Blown Apex Seal???
 

hello all, im already putting on my flamesuit for not searching hard enough (although i did do some searching). here's the issue:

last night i was on the interstate and had to accelarate quickly to change lanes since the one i was in was ending. as my rpm's climb i feel a sudden bog and a slight loss of power. later when i come to a stop light the idle is a little jumpy as the engine is shaking the car and shifter as it feels like its missing. i get home a do a small check in the dark, nothing obvious. i'm already hoping its not a apex seal. this morning a attempt to do a compression check, doesnt work out so good. seems like my new compression tester is broken or something as when i hold the release button down i get no bounces at all but when i dont hold it i get a weak bounce (30psi) then it bump up to like 70 psi and stays (the third is either equal to or less than 70 obviously) this is on the rear rotor. due to mothers day plans i didnt check the front yet. i took a video to show. hopefully you guys can tell if this is a blown apex or corner seal or something else that it could be. from what i have heard about the feeling/ sound of a blown seal, i think this might be it. as you can see, even the tail pipe shakes. also, if it is blown, what are the repercuptions of continuing to drive it? thanks in advance.

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Well, my engine sounds like yours. I dont know if mine have a bad cornel seal too but I checked my compression and I got 90 psi con each rotor. One question, when you test the compression do you hold the acelerator pedal to the floor? You need to have the throttle body butterflies opened. Also, try cleaning your spark plugs. Mines shakes a lot and loose power when one spark plug get fouled. . Just try to clean it.

The compression numbers don't sound promising, but you should definitely test it again with a better tester. If you lost an apex seal you should be seeing 2 rotor faces with the same compression value (usually low to nothing), but your numbers don't exactly show that. Another symptom of a blow seal is poor idle and hard starting, but it doesn't look like you're seeing that (other than the vibration).

Driving it with a bad apex seal isn't going to hurt anything, but a side seal may. Though you may find a bigger loss in power if the seal continues to deteriorate. Sometimes it's a progressive decline.

If it's a blown seal (it does sound like it very well may be) you should not continue to drive it if at all possible. Things can only get worse and wear will be greatly accelerated by having any blown/cracked seals (which reminds me, you may have just cracked one, and if so it could get worse fast). +1 for being fairly cautious about this. I suspect you've blown a side or corner seal, but it could be an apex seal or even something completely different like a bad vacuum leak. See if you can remove the valve in the plug end of your compression gauge, that way the bounces will show the actual compression (it will be fast, but should still be easy to read and you also will be able to see the compression on each face, not just the best one). If you see fairly even compression all around and they're all above 70psi I doubt you've blown a seal. If you see one or two faces with low, but not sub-20psi you may have a cracked seal. Blown or cracked though you're up for a rebuild immediately.

Also, is that a Camden supercharger?

At idle, do you pull less vacuum than you did before? If you notice a loss of power then something is probably gone. By the description you gave of the rear rotor compression test, it would seem that you have more than one seal gone on it (possibly cracked). When I warped RA seals, the car would start and run and drive in vacuum. In boost it would break up. The idle was choppy and the engine would shake at idle like yours.

Josh

its a paxton supercharger, check his sig. i really want one of those superchargers.

my bad on checking the sig.

The 'loss of power' statement seems too ambiguous. I felt a loss of power when I blew my turbo-mani gasket, and I only lost about 1psi average of intake pressure on WOT. Blowing a seal would also result in a loss of power, but it would be a huge difference.

yea when i blew my motor, my car wouldn't get out of its own shaddow under heavy accel. maybe its something else in his case.

Pull the plugs and listen to it crank:

http://www.aaroncake.net/rx-7/blown.htm

thanks for all the input from everyone, i really appreciate it. i didnt even think about the plugs being bad (they were just replaced less than 6 months ago) but then again, i am running pretty rich. in fact, i didnt even look at the one i pulled. i just assumed the worst so that i wont be dissapointed if i assume the best and it turns out that i need a rebuild. :) its been storming out here today tho, but i will check those plugs if it clears up and also try to borrow a better compression tester. thanks again for all the input, i'll update when i know more.

In regard to the plugs: No no, check aaroncake's link. You pull the plugs, leave them out as you crank and listen. If you have a blown apex seal then only 1 of the 3 chambers is sealed: i.e., 2 corners of a triangle completely surround only 1 side. In regard to the rest: good idea.

dont forget to disconnect your egi from your engine box thingy

Dont forget to unplug all spark plug wires, I dont think you want gas and flames shooting out those holes as you crank.

thats what disconnecting the egi does holmes

havent had a chance to check compression yet. it was storming yesterday and today i was working all day. again, i'll keep everyone updated. thanks again for all the support guys.

I checked at youtube and there are some RX7 videos with broken apex seals or cornel seals. You can heard the sound and compare to your car. After view a few of them I conclude that the sound of my car is related to the untune progamable computer indeed a blown corner seal.

Like Aarons listening method, you can use the "poor mans" compression test. Put your hand next to the empty plug hole. You can FEEL the 3 strong bursts of air each time it turns (per rotor). If it's blown, you will most likely find the rear rotor is not giving you 3 good bursts, maybe 2/3. Usually the rear rotor blows that's why I mentioned it. Your symptoms though sound like a dead motor. I remember my car shaking violently and having little power after I blew it. Sure as shit when I checked just by cranking I knew the rear rotor was gone.

Say it ain't so! If it is an apex or corner seal, at least now you can do a little porting while you're in there :D

when using a piston tester you do NOT hold the relase valve on the side open. what u have to do is remove the shrader valve in the portion u thread into the engine. Then u can see all the bounes.

ok guys, heres the deal: i did the :poor man's compression test and EVERYTHING WENT FINE. both rotors were giving 3 strong psssts of air in a nice, even sequence. this was very nice to see since it meant that a rebuild was not neccessary, but it also led me to believe that possibly the plugs were fouled really badly, and yes, they were. so i changed them. much to my dismay, this did not help either and the car is still the same as before. what do you guys think? off timing? not getting spark to one of the plugs (bad wires or coil pack?) or some other kind of electrical prob. all info is appreciated. o, and introvert: i know it sucks, but i was also looking at that as the silver lining too!

Do a real compression test please. Too many unknowns right now, everyone would just be guessing.

Do a spark test first. This will let you know if the coils and the spark plug cables are in good working condition.

i plan on borrowing a timing light tommorow to test for spark at all plugs. i will let everyone know tommorow

got the timing light and was gonna do a compression test but some stuff came up and by the time i was able to touch the seven it was raining and dark.....will update tommorow after work.

you need to do a compression test, with the shrader valve in the end that u thread into the engine removed... and then u dont touch the side valve. then u can watch all the bounces