Typical healthy compression 1.4 Petrol

sciroccorrado

sciroccorrado

A2OC Donor
Quick bit of advise guys please...

Got a 1.4 petrol engine car in that has the following compression readings:

1: 90
2: 120
3: 170
4: 170

From what I can gather from my reading, it's probably best to consider cylinder 1 dead, cylinder 2 "on the way out", but 3 and 4 okay. Could somebody confirm/deny my thoughts, and if confirmed - possible solutions?

All the best
 
Hi,

the 1.4 petrol compression should be between 10 and 15 bar when new with a wear limit is 7 bar. The maximum difference between cylinders should not be more than 3 bar.

Converting from PSI to bar will give:

1: 6.2 bar
2: 8.3 bar
3: 11.7 bar
4: 11.7 bar

From your pressure readings, 3 and 4 are just fine, 2 is just out of the difference specification (when compared to 3 and 4) and 1 is way out. A worn engine is fine (within reason) as long as the wear is even. With so much difference between cylinders it won't be able to run properly.

Cause could be piston rings, values or possibly even head gasket (e.g. a leak between cylinders).

Have you performed a comparison between a "dry" and "wet" test? If compression is better on the "wet" test than "dry" then its likely to be the rings at fault. If its bad on both then its probably valves.

regards

Andrew
 
Last edited:
ajsellors said:
Hi,

the 1.4 petrol compression should be between 10 and 15 bar when new with a wear limit is 7 bar. The maximum difference between cylinders should not be more than 3 bar.

Converting from PSI to bar will give:

1: 6.2 bar
2: 8.3 bar
3: 11.7 bar
4: 11.7 bar

From your pressure readings, 3 and 4 are just fine, 2 is just out of the difference specification (when compared to 3 and 4) and 1 is way out. A worn engine is fine (within reason) as long as the wear is even. With so much difference between cylinders it won't be able to run properly.

Cause could be piston rings, values or possibly even head gasket (e.g. a leak between cylinders).

Have you performed a comparison between a "dry" and "wet" test? If compression is better on the "wet" test than "dry" then its likely to be the rings at fault. If its bad on both then its probably valves.

regards

Andrew
Click to expand...

Thanks Andrew - not looking good then :(
 
Jeremy has the car been running nice and even at idle? I'm Asking because if it's not that's the tell tale sign that all is not good along with the readings you've put up.
 
Ok, as i thought it would be with compressions as wide apart as that.

Is this a car you've been using a good while or has it only just happened?

It could be that the head gasket has gone, giving a low reading on cylinder 1. Have you checked the water expansion tank for combustion gases in there? If there are it's the head gasket gone. Have you any oil and water mixing again head gasket.

The rings could be worn causing low compression, Audi recognised the problem with the piston rings notably the oil control rings and revised the part number in 2004.
 
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