Car Engine Won’t Start Due To Low Compression?

Reader Question: Hi,

My car has just been towed into the mechanic for a diagnosis because the car would not start. I had a mobile mechanic to check and after like 5 hours, he said that the cylinder 2 in the compression is too low.

What does this mean? Is it a major repair then? I am a little worried about the repair costs.


Hey Mel,

That is not good. I would definitely get a second opinion before you proceed with repairs. If the cylinder is low or weak on compression, it means there is internal engine damage. This can be caused by engine overheating, running low on oil or just excessive engine life, miles and normal wear and tear if you have many miles on this engine.

In some rare cases, you can improve the compression slightly by injecting a small amount of engine oil into the cylinder to help seal off any internal compression leaks that are happening.

I hope that your second opinion will reveal a different story.

Austin Davis

Reader Follow Up Hi Austin,

Thanks for your prompt reply. I’ve actually got the result from the second opinion that the head is burnt and it requires a new one. This would mean an overhaul of the engine which costs Aud $2000.. And they mentioned that in order to get to the head, they’ll have to clean the cooling system which costs $300.. Can you explain what the head is?



Hello Again Mel,

The cylinder head is the top half of the engine, the part where the spark plugs screw into. I would ask them if they are going to do a valve job, or are they actually going to overhaul the whole engine…meaning pistons, rings, bearings etc. etc. etc.

I would imagine they are going to perform a valve job and head gasket replacement. I honestly don’t know what they would do to the cooling system to cost that much, you might want to get a written estimate of what they are actually going to do.

I would ASSUME you probably only need to have a valve job done, which is basically overhauling the cylinder head….i.e. the top half of the engine only and not replacing the bottom part of the engine where the pistons and crankshaft and other major components live.

Get a little more info and get back to me.


Austin Davis

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