exvaux

iTrader: (1)

As above cylinder 4 shows 0 on a compression test,car was taken in to have the tappets redone but a check showed the above problem,garage says melted piston but the noise has been there for a while never got round to taking it in as it was just the tappets (alledgedly) car still drives ok,maybe down on power a bit.so are the garage right or could it be something else?

RedScoob

With "0" on a compression test, it would run like a bag of poop and wouldn't be "maybe down on power a bit". Are you sure that the mechanic didn't mean that the compression was unusually low or out of tolerance?

Lateral Performance

iTrader: (20)

They need to do a leak down test, which will identify if it is a piston, or a valve.


Mark.

exvaux

iTrader: (1)

nope it was zero,did the test twice to make sure was zero both times on cyl4 the other 3 made 145-150 each.As said the noise started around 5 months ago,not used everyday but still runs starts and drives ok,even when giving it some beans which obviously i wont be now.He is pretty adament that it is piston thats gone,he is the expert i know hee haw dont think he'd be too happy me asking to do this or that.Whats involved in a leakdown test and is it somethin i could do myself?

johnnyroper

i find it hard to believe it still runs ok with no compression on no4.
it will be way down on the power and running like a sack of ****.
is it very lumpy on idle?
was the only reason for getting the tappets done because of noise?

exvaux

iTrader: (1)

yes thats the only reason,was getting annoying,cant hear it in the car but can from outside so thought sod it,its lumpy when cold but doesnt cut out or anything but when warm is fine,and still enough power to see off an audi tt 225 and octavia vrs but obviously not any more.

merlin24

iTrader: (1)

Burnt Valve in my opinion - a melted/detonated piston will not last 5 months without the engine showing signs of poor running/bad starting/oil consumption/engine sounding like a bag of nails.

Jolly Green Monster

iTrader: (4)

with loss of compression and tapping, one would assume the problem is with a valve / lifter etc.. either way going to take work to fix..

Simon

Slowboy Racing

zero compression ? I would expect it to run like a pile of crap.

Andy.F

Broken ring land..... guaranteed !

It ticks like a loose tappet, loses compression on cranking but will still idle and produce slightly less power. Sort it now and it will only cost you for the pistons. Run it and eventually you will damage the bore and/or cause further damage to the piston.
If unattended at this stage the piston will break, you may throw a rod out the block, the oil will catch fire, the oil on the tyres will cause you to crash and you will be left with a smashed up burnt out wreck !

OK, I over dramatised a bit but you get the message

exvaux

iTrader: (1)

its in a greers andy and it was alan that diagnosed it.......and what kinda guarantee do i get if its not any freebie bits as your car is/was the same as mine obviously it needs opened up no matter what but id be a little peed off rebuilding the engine bolting it together and its a valve thats gone so id rather know for def.Get paid next week so ill give alan a call take it from there see what we can come up with,i got an astra as a runabout so scoobs not goin anywhere

340BHP-WRX

iTrader: (6)

Sounds like a cracked/broken piston ring land to me aswell. The symptoms are the same as what I had,the car would still drive ok just got gradually worse until one cylinder had virtually no compression.

I wouldn't believe it was so serious at first as I thought the car would drive much worse than it did,didn't even use any oil !

Andy.F

I came across another one today, 03 WRX, fortunately diagnosed before I started to map it ! It just sounded a bit uneven when cranking on the starter, a compression check confirmed it.

340BHP-WRX

iTrader: (6)

Oh dear,bet they weren't happy !

What is the most common cause of this then ?

I found out the previous owner of my car had it dyno'd and they confirmed a coil pack was breaking down,and there was a crack in the exhaust manifold,they still ran it numerous times and got 320bhp/318 lb/ft ! I've been told that this could cause a cracked piston ringland with the misfire etc ??

exvaux

iTrader: (1)

an update on mine shows a knackered coil lead on cyl 4,its split where the plug goes in,could this have caused the problem?

340BHP-WRX

iTrader: (6)

No mate,a broken coil lead won't cause a loss of compression !

Would cause a misfire though.