So, what is causing an oil leak from...
 

What would possibly be the cause(s) of an oil leak from the oil cooler bypass valve? (Big nut on bottom of the oil cooler.)

The crush washer could be pooched ( I like the copper ones ), nut loose or there is a crack around the fitting on the cooler from vibration. just clean it well spray it with brake cleaner then just run it and watch you will see the leak right away ... :)

I took it off, cleaned it and put it back on. When I took it off, there wasn't even a copper crush washer on it. I was thinking... Wtf?? Because all of the other oil related lines have copper crush washers.

I wasn't sure if it was a sign of a bad oil cooler bypass valve. I tried to buy an oil cooler bypass valve at O'Reilly the other day, and they don't sell them. Should have figured that.

Tomorrow I am heading to the auto-parts store to pick up a variety of crush washers... A long with some extra oil. I know I will lose some. (Just changed oil today, and tried to "fix" the leak.)

the crush washer is 18mm.

I appreciate that!

Napa, O'Reilly, Harbor Frieght, and Home Depot do not have the proper size crush washer that I am looking for. I went to the local Mazda dealership, ordered and spent $6.36 for part # 995642200 "gasket". (That is what it says on the invoice.)

I've taken it off a few times, completely cleaned it, and reinstalled it. When I first removed it, there was NO crush washer. This thing leaks like a bitch.

Does anyone know ANYTHING about that nut/plug/crush washer (gasket)/oil cooler bypass valve on the bottom of the oil cooler??? The FSM doesn't show much..

Is the order: NUT/PLUG > CRUSH WASHER > OIL COOLER BYPASS VALVE > SPRING ?

I know that I've bought multiple ones... from Autozone, and Chris Ott over at Rotary Performance in Garland. The Autozone one is copper, and the one from RP was made of aluminum. Common sense tells me that once you take one off, YOU DONT RE-USE IT. That goes for one that you just torqued down on once also.

I dont recall one sealing any better than the other, both leaked about a drop a week, it seemed.

MAKE SURE have one on each side of the banjo fitting... thats *4* "gaskets" total, though I'm not staring at one right this second.

I am not talking about a fucking banjo fitting. Look on the bottom of the oil cooler... That big 29mm nut/plug... THAT is what I am talking about.

Nevermind. I found a website that refers to it as a gasket. I typed in the part number... I'll see what I receive from Mazda, because the guy at the dealership couldn't tell me what it was, the size of it, the material it is made of, whether or not it is a crush washer, etc... Luckily on the invoice it said "gasket" and that's what it is showing on this Mazda parts website.

A lot of you had no idea what I was talking about. Which makes me believe that some people are oblivious to the fact that there is a giant nut on the bottom of the oil cooler. This nut holds the oil cooler bypass valve, and requires a gasket... It wasn't 18mm and sure as hell isn't for a banjo bolt.

It is a ~$6.36 USD aluminum crush washer bought at a Mazda dealership, with an inside diameter of 22mm. (This is simply for future reference.)

Agreed. I totally misread your question, or I was just finishing up a 22 hour day... sorry!

they're not? tell that to the countless motors removed and reinstalled without oil leak issues from the oil feed line to the block.

generally i do try to replace them but i can't justify $25 for simple crush washers when unless the old ones are deformed will work just fine(they do come in the gasket kits i order also but only randomly). just like the retaining clips for the FD cooler lines, which are about $35 a piece... some of the aftermarket washers are mushy and cheesy so i try to avoid them.

Even after replacing this... The fucker still leaks... Should I use teflon on the threads or something???

If it still leaks, im willing to bet there is a hairline crack.

I had a similar leak on my GSL-SE on the FMOC. i had to clean it up REAL good to be able to see the small crack.

a good welder will be able to weld that up no problem

Would it have anything to do with a bad oil cooler bypass valve? What are the torque specs on that bottom nut?