The RX started dripping more oil than usual. I found cracks along the threaded end of the pressure valve area of the FMOC.



If you look closely, you can see that it's actually cracked in 2 places.

2 questions:
1. Has anyone ever tried to repair something like this with aluminum soldering or welding? It seems destined for failure to me, but I figured I'd check.

2. How can I tell if this is a 12a or SE oil cooler? The car is an 82, but it's had so many parts replaced, including the engine and radiator, that I want to make sure I get the same part when I buy a replacement.

 

i dont think you want to buy a replacement, new ones are many hundreds of dollars. I *BELIEVE* you can get them tig welded, but i would wait for someone else to chime in here.

 

mine cracked on both the inlet and outlet. I paid a local welding shop in my town $20 and they tig welded both of them.

 

The early FMOCs have the bungs pointing straight out. The SE FMOC has them at an angle. This is because the SE ones mount in front of the radiator and the angle is needed to clear the sway bar.

http://www.mazdatrix.com/b6.htm

Several people have had their FMOC tig welded to fix this. Another option is a used 79-82 FMOC or you could adapt a 2nd gen FMOC. The 2nd gen ones are nice because they are easy to come by and use banjo bolts instead of bungs..basically no chance of having this type of problem. Trochoid has a write-up on the 2nd gen FMOC installation on here.

 

Wow those cracks looks pretty bad. I have heard about some members taking their FMOC to clean and then repair. Trochoid has mentioned cleaning and then v-notching it then taking it in to an aluminum welder.

There is a place in California called Pacific Oil Coolers and they are certified to repair aircraft oil coolers. They ultrasonic cleanse the cooler, repair, and test before they ship it back to you. I just called them because I needed mine to be repair since my motor is going to be out on a rebuild anyways and they quoted me $125. Here is their website:
http://www.oilcoolers.com/

good luck!

 

Clean it very well, then take it to be tigged up. Make sure it's very clean or the welds will leak.

 

I had the same exact problem and all i have to say is for get that piece, just upgrade!! I took my oil cooler in and out about 4 times until i finally opted to upgrade. My buddy works at ford and got his hands on a F350 oil or trans cooler i forget which one. Went to a local hydraulic shop and got some extended lines for $50. then went on ebay and bought a thermostat for around 20 bucks. hooked it all up and its been working great since. I've had it for almost a year and not had any problems or leaks. I also feel now that the longevity of the oil has significantly increase.

 

I did a more permanent fix on Chris' car (Orion84gsl). I bought some weld in -8AN fittings like these:

http://store.summitracing.com/partde...5&autoview=sku

Cut the old piece that was sticking out on the oil cooler off, and welded 2 of these instead. He already had AN lines on his car so it was fairly easy to adapt them in there. Like this you can't crack them, and will seal easier than that crush washer that is stock.

PS: I don't have any pictures of it, but if you PM him he might have some.

 

If you really need to, TIG weld the bungs and have then weld around teh bung also to reinforce it, this is what I had done to mine when it cracked, hasn't leaked since.

 

Mine was way worse than that. I had a local shop cut that part down a little, weld a threaded tube around the outside of the original bung, and i bought a larger plug to match the new bung. All in all it cost me $25.

Isaac

 

I bought a used one from AtlantaRx7. It looks to be in really nice shape and at 1/6 the price of a new one, I'm willing to risk it.

I haven't gotten to hook it up yet because I found a leak in my radiator while I had the oil cooler off so now that needs to be re-welded. Maybe I'll switch to an e-fan I've got everything pulled. On a side note, what a pain it is to drain this radiator, why didn't Mazda put in a drain valve like everyone else does?

Hopefully it'll be another 26 years before I have to worry about it again.

 

I've had several fmocs welded due to over tightening, all of which have been successful. Copious amounts of brake cleaner, (at least 3 cans) are used to clean out the inside. Remove the internal thermostat, reinstall the plug, fill with brake cleaner, shake, then allow to set. Follow up with a good degreaser/Dawn, the flush with clean water. I cut a U shaped groove with an 1/8" carbide bur to insure good tig weld penetration. You can have your welder run a couple of roes of circumferential beads to increase bung strength.

Some rads do have a petcock drain, others don't. Be sure to remove the 14 mm hex head plug from the center iron to drain the block.