Oil pressure low- Not a basic problem

[FloTex]

Just rebuilt. TRSM specs are 4.3 psi @ 650 RPM and 36-71 psi @ 3000 RPM
Readings are ~8 psi @ 900 RPM and ~20 psi @ 2000 RPM+
During the rebuild I shimmed the oil pressure relief valve 7mm so pressure should be excellent. I checked the oil pump clearances and so did the machine shop. I spun/tested the oil pump. I checked the oil filter mount relief valve. I'm running Castrol SynTec 10w30. I did not replace the rings but did install Clevite bearings and reinstalled the mhg, cleaned and copper coated. I used ARP with the ARP engineers direct spec for the 7MGTE of 110 ft-lbs with 30w oil for lube (I stopped at 105 cause I couldn't hold my breath any longer being afraid they were going to strip). A couple cam end journals are scoured but the same as before the build and pressure was higher.
I am going to check my oil pressure sensor, but I did that before with a gauge and air pressure, so I don't think it is just the sensor. Level is full. No bad sounds. Vacuum is good. No oil leaks.
Any ideas?

 

[jdub]

Are you using the stock filter head?

Did you replace the piston squirter bolts during the rebuild?

I would test with a mechanical gauge at the stock sensor location.

 

[jdub]

???

 

[FloTex]

I checked all the squirters (I thought they were crankshaft squirters but I think we are talking about the same ones). I made sure they were clear with a wire run through. They are tabbed and only reinstall one way. I blew air through the block and crank and cam oil passages also.
I will try the gauge hook up. I have gotten a bad sensor before but this one worked OK before tear down and I had checked it previously.
I plasti-gaged the crank/bearings before tear down and they were good. The crank was good. While I was there I installed Clevite bearings. I didn't plasti-gage them because the crank is still stock spec and I don't expect problems with new Clevites.
The mechanical gauge will tell I guess. BETTER THE SENSOR THAN THE BEARINGS!
Any other ideas? THANKS FOR THE HELP TROUBLESHOOTING.

 

[FloTex]

Stock filter head.

 

[jdub]

The squirters are 2 piece...the part you described (nozzle) and the bolt. The bolt is what controls oil flow through the nozzle...it has a ball and spring inside that will allow flow at ~40 psi. The bolt spring wears out and can open earlier, causing a pressure drop (the sensor reads along the same oil channel). IMO the bolts should be replaced during a rebuild.

The stock filter head is another pressure bleed...it has a relief valve inside (another spring) that also opens up at ~40 psi to allow flow to the cooler. Once oil goes to the cooler it's routed back straight to the pan. If it's stuck open, it will cause a huge pressure drop because of it's routing. Since it's external, it's a lot easier to check....in fact, the cooler circuit should be converted to a full flow T-stat controlled circuit. Take a look at this:
http://www.supramania.com/forums/showthread.php?t=62838

This will eliminate the pressure bleed...forever.

 

[FloTex]

So here's the apparent CULPRIT. I pulled the sensor and put it on an air line with regulator. I connected the gauge (wire) and grounded the sensor. Turning on the power (not starting up) and checking instrument panel oil pressure gauge readings showed that when there was 90 psi supply the gauge read 58; 60 psi read 35; 50 read 32; 40 read 23; 20 read 10.

I didn't have the set-up to plug in directly for oil pressure. I will do that tomorrow, but with the readings I had when the car ran at about 22 psi I should have about 40 psi at 2500 rpm. This is not great, especially after 7mm shims in the oil pump pressure relief valve, but it's a start.

I had a bad sensor before so I didn't want to take a chance with aftermarket. The new sender is an OEM Toyota and it is now reading off. It could be the gauge. I will keep posting.

Any gauge feedback?

 

[FloTex]

I will check the gauge per the TRSM later, but for now I know the oil pressure is not good enough per mechanical gauge readings.

Cold: 30 psi@1100 RPM
40@ 2500
50 @ 3000

Warm: 8@900
35@2500
40@3000

Bled air from the mechanical oil gauge plastic line and read again:
5@900
11@1400
25@2500
30@3000

Continuing to troubleshoot. Probably will end up pulling the pan ...
I'll check the oil cooler lines first.

 

[FloTex]

Plugged the oil cooler hoses and retested. Pressure went up.

10 psi@ 800 RPM
40 psi @ 3000 RPM

Reconnected and the pressure went back down:

6 @ 900 RPM
30@ 3000

Oil cooler was not hot- Infrared thermometer read 107 degrees. Holding the gauge in hand and watching the pressure did change from 6 psi to ~4.5 psi when I pinched the hose. So there is a slow flow going through it even at 6 psi.

So this is a problem. I can get to 40 psi @3000 RPM by dealing with the oil cooler lines. I imagine the rest is in the cam bearings. Perhaps the squirter valves. I visually inspected them but didn't pressure test or replace them.

I'm not satisfied with 40psi @ 3000 RPM.

 

[Poodles]

A good general rule is 10psi per 1000rpm... It's not a SBC with over 100PSI...

 

[jdub]

Going to a full flow T-stat controlled cooler circuit will have the same effect as pinching the line on your stock cooler

40 psi at 3000 is ok. I'm betting you have a stuck open squirter bolt too.

 

[FloTex]

Excellent- so I won't pull the pan. I have spent a lot of time going through all past posts on this subject and got the full scoop on ordering the filter relocation parts.

I am thinking a large cooler may not be needed. I haven't seen any posts actually verifying the need for a bigger cooler based on temperature readings.

What about converting to a Canton adaptor and Mocal T'Stat control but keep the stock cooler for now? (If it doesn't cool enough I can add a bigger cooler.)

Thanks for the feedback jdub and Poodles.

 

[FloTex]

As for the instrument panel gauge I figr I kin move the needle up 15 pounds and it'll read accurit.

Or I kin scratch off the stock numbers on the face and paste on some that will match what I read on the mechanical gauge.

 

[Poodles]

Replace the sender (or adjust it). Dunno if jetjock ever did make a writeup on how to do it...

 

[FloTex]

I did a separate post for the sensor calibration question.

I went all Canton including a cooler and 215 degree thermostat.

I will post the list of parts.

 

[Poodles]

Ah, I missed what you said in an earlier post, but no, you can't run the stock cooler with a T stat and filter adapter as it's not designed for full flow.

 

[jdub]

I did a separate post for the sensor calibration question.

I went all Canton including a cooler and 215 degree thermostat.

I will post the list of parts.

A 180 deg F stat is a better choice

 

[FloTex]

I went with all Canton parts because of previous thread posts from Ian. Canton's reason for going with 215 (their standard thermostat) instead of 160 or 180 is to flash any water off as quick as possible.

 

[IJ.]

Really interesting FloTex, I'm using a MoCal 180 T-Stat this time and had used a PermaCool 180 the last build.

Not sure if I agree with Cantons reasoning on this one.

 

[FloTex]

I stayed away from all cast parts. For ease of ordering and a package price I went all Canton. I saw you liked their stuff but didn't realize you went with a different thermostat.

There's some different schools of thought on the thermostat temp. I'll post in a few minutes some more on that.

BTW my daughter just moved to Toowoomba.

... and nobody thought I would live long either. My big event came at age 23 and I have had many of the extra days since then as well. I made it long enough to go beyond flipping the air cleaner top upside down for more horsepower :icon_razz