cmc

ok I got compression test done at mazda dealer today and the tech said that it averaged 7.8 he says that those are very good numbers for a 2004 with 85000 miles on it my first question is what do you guys think are those good numbers, it was first time using that shop and not very trusting yet secondly I had them do overall check of car and they told me rear shocks and springs were no good. they wanted 500 for parts seemed high to me any ideas where I can buy strut and spring assembly thanks in advance for all your advice

dannobre

iTrader: (3)

Compression test should give you six values and an RPM for each rotor so the values can be normalized to 250 RPM

7.8 would be good at 250 or less RPM...but the faster it spins the less the value means

There are a lot of suspension options...from springs and shocks for around $500 for all 4 corners...to 3-6K for coilovers of different qualities. You can likely get a set of OEM takeoffs with low miles for cheap if you are on a budget

poacherinthezoo

7.8 is good - 6 I believe is the failure point and anything above 7.5ish is good and above 8 is very good. However, the difference between the numbers is also of value - as it can indicate which seals (if any) are showing signs of wear. Mazda does have set limits for what is acceptable for the difference between the compression numbers. However, to make any real suggestions we need to know the RPM at which the engine was spinning during the test. The higher the RPM the higher the compression numbers will be, masking a potentially bad engine. Also, do you know if the test was performed on the engine when it was hot or cold - as this too can alter the numbers you get.

If you're on a budget you can probably pick up used OEM springs in the FOR SALE section for not much money. You've got lots of options for shocks ranging from cheap to expensive. Just make sure that they are well balanced to the spring rates or the car will ride and/or handle poorly.