Low Oil Pressure at Idle

[4G63510]

I've been seeing low oil pressure at idle for some time now. By low, I mean Zero at times when warm at idle. I've had sparkles, but no flakes in my oil for about 2 years, but I haven't really had any issues. Thinking I may have a worn oil pump, I swapped that out this spring when I did a new RWD oil pan and some other odds and ends. There was no change. I did check one rod bearing when I did this and I didn't see any issues. I also thought it may be a bad sensor, as I'm running an electronic oil pressure gauge, but it doesn't feel like that is the case.

Yesterday I took the car out for a short drive prepping for the Shootout and after seeing that Zero on the gauge again, it dawned on my that it may be bad oil squirters. This is a 95 block, and if I recall, it is rumored (or perhaps confirmed) that they can stick open and bleed oil pressure. This would confirm my low oil pressure in all scenarios. I used to have 80-100psi on start up and over 20psi at idle. Now it's more like 60psi cold and, as I stated, zero at idle. This was even after switching to 20w-50 Valvoline VR1.

I can investigate this, but the real question is, how to go about it? Replacing the squirters is a "crank out" procedure. Which essentially means everything is coming out except the head. I do have a spare 95 block with stock internals as well. So, do I do the bearing with the head on, or do I swap blocks all together? I assume this means I need to re-deck the head for an MLS headgasket, and along with new piston rings, that would be the only additional cost in using the spare block. It seems like it would be easier to do this work on the spare block, but is it worth it?

I'm really hoping someone can chime in soon to help me make a decision. I have the time, money, and ability to get this done before the Shootout, but a fresh install is always a crap shoot. I don't want to rush this, but I REALLY would like to make it to my first Shootout.

 

[Car Cannibal]

Just to give you some real world info...
On my 1g after an oil pump swap on an engine with 80k it increased the pressure at hot idle a good 6psi. The pump gears were shot, you could wiggle it while it was on the car.

I've also noticed some gauges get crappy at the low readings after many years, I don't get it but I've had this with the digital Cobalt Autometer gauges for sure.

 

[4G63510]

Just to give you some real world info...
On my 1g after an oil pump swap on an engine with 80k it increased the pressure at hot idle a good 6psi. The pump gears were shot, you could wiggle it while it was on the car.

I've also noticed some gauges get crappy at the low readings after many years, I don't get it but I've had this with the digital Cobalt Autometer gauges for sure.

Thanks for the feedback. My old oil pump seemed fine, but it was worth a shot while I was in there. The new pump didn't do anything positive.

My pressure gauge is from Speedhut. I've seen some issues with their older stuff, but I'm not getting the issue others have complained about. I might order a new sending unit any way "while I'm in there".

Right now I'm pulling the motor because it has to come out no matter what. I'm inspecting my spare block for viability and to see how it all works without all the other bits in the way.

If anyone has info on the squirters or other areas I might look at before I tear into this, please let me know.

 

[4G63510]

Looks like this just turned into a longer term documentation of how to fix this. After working on my spare block, I came to the conclusion that the head must be off and pistons removed to do this. I'm not sure what I was thinking before that made me believe it was anything less.

On the plus side, they're pretty easy to remove and shouldn't be difficult to install. But a note to anyone assembling a 2G with these squirters; just replace them when you put your engine together. They're relatively cheap and there's no sense in doing this later if/when they fail.

 

[4G63510]

Update. You can most definitely remove the 2G oil squirters without removing the head. Careful work with a slide hammer on the top of the squirters can drive them out. Be very cautious of the bearing surfaces, as the slide hammer can jump around and bang into things.

All that being said, my oil issues persist. Here is a rundown of all of the things I have replaced or adjusted to resolve this.

1. Front case/ oil pump
2. Oil pan and pickup- running a RWD Mighty Max pan and pickup
3. Oil squirters- new 2G units
4. Oil- running Valvoline VR1 20W50 currently
5. Oil pressure sensor location- I can't find definitive information on the EVO3 unit
6. Balance shaft removal- I had a Mitsu stubby shaft and I'm now running a Kelford shaft
7. Main and rod bearings- ACL race bearings

Things I have not replaced or made adjustments to:

1. Oil filter housing- I'm using an EVO3 unit that has been ported to reduce top end pressure issues
2. Oil pressure sensor- Speedhut electronic pressure guage and sensor

That's all I can think of. I'm out of ideas here. I didn't have oil pressure issues when I first put the engine together. It seems to have "deteriorated" over time. The only instance where I am worried about the low pressure is when it is warm and at idle. I see less than 10psi and as little as zero at idle. Cruising at 2k-3k RPM, I see 50-60psi which is normal to me. I tried a manual oil pressure gauge and still saw zero at idle at times, so I'm not confident that the electric gauge or sensor is bad. I'm open to any ideas or places to look. I'm going to swap out the oil pressure sensor soon to see if that is just giving false readings. Failing that, I will try a stock OFH.

 

[1990TSIAWDTALON]

Have/did you check rod and main bearing clearances when you changed bearings?

 

[4G63510]

Have/did you check rod and main bearing clearances when you changed bearings?

Honestly I didn't bother since they old bearings were good (with some grovving from junk). I guess if they are too lose they could cause low oil pressure. I can't imagine they would ever be that far out to still have zero pressure with 20W50. If I decide to pull the pan again, I'll measure them.

Good suggestion though. What measurement would cause the pressure to be that low?

 

[1990TSIAWDTALON]

More than .003" on any of them. I keep my mains at .002" and rods no more than .003". If you have .005" or more, it's going to lose pressure by it escaping out the sides of the bearings. Just asking if you checked and what the clearances were if you did.

 

[donniekak]

More than .003" on any of them. I keep my mains at .002" and rods no more than .003". If you have .005" or more, it's going to lose pressure by it escaping out the sides of the bearings. Just asking if you checked and what the clearances were if you did.

We ran some really big clearances in stock block casting big power builds. There is a hard drop after .0045” clearance in pressure even with all squirters and balance shafts deleted. In those engines dominator straight 60 had to be used as well.

As for the op’s issue I seem kind of stumped too. I’d go back and visually check the squirters and balance shaft bearings and main bearing clearance at least.

Lots of times the first parts to start wearing in an engine are the center mains.

 

[1990TSIAWDTALON]

Thanks for that information Donnie. Means A LOT to me. Hopefully helpful to our OP also!

 

[We're on Boost]

We ran some really big clearances in stock block casting big power builds.

Kiggly says in his "oil pumps" pdf:
Wide bearing clearances (0.0035") need to be run to keep bearings alive at high power levels. He said he used Pennzoil GT Racing 25w50 and a variety of 20w50 oils. He did not use lighter weigh oils due to the large bearing clearances.

Kiggly is talking about some really high power and high rpm engines though. I would think if you are in the 350 - 500 whp range you would want your clearances to be about like what Marty suggested.

In his "oil filter losses" pdf he shows oil pressures up to 112 psi or so, as measured before the filter (which is the usual place our sensors go). He also shows oil pressure after the filter so you can see that the difference (drop across the filter) can be as much as 20 psi. Which was really the point of that particular paper.

Those papers are on his Kiggly Racing web site in the Tech Data section:

Tech Data | Kiggly Racing | United States

This section exists to help give back to the community by explaining some of the technical challenges we've faced along with their solutions.

www.kigglyracing.com

 

[DSMPT]

Just one of possibilities but if the pressure is fine most of time and it happens only after the engine gets hot, perhaps you have the oil temp too high for some reason. Did you check what oil temp it has when the low pressure issue is occurring?

 

[1990TSIAWDTALON]

Another nice observation and question Hiroshi. Good for the thread. We all want to try to figure this out.

 

[donniekak]

Kiggly says in his "oil pumps" pdf:
Wide bearing clearances (0.0035") need to be run to keep bearings alive at high power levels. He said he used Pennzoil GT Racing 25w50 and a variety of 20w50 oils. He did not use lighter weigh oils due to the large bearing clearances.

Kiggly is talking about some really high power and high rpm engines though. I would think if you are in the 350 - 500 whp range you would want your clearances to be about like what Marty suggested.

In his "oil filter losses" pdf he shows oil pressures up to 112 psi or so, as measured before the filter (which is the usual place our sensors go). He also shows oil pressure after the filter so you can see that the difference (drop across the filter) can be as much as 20 psi. Which was really the point of that particular paper.

Those papers are on his Kiggly Racing web site in the Tech Data section:

Tech Data | Kiggly Racing | United States

This section exists to help give back to the community by explaining some of the technical challenges we've faced along with their solutions.

www.kigglyracing.com

We usually shoot for .0035” in the high powered stuff but went as big as .0045” in a 6bolt 4g63 block that trapped 180 mph in a 3000gt.

The issue was the block and crank flexing and making contact at the main bearing. A little more room and the parts stopped wearing.


The amount of high quality data kiggly released to the community is invaluable. It keeps everyone from having to start at zero.

 

[We're on Boost]

We usually shoot for .0035” in the high powered stuff but went as big as .0045” in a 6bolt 4g63 block that trapped 180 mph in a 3000gt.

The issue was the block and crank flexing and making contact at the main bearing. A little more room and the parts stopped wearing.


The amount of high quality data kiggly released to the community is invaluable. It keeps everyone from having to start at zero.

Thanks for that post, that is some really interesting info.
When you had an engine with the clearances set to .0035 inches, what kind of oil pressure would you have after full warm up at 5,000 to 7,000 rpm or so? Assuming straight 60 oil I guess?

 

[blktalon3]

Interested in this. Just got mine back together. 6 bolt non turbo block, so no squirters and no balance shafts. .0030 on the mains and .025 on the rods. Newish stock straight cut gear pump. I’m still running conventional oil but 20w-50 and the oil port teardrop mod is done on the head he. I started out checking the pressure and feeding from the head(with no restrictor). Oil pressure dropped very low when it got warmed up, like 1-2 psi @ 950rpm. I read on here that feeding from the head with no restrictor will drop the pressure in the head( the stock turbos are restricted)because it basically opens up a big drain in the head. Sooo I moved the turbo oil feed and the gauge tap to the ofh. Oil pressure of course jumped up but still seemed low when hot. I was getting around 11psi @950 when hot. I also read the ffofh read low because the oil tap is post filter(I’m not sure how much of a pressure drop there is across the filter). So taking all that into consideration I think I’m ok.

 

[4G63510]

Just one of possibilities but if the pressure is fine most of time and it happens only after the engine gets hot, perhaps you have the oil temp too high for some reason. Did you check what oil temp it has when the low pressure issue is occurring?

Lots of great info from everyone! I'll check out that Kiggly article.

As far as oil temps, I do have an oil temperature gauge. I put it inline with my oil cooler since I couldn't find any good info on the EVO3 housing. I understand the best location is in the pan, but I didn't want to put a hole in the pan just for this. With it in the oil cooler line, it should read straight from the pan with oil flow. I have never seen oil temps over 200*, but I have had a suspicion that the cooler may be lowering the oil pressure. I can't imagine it drops it 10psi+, but I have considered looping the cooler lines to see what affect this has.

Barring that, I will swap the OFH just so I don't have to pull the oil pan yet. If that doesn't resolve it or give me other readings, then I will pull the pan to check bearing clearances. I can't imagine they are beyond stock, but I'm chasing my tail here. Thanks for all of the great replies. Keep it coming if anyone has other good info.

 

[danl]

You really are running out of things to check. Did you verify your bse block off is correctly done? Is the oil pressure relief spring in good condition? How much oil is your turbo feed flowing? Other than that, you need to check the mains which I understand is a lot of work.

 

[4G63510]

You really are running out of things to check. Did you verify your bse block off is correctly done? Is the oil pressure relief spring in good condition? How much oil is your turbo feed flowing? Other than that, you need to check the mains which I understand is a lot of work.

The BSE has been on the car since it was "new". I did a basic rebuild before putting it in the car. It now has about 23k miles. The low oil pressure showed up about 2 years ago.

Yes, the turbo oil feed. I was going to check that too. Obviously it's difficult checking on a hot engine, but I think the 5 seconds it will take to check will be more than worth it and give plenty of insight into what the true oil pressure is from the OFH.

 

[donniekak]

You really are running out of things to check. Did you verify your bse block off is correctly done? Is the oil pressure relief spring in good condition? How much oil is your turbo feed flowing? Other than that, you need to check the mains which I understand is a lot of work.

I forgot all about the pressure relief. It’s very easy for the piston to stick in the bore. It may be closing, but not all the way.

 

[donniekak]

Thanks for that post, that is some really interesting info.
When you had an engine with the clearances set to .0035 inches, what kind of oil pressure would you have after full warm up at 5,000 to 7,000 rpm or so? Assuming straight 60 oil I guess?

The .0035” engines are fine with 20w-50. They’ll peg a 100psi gauge at 7,000+.

 

[danl]

I forgot all about the pressure relief. It’s very easy for the piston to stick in the bore. It may be closing, but not all the way.

Yup. A piece of debris like casting flash or carbon can also lodge in there, interfering with how it closes. It would also explain why he still sees normal oil pressure at moderate rpm’s.

 

[92AWDHX40]

Yeah it doesn't seem too consistent just random.

 

[4G63510]

I forgot all about the pressure relief. It’s very easy for the piston to stick in the bore. It may be closing, but not all the way.

I wasn't aware this was an issue. It seems to only affect warm idle pressure. Does the thermostat have anything to do with this? I'll have to dig around to see what info I can find on the relief valve unless someone has good info handy.

 

[We're on Boost]

The .0035” engines are fine with 20w-50. They’ll peg a 100psi gauge at 7,000+.

Ok Thanks!