Writeup: Rebuilding S4 Metering Oil Pump
 

Decided to go through this becuase I didnt see anything like this in the archives with any specific part numbers and mainly I wanted to keep my OMP working.

The OMP tends to leak at the end cover plates or at the lever. These areas have orings that get hard stop sealing correctly.
https://www.rx7club.com/attachment.p...d=163307&stc=1

First thing to do is disassemble everything, you will need a phillips screw driver and a 10mm wrench. Make note of how things go so that its easier to put back together. Take a small toothbrush and aerosol brake cleaner and clean/degrease everything.

Leaking lever Oring:
This where I have seen most of the oil leaks coming from
https://www.rx7club.com/attachment.p...hmentid=163309
The oring gets rock hard and doesn't seal any more.

Replacement Oring:
The original oring is a triple seal type and pretty thick
https://www.rx7club.com/attachment.p...hmentid=163310
After a few measurements I started sourcing different types of orings. The best one I came across was from McMaster Carr http://www.mcmaster.com/asp/enter.asp?partnum=9464K109. The Oring is made of Viton, the ID fits tightly where the old one was and the OD makes it fit snugly in the bore. The only thing is that the Viton Oring is not as wide as the original.
https://www.rx7club.com/attachment.p...hmentid=163311

Sealing the endplates
I couldn't find any orings to replace the orings so I used black rtv. You want to use the rtv sparingly, just enough to fill in the areas where the orings would be and enough to seal the plate to the pump body
https://www.rx7club.com/attachment.p...hmentid=163308


After putting everything together, I used more rtv to reattach the pump to the front cover. Even if you use a new Oring at this point, wait a while until the rtv sets.

I have been running my rebuilt omp for about 2 weeks now, over 1200 miles ,and still no leaks.

Hopes this helps some people. As my usual disclaimer, try at your own risk, this worked for me but not guaranteed to work for everyone.

Why didn't you use the OEM o-ring?

Awesome work. Seems pretty cool... I might try it.

People have a few reasons not to use the factory O'rings.

1st availability...If you realy work at a Mazda parts counter you may be able to let us know if they are available from Mazda? What are the factoy part numbers and how much do they go for? Even if you could get them they would probably be made of BUNA-N though.

2nd Viton is better... Higher heat capacity rating +400°F vs 230°F for BUNA-N. More chemically resilient. Reasonably priced. Only caution is for cold wheather aplications since viton doesn't have the same low range properties -10°F vs -30°F for BUNA-N.

3rd... Once you know the sizes and material you don't need Mazda anymore. You can buy your o'rings anywhere you want. If you buy your O'rings from a Parker or GreeneTweed distributor you can get the double seal type O'ring in Viton.

I believe the sizes of the O'rings that you need for a complete rebuild are:

1 x 7/32" x 13/32" (-107) - Actuation Lever Seal (Double seal type O'ring optional)
1 x 3/8" x 1/2" (-12) - Drive Bushing/Retainer Seal
2 x 11/16" x 13/16" (-17) - End Plate Seals

I have extras if you can't find them. PM me if you like.

The o'ring for the OMP lever is not in the parts fische for the RX-7.

Good job.
I wanted to post so something like this a long time ago, but I never bothered cause we just chuck that crap and go pre-mix.
I knew about the diamond shaped o-ring in the back, but the o-ring on the shaft is a good find!
Everyone else (*cough*Mazdatrix*cough*) tells you to replace the copper crush washers / gaskets up front, but no mention of the other two areas...


-Ted

It's funny you brought this up, I just bought those copper crush washers and o--ring in the back, from somebody a few months ago, and there's oil coming from the lever now. Before I did the washers most of the oil came from there. Now it has found a new place to leak from. Maybe I should just go pre-mix after all.

Hey, B.T.W. why is that end plate on the left of his first picture there anyway. Mine doesn't leak and come to think of it I think there was some ATV coming out from behind the plate. Is it just for access to the inside parts behind the four holes? Or did some models (or older rotaries) have something that bolts there or what.

Covers are to access the internal rotating parts as shown in the jpg:

Bloody hell, stole my writeup. :) I had just finished writing the metering oil pump rebuild for my website. Oh well...When this thread finishes I'll copy it to the Archives.

very nice write up, im going to save this .

Thanks!


Jason NYC

Bookmarked.

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