This is topic 03 cobra low compression need advice in forum Tech Talk at Northern California Ford Owners .
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Posted by Mr.10psi (Member # 11062) on
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Hey guys, im looking at buying an 03 cobra that had a compression test done and the results were 146psi across the board with one cylinder being i believe 141psi. Basically 7 cylinders were the same except the last one. When i heard this, the first thing i thought was that this is low and the motor must be tired even though the car only has 25k miles on it. Before i forget to mention, he did the compression test on a cold morning. Motor hadnt been fired at all that morning before the test. Any advice is appreciated. 5307748968 if you guys want to text me what you think or just reply here.
Posted by Martinna (Member # 12493) on
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5 psi off doesn't sound like much. Test that cylinder again and retest a 146 psi one. Lots of things can cause one cylinder to be low. A worn O ring. The adapter not fully tightened. Battery getting low. Inconstant number of cranks between cylinders. If all this checks out, put a tea spoon of motor oil in the cylinder. If it boosts the number, the rings could be worn.
Posted by SLOWSN95 (Member # 8269) on
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That doesn't seem bad. It is an 8.5 to 1 motor.
Posted by JohnB (Member # 969) on
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I wouldn't put a lot of faith into a compression test. You really need to perform a leakdown test to see what's going on.
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