FD OMP question
 

About how thick is the specialized copper crush gasket (i.e., piece of copper with 2 holes in it) on the FD oil metering pump? This would be the one that goes between the OMP banjo lines and the pump.

Long story short - My FD was purchased without an OMP, but the PO provided 2x good low mile OMP's for me when I bought the car. Along with my rewire of the Link G4+ ECU, I restored the factory OMP, with the RA OMP adapter & tank mod so I can run premix thru it. Since I had plenty of the correct size regular copper crush washers on hand, I figured I could use 1 of them on each side of the banjo fittings where the lines bolt up to the pump, thinking they would do the same job sealing up the lines as that funky Mazda copper gasket with the 2 holes would do. Apparently I was wrong - I can't get the damned fittings to not leak premix lube! Tried replacing the crush washers, and made sure the banjos were torqued to FSM specs with no joy. My only theory as to why it's still leaking is maybe the specialized Mazda copper gasket is significantly thicker or thinner than the regular crush washers I'm using.

IIRC they are a bit thicker...a guess is maybe a millimeter. Gotta be someone that’s removed their OMP and has one lying around. Or see if Ray Crowe has them.
That said, are you sure it’s leaking at the hoses and not from that equally funky 'O' ring on the body of the OMP? They get pretty flat and stiff and will leak.

Interesting..... I did the stainless omp line swap for someone and used the crush washers that came in the kit and haven't had a single leak. They looked like regular ones to me. You sure your surfaces are good?

Well I'm confident the source of the leak is the sealing surfaces between the banjo bolts and the pump - with a gravity fed tank full of pre-mix, it was easy enough to test. Just pinch off the oil supply hose, clean the mess in the OMP area, then un-pinch the hose and patiently wait with a bright flashlight shining on the OMP area. Didn't take too long for the oil to show up again as a bead right at that junction between the banjos & pump.

Anyway, all the mating surfaces were clean and flat, and the RA OMP kit came with a pair of the new oval O-rings, which I used a little Hymolar to keep in place while assembling the OMP/RA Adapter to the front cover, and I did this job with the motor out of the car on a stand, so all the usual PITA accessibility elements that would make it easy to F-up the job weren't there.

I'm thinking it's a thickness issue - might try doubling up on the crush washers on the OMP side, and if that doesn't work, I'll be calling Ray for the OEM parts.

My caliper says that it is 1.45mm thick.

Thank you sir! The washers I have are only about 0.8mm; I'll try doubling up on the washers and let you all know if it stays leak free.

Doesn't seem like the stock double crush washer is that much thicker but that makes sense. You may be bottoming out the bolts without the washer fully crushing.

Also may be worth re-annealing the washers you've used as stated - heat with a torch to cherry red. That expands and "de-crushes" the washer.

Dale

Well the doubled-up washer idea is working so far - been on there for almost 2 hours with zero signs of leakage. With the single washer, it would show signs of leakage within 15 minutes. So I'm going to just leave the car untouched on the lift overnight - if it's still dry tomorrow morning I'll call it done.

I don't understand why you went through so much headache instead of just buying the OEM washers.

I have a bags full of "OEM washers" in the shop; they are nothing more than M10 copper crush washers. What I didn't have is the oddball copper seal with the 2 holes in it that I would have to order and wait for, so I figured I could just substitute the regular crush washers on both sides of the banjo fitting instead - but I didn't realize the thickness of the OEM oddball seal would make that much of a difference. I was obviously wrong!

An update to this annoying damned leak.... After getting the oddball Mazda OEM copper double washer & regular crush washers, it still leaks premix from the same place - looks like its coming from the joint where the lines mate up with the pump.

One thing I noticed is it leaks worse when the external pre-mix tank is full; if I fill it less than half, it barely leaks at all, and the rate of leakage is worse when driving. Don't worry, I'm running pre-mix with the gas.

So at this point I'm left with 2 theories that might explain the leakage:

1. There may be a hairline crack in the OMP machined casting under where the banjo bolts mate up to it
2. Longshot - the SS lines that came with the car may be blocked, and oil flow is taking the path of least resistance out.

I have a 2nd spare OMP, so plan is to pull and inspect the one that's on there now, and if necessary, replace it with OMP #2. The one that's on there now is a lower mileage part, and appeared to be in much better shape than used OMP #2, hence why I used it. Also, I've gone thru the drill of calibrating it and electrically testing it with my Link G4+ ECU, so I know it functions properly.

Any chance that a banjo bolt is cracked?

How is the sandwiched adaptor sealed to the pump and front iron?

That's a possibility too, but since it was easy enough to inspect the banjo ends in place (removed from OMP), I did so and there was no signs of it being cracked.

The RA OMP adapter seals up to the front cover with the same oval O-rings Mazda uses to seal the pump to the front cover, and the RA adapter has a groove in it for the ring to seat in for where it mates to the front cover. The other side of the adapter is flat where it mates up with the OMP (OMP has a seating groove for that O ring). The kit comes with 2x of those oval O-rings and longer M6 mounting bolts for the install. There's zero signs of it leaking from either of those points though, and when I installed it I had no issues with the rings walking out of their grooves - used some Hylomar sealant to keep them in place.

Is it possible that the SS lines themselves have some kind of issue with the fitting on the end?

It could be, I've cleaned them and the whole area multiple times, but unless I were to sit there for hours watching & waiting for that first oil bead to emerge, I wouldn't be able to catch that as a leak source - By the time I see it, gravity has already moved the oil to the low spot, right on the bottom of the banjo where it beads up. Which gives me another testing idea.... Maybe I can rig up a hand pump (Mity-vac working in reverse, or my Motive pressure brake bleeder) to pump a little oil thru the RA OMP adapter's oil feed port at low pressure? The pump could give a greater pressure differential than what it would see with the gravity fed oil tank, which should speed up the leak process and hopefully make it visibly obvious. No more than 5psi should do the trick without breaking anything

You know, the only reason I'm using the SS lines is because they came with the car and I assumed they were good - passed visual inspection at least. I actually would prefer a new set of OEM lines, as they last a long time and I can see my pre-mix oil flowing thru them.

It may be worth doing that, but changing lines can be a pain. If you are single turbo without all the rat's nest it's not as bad.

I prefer the OEM lines, they fit awesome and really have zero problems for 100,000+ miles, especially if you don't touch them.

I had a writeup ages ago on how to pre-fill new lines with oil, may want to look for that.

Dale

So for those of you who guessed it was the banjo fitting/SS line, you were right. I rigged up my Motive pressure bleeder to create a controllable source of low pressure air, and used it plus some tubing and a small reservoir (from my Mity-vac kit) to supply a some pressurized pre-mix oil to the RA OMP adapter's oil inlet port. At about 7~10psi, oil became visible on one of the two lines, coming from just below where the SS line is crimped onto the banjo fitting.

Time to give Ray a shout and get me some new lines!

Glad you finally ID’d the leak but...ugh...I don’t envy you having to fish those lines off and new on.

No worries - Single turbo here, takes me about 10 minutes to pull the UIM off with no rats nest to deal with. And with the Staubli leak free fuel line couplers the PO was smart enough to put in, I can have the fuel rails & injectors out of the way in another 5 minutes without stinking of gas :nod: