My S4 13b rebuild
 

Well I got my engine apart yesterday and to my surprise the engine internals are imaculate excepting the carbon buildup. About a month ago my buddies and a mechanic friend of ours did a compression check on the motor and got 90+ psi on the front and nearly 0 psi on the rear. Also the engine was acting like a low compression motor so I had no doubt the rear rotor was dead.
As soon as I get my hands on a feeler gauge I'll spec out everything, maybe the housings are just worn beyond use. I'm wondering if maybe the low compression problem was caused by not having enough oil in the housing, since I was having oil pressure problems beforehand. Also when disasembling the engine I discovered one of the OMP lines had broken at the injection port, but had not come off so it wasn't obvious.

Here's the pics.

https://oregonstate.edu/~scottca/Rot...%20Housing.jpg
https://oregonstate.edu/~scottca/Rot...%20Housing.jpg
https://oregonstate.edu/~scottca/Rot...ont%20Iron.jpg
https://oregonstate.edu/~scottca/Rot...%20Housing.jpg
https://oregonstate.edu/~scottca/Rotary/Rotor1.JPG

you're right. that stuff looks really clean for a first teardown. if the engine ever sat for a while or overheated, then that may have caused your lack of compression due to seal springs that are dead and provide no rebound for sealing.

good luck with this project. document it as much as you can. :)

Dang 0PSI is not good....Was all the Apex Seals almost missing? How does your crank and rotor bearings look?

The bearings and crank are solid. The apex seals seem really flimsy to me personally, also one had a bite out of it, so maybe that was it? I'll have to replace the rear apex seals because they fell off when I pulled the rotor off the e-shaft and I don't know how they were on.

Personally I don't like the dark areas or the lines on the rotor housings. It looks like the housing may be warped allowing compression and blowby past the apex seals. The lines look like apex seal chatter probably from a lack of oil. But, hey, what do I know? Well, I'm pretty sure the compression tester didn't lie, but that's about it.

Locketine- 1 apex seal broken would only mean compression would have registered twice then once zero when that broken apex passes.
The crank should have no discoloring or scratches at all on it, also the rotor bearings should be replaced

The oil line that broke which housing was it? If it were the rear then that would explain alot. The chatter marks are an indication of not enough oiling and or low spring tension. Springs get weak and then when you go to higher revs they like to skip and not stay on the rotorhousing face and that's when you get those chatter marks. Built a motor for a friend of mine who drove the piss out of it for over a year. He himself admitted to abusing the motor which he was not surprised that it went out on him. Also same thing happened that he did not have one of the oil lines properly secured and was driving around for a few months with no oil getting into the rear housing. Pulled the motor apart and the housings were shot and the springs out of spec, flatend out, but surprisingly the apex seals were fine and in specs with no unusual wear pattern on them. Since motor was out I put an even bigger streetport on it, cleaned it up and put it together with a set of good used housings and new apex seal springs. Didn't have to change the bearings they were all in spec. I just polished them a bit with very fine #0000 steel wool. Cleaned everthing up and assembled the motor. Whoa and behold motor turns on first try after engine oil was primed. Adjusted the carb alittle and holds idle perfect.

That is incorrect because you should only get one compression reading with one broken apex seal. The one broken apex seal shares two chambers so those two chambers would show low compression. The one lone chamber that is not conected to that broken apex seal will be the only one to show compression. If you have more than one apex seal broken you won't get a read on any of the rotor faces.

are you sure about that 13BTNOS? that is would show two at zero?

Also when measuring rotor bearings they should be replaced anyways its a low cost replacement while the motor is dis-assembled..

Just think about for a minute and imagine that apex seal that is broken. It seals not just one rotoro face but two of them and if that seal is broken then both those rotor "chambers" would show low compression because of the blowby caused by that broken apex seal. Think about it as one big chamber as opposed to two separate chambers you are occupying more space/volume and the pressures for the given amount of intake will not produce as high of "chamber pressures". Also a stock bearing in excellent condition is preferred over a new bearing. Especially when you are reusing the complete assembly everything is matched so as long as they are in spec you do not need to replace them. Waste of money and time. Also you don't have to worry about breakin time that new bearings will require.

To me it looks like the corner seals are also frozen. By the way, how many miles on this engine?

it's supposedly a 94k mazda reman. I'm being way too slow here in getting a cleaning agent to clean everything up so I can inspect it. I'm planning on going down to autozone and grabing a couple jugs of ATF and just soaking everything with it. It's hard rebuilding a motor, looking for a summer job and housing for next school year at the same time.

Huh, I hadn't even noticed those lines on the housing till now, good catch. I'm pretty sure the rear housing was oil starved, if not both, due to having low oil pressure a week before puting the car to pasture for a long while.

The corner seals came out fine, I was able to pull em out with my fingernails till I realized I could just push em out with one of the apex seals.

13btnos is right, it even mentions that in my haynes manual. I had completely low compression on the gauge so whatever was bad was universal for the rear. Since all my seals were healthy and intact I'm guessing the housing just whent.

yes, he is right! :) one busted apex seal will screw 2 chambers!

dead springs or frozen seals will kill compression. my advice is change them.

well I think I got it all clean. Here's some pics.
I can't seem to get that crap off the sides of the iron portion of the face, even with my careful use of a paint remover wheel.
http://oregonstate.edu/~scottca/Rotary/RotorFace1.jpg
http://oregonstate.edu/~scottca/Rotary/RotorFace2.jpg
I prolly could take the rest of the carbon off but at a great expense of my time. Would it be worthwhile?
http://oregonstate.edu/~scottca/Rotary/CombSide1.jpg
http://oregonstate.edu/~scottca/Rotary/CombSide2.jpg
Ah JetCleaner's are cool.
http://oregonstate.edu/~scottca/Rotary/Housings.jpg

I've sprayed everything with penetrating oil to keep them rust free while I wait for spyder to get over his flu and come down and help me spec the housings.

I used primarilly kerosene as per hayne's instructions for cleaning the rotors, but after some recomendations from various forum members I whent over them again with simple green which got a little more off just sittin there than my best efforts with the kerosene. However the kerosene didn't give me the little rust dots that the green stuff did.

Well, both rotor housing have a groove dug into them from the corner piece of the apex seals. The apex seals didn't pass all their tests either so I'm getting new ones. Everything else is fine.

Replacing:
2 N/A rotor housings or TII if I can get em cheep, so I don't have to grind baffles.
All soft seals except the main semi hard ones.
All 6 apex seals with either mazda or RA ones, springs are fine except I lost one somehow.
Oil pump apears shot to spyder, I'll check it tomorow with some good feelers to make sure.
Clutch disc.
OMP lines.

That's it so far, if anyone has leads on both cheap and good housings please let me know. Also a clutch disc, I've been told I can get one cheep on ebay, so I'll be looking there.

well I revisited the rotor housings and inpected them using the bruce torrentin method and they passed his requirements except I can sorta catch my nail on a little groove on the edge of the housing, but I figure with a little light sanding I can fix this problem.

What I want to know is, does this course of action seem sound? I want engine rebuilder opinions only, since casual home rebuilders probably haven't heard the story of how they worked out down the road.

I use a high rpm die grinder and a wire wheel to clean mine.

wow those are some rusted rotors. huh, never knew you could attach thumbnails....that might have been nice for people. I have been told not to use nething but a toothbrush on the rotor sides (not combustion surfaces) because it is a light alloy compared to the faces.

Oh something I found out after getting everything this clean is you can pick up a large can (2x pain bucket size) of "cold parts cleaner" at autozone for 10 bux. I woulda liked to know about that earlier since that's what bruce used in his rebuild video I'm pretty sure. I didn't look too closely because I didn't need it but it looked exaclty like what bruce used.

To me if a rotor housing is bad sanding it won't help much. Now on a good housing I do sand on them some. I do a cross hatch pattern using 400 grit wet/dry sandpaper. Dry sanding is fine just make sure the housings are clean before starting as you don't want to sand big chunks of dirt into the housing surface.

That's not rust! That's how my rotors looked after I let them soak in my parts washer for 20 minuets. The parts cleaner strips all the oily residue and decreases the rotor. What was left behind was the dried up powdery carbon. This is when I used the wire wheel and die grinder. You don't want to use the wire wheel on an oily rotor. What will happen is the wheel will pick up the oily carbon and sling it across the room. Also some of the oily residue will stay on the wheel and it will keep putting it back on the rotor. That's why I degrease the rotor first before I use the wheel on it. You get much cleaner results in the end.

Below are the pics of the rotors before soaking them in the parts washer.

ahhhh..... it sure looked like rust from that picture. You did a really good job it looks like. A lot of people just dip their rotors in simple green or puple power for 24 hours and they come out new, suposedly. Did you take a die grinder to the sides of the rotor faces where I can't get the gunk off? I'll try that a little bit when i get a die grinder to do my mild porting.

Yep! I use the die grinder all over the rotors like I'm trying to polish it. Takes about 10 minuets each rotor and will remove that gunk your talking about. My rotors had the exact same thing. I would do the 24hr soaking thing but I hate waiting. I also let then soak in some acetone to break down the carbon in the seal grooves. Acetone works like a MOFO. :D