I've read several articles on what the pressures are supposed to be, an low readings that it normaly leads to the o-ring being shot in the front cover. I was thinking that I might have messed up the front o-ring when I blew out the oil cooler lines with compressed air. What I'd kinda like some info on is what would cause oil pressure to sit about 30psi on a cruise at 3k rpm, but as soon as you let off the throttle the oil pressure wants to come back up to 60psi or so?

 

Could be a bad gauge or sender. It's kinda odd that the pressure goes up when you let off the throttle.

My advice would be to use a mechanical gauge and see what that shows and go from there

 

Finaly got a mechanical gauge put in shows 60psi when cold about 15+ at full temp. I did notice that the oil pressure rises about 5psi when I let off the throttle to coast. I'm thinking the oil pump took a crap too since it shows 45psi around 3k rpm.

 

These oil pumps usually don't take a crap. They are very very very simple machines, and usually many other various vital seals will blow before the oil pump goes. Usually low oil pressure is a sign of an old, tired engine, and if your oil pressure is showing 60psi cold above 3000rpms, that's low. How is the compression?

 

Tex - its 60psi cold at idle. Compression is 75psi front an rear 3 equal bumps on all sides.
The motor has 108k+ on internals an about 5k since I had to replace the front plate an water seals.
Also if the bearings are taking a crap would the oil wash all the debris into the pan kinda like a piston engine?

 

You've got low compression. At least all the seals seem ok from your test and the front and rear are close. You can drive the thing into the ground if you want, I'm sure it would last a while, but I'd start planning a rebuild.

As far as your question about the bearings I'm not sure. I'd think so.

 

So what is compression supposed to be? Thought I read somewhere that it's supposed to be 85psi.

 

Uh no... 85 psi is like verge of death. I'm amazed you can run the car at 75psi actually. My engine was blown with 100psi in the front rotor and 80 in the rear. A factory fresh engine should have damn near 120psi while a good rebuild should be well over 100psi.

With my freshly rebuilt engine and when running 20w50 I see 70psi in my aftermarket oil pressure gauge over 2k rpms or when cold. Occasionally it will go as high as 80psi when cold. At idle when warm it will stay around 40psi and drop to 30psi only if the oil gets real hot (read: traffic jam)

 

These cars will run just fine at 75psi compression, just don't expect any real power or easy starts.

 

How does that work? You sure your mechanic didn't just want to charge you for a rebuild? I have compression tested engines w/ 70/60 f/r and had them start up and drive just fine.

+1

 

^ my mechanic is me (you should know that about me ya?) my engine was certainly blown. I have the old chipped apex seals to prove it. Sure enough if my tune was better it might have started on that compression. Still I'd be willing to go out on a limb and say that most engines will not start on 75 psi without some oil to coax it.

 

Sure they will. You shouldn't be so absolute.

 

ive had problems like this with leaky oil cooler lines, or oil being too old.

change the oil and see if it helps.

check for oil leaks in the lines.

 

Changed the oil an Mazda filter still the same thing. Definately no leaks in the cooler lines. Does anyone have a good pic or diagram of the bypass thing in the cooler, just want to make sure it's in there correct.

 

Have'nt torn down the whole motor yet but I'm fairly sure this is gonna cost me.

Front stat gear outside ---^

Front stat gear inside ---^

An this is what I'm guessing is the seam ---^

 

Basic rebuild with new bearings, new pump chain.... the works. If you do it yourself it will be cheaper of course, I think a full rebuild kit form atkins costs about $850?

 

i have an 88 and recently did an s5 swap. put my front cover omp etc on it. put it in fires up and runs now but has a miss to it and oil pressure gauge is not moving. any suggestions? id appreciate it. was hoping to be done w my project and get to drive the thing.