# Low Oil Pressure Light - Next Steps?



## GFT 12:17 (Jul 26, 2014)

I have a 66 GTO with a 73 400 CI motor. Last week I noticed my oil pressure light was coming on periodically. As a result, I changed my oil (10W-30), new filter and new oil pressure switch. Filled with 5 quarts of oil and level is correct. Now my oil pressure switch comes on at idle once the motor has warmed up. Today I took my car to a shop that hooked it up to a mechanical gauge and confirmed it was running at 8 psi at idle and about 45 psi at 2,500 rpms. The guy at the shop recommended going to 20W-50 oil and see what happens, maybe the heavier oil will raise the psi a few lbs? Another switch? Filter? My motor isn't making any noises, leaks a little oil, but nothing major. Not interested in pulling the motor and rebuilding if I don't have to. Any thoughts on next steps. Thanks.

Tim


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## Red1970GTO (Jun 25, 2011)

*Troubleshooting*

 Read this: Troubleshoot Low Oil Pressure


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## PontiacJim (Dec 29, 2012)

Looking at a Chilton Repair manual, for 1973, the 400 rated oil pressure is 55-60 PSI above 2,600 RPM's. Now for 1972, the oil pressure rating for all engines was 35 PSI @ 2000 RPM's.

What is your idle speed set at? If it is too low, oil pressure will be lower. Your engine's idle speed for all 1973 engines is 650 RPM in gear for automatics; 900 RPM for stick/with electric solenoid activated, 600 RPM setting with solenoid disconnected. As I recall, the oil light comes on at 7 PSI. You might want to bump it up 100 RPM and see if that brings up you idle pressure, but also be aware of how much brake pressure you need to keep your car stopped -if an automatic. If it is too much, you'll add more wear to your brakes trying to over come the higher idle speed.

Personal opinion here - I think the new formula oils seem to be "thinner" to me compared to the older oil formulas. Your engine needs a zinc supplement if you are using the "newer" oils. I have just started to use Rislone Engine oil Supplement with Zinc Treatment in my '92 S-10 as it needs the zinc. Can't make any comments on it because I have just recently put it in and don't drive the truck much, but I don't think it will hurt.

It is also* my opinion* that if your car needs the older oil formula with zinc and you use the newer oils, that it will prematurely lead to wear of the engine/bearings. I have a '97 Toyota that had over 175,000 miles on it and was getting 2,000 miles to a quart -changed every 3,000 miles. The "new" oils came out minus the needed zinc, and I watched my oil mileage literally drop after each oil change and could not explain it. At that time, I had no idea that the formula had been changed and zinc removed. I did notice the oil looked thinner. Finally figured out about the zinc additive from these forums. Now have 244,000 miles on my Toyota and get 800 miles to a quart.

Heavier oil, 10w-40 may help raise your oil pressure a little, but this may only be a band-aide. If your bearings are worn, then the only true fix is to replace them.


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## GFT 12:17 (Jul 26, 2014)

Thank you for the responses. I have a 4 spd. and it idles at about 900 rpms.


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## PontiacJim (Dec 29, 2012)

GFT 12:17 said:


> Thank you for the responses. I have a 4 spd. and it idles at about 900 rpms.


OK, thanks. Now on a 4-speed car, I have read that another culprit for lowered oil pressure is a worn thrust bearing. A manual transmission is much harder on the thrust bearing than an automatic because as you push in the clutch, you are applying pressure to the thrust surface -which means a higher wear rate.

If your idle is 900 and you are having the low oil pressure, and you have done all your preventive measures, then I would think it is time for bearings *OR*, a new oil pump. The oil pump could be on its way out as well. 

In either case, engine removal will be needed to check. It is possible your bearings are OK, but your oil pump is on its way out, but again, you won't know this until you can inspect them. Replacing a bad oil pump when all else is good will save the engine and you can keep on going if your bearings look good -unless you are ready for a rebuild/refresh on the engine.


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## GFT 12:17 (Jul 26, 2014)

Curious, if it is just my oil pump, what could I expect to pay to have my motor pulled and reinstalled. Are there any symptoms I should be looking for to determine if bearings need to be replaced?


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## PontiacJim (Dec 29, 2012)

GFT 12:17 said:


> Curious, if it is just my oil pump, what could I expect to pay to have my motor pulled and reinstalled. Are there any symptoms I should be looking for to determine if bearings need to be replaced?


How many miles on the engine? Does it burn oil between oil changes? If you go through all the trouble to pull the engine, might it be advisable to simply rebuild it at this time?

To get your engine pulled and reinstalled could be any price, $500-$800?. This is where you would have to call around. Not a small job. If you can't do this yourself, then you will have to have a qualified shop do this and they would also be the ones changing the oil pump and inspecting the bearings. You may want to check out your local machine shop and tell them your concerns and then see if they can recommend someone to pull the engine, deliver it to the shop, and let them inspect it. Some shops do pull engines, but they usually know someone who can pull engines.

Found this thread about the oil pump relief valve. This is what happened to my 400CI that lost its oil pressure and has been covered here on our forums. Still means the engine has to be pulled to replace. http://forums.hotrod.com/high-perfo...ain-upgrade/400-with-no-oil-pressure-at-idle/

If the bearings are worn, (which might be seen visually or crudely checked with plastigage by a home mechanic- but a machine shop is going to use micrometers) you will have to replace them, now you are looking at additional work. I don't know if many shops will replace bearings without wanting to pull the crank to check it or turn it. So if you have to do this, then you might want to consider a rebuild and its cost so you are aware of what it could be should your engine need to go this route.

That said, there really is no good answer as to what you can do and whether or not the results will be good or bad -because you will not know until you are able to view/check things. You could leave well enough alone, add heavier oil/STP to see if the oil pressure comes up a bit, and drive it until you lose oil pressure altogether. I did this with my last engine knowing I had an oil pressure problem and was going to have to pull it and rebuild it. The oil pressure slowly got worse, finally lost oil pressure and that was it. Bearings were wiped out and the crank scored up. Luckily the oil pressure died in my yard and not on the road where I would have incurred a towing bill. Another 350CI engine I had lost oil pressure-red light came on and stayed on. I caught it quick. I could not afford to rebuild it at the time and knew I was going to replace the engine anyway as it was worn & tired, so took *a chance* and simply replaced the oil pump and never inspected the bearings. Oil pressure was good and I just kept on driving it for some time with no problems until I installed the 400CI.

I don't think there is any definite answer for you that doesn't include "risk" short of making the call to rebuild the engine. With that in mind, I would then get it to the machine shop and see IF it would be possible to just put in an oil pump and go with it. If he suggests you need bearings, etc., then you will not be shocked to know you will have to rebuild. In this case, assume the $worst and hope for the best.:thumbsup:


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## geeteeohguy (Feb 2, 2008)

What Jim said. My gut tells me that you simply have an engine with bigger bearing clearances due to wear. I'd run a thicker oil for now, and save your money for a new engine. There are some reputable guys online that sell plug-and-play 400's and 455's for under $4k. Ready to go. Since you are running a non original block anyway, that would be the easiest way to go. Or, you could find a period correct 389 and go that route. You may get several more years out of your current engine with thicker oil. With the value of your car, though, it warrants a nice engine! Keep us updated....


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## Goat Roper (Oct 28, 2014)

I am having the same issues 55 lbs cold @ idle and drops to 8 when warmed up.
Engine isn't knocking and no valve rattle.
The top end was redone but the guy I bought it from knew nothing about what was done only that it was "fixed".
It is the original engine, parts matching car and it runs strong I just don't want to puke the bottom end and destroy the block.
I can't find a reputable engine builder out here in So Cal and researching the group I found this place recommended by Bear.

Central Virginia Machine Service - Home of the ***** Engine!

The engine is a stock 400 335 HP and I want to go to a 360 and I think I am going just bite the bullet and give give them a call after the 1st of the year, pull it and ship it off.
I can pull and install no problem but rebuilding it is way beyond my pay grade and I want it done right.


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## geeteeohguy (Feb 2, 2008)

I will second what Mr. Bear says.....you can't go wrong with Jim Lehert. His reptutation is excellent, and he is a stand up guy. If I were going through this, I would do the same thing and just suck up the shipping costs. Good choice!!


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## Goat Roper (Oct 28, 2014)

geeteeohguy said:


> I will second what Mr. Bear says.....you can't go wrong with Jim Lehert. His reptutation is excellent, and he is a stand up guy. If I were going through this, I would do the same thing and just suck up the shipping costs. Good choice!!


I agree, I want a Pontiac builder to rebuild this engine and don't mind paying more to get it done right.
I will be ordering a cradle for the engine and building a crate for it, I restore high end pinball machines and ship them all over the world so crating and shipping isn't a problem.


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## GFT 12:17 (Jul 26, 2014)

The motor has about 93K miles on it. Unfortunately, I haven't owned the car long enough (6 months) to determine how much oil it burns. I have driven the car about 60 miles since I changed to the 20W 50 oil and the low oil pressure light only came on once at idle and after the car had been running for awhile. So there is an improvement. 

I did notice some oil leaking at the rear of the engine when it connects to the transmission. There is a large housing that connects the engine to the transmission. At the very bottom of this housing there is a metal flap that folds back towards the transmission. At the end of the flap there is a bolt. That is where I'm seeing some oil drip to the floor. Over the course of 24 hours, maybe 10 drops of oil. I don't see that as significant.

From a pure observation standpoint, I was surprised at how dirty my oil was once I drained it given it was only in the engine about a week.

Geeteeohguy - Your comment about a period correct 389 is where my mind is headed. Take my time and find the correct block, etc. 

I'm hopeful I will be able to enjoy the car for a while before the engine proves to be a real problem. Thankfully it's not my daily driver.


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## PontiacJim (Dec 29, 2012)

93K, then its probably been used seeing its a GTO, so its most likely worn out.

The oil leak sound like a rear main seal as the oil is dripping from the inspection cover at the bottom of the bell housing. However, it could be the front seal at the transmission. Trans uses 80W-90 gear oil and usually has a distinct odor. You should check your trans fluid level as you don't know the last time this was done. Do the rear axle fluid while you're at it too. Easily done at the same time on a lift.

Me, I'd get an under the dash mechanical oil pressure gauge so you can see the actual oil pressure. I'd just drive it and keep and eye on the pressure and wait until I saw a noticeable drop. I would also have AAA Plus roadside assistance which will tow your car for free up to 100 miles -that's what I have. You could look around for a 389CI or begin setting money aside for your current engine's rebuild.:thumbsup:


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