FMOC conversion
 

So my SE oil cooler has developed the usual leak by the fitting. Rather than take it off, weld it, and try again I was wondering if the 2nd gen coolers are beefier? Or do they develop the same cracks?

the se coolers are nice because they bolt right up to 84-85 cars. no need to fab mounts. the 2nd gen coolers are probably a little better as far as cracking goes, the main advantage though is that they are dirt cheap, lol.
if you wanted a serious upgrade find an old rx4 or repu 8 row oil cooler.

if i was you i would just get it welded.

Upgrade to 2nd gen , they are cheap and can be found easily! I just picked one up like new w/ lines for $50.

you were probably the one I was bidding against *LOL*

I picked mine up locally. :bigok: Good luck!

i got one of these, i thought about selling it. maybe ill install it on the DD instead of the FC cooler.

You can have them welded or you can weld them yourself around the boss. I had mine welded up for 20 bucks and hasnt leaked since.

81 and 82 cars had a fmoc as well... i used a cooler from a 82 to convert my 85 gsl to fmoc, instead of beehive... works out very well...

Agreed with dayton. I did the same for my 84gsl. I used RB SS lines n fittings

When I overtorqued the RX-4 oil cooler, I had it welded, but that didn't fix it. I then had 2 SE oil coolers welded as well since they all leaked but they still all leaked. But double checking it, I then used teflon string (the same they use for the faucets) and the leak stopped.

Double check to see if it's a cracked base for the bolt or it could be just in need of teflon string to seal the leak (in my case, it was both).

good tip - thanks :)

Weld repair
 

I just had one weld repaired, although I have not used it yet. My hydraulics expert welded it for me, and then he put the fittings in with a generous coating on the threads of Loctite 545. He seemed very confident it would not leak. He uses the 545 thread sealer on 2,000 psi hydraulics, says there should be no problem with 100 psi oil pressure. The weld repaired cooler is a stock 79-80 unit, and will just be a spare.

I ended up using a REPU oil cooler that I had, just had to fabricate some brackets for it. My understanding is that the REPU is the most robust and highest capacity of all the Mazda oil coolers. As someone said, it has 8 rows (instead of 7) and hangs down about 3/4 inch lower than the stock RX-7 coolers.

All these problems with cracked bosses on the oil coolers is the result of a very poor design which Mazda should have corrected in the beginning. If they had simply welded on a piece of 1/2 inch plate, bored and tapped for the fittings, there would never have been a cracking problem.

I was doing a 13b swap into a 79, and will post separately some info and photos.