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Old 07-12-2017, 10:31 AM   #29
John V
No more BMWs
 
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Join Date: Apr 2005
Carmudgeonly Ride: Ram, MS3, CX-5, RX-8
Location: Glenwood, MD
Posts: 14,753
AF,

If the dealer did a correct compression test, he should be able to provide you the compression numbers per chamber, per rotor. Could you please ask them to provide this, and then share it with us? "Low" compression can mean a lot of things. The manual used to specify less than 600kPa (dealer might report this as 6.0) as low. A well-built new engine should be between 7.5 and 8.0 (or more!). Typically well-used rotaries may be 6.5-7.0 on the front rotor and 6.0-6.5 on the rear.

There are two main failure modes on the RENESIS as far as compression goes. One, the engine simply wears out - the apex seal springs get weak or the seals wear, or the housings wear. This will manifest as low compression across all chambers. "Cleaning" the chambers will do nothing.

Two, if the car has been sitting a long time without being driven, one or more seals (typically one) can become stuck. This is pretty rare, and really affected older rotaries more than the RENESIS. If this is the case, in some instances the seal can be un-stuck by putting some oil with high levels of detergents (typically ATF) into the chamber and letting it soak. I think this is pretty unlikely to be the case with yours based on what you've posted.

My advice (you didn't ask for it but it's free, so take that for what it's worth) is to have them do the coils and plugs and not the cleaning. Have them provide the compression numbers. This will inform you of what steps to take next. From what you've described the engine might have low compression, but it sounds like it's fine. These cars can run for many years with low compression in the rear rotor and other than a little loss in power and sometimes some hot hard-starting have no other ill effects.
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