Had this posted in another person's thread and decided not to hijack his:

I also just got compression results today this is what I have (PSI):

FRONT
77 82 70 @ 204 rpm
69 66 64 @ 197 rpm
73 71 68 @ 202 rpm
73 71 69 @ 205 rpm
72 70 74 @ 209 rpm

REAR
74 76 76 @ 199 rpm
75 74 77 @ 201 rpm
76 75 73 @ 200 rpm

I looked at the chart and if I'm reading it right, it looks like I'm below minimum. How bad are these numbers?

Thanks for the help - this is my first compression test and I have 41k miles on a 2005 MT car. I bought it with 12,000 miles on it two years ago. I have used redline 5w-30 since about 20,000 miles and I just switched to try Amsoil. Since about 20k I have also periodically premixed with MMO (about 4 oz per tank).

If indeed the numbers are low - what would cause low overall compression? It doesn't seem one face is causing significant problems (given my limited understanding) so what conditions would cause compression to be low everywhere? I don't feel driving that there is anything especially problematic with the way the car is running. Bottom line, should I be concerned? Do I need to prepare myself for trying to get Mazda to give me a new motor in the near future?

Penny for all your thoughts...?

 

We need to "normalize" those readings to see if you really failed:
These are rounded.

FRONT
77 82 70 @ 204 rpm = 93 99 86 @ 250rpm
69 66 64 @ 197 rpm = 87 84 82 @ 250rpm
73 71 68 @ 202 rpm = 90 88 85 @ 250rpm
73 71 69 @ 205 rpm = 89 87 85 @ 250rpm
72 70 74 @ 209 rpm = 87 85 89 @ 250rpm

REAR
74 76 76 @ 199 rpm = 92 94 94 @ 250rpm
75 74 77 @ 201 rpm = 92 91 94 @ 250rpm
76 75 73 @ 200 rpm = 94 93 90 @ 250rpm

Normal is 120psi
Minimum is 98.6
Yup... time for new engine!

 

OP do you track your car?

 

No, it's been on the track one time.

 

05? sounds about right

 

so if you have low compression what need to be done to the motor to get it right, apex seal change, new rotors.....just wondering, still learning about this engine

 

you need a new engine, mazda has an 8 year 100k mile warranty on these engines so you can take it in and get a new one free of charge as long as they dont say youve raced it or if you have boost

 

ok that dosent answer the question I asked. " what needs to be done to fix that engine" sure they are gonna give you a new engine, but they are also going to rebuild that one too

 

I thought HomicidalApple's answer was very clear on what you should do if still under warranty.
If not, then you need to have someone with experience rebuilding rotaries take the engine apart and replace the seals, and possibly the housing depending on if there is significant damage.

 

Word has it Mazda has prisoners rebuildem

 

I've been doing oil changes for it on my own using redline every 3000 miles. Will the dealer give me trouble about using a synthetic in the car? (Will they even ask for proof of the changes at which point I'd have to provide receipts of my redline purchases?).

I confess I'm a bit nervous about showing up and asking for a vacuum test already knowing the probably results and then not having dealer service records to back me up on top of using oil which is not recommended.

 

You don't need to take it to the dealer for service to get it covered under warranty. But you do need proof that you changed the oil via receipts or some record you've kept track of.

If you're in the states, I think all 04-08 manuals say nothing against running synthetic and only "recommend" 5w-20. Since they do not state that 5w-20 is required they cannot use it against you.

 

I entered my record of maintenance in the mymazda site (admittedly sometimes long after I did the maintenance), and I do have the receipts of the cases of redline (bought it bulk) which show I had the required oil on hand to perform the changes I said I did (which I actually did do)

and yes, I am in the states

 

If you have all changes you did and owned the car from day 1 if you're the first owner then you should be fine. They can't refute the receipts that show proof you've bought oil/filters to change it and entering it online is another good step (which I should do myself).

If you didn't own the car from day 1, then hopefully they're not **** enough to say oil could of been never changed from who owned it beforehand but if you bought it from a dealer I think that should be fine. Just basing this off what I've read here from stories, I haven't personally knocks on wood) had to go through this.

 

I bought it from a Mitsubishi dealer with 12,000 miles on it - hopefully that's not a problem

 

What made you decide to do a compression test? Where you having hot starting issues or anything?

 

That's the problem right there.


You should have bought an EVO.

Warrenty is VOID.

 

Fixed.

 

I didn't have any hot start problems, in fact, the motor feels fine - it seems to pull great and I don't have issues. I just passed 40,000 miles though so I figured it couldn't hurt to see some numbers on how the Renny is holding up. Then the results came back and it appears they're not good - so now I'm trying to determine if anything needs to be done. I suppose it's not urgent as things seem to be running fine, but getting input here always helps cause it won't run fine forever.

Is there actually a clause in any warranty which would suggests that possession or purchase by/from a dealer other than Mazda effects that warranty? I've never heard of that...

 

The engine is covered 8yr/100mil no matter where you bought it.
You can take it into any Mazda dealer too.

 

That's what I thought - but I wouldn't put it past some companies to put a clause like that in a warranty so I had to ask.

 

Just wondering, does the warranty cover our cars even if it has a salvage title?

 

No.

 

Welcome to 2007.

Mazda opened a purpose-built facility in Virginia to supply remanufactured engines, cutting Williams (the notorious prisoner-employer) out of the loop.

 

who did the compression test? I assume it wasnt a dealer?
OD