sudden reduction in oil pressure

[Dave WM]

SROP syndrome,,,,

Normally when engine is cold (70's f) starting the engine I get up to about 2/3 of the 90psi scale, as it warms up I am around mid point for typical driving. Idle drops down to about 1/8 scale.

The other day I noticed the oil pressure never really gets much above the mid point regardless of RPM or temp. Idle pressure seems about the same. A mechanical gauge was used and blipping the throttle would get it up to about 55 psi, idle was about 15psi iirc.

Only recent work done was the replacement of the timing cover/timing chain/guides and tensioner. New oil pump gasket (felpro) used in conjunction with the timing cover having to come off.

The pressure was fine after this work done weeks ago. the SROP only happened in the past few days.

I have a new Nissan oil pump on  the way, I tried a different sending unit (the one off my spare engine) and I have a brand new beck arnley unit to try out as well.

I cant account for the sudden drop as normal wear, so any ideas on mechanical failures to account for it?

I doubt it could be the pump but they are not expensive so will give it a try. Also will use a Nissan pump gasket.

I removed the valve cover, pulled the plugs and cranked the engine. It took a while but there was a generous amount of oil squirting out of the cam lobe oiling tube, enough to actually squirt out, not just dribble out (like I remember when testing before). I also pulled the cap off while the engine was running and a great deal of oil was indeed getting sprayed, base on what was ejected from the open valve cover.

I plan to use a fitting that will let me attach both the sending unit AND a mechanical gauge so I can calibrate the electrical gauge.

It just bother me that there seems to be no single event that I can account for the SROP indicated.

 

 

[grannyknot]

I think our oil pressure gauges are the real problem, they are very slow to respond to a change in pressure and it seems always read lower than what the oil pump is actually producing. My first Z did the lazy needle thing so I set up a temporary modern pressure sensor and gauge in the engine bay just to reassure myself that everything was good, it was.

[Dave WM]

well the problem is it was such a sudden change, I just can't account for why it suddenly reads about 10-15 psi lower that it was a week ago. The gauge acts the same as always (as you mention slow response etc...) just a lower reading once I get to a prolonged steady RPM.

[Zed Head]

You can get BSP to NPT adapters from McMaster Carr.  Can't remember the exact size I think I've posted about it before.  I wouldn't trust the dash gauge.

https://www.mcmaster.com/standard-pipe-fittings

[Dave WM]

thanks ZH already on it, will report back (video) as soon as everything arrives. Would like to do a pre and post new pump video as well with a proper mech gauge just to see if there is any difference. I am going to check the oil for any metal sparkles as well. I dont know if its possible to have a bad bearing that would cause a loss of oil pressure with no other symptoms (other than metal in the oil). The main thing is just how it happened seemingly in one day. That is the puzzler. I also did a quick test with an ill fitting gauge, my test engine got to over 60psi no problem, but the engine in the car was more like 50-55 max. this makes me feel its a real drop, but will confirm and report back.

[Dave WM]

tiny tiny bit of metal in the pleats of the filter, not a lot, just a few here and there. This is on a filter that I replaced after the timing chain guide came loose. there was some material worn from the chain were it rubbed against the guide.

[240260280]

Put a super magnet on bottom of oil pan.

[Dave WM]

3 hours ago, 240260280 said:

Put a super magnet on bottom of oil pan.

inside or outside?

[Dave WM]

I wonder if its possible some of he timing chain fragments could have got sucked up into the pump and scored it. I presume the filter would have protected the engine but not the pump as I assume the filter after the pump.

[siteunseen]

The screen pick up in the pan feeds the pump then it goes through the filter before the motor. There's a high pressure relief with a ball and spring at the filter. If I recall correctly.

[240260280]

42 minutes ago, Dave WM said:

inside or outside?

On the outside near the bottom by the drain. Metal floating will stick to it. Pull it off before you drain and the metal will flow out.

[240260280]

Put on pan. Not on oil filter.  The filter can capture the fine stuff.

A magnet on the outside is fine... or you can buy a magnetic plug.

 

Edited November 4, 2019 by 240260280