Oil pressure issues. I'm running out of ideas...

[rtrdpenguin]

I've been having a strange oil pressure issue ever since I've had my current 7M-GTE. A short history of it:

-Bought as a JDM import engine, cleaned it up & installed new HG and dropped it in. Ran for maybe 600 miles and rod knocked. During this time my oil pressure gauge was not hooked up so I don't know for sure, but the most likely cause was the low oil pressure problem.

-Rebuilt completely -- new bearings, pistons, rings, gaskets, MHG and ARP studs, etc. Didn't replace oil squirters or oil pump! So it had low oil pressure and developed the very faintest knock. Bearing clearances all on the tight side of TSRM specs, except 2 mains that are on the loose side.

-Decided to take it all apart again to put in a brand new OEM oil pump (shimmed 4mm) and squirters. Started it up yesterday and oil pressure seemed ok (~5 psi at hot idle, rose up to about 15 when I revved it to 2kish)

-Today I let it idle for a while checking for leaks and all that, and when I looked at the gauge again it was sitting almost at the zero line (maybe 2 psi). Revving it made it rise a tiny bit. No odd noises yet.

-Drove it up and down the street for just under 1 mile, pulled into the driveway and the oil pressure is pretty much sitting on the zero line and stays there. Revving makes it go up to maybe 4 psi at 2k rpms

-I'm running the stock oil filter head and cooler circuit and my cooler relief valve spring is loose so I plugged the oil cooler hose to see if it helped oil pressure and it only upped it by a very tiny amount.


So what else could cause low oil pressure? I'm out of ideas. The only thing that comes to mind is maybe those two main bearings being on the loose side (still within TSRM spec, but at the edge) or a crack in the block somewhere causing oil to leak back into the pan. :cry:

Cliffnotes:
-really low oil pressure, almost zero at hot idle according to stock gauge
-doesn't rise anything close to 10 psi per 1k rpm.... more like 1 psi per 1k rpm
-Rebuilt engine, good bearing clearances
-new oil pump shimmed 4mm and new squirters
-oil cooler circuit plugged off, minimal difference.
-oil pump driveshaft is good
-no visible oil leaks
-no idea what is causing this anymore!

 

[GrimJack]

Are you using the pressure sensor from the USDM engine or the JDM engine?

 

[rtrdpenguin]

Ah I knew I forgot something! I'm using a USDM pressure sensor off of a 7M-GE. From what I understand they're the same between GTEs and GEs right?

 

[GrimJack]

That should be fine... however, there are issues with faulty sensors. Have you hooked up a manual gauge and verified it against that?

 

[IJ.]

That should be fine... however, there are issues with faulty sensors. Have you hooked up a manual gauge and verified it against that?

x2

 

[rtrdpenguin]

Not yet but that was my next plan of action

I should probably mention there is a slight tapping noise starting to come from the engine.... very similar to the past 2 tapping noises that led to rods a knockin' though.

I really don't believe there's zero oil pressure though so a mechanical gauge check might give me better readings, but I'm pretty convinced the pressure is lower than it should be.

 

[supraguy@aol]

remember that you'll hear the injectors tapping quite loudly, so see if it's a high tapping noise- clicking, or a lower tone. Best of all, use a mechanic's stethescope to find out where the noise is coming from.

 

[rtrdpenguin]

I'm pretty sure it's the rods, I've been listening to this engine for ages now. Just went out to make sure the gauge sender and wiring was all in order (no transportation to go get a mechanical gauge right now) and it's all still the same. Tapping sound is louder, sounding just like last time

 

[GrimJack]

When you had it apart, did you pull the plugs out of the crank and get the galleries in there cleaned out?

 

[rtrdpenguin]

I didn't personally but the shop that checked and polished the crank did. The plugs looked shiny and new so I trust it was done. Are you thinking metal particles are in the engine?

 

[GrimJack]

No, I was thinking that you might have two entirely unrelated problems - a malfunctioning sensor causing the gauge problem and a clogged gallery causing your knock from oil starvation.

Verify the pressure with another gauge, first. If you end up pulling it apart and it's always roasting the same bearing(s), it has to be oil starvation.

 

[Rennat]

and a shimmed pump with 4-5mm (which is what mine is at) when im sitting at an idle, i NEVER go below 20psi on the oil press. gauge... its only when i start my car hot does it go under that.

and i've pegged the gauge out on really cold days. so you have some pretty bad issues if your cant even get yours to pump above 20psi.

 

[supramang]

Is it the pick up tube on the oil pump that isnt long enough? That's what ive heard. Idle at about 4psi is normal correct? I just check my oil basically before I start it... every single time I drive it.

 

[GrimJack]

Is it the pick up tube on the oil pump that isnt long enough? That's what ive heard. Idle at about 4psi is normal correct? I just check my oil basically before I start it... every single time I drive it.

No, that's only a factor if you are running low on oil. There's been rumor of the occasional guy managing to starve the oil pickup doing hard track days with a lot of constant G-forces, but I've never seen any hard evidence.

 

[rtrdpenguin]

Ok, big update! I got myself a manual gauge test kit thing (surprisingly hard to find at local stores...) and here are the results:

Cold start
50 psi at 1200 rpm
lowers to 40 psi after approx. 10 seconds
gets down to 30 psi and the coolant temp is starting to rise

Hot idle @ ~900 rpm (this is a bit high isn't it?)
20 psi and stays there for a good 5 minutes

I rev the engine to 2k and 3k, checking the pressures, and it rises quickly to around 35 psi at 2k and gets a bit over 40 psi at 3k

But then when I let it idle again (now idle is at ~700 rpm) it's at 8 psi!
And I can hear the tapping noise again faint, but it's loudest at the back of the oil pan... The first time I got rod knock the worst bearing damage was #3 from the front and second worst was #1 from the front. The rest weren't too bad... odd right?

It stays at 8 psi and the tapping remains, even after more revs (pressure still rises satisfactorily).


I'm hearing this tapping and I swear it sounds just like last time, but I'm starting to wonder if I'm just paranoid after the previous incident. Could the clutch/flywheel be tapping? I torqued everything to spec but it's the same old assembly.

 

[IJ.]

No, that's only a factor if you are running low on oil. There's been rumor of the occasional guy managing to starve the oil pickup doing hard track days with a lot of constant G-forces, but I've never seen any hard evidence.

If you're even slightly low on Oil and have to get on the brakes hard at high speed you can't RK these motors with the stock pan.... ask me how I know

 

[Supracentral]

No, that's only a factor if you are running low on oil. There's been rumor of the occasional guy managing to starve the oil pickup doing hard track days with a lot of constant G-forces, but I've never seen any hard evidence.

If you're even slightly low on Oil and have to get on the brakes hard at high speed you can't RK these motors with the stock pan.... ask me how I know

IJ.'s right Dave. I've seen it personally. I was running a MKIII with a slight oil leak in one of the turbo seals on Road Atlanta a couple of years ago. Nothing worth mentioning. No visible smoke, just some slightly oily smelling exhaust. Nothing that would fail tech. I was waiting on a replacement from Dallas Turbo at the time and didn't want to miss my track day. It burned off nearly a quart off during a hot summer day. During hard breaking down into turn 10A (for those that know the track) I oil starved it and spun a bearing.

Road Atlanta is pretty hard on a car. I always run an extra quart on it, especially in the MKIV with R-Compound tires. There are several turns where I can pull over a G for a pretty long period.

 

[IJ.]

Mine happened on the return leg of an 1800 Km round trip (my fault I forgot to check the Oil before I left to come home) and as I was still 700 Km's from home and a tow wasn't an option I just dumped 2 Qt's of 90 weight gear Oil in and limped it home.

It was fine if I didn't push it hard.

 

[rtrdpenguin]

If it's worth anything I also bent the pickup tube down so the screen is just above the bottom of the pan and the oil's always been full since the rebuild.

I have good oil pressure verified by a mechanical gauge now, but still hear the tapping noise. It didn't actually get rod knock anytime after the rebuild, just before it. What else can make RK type noises near the #6 rod bearing? It could be something outlandish so I'm hoping one of you with tons of experience will think up something

 

[IJ.]

Auto or manual?