oil pressure relief valve problems

[jp928]

Na8, 1996. Transplanted into a clubbie recently. Came from a stat writeoff, that occurred in 2005, and may have sat around for a while. Seemed to run ok for us initially, then we saw very low oil pressure, then very high (>100psi, on a real gauge), then very low again. This morning, nothing at all...except rattles in the HLAs.
Sump off, and as we expected the relief piston seems stuck in the bore. There was quite a lot of pressure on the spring when I pulled the split pin out (judging by the load on my thumb holding the washer in place). At first the bottom of the piston was 25mm from the base of the oil pump body(measured with a caliper).
I would rather not have to pull the whole pump, what with all the other stuff that has to come off for that, so can anybody suggest how to get the piston out? I have tried picking it up with a M12 tap, but I think it turns and is too hard for the tap to bite into it. expanding pliers ?

thanks
jp

[jp928]

Tried the dealer for a new relief valve piston - cheap, but special order on japan - 4-8 weeks. New pump, 8-12 weeks, $400. And the special sealant - $200 a tube!
Bugger that.
Initially the M12 tap wouldnt bite, but pushing a small screwdriver blade down one of the flutes pushed the tap sideways, and it finally bit. With vise grips on the end of the tap pulling, and tapping downwards on the grips, it came out in a couple of stages. It was REALLY stuck in there.
There was a large very shiny patch on the side, and the rest was well scratched. An hours work with some 600 wet'n dry, and some final polishing, and it would slide in and out smoothly. As I was doing final reassembly, coated in oil, the piston would fall to the bottom under its own weight - beautiful! Only took a little pressure to hold the bottom washer in place while inserting the split pin.

Buttoned up the sump - no small job by itself, let the sealer rest a bit, filled it up, lowered to the ground....started.

Pressure came up in 10-15 secs, up around 50-60psi! Fabulous! Wouldnt go past ~70psi on a blip, so fingers crossed we are back on track. Had worried a bit about the pump priming, but it wasnt an issue.
You live and learn.

jp

[davekmoore]

That's persistence, that is.

[jp928]

Well, compared to the option of a new pump, and the extra work to fit one, its paid off. Went for a 25k run yesterday to get it fully hot through,after letting the gasket goo dry off, oil pressure all good, and no leaks so far. Didnt enjoy applying the goo everywhere and fitting the windage tray, and pulling the sump up, but compared to the other options, cheap way to go.
jp

[jp928]

More things.
On cold starts now we are seeing oil pressure way higher than the supposed pressure relief point (65psi) - 100,110,120psi. We were a bit concerned about this being a bad thing, so we let it warm until peak pressure was around 60-70 before driving. I spoke recently to a man who hots up Mazdas, and he said this was common with the make, and take no notice of it....I have seen remarks elsewhere that the relief hole in the pump body is too small to properly relieve high pressures.
Anybody have any experience in this area please?

tks
jp

[NitroDann]

Yes the relief hole is too small, high hp high rpm track cars have broken the gears numerous times, and the valve is well known for getting stuck.

Its easy to fit an external relief valve.

Dann

[Magpie]

NitroDann is correct, this is why some track cars use a Peterson's Remote Oil Relief Valve, shim out the OEM oil relief valve and install oil pump gears like Boundary.