Rotarian 1126

Arright I just did a quick oil change the other day, I couldn't get a Mazda OEM filter so I got a Purolator. No more than 50 miles I would say with this thing, my oil pressure starts to drop at idle, like around 10-15 psi!! I even saw it drop to like 5 or less psi once! I called Skip at KD Rotary and he pretty much slapped my hand over the phone for not using a Mazda filter. The new Mazda filter is on its way, and I'm definitely hoping that fixes the problem. Oh yeah, and with the pressure loss, I checked the oil level and it was perfect! And there is no oil in my air filter so I wasn't concerned with blow by. Apparently the Mazda filter has a check valve, that regulates the perfect oil pressure. Oh, and Skip told me that "Fram" oil filters are a quick death sentence on rotaries. Can't imagine why, but..... Anyone else ever have this problem before?

turbovr6

all filters have a check valve in them, they are there for lazy people. if you never change your oil, the filter will get clogged and won't pass oil. so that valve opens up to bypass the filter so you don't starve the engine of oil. As for brands, I have used Fram, purolator, and mobil one in the past. never had a problem. Now I use K&N oil filters. I think you got a defect, thats all

Rotarian 1126

^ Figures.....

Rotarian 1126

It's weird too, I mean I have great pressure under load, it's just while idling it is real bad. Especially when it's warm, and I do a quick little rev. Than the pressure drops to like 5 psi, than very slowly climbs back up to around 30. - usually...

turbovr6

you may want to check the plug for the oil pressure switch. it sits right under the filter housing, you may have knoced it loose, or I have seen when they get oil spilled on them ther cause the gauge to read funny. If it's got oil on the plug, disconnect, and spray everything with some carb, or brake clean.

maxcooper

A clogged or merely restrictive oil filter will tend to increase the oil pressure, since the sensor is before the oil filter.



I think your situation of the pressure appearing to drop at idle is the common "oil pressure gauge gone wild" problem that is really the sensor not reading correctly, rather than an actual low pressure condition. It could be from the connector getting dirty, or from the sensor itself going bad. Someone opened a "bad" sensor and found a spring all stretched out causing erratic readings at low pressure (and probably an overstatement of mid or high pressures). It's possible that high pressures from a clogged filter, thick oil, or both could cause the spring in the sensor to stretch out prematurely, but it seems to happen even with things in good order.



Another possibility is that the thermo pellet at the front of the eccentric shaft has failed and is stuck open, leading to low pressure. The pellet is open when the engine is cold to keep the pressure down during warm-up, but it should close after the oil warms up a little. However, I think the pellet failing is unlikely -- most likely it is just the sensor for the gauge, since that seems to happen to most or all FDs at some point.



Most oil filters have a bypass valve that opens when the pressure drop across the filter gets too high. If the filter gets clogged, the bypass valve prevents starvation by letting unfiltered oil through. There is also a check-valve-like device called an "anti-drainback" valve that keeps oil in the filter to prevent starvation at start-up. The anti-drainback valve also helps to avoid a mess when you change the filter by keeping the oil in the filter.



-Max

jspecracer7

Don't trust the stock gauge. Go get yourself a good aftermarket oil pressure gauge and you'll see your oil pressure is fine. I know when I have to change my oil...my oil pressure drops at idle

Signal 2

I've got the same problem and went into a mild panic too when I first noticed it. Since then I read alot of other posts and think I've traced it back to the oil pressure sending unit like Max described. Even so, I recently tried an OEM mazda filter and it kinda seems like the inidicated pressure at idle has improved...a little. I'm gonna have to get another sender soon.

Rotarian 1126

Well I just put the OEM Mazda filter on today, and used Castrol GTX 20w50 and my oil pressure is perfect!