Home » Public Forums » GMCnet » Low Oil Pressure (getting lower?)
| Low Oil Pressure [message #353543] |
Tue, 07 April 2020 12:44  |
Dreamweaver
Messages: 16
Registered: November 2018
Location: Tampa, FL
Karma:
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Junior Member |
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1975 Palm Beach 70K miles
I wasn't there when they started it after sitting a long time. I don't know what preparations they went through, if any. When I bought it the factory oil gauge read about 1/4. Having a '99 Tahoe that has always read low but has 250K miles, I didn't put much stock in the gauge. I should have. All I know is what I can garner from sparse old records. I think it could have sat for up to 20 years.
I drove it home from Chattanooga to Tampa. It has 70K miles which seems to be confirmed by wear on other parts which I won't go into. I think it had about 69K miles on it when it was first started. It was driven from South Carolina to Atlanta to Chattanooga and the engine held together. I drove it to Tampa and have put about 1,400 since picking it up so it has an estimated 2,000 - 2,500 miles since having been stored. These are my estimates, the best I can do. The gentleman that owned it passed away. I cannot get any further info other than what I guessed at here.
It starts and runs great. Good compression, 170# all around. Then during a visit to Alex Sirum for new batteries, etc. Jeff said I had low oil pressure, which brings me to this forum. I installed a new manual gauge. The Auto Meter gauge reads 43# on start up then when hot reads about 17#, then about 5# at idle. Based on what Larry wrote (below), the diagnosis is quite likely dry bearings when started causing scarring and dropping the oil pressure.
The following is a good write-up I found in the forum:
- Starting an engine that has been sitting for an extended period. [message #336250] Tue, 21 August 2018 17:18 Go to next message
Larry is currently offline Larry United States
Messages: 2385
Registered: January 2004
Location: Menomonie, WI
Karma: 15
Senior Member
The following is just my humble opinion. I offer this FYI. Your milage may vary.
Over the last 15 yrs I have seen a number of people get into GMCing buying a GMC that has been sitting for a number of years. In several of those cases, they were able to get the GMC started, put it in gear and drove it home. Sometimes they didn't make it when the engine went bad. Sometimes they made it home, but within a short number of miles the engine went bad. I have a theory about engines that go bad after sitting for an extended period of time.
Gravity is an idle engine's worst enemy. Over long periods of idle time, gravity will pull oil off of everything that needs lubricant, into the pan leaving bearing surfaces, cam lobes and cylinder walls dry. So, when a person pulls the air cleaner off and squirts a little gas or starter fluid down the carb, and the engine starts right away, it may run for...who knows how long before oil can get to those surfaces. No oil and there is immediate metal to metal contact and excessive wear that takes place during the first few minutes of operation. Then it is only a matter of a short time before you have cylinder wall scoring, cam lobe and lifter scoring and rod and main bearing scoring. The rod and main bearing being the most critical, because that can leave you on the side of the road within a couple of hundred miles.
May I suggest the following to reduce or eliminate the inevitable.
If the engine has not been running for extended periods, do the following.
Do not start or try to start or even turn the engine over without first doing this procedure.
Drain and replace oil in the oil pan and oil cooler.
Replace the oil filter, filling the oil filler with oil before spinning it on.
Refill with 5w30 or 5w40 of your choice. (the 5 weight will flow to bearing surfaces quicker)
Pull all spark plugs out and put a couple of squirts of the same oil into each cylinder.
Leave the plugs out for now.
Turn engine over by hand to line up timing marks with #1 cylinder at TDC compression.
Pull the distributor out making note of where the rotor is pointing with engine at TDC compression.
Pull both valve covers off.
Using a extender/adaptor where the distributor was, drive the oil pump with an electric drill until you can see oil coming out of the rocker arms....ALL OF THEM.
Now you have fresh oil to all bearing surfaces.
Using a squirt can, oil down the valve train on the heads and put the valve covers back on.
Turn the engine over with the starter, with the plugs out, only long enough, until you can see oil pressure at the gauge. As soon as the gauge needle starts to move, stop turning over.
Now you have oil on the cylinder walls. All that is left is oil to the cam lobes. To get oil to the cam, you must start the engine.
Turn engine over by hand and line up timing marks with #1 at TDC compression.
Drop the distributor in with rotor pointed as noted earlier.
Put plugs back in.
Put the cap back on and put plug wires to proper cylinder (1,8,4,3,6,5,7,2 accept for the Cadillac engine. Which is 1,5,6,3,4,2,7, 8.)
Prepare to start the engine.
Confirm that there is gas in the carb, and that there is spark, and you are at TDC compression.
Squirt a little fuel down the carb primaries, put the air cleaner back on incase of a backfire.
Turn the engine over to start and bring to 2000 RPM immediately.
Run at 2000 RPM for a minimum of 1 minute to lube the cam and lifters. At 2k RPM, the rods will be throwing lots of oil on the cylinders and camshaft.
There will be lots of smoke out the tail pipe from the oil you squirted into the cylinders earlier.
Set the timing to factory specs.
Now you can check all other things, like brakes, antifreeze, transmission fluid...etc...etc. and other essentials before you drive it home.
This procedure should significantly reduce the amount of start-up wear on long sitting engines, leading to normal engine life, taking you many trouble free miles. JMHO
Larry Smile
78 Royale w/500 Caddy
Menomonie, WI.
First, a tip of the hat to Larry!
Before I jump into the arduous task of dropping the engine out the bottom in my driveway, onto a dolly, into the garage and up to the engine stand via chain hoist, I'm searching for any clues to avoid an overhaul. I was given these two suggestions which I will work on before removal.
"Take the block off of the filter adapter (round part the hoses go to) and reinstall the filter. That eliminates the cooler completely"
and:
"Do check the small spring loaded relief valve in the oil filter mounting adapter (three bolts to block) , it is designed to allow the oil to flow if the filter is plugged"
If anyone can offer anything else, I would be grateful
Thanks
John Kent
Tampa, FL
1975 Palm Beach
[Updated on: Tue, 07 April 2020 12:47] Report message to a moderator |
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