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Old 03-11-2012, 11:58 AM   #1
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Default Ignorance Is Bliss - Oil Pressure Issues

If I didn't have a fancy oil pressure gauge, I would have no idea there were any concerns. I put together a motor this winter for my track car (if you are REALLY bored there is a build thread in my signature). The build was done on a tight budget but everything went together and is running fine except for my extremely high oil pressure.

The break in oil is still in - whatever 10-30 was on sale at O'Reiley's - and when cold I'm pegging the 90psi OEM gauge (real gauge from a 1990). Once the oil gets nice and hot, the pressure drops to around 60psi at idle but will go back to 90 when cruising gently ~3k rpm. Anything above that, and it will go back to the peg.

Reading searches for variations on 'High Oil Pressure' on the various forums all suggest a sticking pressure relief valve which certainly sounds likely. It occurs to me though that easily 100,000 miatas with 1.8 BP motors and fake/idiot gauge oil pressure senders will be started today and show 'proper' oil pressure. How many of them have a sticky relief valve and have no idea?

This is a dedicated track car and as such, it will spend most of its life at WOT above 5k rpm. If this valve is really stuck, I could be pushing 150+ psi through the system. If something were to blow on the track the best possible result would be a black flagged session with an oil slick. The most likely result would be that and catastrophic engine damage. The result I fear most is all of the above plus 4 quarts of oil hitting the outside rear wheel at 1.3g right after I pin the throttle hitting an apex causing me to take out myself and 2 other cars. Bent metal and injuries or worse.

I'm going to try a few simple things to troubleshoot my car before I go through the PITA of pulling the engine and putting in a new pump. First, I'm going to put a new filter on just for grins. Next, there will be a gentle tap with a hammer on the oil pump case while it is running. Don't get excited - I'm not suggesting winding up with a 10# sledge. Lastly, I have another OP sender that I will install just to make sure I get the same behavior.

This pump might be fine if I unstick the valve but considering my time is around 2 full days to R&R the motor and oil pump (working on jackstands in my 2 car garage by myself, pan and whole front comes off, etc…), I'm just going to put a new pump in to minimize the chances this will need to happen again.

One way or the other, I'm going to get the oil flowing properly through this engine before I take it to the track but I do wonder how may cars out there have this exact problem and never know it because they just have the idiot light gauge. Ignorance is bliss...
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Old 03-11-2012, 12:26 PM   #2
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My stock gauge says I'm over 70psi when above 3000rpm and it's said that for about 4-years.

Which gauge do you have and how do you know its accurate/calibrated?
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Old 03-11-2012, 12:39 PM   #3
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Tap in a real mechanical gauge where your sensor is and see what your true readings are before pulling it apart. Tape the gauge to your windshield or run it inside so you can watch it.
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Old 03-11-2012, 01:16 PM   #4
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Originally Posted by olderguy View Post
Tap in a real mechanical gauge where your sensor is and see what your true readings are before pulling it apart. Tape the gauge to your windshield or run it inside so you can watch it.
I've taped a telephone to the headlight motor mechanism and done video before, it works. I was bored and wanted to see how much the turbo glows, lol.
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Old 03-11-2012, 01:21 PM   #5
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The gauge is the OEM in the stock '90 cluster. The sending unit is from a '92 and I don't have any confidence it is calibrated correctly. Part of my process was going to be to put a different sending unit in. The gauge was working when I pulled the 1.6 earlier in the winter but this particular sender is a variable. I will try a mechanical gauge too although I hate dealing with the BPT/NPT thread crap. I'll need to look up which is which and then try to find an adapter.
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Old 03-11-2012, 01:38 PM   #6
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Originally Posted by mr_hyde View Post
The gauge is the OEM in the stock '90 cluster. The sending unit is from a '92 and I don't have any confidence it is calibrated correctly. Part of my process was going to be to put a different sending unit in. The gauge was working when I pulled the 1.6 earlier in the winter but this particular sender is a variable. I will try a mechanical gauge too although I hate dealing with the BPT/NPT thread crap. I'll need to look up which is which and then try to find an adapter.
VEI makes a cool gauge.
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Old 03-11-2012, 05:00 PM   #7
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take the sender out and hook it up to your air compressor.
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Old 03-11-2012, 09:05 PM   #8
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Here's something odd. I warmed up the engine and got the same results. I turned it off for a minute and then pulled the oil filter which was warm and full of oil. While I was reaching for the other filter, over half a quart of oil ran out the filter housing.

I normally lose a few tablespoons of oil out of the filter when I change the filter but not more than a single shop towel can collect. Here's my logic (and tell me if I'm wrong): When the relief valve is working, and the motor is turned off, it will pop into a position that will allow the oil that had just been pumped up into the block to drain back into the pan. In my situation, the pressure relief valve is also acting like a check valve.

Does someone have an oil pump around that can confirm how everything flows?

No, I haven't tried a different sender or mechanical gauge yet. I'm trying the simplest and least invasive things first. This little oil spill is leading me to be even more certain that this pump has to come out. Thoughts?
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Old 03-12-2012, 01:24 AM   #9
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I just borrowed a spare/used oil pump to see how this works. I think I'm going to just pull the pump and put in a new one... Crap...
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Old 03-12-2012, 07:52 AM   #10
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Your experience with the oil filter makes me wonder if you don't have blocked oil passages, which would be really bad. Not saying that you do, but if you can get hold of an oil flow diagram and see if that makes sense . . . . Would hate for you to pull the engine and replace your pump only to find that the oil pressure is still sky-high and something critical is being starved for oil.
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Old 03-12-2012, 01:56 PM   #11
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I've thought about that too. The most logical place for that to happen would be the head gasket but I can't think of an orientation to put the gasket on that would block an oil passage yet still allow me to insert all the head bolts with no interference AND allow the cooling system to function normally as it has through several heat cycles.

I may be chasing a ghost with the 'oil gushing out from a removed filter' observation. I never change the oil on a hot engine so my experience about there being so much more oil than normal isn't valid. New OEM pump ordered - thanks MMD!
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Old 03-12-2012, 03:38 PM   #12
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Different OEM sender behaves identically. Finding a BPT adapter locally wasn't possible so out comes the engine. Start the timer - 11:45 local time. How long to have it out with the engine upside down on a stand?
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Old 03-13-2012, 02:08 AM   #13
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This pump is a mystery. I'm just going to move on to a new OEM pump and cross my finger something else isn't wrong. As far as the time, I had the motor out hours ago, pulled the tranny, clutch/flywheel so I could mount it on the engine stand, pulled the front off... blah, blah, blah. I'll chime back in the thread when the motor is reassembled and running. Hopefully, by the end of the weekend - parts on order.
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Old 06-10-2012, 03:01 PM   #14
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Sorry to bump this, but im curious if you resolved your problem.
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Old 06-10-2012, 03:48 PM   #15
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I don't really want to talk about it because I am a freaking moron but since you asked...

I tried two different OEM senders and the OEM wiring plus a direct overland wire with the same results. I did NOT try a different OEM gauge. After installing the new pump, I had the same pressure readings. Only then did I go through the trouble of a mechanical gauge which confirmed perfectly normal oil pressure. I have a bad OEM gauge (or two identically bad senders).

It may not have been a total waste of time though since the pump I took out had a few curious wear marks on the gears that I'm pretty sure weren't there when I measured tolerances. Being stupid might have saved the engine and most days I'd rather be lucky than good...
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Old 06-10-2012, 03:52 PM   #16
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Quote:
Originally Posted by olderguy View Post
Tap in a real mechanical gauge where your sensor is and see what your true readings are before pulling it apart. Tape the gauge to your windshield or run it inside so you can watch it.
...and yes, you are welcome to say 'I told you so...'

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