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Low oil pressure
https://slantsix.org/forum/viewtopic.php?t=49697		 Page 1 of 1
Author:  plymouthfury [ Sat Sep 01, 2012 9:12 pm ]
Post subject:  Low oil pressure
I'm having some oil pressure issues with my '64 Valiant.

I have a 70s model 225 Slant 6 installed in the car. I had bought the motor rebuilt from another individual. I installed a '64 pickup and oil pan and installed it in my valiant.

After driving her for a while I would notice that on very hard braking and some hard turns the oil light would come on. Recently the light started flickering on and off at idle and even while driving. That got a bit nerve racking so I decided to look into it.

I figured that the oil pressure sending unit on the pump could be at fault so I replaced it. It didn't help. I then got a mechanical gauge to test the actual pressure. When I first started cranking the car the oil pressure went up to 40psi then quickly dropped to 20psi before settling under 10 psi. Further tests only brought the pressure up to under 10psi never getting higher even with higher rpms. I disconnected the gauge and tried spinning over the engine to see if I could get oil to come out of the mechanical gauge tubing. The pump didn't seem to be able to pump hardly any oil up through the tubing..and no oil ever made it out of the tube. (It is a good 4 feet long)

I replaced the oil filter with a new one and that seemed to bring the oil pressure down even lower.

I pulled out the pressure relief valve and inspected it. It came right out and there was no gunk in it. The valve had some fine wear marks on it. I cleaned it up good and reinstalled it. I didn't have any crocus cloth on hand to polish on the valve itself.

I took the filter off and spun the car over to see how the oil pumped. It did pump oil, nothing super high pressure or anything...it pumped rather slowly it seemed.

The engine doesn't rattle or knock and seems to run fine.

I haven't pulled the pan off yet...but there might be some issues with the pickup possibly. Maybe a crack in it?


Anyways, Do you guys have any other suggestions before I tear into the bottom end?

Thanks
Author:  SlantSixDan [ Sat Sep 01, 2012 9:59 pm ]
Post subject: 
You've already done all the right preliminary steps. What grade of oil are you running?
Author:  plymouthfury [ Sun Sep 02, 2012 7:05 am ]
Post subject: 
The car has 10w 30 in her. Whatever the issue is it was a slow progression until it got to where the light was on constantly.
Author:  ceej [ Sun Sep 02, 2012 8:41 am ]
Post subject: 
Lift the engine up off the mounts, and remove the oil pump.

If you have an FSM, it goes into detail on checking pump clearances out. Probably not worth the trouble. Just replace the pump.

When you cranked it over to watch the oil come from the pump, you had all the spark plugs removed, right? This allows the engine to be turned over fast enough that you should see some substantial oil flow. Under compression, there really isn't much volume until the engine starts.

2¢

CJ
Author:  plymouthfury [ Sun Sep 02, 2012 9:37 am ]
Post subject: 
Sparkplugs were out. With the filter on the pump doesn't build up enough pressure to make much oil flow into the tubing of the mechanical gauge.

With the filter off...the oil comes out of the hole..but not with much pressure...it flows out slowly.

I'll see about getting a new pump. If that doesn't work then I guess I'll be taking the pan off...
Author:  plymouthfury [ Sun Sep 02, 2012 11:45 pm ]
Post subject: 
I removed the oil pump...after wrestling with the engine a bit.

The pump appears new. Not much wear is evident at all. I havent checked the clearances/tolerances yet.

I'll be pulling the pan off tomorrow to inspect the oil pickup.
Author:  Jeb [ Mon Sep 03, 2012 6:25 am ]
Post subject: 
Might want to check your pickup to pan clearance.
Author:  Chuck [ Mon Sep 03, 2012 8:33 am ]
Post subject: 
...and check the pickup tube. Some of these get so clogged up with carbon deposits that they don't allow enough oil flow. We used to soak them in carb cleaner in my shop, and after the first soaking, the really bad ones would sound like maracas because of all the loose carbon particles rattling around in there. It could take several soakings in an agitating carb cleaning tank to get all the junk out.
Author:  Rick Covalt [ Mon Sep 03, 2012 2:04 pm ]
Post subject: 
Also check the pick up tube for cracks right below the threads. They can crack and suck air

Rick
Author:  plymouthfury [ Mon Sep 03, 2012 2:45 pm ]
Post subject: 
After taking the pan off I was disappointed. I didn't really see anything that looked like the 100% culprit.

The pickup screen was slightly misaligned and wasn't sitting flat on the bottom of the pan by about 1/2 inch. This was the only thing I found that was a potential problem.

I checked the tube for cracks and there were none...there were places halfway up the tube that had been scraped by visegrips from when the tube was originally removed by the person I bought it from. I didn't see any cracks or holes around there either.

The pickup itself was not clogged. I had cleaned it prior to installing it in the motor and it was still perfectly clear...

The oil pan was clean inside...no trash, metal fragments or anything. The motor was well coated in oil even after sitting for 2 days. The cam and other internals of the motor looked nice and lubricated. Hardly any wear on the cam lobes. I haven't pulled off any caps yet..but I'll bet they are fine.

Drive gears on pump and cam are in good shape as well...

So now what?

:x
Author:  SlantSixDan [ Mon Sep 03, 2012 3:01 pm ]
Post subject: 
Now it's either excessive bearing clearances (cam bearings...?) or a weak 'n' wimpy oil pump.
Author:  plymouthfury [ Wed Sep 05, 2012 11:12 pm ]
Post subject: 
I bought a new oil pump and installed it.

I checked one of the main bearings and it was in spec with no damage/wear. At this point I decided to just put the engine back together because if there was any issues then I would be better off pulling the engine out of the car.

I reinstalled the oil pickup with thread sealer and made sure it was in nice and tight.

Got everything back together and spun the car over and bled the mechanical gauge. At this point I knew I had much more oil pressure than before since I couldn't even get any oil out of the line previously.

I fired her up and she read 40 psi at idle and 55 psi at high rpm. Looks like the problem is fixed.

So either the oil pump was junk or the oil pickup was possibly sucking air around the threads.
Author:  SlantSixDan [ Thu Sep 06, 2012 1:55 am ]
Post subject: 
Hoorah for (relatively) easy fixes!
Author:  Jeb [ Thu Sep 06, 2012 3:14 am ]
Post subject: 
Awesome, glad to hear it.

Send your old pump to Doc and he can rebuild/blueprint it for you.
Author:  Pallazzo [ Wed Sep 02, 2015 7:26 pm ]
Post subject: 
Hi... i have the same problem. When idle on P or N the oil light is off... when i put any speed whit brake or "hand foot" brake. the light turns on. When acelerate the light is off. I build the slant recently. And the bearings and clearances are ok. And the oil pikup is ok and well threaded. The engine is lubricating nicely in the rocker arm. Now. The oil pump was re ring and cleaned before mount and i replace the pressure unit for a new one. The question. I put a 20w50 shell oil on it. Maybe the oil is the problem. .. or the pressure unit maybe... or the pump completly... thanks
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