How hard is it, really, to replace apex seals?

"Jake - Has Bad Luck So You Don't Have To" (murdersofa)
01/25/2016 at 10:20 • Filed to: I wankel constantly

I just bought a car and I’m already thinking of what’s going to replace it. After watching Jeremy Clarkson’s gushing review of the Mazda RX-8 I have started thinking that I really should own one at some point. Clarkson says “it’s not as simple as just replacing the piston rings in a regular engine” but... isn’t it? I mean, both require that you remove the engine (usually), tear it down a fair bit, and if I’m replacing rings you better bet I’m going to hone that bastard and clean up the piston and heads while I have them off. So how hard is it really to repair a low-compression Wankel engine?

DISCUSSION (9)

themanwithsauce - has as many vehicles as job titles > Jake - Has Bad Luck So You Don't Have To
01/25/2016 at 10:26

In the realm of engine rebuilds, a NA wankel is probably one of the easiest. It is also the most frequent. I can’t think of any other manufacturer besides subaru that nearly demands a rebuild after 75k miles for a “normal” car. Even an enthusiast one. Oh and maybe mitsubishi evos. But even then on subarus and evos it’s often because people beat and tune them hard. Mazda it’s just.....”Yeah we know. Yeah it happens. Now do it.”

DrJohannVegas > Jake - Has Bad Luck So You Don't Have To
01/25/2016 at 10:29

Lots of clearances to get set up on the seals. If you’re in there for the apex seals, you usually do the whole lot. Rotor side seals, housing seals, etc.

I like to think of rotaries as simple, but fiddly, engines.

Jake - Has Bad Luck So You Don't Have To > DrJohannVegas
01/25/2016 at 10:30

Clearances? So there is adjustment to keep your new seals from binding up on the side of the peanut they’re rotating around in? I suppose that makes sense.

DrJohannVegas > Jake - Has Bad Luck So You Don't Have To
01/25/2016 at 10:36

Yea. Short version is that every one of those little seals (long side seals, apex seals, corner seals) need to have some clearance to deal with thermal expansion. IIRC, most kits get close, but each rotor is a bit different (as is each housing), so you need to measure and check. A buddy of mine just bought an RX8 with toasted seals (one housing is totally gone) and is doing the rebuild.

https://www.reddit.com/r/Justrolledin…

Needmoargarage > DrJohannVegas
01/25/2016 at 10:37

I’ve been following his rebuild!

Will with a W8 races an E30 > Jake - Has Bad Luck So You Don't Have To
01/25/2016 at 10:50

Usually when an apex seal blows it takes a chunk of the rotor housing with it. Much cheaper and easier to simply replace the engine. IIRC (been a few years since I looked ) a set of apex seals in in the ~$500 ballpark, and a full rebuild kit can cost north of $1000. Gently used engines don’t cost much more. Takes an afternoon in an RX8 if you know what you’re doing, weekend if its your first time.

Rustholes-Are-Weight-Reduction > Jake - Has Bad Luck So You Don't Have To
01/25/2016 at 11:02

It is quite easy to change the apex seals.
I did it on my RX-8 last year with the help of my father (I also street ported it for some more fun). He has run a shop for years that I grew up in, but it shouldn’t be a problem if you are motivated and a bit handy.
My engine was just a bit tired though, if an apex seal broke you might have to replace some more parts. But even if it’s the case, it shouldn’t be too difficult, only more expensive.
But before you buy one, be aware that the apex seals are not the only weak point on the car, the ignition coils, wires and plugs need to be changed regularly, the clutch can wear quite fast, the transmission can break.
It really depends on who you buy it from. Be sure to get one that has been treated well, or if you’re prepared to work on it, get the cheapest one you can get and spend your time in the workshop (what I did).

Scott > Jake - Has Bad Luck So You Don't Have To
01/25/2016 at 12:25

Basically your right, it’s not that much more difficult. The issue is largely fear of something new or different. If your having someone do it, your likely going to pay a lot in labor, if you can find someone willing to do the work. Most mechanics simply will not touch a rotary engine because they are not familiar with them. I'm sure most would have no problem working on their own, but as a business they do not want to take it on. Those that will work on them, will often charge a premium, because they have knowledge and experience that others do not.

If your doing the work your self, it is much like the first time doing a rebuild on a regular engine. STUDY, STUDY, STUDY. While the basics are very simple, in fact far simpler than a regular engine, everything will be different. That said if you can do a rebuild on a regular engine, and your prepared to do your homework, than really it’s not that much more difficult, just different.

TheD0k_2many toys 2little time > Jake - Has Bad Luck So You Don't Have To
01/25/2016 at 13:25

step one: remove engine

Step two: replace with $200 5.3 LS

Step three: ??

Step four: profit