Re-using stock seals
 

I have never been one to re-use anything for a rebuild. But I'm building a motor for a friend (6 port NA), nothing serious. The motor only has 60k on it. But the water seals went and it needs to be torn down. I have a spare "overhaul" kit. Just the water jackets and basic gaskets to re-build it. So he wants me to re-use the side, corner, and apex seals. I have always been against putting old used seals back in the motor, but it's not mine, so whatever... Anyway, for those who have re-used the hard seals. How do i go about checking them for excessive wear?

The factory service manual has an extensive section on checking for wear. There is really nothing wrong with using the old seals over again, as long as they are in spec (although I am a little sceptical of 3-piece seals). If the engine really only has 60k on it, you may be ok, my guess is that the apex seal will be worn on the side, causing it to fit the groove loosely.

I hope that your friend understands that if the parts don't spec out, you will have to replace them. (I think that apex seals alone are about $360.00 if you buy them from the Mazda dealer).

I tore down an 80,000 mile rotary once that had in-spec apex seals. I have seen many more with similar mileage that had the sides of the seal worn.

If I could find an old seal (I don't remember where I put my seal stash) I could get you a picture.

As has been said. The FSM is your friend when it comes to seals. I for one do not understand the thought process of individuals who 'do not use the old seals'. It's just a camp that doesn't make sense to me (no offense). I've gotten into a 'discussion' on the other forum about this once and it really boiled down to some one just wanting a 'feel good' reason about their engine (he literally said "I'd rather take the false sense of security rather than use the old seals).

If the seals are in-spec, then there's really no reason not to use them. Brand new seals still need to be spec'd before install and they also need to be checked for by the same criteria as the used seals. I've even done the math/research on this forum (this particular sub forum to which I'm referencing) about seal wear. Apex seals wear extremely slowly. I think I figured out barring any abnormal circumstance the apex seals would last a good 800,000 miles with peak conditions, but then factored in a measure of safety which brought the wear life down to around 3-400,000 miles. Though I'd have to double check what I wrote in the other thread to be certain (it dealt with oils).

Now with this comes a grain of salt. Some old seals are outdated by their material or design. For instance the 3-piece apex seals. I am of the belief that they should be replaced for the newer 2-piece design.

In all honesty the NA engine will be fine with some soft seals and springs if everything spec's out.

My wear numbers were a little off: http://www.rotarycarclub.com/rotary_...3&postcount=12

Apex seals generally need to be changed, especially on an original motor.
Check with FSM, but I think they are:
8.0mm new
7.5mm replace with new inner apex seal spring
7.0mm wear limit - replace apex seal

Side seals in general don't need to be replaced - FSM has wear limits.

Corner seals are the same as side seals.

If side or corner seals are out of spec, I'd question if the engine was overheated or loss of oil pressure or no oil injection / premix.
Excessive side and corner seals imply internal lubrication is inadequate.


-Ted

You can do it by the book (Mazda rotary rebuild schedule) then it will be fine. Just makes sure you clean everything spotless and measure ALL of the things they tell you to do.

If your reusing seals make sure you put them back in the same spot they came from.

I had the FSM downloaded before on my lap top, which i no longer use due to it being a piece of shit.

So, can someone post a link for me to download it again?

Thanks in advance...

It's in the second gen Archives if you want it (I would post the link, but I'm tired and lazy right now--Just drove 200 miles in my 7 that can not get above 3200rpm... I need that stand alone sooner rather than later).

Cough, ahem MoTeC cough sneeze pussy just do it cough

RotaryHeads.com

There's upper and lower limits, most used seals that I have come across have been towards the lower limits so you make that call. Not to mention side seal clearance etc, etc etc. The engine won't be any stronger than when it was pulled apart, soooooo how strong/tight of an engine do you want? Side/Corner seals are what, $200 to do an engine?