Low Oil Pressure
Thread Starter
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Strokin Okie
Joined: Apr 2004
Posts: 1,883
Likes: 21
From: Oklahoma
Low Oil Pressure
I just recently built a stock 352 into a 390 standard bore, .020 on mains and rods. Rods were resized and mains were line bored. I have under a 1k miles on the rebuild when I noticed my oil light flashing when at stop. Once I accelerate it goes off. It didn’t concern me too much because my oil pressure at first start up after rebuild was between 50&60 PSI. After checking with my test gauge when hot it was about 10 PSI.
I then ordered an Autogauge Oil Pressure/Voltage/Coolant Temp set. At cold start it jumps to 60 PSI. The more you drive and heat it up it drops to 25-30 at highway speeds. When stopped at idle, it drops to 2-5 PSI.
When I primed the engine both oil rails were oiling, one a little more than the other but nothing too concerning. Does this sound pump related since it has good pressure when cold but poor at operating temps? Coolant temps are running 180-185.
Thanks in advance.
I then ordered an Autogauge Oil Pressure/Voltage/Coolant Temp set. At cold start it jumps to 60 PSI. The more you drive and heat it up it drops to 25-30 at highway speeds. When stopped at idle, it drops to 2-5 PSI.
When I primed the engine both oil rails were oiling, one a little more than the other but nothing too concerning. Does this sound pump related since it has good pressure when cold but poor at operating temps? Coolant temps are running 180-185.
Thanks in advance.
Fleet Mechanic
Joined: Jun 2009
Posts: 1,312
Likes: 327
From: San Antonio, TX
When stating what your PSI is, I'd focus on 2 things - rpm and whether the engine is warmed up or cold. Stating that it was 60 psi after a rebuild needs to be qualified with what rpm that was at. On a related note, the general rule of thumb is 10 psi per 1,000 rpm.
Having said that, I would expect more than 2 psi at idle from a freshly built engine, but it sounds like you're using an electric gauge. I'd check with a mechanical gauge before I got too furballed up about this.
Having said that, I would expect more than 2 psi at idle from a freshly built engine, but it sounds like you're using an electric gauge. I'd check with a mechanical gauge before I got too furballed up about this.
Thread Starter
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Strokin Okie
Joined: Apr 2004
Posts: 1,883
Likes: 21
From: Oklahoma
When stating what your PSI is, I'd focus on 2 things - rpm and whether the engine is warmed up or cold. Stating that it was 60 psi after a rebuild needs to be qualified with what rpm that was at. On a related note, the general rule of thumb is 10 psi per 1,000 rpm.
Having said that, I would expect more than 2 psi at idle from a freshly built engine, but it sounds like you're using an electric gauge. I'd check with a mechanical gauge before I got too furballed up about this.
Having said that, I would expect more than 2 psi at idle from a freshly built engine, but it sounds like you're using an electric gauge. I'd check with a mechanical gauge before I got too furballed up about this.
Hope that helps.
Fleet Mechanic
Joined: Jun 2009
Posts: 1,312
Likes: 327
From: San Antonio, TX
So, I don’t have a tach installed but by ear I’d say it idles between 800-1000 rpm. Maybe a little lower while in gear. When I say 60 PSI, it’s been at idle and cold. My test gauge (Harbor Freight) and the new AutoMeter gauges I installed last night are both mechanical gauges. I bought the copper tubing kit for the oil pressure gauge.
Hope that helps.
Hope that helps.
Did you install a new oil pump? If so, I'm assuming it was just a standard pump, not high pressure or high volume.
What weight oil are you running?
Did you assemble the short block? If so, do you recall the clearance on the rod bearings and main bearings?
Thread Starter
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Strokin Okie
Joined: Apr 2004
Posts: 1,883
Likes: 21
From: Oklahoma
If you have two mechanical gauges reading the same, I'd say that's a legit reading. If it was a well-used engine, I'd say run it and you should be fine, but since it's a fresh engine, I'd be a little concerned, too.
Did you install a new oil pump? If so, I'm assuming it was just a standard pump, not high pressure or high volume.
I did, Melling standard pump.
What weight oil are you running?
I believe the initial oil was Castrol 10w40 with a break in additive. I changed the oil on Saturday with Castrol 10w30.
Did you assemble the short block? If so, do you recall the clearance on the rod bearings and main bearings?
I did, and did check the clearances and they were right on where they were supposed to be (based on the book) I don’t have it in front of me. I used calipers and mics not plastigage. Going off of memory .002 rings a bell. Sorry this was back in July when I actually built the lower end.
Did you install a new oil pump? If so, I'm assuming it was just a standard pump, not high pressure or high volume.
I did, Melling standard pump.
What weight oil are you running?
I believe the initial oil was Castrol 10w40 with a break in additive. I changed the oil on Saturday with Castrol 10w30.
Did you assemble the short block? If so, do you recall the clearance on the rod bearings and main bearings?
I did, and did check the clearances and they were right on where they were supposed to be (based on the book) I don’t have it in front of me. I used calipers and mics not plastigage. Going off of memory .002 rings a bell. Sorry this was back in July when I actually built the lower end.
If you have two mechanical gauges reading the same, I'd say that's a legit reading. If it was a well-used engine, I'd say run it and you should be fine, but since it's a fresh engine, I'd be a little concerned, too.
Did you install a new oil pump? If so, I'm assuming it was just a standard pump, not high pressure or high volume.
I did, Melling standard pump.
What weight oil are you running?
I believe the initial oil was Castrol 10w40 with a break in additive. I changed the oil on Saturday with Castrol 10w30.
Did you assemble the short block? If so, do you recall the clearance on the rod bearings and main bearings?
I did, and did check the clearances and they were right on where they were supposed to be (based on the book) I don’t have it in front of me. I used calipers and mics not plastigage. Going off of memory .002 rings a bell. Sorry this was back in July when I actually built the lower end.
Fleet Mechanic
Joined: Jun 2009
Posts: 1,312
Likes: 327
From: San Antonio, TX
Ok, was the oil pressure initially higher and then it dropped or has it been consistently like this?
If it's dropped, did it drop after you went to thinner oil? If so, I'd go back to 10w40.
Are you getting lifter noise at hot idle? You should be hearing some clatter if it's below 5 psi.
Another possibility is that after 1,000 miles, the oil had gotten diluted by fuel and that's thinned it out and lowered the pressure.
A spun bearing would cause low pressure, too, but you'd likely hear something. However, if you still have your old oil filter, I'd cut it open to look for metal.
Other possibility is a galley plug that's backed out, but then you'd have very little pressure at highway speeds, too.
.002" should be right on the money on bearing clearances.
Here's a recent thread on the FE forum about low oil pressure - some pretty sharp folks chiming in -- https://www.fordfe.com/low-oil-pressure-t166930.html
If it's dropped, did it drop after you went to thinner oil? If so, I'd go back to 10w40.
Are you getting lifter noise at hot idle? You should be hearing some clatter if it's below 5 psi.
Another possibility is that after 1,000 miles, the oil had gotten diluted by fuel and that's thinned it out and lowered the pressure.
A spun bearing would cause low pressure, too, but you'd likely hear something. However, if you still have your old oil filter, I'd cut it open to look for metal.
Other possibility is a galley plug that's backed out, but then you'd have very little pressure at highway speeds, too.
.002" should be right on the money on bearing clearances.
Here's a recent thread on the FE forum about low oil pressure - some pretty sharp folks chiming in -- https://www.fordfe.com/low-oil-pressure-t166930.html
Thread Starter
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Strokin Okie
Joined: Apr 2004
Posts: 1,883
Likes: 21
From: Oklahoma
Ok, was the oil pressure initially higher and then it dropped or has it been consistently like this?
If it's dropped, did it drop after you went to thinner oil? If so, I'd go back to 10w40.
Are you getting lifter noise at hot idle? You should be hearing some clatter if it's below 5 psi.
Another possibility is that after 1,000 miles, the oil had gotten diluted by fuel and that's thinned it out and lowered the pressure.
A spun bearing would cause low pressure, too, but you'd likely hear something. However, if you still have your old oil filter, I'd cut it open to look for metal.
Other possibility is a galley plug that's backed out, but then you'd have very little pressure at highway speeds, too.
.002" should be right on the money on bearing clearances.
Here's a recent thread on the FE forum about low oil pressure - some pretty sharp folks chiming in -- https://www.fordfe.com/low-oil-pressure-t166930.html
If it's dropped, did it drop after you went to thinner oil? If so, I'd go back to 10w40.
Are you getting lifter noise at hot idle? You should be hearing some clatter if it's below 5 psi.
Another possibility is that after 1,000 miles, the oil had gotten diluted by fuel and that's thinned it out and lowered the pressure.
A spun bearing would cause low pressure, too, but you'd likely hear something. However, if you still have your old oil filter, I'd cut it open to look for metal.
Other possibility is a galley plug that's backed out, but then you'd have very little pressure at highway speeds, too.
.002" should be right on the money on bearing clearances.
Here's a recent thread on the FE forum about low oil pressure - some pretty sharp folks chiming in -- https://www.fordfe.com/low-oil-pressure-t166930.html
I am not hearing any noise altering hot idle. She sounds happy all the time. I am going to bleed the oil pressure tube to the gauge to see if that changes anything and put another quart of oil in it. Also, when I changed my oil, it didn’t smell like gas so I’m assuming that’s not the issue.
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Fleet Mechanic
Joined: Jun 2009
Posts: 1,312
Likes: 327
From: San Antonio, TX
Thanks for chiming in and sharing that thread.
I am not hearing any noise altering hot idle. She sounds happy all the time. I am going to bleed the oil pressure tube to the gauge to see if that changes anything and put another quart of oil in it. Also, when I changed my oil, it didn’t smell like gas so I’m assuming that’s not the issue.
I am not hearing any noise altering hot idle. She sounds happy all the time. I am going to bleed the oil pressure tube to the gauge to see if that changes anything and put another quart of oil in it. Also, when I changed my oil, it didn’t smell like gas so I’m assuming that’s not the issue.
Let us know what you find out. Curious to hear exactly what the issue is.
Scott
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Logistics Pro
Joined: Feb 2011
Posts: 3,522
Likes: 11
From: Townsend, MT
Did you reuse the old rocker assemblies? Worn rockers will bleed off a lot of oil pressure...
Did you put new cam bearings in? If so, did they have to ream the bearings to get the cam to fit? FEs can suffer from poor cam bore machining that will also bleed off a lot of oil pressure...
Did you put new cam bearings in? If so, did they have to ream the bearings to get the cam to fit? FEs can suffer from poor cam bore machining that will also bleed off a lot of oil pressure...
Thread Starter
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Strokin Okie
Joined: Apr 2004
Posts: 1,883
Likes: 21
From: Oklahoma
Did you reuse the old rocker assemblies? Worn rockers will bleed off a lot of oil pressure...
Did you put new cam bearings in? If so, did they have to ream the bearings to get the cam to fit? FEs can suffer from poor cam bore machining that will also bleed off a lot of oil pressure...
Did you put new cam bearings in? If so, did they have to ream the bearings to get the cam to fit? FEs can suffer from poor cam bore machining that will also bleed off a lot of oil pressure...
Yes I reused the rocker assembly. I have a known good set to try out.
Yes on the new cam bearing. They didn’t mention renaming the bearings tho.
Thread Starter
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Strokin Okie
Joined: Apr 2004
Posts: 1,883
Likes: 21
From: Oklahoma
I did that about a week ago and there was no metal or anything sparkling in the oil. Looked normal.
Cargo Master
Joined: Oct 2020
Posts: 2,681
Likes: 787
To be that low it sort of sounds like a galley plug was left out of the engine somewhere. FE blocks have 3 galleys and 2 plugs at the front with one in there back behind the distributor, one on the main galley and one more that's plugged with the thrust plate bolt could one of those have been left out?
Cross-Country
Joined: May 2006
Posts: 75
Likes: 15
An important question was asked earlier but I do not believe you answered it.
Was the pressure Ok when you first rebuilt the engine?
If not, this is an indication you may have an internal leak.
I once did not tighten the pump bolts fully and had a similar problem. Was there a gasket on the pump pick up tube?
Was the pressure Ok when you first rebuilt the engine?
If not, this is an indication you may have an internal leak.
I once did not tighten the pump bolts fully and had a similar problem. Was there a gasket on the pump pick up tube?
Thread Starter
|
Strokin Okie
Joined: Apr 2004
Posts: 1,883
Likes: 21
From: Oklahoma
An important question was asked earlier but I do not believe you answered it.
Was the pressure Ok when you first rebuilt the engine?
If not, this is an indication you may have an internal leak.
I once did not tighten the pump bolts fully and had a similar problem. Was there a gasket on the pump pick up tube?
Was the pressure Ok when you first rebuilt the engine?
If not, this is an indication you may have an internal leak.
I once did not tighten the pump bolts fully and had a similar problem. Was there a gasket on the pump pick up tube?
It was good using my test pressure gauge, but I did t leave it hooked up at until it was up to temp. I really didn’t that was necessary (obviously think differently now). So the answer is, I can say the pressure never dropped low enough to make the light flash until the last drive I was on.
I looked back at the pictures and the pump and screen both had gaskets and looked tight for what it is worth. I have a few projects I need to finish before I can pull it back out and inspect it. I hope it is something simple.