AJP engine noise - I found the cause - warning XXXX content!
Discussion
Having stripped down my AJP for what sounded like a "top end" noise, I even thought timing chain, I have found a fairly decisive reason for my rattle.
Seems fairly conclusive
The worrying thing is that 2 out of 8 have cracked like this
The engine was only rebuilt 9,000 miles ago and they are genuine AE pistons (and therefore I assume gudgeon pins). Looking at them I can only assume that they have been over hardened and got brittle. Whatever, it certainly looks like a production fault and one that I intend to raise with AP - any legal eagles on here who can guide me on the liklihood of me getting another set of pistons out of them?
Anyway, I must say that, overall I feel incredibly lucky that I trusted my instincts and pulled the engine out rather than just risking it. What will be a few hundred quid now would most definitely have run into thousands had I let this go on any longer. I also found a couple of other little faults that I can rectify along the way and will know that I'm putting an engine back together which will provide me with miles and smiles not worry and bills.
Seems fairly conclusive
The worrying thing is that 2 out of 8 have cracked like this
The engine was only rebuilt 9,000 miles ago and they are genuine AE pistons (and therefore I assume gudgeon pins). Looking at them I can only assume that they have been over hardened and got brittle. Whatever, it certainly looks like a production fault and one that I intend to raise with AP - any legal eagles on here who can guide me on the liklihood of me getting another set of pistons out of them?
Anyway, I must say that, overall I feel incredibly lucky that I trusted my instincts and pulled the engine out rather than just risking it. What will be a few hundred quid now would most definitely have run into thousands had I let this go on any longer. I also found a couple of other little faults that I can rectify along the way and will know that I'm putting an engine back together which will provide me with miles and smiles not worry and bills.
Edited by itiejim on Monday 7th September 21:25
Edited by itiejim on Monday 7th September 22:40
ridds said:
That's not good. Who are AP, I'm either being a little dim as I don't remember hearing of them.
Looks like you'll be needing some new little end bearings too.
Are the pins all free in the rods and pistons?
I'll definitely need little end bearings! I'll do all of them and the pins plus I think I'll need a couple of pistons due to the cracked pins scoring them slightly. All the others seem fine.Looks like you'll be needing some new little end bearings too.
Are the pins all free in the rods and pistons?
Edited by itiejim on Monday 7th September 22:41
sk7ine man said:
Holy sh*t. You;ve done well to diagnose it before it really let go. What was the noise/symptoms?
Can't really say I diagnosed it until I found this today.I was just sure that I wasn't happy driving it as it was!Symptoms were a tapping noise just like a loose valve clearance, the only difference being that this noise was load related - quieter under load and louder on the overrun. Also it was most pronounced between about 2000 and 3000 rpm. Over that it was hard to hear and at tickover it was a very light tap.
It never pinked at all, I think the pin has just been over hardened. They should just be case hardened to allow a little bit of give, these are rock hard all the way through and consequently have shattered like glass!
Don't worry about swarf, the whole thing will be stripped down and washed professionally!
Don't worry about swarf, the whole thing will be stripped down and washed professionally!
Piston crowns are perfect, as are the big ends, so I'm going with the manufacturing thing.
I only ever had one noisy bearing - not all 8, so I suspect that the little ends were reamed OK.
I only ever had one noisy bearing - not all 8, so I suspect that the little ends were reamed OK.
fatjon said:
detonation would be my guess for that kind of damage. The clue will be in the big ends and piston crowns, if they show damage then start thinking about a timing or weak mixture problem, if not then I agree with the faulty pins diagnosis. One other pissble cause it that the little end bore is worn or has been reamed to large and there is slop in the fit to the pin causing hammering.
Jon
Jon
I'd be keen to hear if you can source some non-tapered pins, otherwise I'll have to get my local engineering shop to search around or knock something up.
Have you ever approached AE about these failures?
Have you ever approached AE about these failures?
nemasis said:
yes they were AE,this is the 4 th ajp8 that i have had with this problem 1x 4.5, 3 x4.2 . Dont know if it is a manufacturing fault as each car has done varied mileage and not close to each other. May just be the fact that it is the taper walls and the pin being brittle who knows, but i am in the process of trying to source none tapered pins, to see if this gives longer life.
itiejim said:
Blimey, Were they AE? I'm wondering whether I'm better off adapting something a little heavier duty?
Brummie, the original pins are 5cm long, with a diameter of .827" (2.10058 cm according to my online converter). They weigh 70g each.
I'm going to try to see what AE can do, but I'd certainly be keen to hear if you've got anything that would do the job.
I'm going to try to see what AE can do, but I'd certainly be keen to hear if you've got anything that would do the job.
nemasis said:
not approached AE YET but may be worth ago and see what they say, will keep everyone upto date on progress and see what comes through.
itiejim said:
I'd be keen to hear if you can source some non-tapered pins, otherwise I'll have to get my local engineering shop to search around or knock something up.
Have you ever approached AE about these failures?
Have you ever approached AE about these failures?
nemasis said:
yes they were AE,this is the 4 th ajp8 that i have had with this problem 1x 4.5, 3 x4.2 . Dont know if it is a manufacturing fault as each car has done varied mileage and not close to each other. May just be the fact that it is the taper walls and the pin being brittle who knows, but i am in the process of trying to source none tapered pins, to see if this gives longer life.
itiejim said:
Blimey, Were they AE? I'm wondering whether I'm better off adapting something a little heavier duty?
Nick,
thanks for the steer re: Austec, I'll have a chat with them.
As for the marking on the pistons; all of the retaining clips were present and the contact faces of the pistons are in very good order. The only damage I can find on them is where the cracked pin has partially reamed the hole in the piston, therefore two pistons will be required. Each piston had been marked with an X to designate which way round they were fitted (all the X's pointed forwards if I recall correctly). The other mark you refer to is a superficial mark which looks like it's bee caused by whatever dremmel etc was used to mark the 'X'. Either way, nothing of any concern.
thanks for the steer re: Austec, I'll have a chat with them.
As for the marking on the pistons; all of the retaining clips were present and the contact faces of the pistons are in very good order. The only damage I can find on them is where the cracked pin has partially reamed the hole in the piston, therefore two pistons will be required. Each piston had been marked with an X to designate which way round they were fitted (all the X's pointed forwards if I recall correctly). The other mark you refer to is a superficial mark which looks like it's bee caused by whatever dremmel etc was used to mark the 'X'. Either way, nothing of any concern.
Nickccc said:
Maybe have a word with Paul from Austec, when they rebuilt my engine different pistons and pins were used, I got the impression the wrist angle could have been better on the originals.
Also, while I have no doubt in your engine builders skills, on your picture the piston has scratching on both sides, more so on the left.
Since you stripped the engine, you would have mentioned if a retaining clip wasn't present, looks like something rubbed the piston, there seems to be a small x mark on the right hand side, did you mark it as a point of damage?
Also, while I have no doubt in your engine builders skills, on your picture the piston has scratching on both sides, more so on the left.
Since you stripped the engine, you would have mentioned if a retaining clip wasn't present, looks like something rubbed the piston, there seems to be a small x mark on the right hand side, did you mark it as a point of damage?
Edited by Nickccc on Wednesday 9th September 13:05
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