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Cracked Pistons


Mark from OZ
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Hi all. Can somone please tell me why i am cracking pistons ?

Engine E 6 320 standard fuel not over heated oil squirters ok

timing 24 degrees by plate on pump and by book

Re built jan 07 242858ks

No 2 and No 4 cracked 6 / 08 340480 ks

Now. pistons are genuine Mack from Mack but made in INDIA

all after production pistons made there now. Never had any trouble ever before

Got me beat.....Mark

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Are you possitive the piston coolers are aimed correctly!the coolers got to hit the piston correctly or they can over heat!We have cooler targets to check em after liner install.

the spray for the cooler needs to head basicly straight up from the nossle hitting 5 or 7 oclock on the piston, stick a welding rod in it and see where its heading!

as you said the injector spray looks fine

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Hi fjh I have the target for the piston cooling jets. They were in the

spec and careful when fitting the rods down the bore. The brown stain

inside the piston is uniform on all........ Mark

Heat checking on a high millage engine is not uncommon. What condition were the rings in? Damage from detonation is more common to a gasoline engine, but from what I can see the top ring land has had too much heat. Check the ring ends to see if they have butted. If that is the case slip one into the bore and check the end gap. I can't think of another reason to fracture the second ring land. If the ring gap is correct, and the rings have butted together, You are putting too much heat into it.

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bolweevill thanks

Now the engine was fully Rebuilt

pistons rings liners whe whole deal Jan 07

ring gaps spot on

done 41833 ks cracked 2 /4 nov 08. put it down to bad luck

Now No 5 cracked in the steel insert, done 139455 ks sept 09 piccy later.

the thing is pistons 1 3 6 are still good

standard fuel pyro never goes over 4/12 to max 5 degrees C.

owner driven by me. Sitll 99% cross hatch marks in the bores.

Me thinks crap parts. Remember the original pistons were in there for

11 years and were still serviceable.......Mark

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bolweevill thanks

Me thinks crap parts. Remember the original pistons were in there for

11 years and were still serviceable.......Mark

Have to agree!

An old Bob Serger song comes to mind!

Take them old pistons off the shelf

put em back in there by yourself

todays pistons anit got the same soul!

So put em back in there respective holes.

You get the drift! biggrin.gif

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Have been thinking of PAI rebuild kit this time

have used PAI in the past with no worries at all

if Mack can only supply the after market stuff

they have lost me.

Is PAI still made in the US? may bee they have better quality controll.

going at this rate i will have to put zippers on the heads........Mark

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Have been thinking of PAI rebuild kit this time

have used PAI in the past with no worries at all

if Mack can only supply the after market stuff

they have lost me.

Is PAI still made in the US? may bee they have better quality controll.

going at this rate i will have to put zippers on the heads........Mark

They still have pistons listed on their on-line catalog, didn't say who made them. 770 822 1000 is their number.

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Have been thinking of PAI rebuild kit this time

have used PAI in the past with no worries at all

if Mack can only supply the after market stuff

they have lost me.

Is PAI still made in the US? may bee they have better quality controll.

going at this rate i will have to put zippers on the heads........Mark

Gday mate. I got a PAI kit from gleemans and it was a good price. Its a 285 EM6 and its used oil from day one. I took the heads off and all of the bores are shiney. Its had RX super in it the whole time. Its done about 150000Kms. Hard to work out, and it may be a once off, but if I had to do it again I would be thinking of using genuine parts. Skip

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Thanks Bollweevil Gleemans have a kit in stock

Skip don't know why your's pollished the liners

I use rx super and never had an oil related problem

My engine has 98% hone marks still in the liner

Its just crap parts. Saying that it most probably

was a faulty batch

pistons 1 3 & 6 are still good

piston 5 was still good til this week

2 & 4 cracked at 41833

2 & 4 replaced at that K's still good

Mark

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Picked up the Re build kit. It seems that all the 2 valve pistons

are of the later design. I am sure that it was just a faulty batch.

They seem to be a little better finish. After a lot of reserch i now know the

company's that manufactured them. Never had a piston failuer in 30 years of

Macks. The PAI Kit was $2772.25 AUD so not too bad. Time will tell.........Mark

25092009137.jpg

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Regarding the difference in piston top configuration, I recall seeing a Mack service bulletin back around the mid 90's discussing that change, and the fact that more combustion "rattle" would be noticeable in engines fitted with the new design pistons.

I put a set of those updated Mack pistons into a 237, and also put a set in a 285 back around that time and never had any problems with them. But that's when Mack parts were still being made by Mack and not subcontracted to some low bid company in India.

Perhaps V*lv* has subbed out all the Mack replacement parts manufacturing to 3rd world sweatshops.

.

"If You Can't Shift It Smoothly, You Shouldn't Be Driving It"

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Thanks HK.

I have been pulling my hair out or what's left over this.

They jus talk round in circles down a Mack now as they are non current item now

I have learned how to decipher the markings and serial No's on the piston tops

and the different suppliers. All made over seas now.

I put it down to a bad batch / quality controll on the day.

The set i have now is fron a different builder and looks a better finish itm

I'll put them in and see what happens. Thanks Mark

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