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I have been having trouble with my Corsa. It sometimes just cuts out or does not want to start at random times. I have had the car serviced, I have had the starter motor replaced & am now having a new fuel pump relay replaced.
I was told today, that cylinders 2 & 4 have low compression.
What causes this to happen? Do I have to have it fixed? I was told that it could cost me anything from R5000 - R10'000. PLEASE ADVISE.
Thanks Benita

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2  
Do you know what the compression reading were? – Move More Comments Link To Top Jul 3 '13 at 15:42
    
When it is having problems does the motor not turn over or does it turn over but not fire? Does the check engine light come on? – mikes Jul 4 '13 at 0:33

Background

The Corsa has dual overhead cams. The cam rides directly on a bucket that sites above the valve stem and valve spring. In order to adjust your valves you have to properly size shims that sit between the bucket and the valve stem. Over time, the valve face, in the combustion chamber, gets worn into the valve seat. As valve clearance is taken up by this interaction you need to occasionally have a valve adjustment done. If you don't, when all the valve clearance is taken up, the valve can leave a tiny crack open in the combustion chamber when the engine heats up. This can effect your compression reading.

Possible Causes

  • Adjust valves to ensure the proper clearance between the bucket and the cam lobe. This is a normal tune up procedure as called for by the manufacturer at particular mileage points.

  • Worn rings and cylinder bore - Causes are numerous. If the engine ever overheated the cylinder bore can become glazed. If you ever seized the engine from overheating you could have damaged the bore, the rings and the piston.

  • Valve Face or Seat Damage - If you have run the car in a lean condition for an extended period of time you could have burned your exhaust valves thereby creating a 'leak' in your combustion chamber that effects your compression numbers.

  • Head gasket - You could have a blown head gasket that is leaking into your crankcase that has led to your poor compression numbers.

  • Cracked Head - Your head could be cracked thereby effecting your compression figures.

  • Warped Head - If you have overheated your vehicle you could have warped your head thereby creating a compression leak to the atmosphere, crankcase or cooling system.

These are only theories as I am trying to answer this question so it doesn't show up as an answered question anymore. Seeing that you haven't logged in since July 2013 I doubt you will ever know any of this has ever occurred.

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I would imagine that it is because you have bent valves or you may have blown a gasket. It shouldn't cost you more than R3000 to R5000 in the worst case. And that's just because whatever the reason, they're going to have to take the top off the engine to get at whatever's the problem.

If you're in Cape Town, I would highly recommend AutoWorks in Milnerton. They did excellent work on our Astra and Corsa and they've got excellent after-sales service.

Also, as drake below mentioned "There's also the possibility of blown rings, scored cylinders, or fuel washing out the cylinders."

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There's also the possibility of blown rings, scored cylinders, or fuel washing out the cylinders. Often, pushing a small amount of compressed air using a compression testing adapter (running full 90psi shop air is too much) into the cylinder can give you a good indication by listening (exhaust/intake for valves, oil fill tube for rings/cylinder, bubbling in radiator for head gasket). – Drake Clarris Jul 10 '13 at 5:11
2  
Naming as many things that you can think of that will result in low compression is neither an answer nor a way to help the original poster understand what is going on with his vehicle. – cinelli Jul 10 '13 at 7:55
1  
Well, he didn't provide much information, so accurate diagnosis isn't really possible, to be fair. – I have no idea what I'm doing Feb 24 at 8:26
    
Also Benita is a she, not a he. – Juann Strauss Feb 25 at 9:57

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