Need help for piston low compression

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Anonymous

Guest
Need Advice ... :(
Yesterday my mechanic test my enjine with compression tester and found that the third piston not giving any compression at all...what shall i do ? change the whole enjine or just rebuild the piston at machine shop .....
 
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AJ4

Guest
I'd try and find out what is causing the problem first :D It could be a bent valve not shutting properly or a piston ring, or a holed piston etc. Would be easier to decide what to do if you knows whats causing it...
 
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n7dge

Guest
Like AJ4 says, you need to find out whats causing the low compression first. It could be something that's easy to fix :!:
This is what I would do :-
Take off the rocker cover and check for visible damage (timing chain & cam lobes, also broken or dislocated valve springs ).
Then with the plugs out turn the engine over with the starter motor. Watch all the cam followers / valves for roughly the same amount of movement (are any valves stuck down [open] ) If youv'e found the problem by now, and it's anything other than a valve stuck open, you may be able to repair the fault without removing the engine or the cylinder head.
If the problem is a valve stuck, its probably bent, either way, the next step is to remove the cylinder head. Bit of a nightmare this I think, due to brackets and stuff on the back of the inlet manifold / plenum chamber.

With the head off you may have found one or more bent or burnt valves. if this is the case then strip & overhaul the head replacing any knackered valves or other bits as neccessary. This proceedure is quite an in-depth story on its own, too long to go into detail here but you may find it described elsewhere on this site. You may also want to considder purchasing an exchange reconditioned or TUNED cylinder head :D :D

If with the head off you have found a valve head compleatly snapped off and lumps of metal missing from the cylinder head and piston crown, then seek advice from someone local who can examine things in detail, with a view to either repair or replacement of complete engine.

If with the head off you have found no damage to the cylinder head, then I'd immagine (with zero compression as you said ) youre looking at a hole which has been burned through the piston crown due to DETONATION. If so it serves you right :twisted: for turning up the boost without getting the fuelling checked on a rolling road :shock: :shock: :!: LOL.

If at this stage you've found no damage to the head, and no hole in the piston (unlikely) examine the cylinders for cracks / scores.

Still nothing found ! , are all four pistons still connected to the crank ? , Put the car in gear and push it back & forth to check this (maybe you have a snapped Con Rod, or lost a Big End Cap :?:

Good luck Fella,
and dont forget to let us know how you get on.
Nij.
 
Fast Guy

Fast Guy

Moderators
Staff member
Guys, you've both forgot the simple option..........it may just be the head gasket :wink:
 
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n7dge

Guest
Guys, you've both forgot the simple option..........it may just be the head gasket
Click to expand...
Oh........er.........and when you pull the head off, don't forget to check it's not just a blown head gasket :oops: :oops:

I was rushing when I wrote that, cos the missus was giving me a bad time. Something about getting on with rebuilding my R, and removing gearbox, transfer box & steering rack from the KITCHEN :!: tut. :twisted: :D
Anyways, thats my excuse :p
 
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Anonymous

Guest
well thanks a lot dudes...i'm gonna check it out today...hope it won't be the worst....anyway i'll get back to you guys asap once i know what cause it...ok c ya'll thanks again for the advice
 
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n7dge

Guest
Not likely to be just a broken ring if it's not showing any compression at all, but don't be scared ! strip it down and have a look :cry:

What's the story of it's final minute beffore death :?:
Did it die suddenly or gradually over a minute or so period ?
Any noise ? what kind a noise ?
Were you loosing power beffore it died ?
Did it loose all 4 cyls & totally cut out, or just one and chug allong on the other three ?
Any smoke or steam (blue or white) ?
Was it being thrashed at the time ?

All this sort of stuff helps with the diagnosis.
Have ya started the strip down yet ?
 
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Anonymous

Guest
1) the final moment is when i drag with super mod mivec when it comes to 3rd gear i already won but then suddenly i feel my car like vibrating ...then followed by whole bunch of holy white smoke ....
2) it comes suddenly
3) not making noise from the engine
4) right after 3rd gear at rpm 6/7
5) white smoke comes out a lot

i'm going to open it up today ... for sure
i'll ley ya all know ..allright
 
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n7dge

Guest
Head gasket,
Holed piston, or maybe
cracked block.
These are what I'd be looking for from what you describe.

I have one of those 4w dashboard / side light bulbs, soldered on the end of a length of realy thin 2 core wire. You can see quite alot of the inside of the cylinder and the piston crown if you put this through the spark plug hole right into the cylinder . Put your jacket or something over your head to block out all the daylight.
I made up a small mirror on the end of a piece of thin solid wire (stripped off some household twin+earth cable) was able to inspect the valves this way, but it's very fiddly :!:

Anyway let us know what you find.
Nij.
 
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