24 Nov 2010, 04:55 PM   #41 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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ID be getting the oil pump off as well and clean or replace that just incase there is a lack of oil feed to the crank bearing theres little holes under the shell bearings that feed the oil to the crank lubricating the shell bearings in the rods around the crank possible they may not be clear enough to feed sufficient oil the the bearings or even blocked so it would only get the oil being thrown around in the oil sump and slowly finding its way around and thats would cause it,ive had these rod shells go before and the little notch in them that helps hold them in the correct position breaks off and can get stuck in these oil ways in the crank,he would have seen it im sure but with things the way they are it may be worth you checking this your self if you can..see what state the crank bearing faces are any scores etc,some thing just isnt right is it?
Whoa! Getting really quite technical now. But yeah, something just isn't quite right. I'll raise with the mechanic the issues of oil not getting to the crank and do visual checks myself once they've stripped it down. I'm trying to read up online to familiarize myself with the intricacies of the cylinder block to try and understand the technical issues you have pointed out. I'm not as knowledgeable in mechanics, electronics is my field. For the umpteenth time, thanks.
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Old 25 Nov 2010, 12:55 AM   #42 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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Whoa! Getting really quite technical now. But yeah, something just isn't quite right. I'll raise with the mechanic the issues of oil not getting to the crank and do visual checks myself once they've stripped it down. I'm trying to read up online to familiarize myself with the intricacies of the cylinder block to try and understand the technical issues you have pointed out. I'm not as knowledgeable in mechanics, electronics is my field. For the umpteenth time, thanks.
thats why i said it so youd have some idea!!i understand your knowledge is low in this field but it was just to help,theres no pressure on you to do it!just some thing for you to go on as you have no knowledge..thats why your here asking these questions is it not?small search online with images and youl get the picture..,even a haynes car manual will point out what to look for or expect.
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Old 25 Nov 2010, 04:27 PM   #43 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

[IMG]D:\subaru\1.jpg[/IMG]
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Old 25 Nov 2010, 04:45 PM   #44 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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Old 25 Nov 2010, 05:20 PM   #45 (permalink)
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Re: Blown Piston after crankshaft and piston replacement

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First off guys thank you so much for the help you have give me so far. Thought I should post some pics to give a clearer picture of what is happening. Something important I think I should mention is that all the problems with the pistons and the rods are happening only in cylinder number 4. The first time I had the rod knock it was piston 4. The new piston was put in cylinder 2 and the one that was in 2 was put in 4. The first time it had the rod knock, the piston 4 (which I threw away) looked just as the picture above (this piston is actually for the second rod knock, the third time the car broke down). Hope I'm putting this through clearly.

http://sphotos.ak.fbcdn.net/hphotos-..._7095232_n.jpg

The picture above is after the piston blew. This happened after I had driven the car for about a week and I was doing 5000rpm at about 140kph. Today the mechanic informed me that this also happened on cylinder 4. But this was not the new piston as he had put the new one in 2.

He then put in a new piston in cylinder 1 and put the one that was in 1 into cylinder 4. The car started producing the knocking sound shortly after during the road test. The mech opened it up and found that the main bearing was gone (badly scratched). There was no damage on the con rod or the con bearings. Below is the piston.

http://sphotos.ak.fbcdn.net/hphotos-..._4815627_n.jpg

This time also the bore was scratched. The garage gave me some reprieve though. They said that they will put in new bearings, piston rings, piston, oil pump. They also said that they will put half block for the side with piston 4 that is damaged. By the way, how safe is it to replace half the block? All this they will do for free.
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