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Car Forum / Mazda / Mazda Miata / December 2004Bad oil pump??
My '92 Miata with about 90K, has been pegging the oil pressure gauge at the 90 psi mark during acceleration. Thinking it was the gauge or sending unit, I took it to my mechanix. He said the both were fine and the oil pressure was actually in the 70-90 psi range at 2500-3000 rpm. He said the oil relief valve in the oil pump has failed and a new pump is required at huge $$$. A big labor job... Is this possible?? Any way to find out without the big $$? All input is welcome. Thoughts. Thanks! > He said the oil > relief valve in the oil pump has failed and a new pump is required at huge > $$$. A big labor job... > > Is this possible?? Any way to find out without the big $$? Sounds plausible to me. Mine's a 94, but the shop manual for it says the oil relief valve is designed to kick in between 50 and 63 psi. The danger with your high pressure is that it could blow out the filter element in your oil filter and send it and all the crud thru your engine. Hope I'm wrong, but it does sound like big bucks. Might be cheaper to buy a used engine in known good condition than to spend the labor to rebuild the one you have. Engine usually has to come out to change the pump - unless your mechanic is really good. This happened to a friend of mine. Before you spring for a new pump, think about adding about a quart of Rislone or a similar product, making sure that you do not overfill. Next, with a new filter( pre lube it with the oil mixture, start and run a few minutes, watching the oil pressure and engine temperature.) It may take several cycles of this, with cool down between (allows the solvent to work) to clear the muck from the system. Another additive that has a similar effect is about the same amount of automatic tranny fluid. We always used a straight grade oil with either solvent. If you manage to clear the problem, go to a recommended oil and change it more frequently than was done in the past. It's possible that the problem is also related to the brand and type of oil used. >> He said the oil >> relief valve in the oil pump has failed and a new pump is required at [quoted text clipped - 14 lines] > rebuild the one you have. Engine usually has to come out to change the > pump - unless your mechanic is really good. Thanks for the suggestion. I have the car at another shop today for a 2nd opinion. I watched the gauge very closely as we drove this weekend, and it does start out getting at or near 90 psi with the engine cold, but within 2-3 minutes as the motor warms up, the pressure begins to hang out at or below 60 psi, and I can see the relief valve working as I run up the RPM's. Appears the pressure climbs until about 62-65 psi, as RPM increase, then at about 2500-2700rpm, the pressure drops back to slightly under 60 and pretty much holds there as we drove. At idle, I have about 30 psi, again, all on the car gauge. I'll update this message tonight. Thanks to all who posted. In article <502d9a56b2bf83239f379ea6d7e74c0a@localhost.talkaboutautos.com>, > I watched the gauge very closely as we drove this weekend, and it > does start out getting at or near 90 psi with the engine cold, but within [quoted text clipped - 4 lines] > and pretty much holds there as we drove. At idle, I have about 30 psi, > again, all on the car gauge. You've just described the normal operation of a healthy Miata engine with a real oil pressure gauge. Stop worrying.  SignatureLanny Chambers, St. Louis, USA '94C the alignment page: http://www.hummingbirds.net/alignment.html I'd agree, since the idle oil pressure is more or less normal. The 90 psi (if actual) is a bit high though, unless heavy oil is used. Given the factory oil pressure gauges, I'd want to check with an accurate gauge before deciding to do anything. > In article > <502d9a56b2bf83239f379ea6d7e74c0a@localhost.talkaboutautos.com>, [quoted text clipped - 11 lines] > You've just described the normal operation of a healthy Miata engine > with a real oil pressure gauge. Stop worrying. > The 90 psi (if actual) is a bit high though, unless heavy oil is > used. It's perfectly normal for 10W-30 in subfreezing weather. SignatureLanny Chambers, St. Louis, USA '94C the alignment page: http://www.hummingbirds.net/alignment.html >> The 90 psi (if actual) is a bit high though, unless heavy oil is >> used. > >It's perfectly normal for 10W-30 in subfreezing weather. Yes, 90 cold is, even at idle if sufficiently cold. But the cited numbers when the oil is fully warmed up, like 30 at idle, seem too high. I could imagine that the mechanic who wanted to change the $$$ oil pump, and who was apparently unaware that the oil pressure depends on oil temperature, put in the wrong weight of oil. If the oil pressure after say 30 minutes driving is not well below the 30 mark, say 20, I would take the safe route and replace the oil. Leon SignatureLeon van Dommelen :) Bozo, the White 96 Sebring Miata .) rammm@dommelen.net http://www.dommelen.net/miata EXIT THE INTERSTATES (Jamie Jensen) I took it to another respected shop today and they said all was well, and they did not recommend doing anything but driving it and having a good time. They said you must check the pressure after engine warmup, and mine had very normal pressure at that time, and at all RPM's. Thanks everyone for all the input. Happy holidays! Great Christmas present! Now, you need to make sure you never, ever, go back to the shop that wanted to replace your oil pump unless it is to tell them they are buffons. Tom 92 Red > I took it to another respected shop today and they said all was well, and > they did not recommend doing anything but driving it and having a good > time. They said you must check the pressure after engine warmup, and mine > had very normal pressure at that time, and at all RPM's. Thanks everyone > for all the input. Happy holidays! |
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