Slant Six Oil light coming on — need a new pump?

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ScampNYC

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Hello, I have a 1971 Scamp that I recently found in a "barn" (small garage) as part of an estate sale in Brooklyn, NY. The last time it was on the road, according to documents, was 23 years ago.

The oil light is coming on and I'm trying to figure out if I have a big problem.

I brought it back to life and she runs great for the most part. Part of "bringing it back to life" was of course changing the 23+ year old oil and oil filter. The filter was seized to the oil pump so badly that I had to get a strap wrench and apply lots of torque to get it off.

I have been tooling around a bit in it, and noticed that on start-up, the oil light was coming on and going away after about 15-30 seconds.

Then I decided to take it for a longer drive, and after about 30 minutes of driving, the oil light was coming on at every stop sign. I live in the outer boroughs of NYC, so there are a lot of stop signs. Once I picked up revs, the oil light would turn off. This freaked me out so I drove back home. As I was driving home, the oil light came on more and more, and higher and higher rpms were needed to keep the red light off.

So today, I decided to try and hook up a mechanical gauge to get an actual read on my PSI. The idiot light sending unit was frozen on there pretty bad. It also looks to be a lot larger than the 1.8" NPT I was expecting. The sending unit doesnt want to come off and is right now soaking with PB Blaster. Curious, is there anywhere else to hook up the mechanical oil gauge?

But I noticed something really weird. In the nipple that the oil filter screws, there appeared to be a piece of debris sitting on top of the spring. I thought maybe this was the source of my problem. I picked up the piece of debris, and it looked like a mechanical part. What is this thing? Do I need to put in a new oil pump? Can I do so with the engine in the car? See photos...

Thanks!

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Looks like a check valve of sorts. Maybe @slantsixdan will chime in and ejeekate us. As for the oil light, you likely have the same issue my car had. It sat up from about 1980 to January 2019, when I brought it back to life. Same symptoms. Took a while for the oil light to go out on cold startup and the oil light would sometimes flicker at idle when hot. I yanked the engine and trans, removed the oil pan for inspection and there was about a solid 1/2" of sludge in the bottom of the pan and surrounding the oil pickup. I cleaned all that out, cleaned the pickup and Inspected the rod and main bearings. They were actually good, but I have a hoard of slant 6 parts, so I put new bearings in the bottom end, new timing set and a new oil pump in it. I had it out of the car after all, so why not? Needless to say, it solved the issue. That was the 170 original to the car. Although I have a pretty hot 225 in it now, I still have the original 170 on a dolly on the shop floor. I bet something similar may be up with yours. If you get low pressure on the manual gauge, and you likely will, I would recommend pulling it and inspecting it like I did mine.
 
Thanks for the reply. I'm wondering if there is anything I can do without having to pull the engine. The nipple that the filter spins onto has a hex head, can this be replaced? Then maybe run some kind of cleaner through the oil system, replace with a heavier weight of oil and I'm good to go? Sorry to sound a bit ham-handed but I'm wondering if I can get away without making this a big to-do, especially if I plan to do a small block swap in the future.
 
ScampNYC said:
Thanks for the reply. I'm wondering if there is anything I can do without having to pull the engine. The nipple that the filter spins onto has a hex head, can this be replaced? Then maybe run some kind of cleaner through the oil system, replace with a heavier weight of oil and I'm good to go? Sorry to sound a bit ham-handed but I'm wondering if I can get away without making this a big to-do, especially if I plan to do a small block swap in the future.
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Yeah, everybody wants a magic wand to not pull it, but if it has low pressure on the gauge, the pan will have to come off one way or the other and the easiest way is to get it out of the car. Everybody thinks it's their worst nightmare, but my God, it's probably only about 20 bolts and you're there. Compared to pulling the engine on a new car, a child could do it. If you get hung up on something, we can walk you right through it if it has to come out. I sure as hell wouldn't do it laying on my back under the car. Good luck!
 
ScampNYC said:
Okay. Any recommendations for an oil pump brand? Should I get a high volume unit?
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Melling and no. HV oil pumps on a slant 6 are not a good idea. It can stress the oil pump and camshaft drive gear and ultimately wipe them both out. The Melling M66-C standard volume pump is plenty adequate. I just replaced all that I did on mine because I already had it, it really didn't "need" it and yours may not either. I'm just particular like that. I figured since I had the thing all the way OUT and the pan off, there was no better time than the present. Know what I mean Vern?
 
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More than likely the sludge in the pan is clogging the pickup.
Never did I see that object in a oil filter before and it looks like a spring is in there too.
Somebody must have bought a JC Whitney anti drain back fix all at one point.Take it out.
Mopar Slants had a stand pipe in the pump but in the later years did away with them.
Now it sounds like you do not want to pull the engine or at least the oil pan.
Doubt there is anything wrong with the oil pump other than gunk and sludge.
You can TRY a oil change of 4 quarts and one Quart if Dextron transmission fluid.
Run it for awhile Maybe a day or two.Check the dip stick for a color change (dirty black).
If so the Dextron is working. Change it again doing the same and look for the results.
Slant sixes are cold blooded and many mom and pop drivers never went far enough to get the oil hot to burn off
moisture causing buildup over the years. I'm sure the valves were never adjusted either.Pull the valve cover and you will most likely find loots of sludge.. I like Rusty have had my share of Slants over the years and more than once have done this procedure. It just takes some time.
Slants are tough and will last forever with a little maintenance.
 
...and lordy, I ain't tryin to tell you "my way or the highway". People have done this a lot with the engine in the car. But here's my main reasons. First, I ain't a young man anymore. I find it difficult lying on my back under a car anymore. Well......maybe more difficult getting out and back up. lol But there are a couple of things. First, the slant 6 has a rear main seal retainer similar to a big block. The lower half is aluminum and you have to remove it to access the lower half of the rear main seal. Also, the oil pan has a four piece gasket. Two cork side pieces and two rubber end pieces. It's just SO much easier "for me" to get that thing out and on the stand. And I always pull the transmission too, because it's just too much trouble "for me" to crap around with bellhousing bolts in such tight quarters. I'll put it like this. I'm 59 and my wife is 66. The last time we pulled one was about three years ago when we swapped in the 225. We had the 170 and transmission out in less than an hour with hand tools. Now I am a retired mechanic, so I did it for a living for a long time. But the rear seal retainer and the four piece oil pan gasket are deal breakers for me now, because it's just too much trouble fumbling around with on my back under the car. You may have better success with it, though.
 
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I would say what you found is the anti-drain back valve, most oil filters have them. Discard the pieces and install a new filter, over and done with. You did not mention what weight oil you went with, I would go with a straight weight oil maybe a 40 OR 50 weight. Rotella makes a pretty good oil in this weight class.
Usually when you find a car like this...is probably why it was parked and forgotten. Best of luck, it is a cool old car.
 
Another sludge cleaning method I used is as follows:

Buy your favorite 100% synthetic oil (I like Mobil1) and favorite filter (Wix or Puralator) along with 3Qt Marvels Mystery Oil.
1. Change oil and filter
2. Add synthetic but replace 1 quart with Marvels.
3. Run at IDLE or slightly more for 10-15 minutes ensuring car is fully warmed up. Do not drive it or get rev-happy.
4. Drain while hot and replace filter at the last change.
5. Repeat 2 more times.

If its the sludge issue noted, the oil will go in nice and transparent and come out black or chunky. If its worn bearings, this will not help you other than making the inside nice and clean.

You can do the same with DexMerc3 as it is high in detergents, but I find the Marvels is more aggressive and can move that sludge.

Good luck.
RGAZ
 
^^^ Yep all above!!!!!
I have had many slants and many various old Mopars. A lot of slants were not well taken care of, as in oil changes and thus huge amounts of sludge can be found in the pan, and oil mist be moved thru the engine! clogged up pickup, passages, clogged up everywhere? I have mopre than a few like RRR's!
Then there is the cooling system!!!!
I also always pull the gas tank to see if clean and if the pickup still has its sock filter.
I like to add a mechanical oil pressure gauge. That way I can always see what the pressure is showing. I like a mechanical temp gauge and a volt gauge. Just 3 small gauges I add under the dash> There are reasons the idiot light s on the dash are called such!!! :thumbsup: ( Sarcastic humor!!! :BangHead:Cheap gauges because, well, I am cheap!!!!
 
I found a '74 Valiant in similar condition so pulled the engine and had it rebuilt. I neglected to have the gas tank boiled out and when I put fresh fuel in there it loosened all the junk and caused issues with the valves. Bent some pushrods doing it. The machine shop took the head back and cleaned it up for me. They said doing what I did was like putting sugar in the fuel. When it flows to a hot engine it will gum everything up, and it did. Pull your tank and have it flushed or replaced.
 
Awesome, thanks for the input folks. I am going to try the method of least effort first—ie, a "cleaning" as described with oil and Marvel Mystery Oil, and few oil changes. If that fails, I will look into pulling the motor and replacing the pump.

So should I pull out that spring that appears to be inside the nipple? Or is that factory? I am wondering if it is part of the old seized oil filter that would not give up the ghost. I had to really destroy that old 23+ year old filter to get it off.

As for the discussion on fuel, I replaced the fuel pump, sending unit, and all fuel lines before trying to start the engine. The inside of the tank looked like it came off the Titanic! [EDIT: I replaced the TANK too!]

Oh, also, the idiot light sending unit doesnt want to come off. I can keep working at it, but is there any other location to hook up a mechanical gauge? Thanks!
 
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ScampNYC said:
Awesome, thanks for the input folks. I am going to try the method of least effort first—ie, a "cleaning" as described with oil and Marvel Mystery Oil, and few oil changes. If that fails, I will look into pulling the motor and replacing the pump.

So should I pull out that spring that appears to be inside the nipple? Or is that factory? I am wondering if it is part of the old seized oil filter that would not give up the ghost. I had to really destroy that old 23+ year old filter to get it off.

As for the discussion on fuel, I replaced the fuel pump, sending unit, and all fuel lines before trying to start the engine. The inside of the tank looked like it came off the Titanic!

Oh, also, the idiot light sending unit doesnt want to come off. I can keep working at it, but is there any other location to hook up a mechanical gauge? Thanks!
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OIL pan pic up? Gunked up oil pan and pickup NOT getting oil?? Gas tank..Titanmic?? Maybe a new FeeBay gastank..cheap enough.. I have made dual deal at pump for mechanical line and also provision to keep sender. Worked for me.
 
What kind of tool are you using to remove the oil sending unit.
 
This past winter I bought a slant 6 and trans that was sitting on the dirt on a barn floor.
I had to buy the whole engine and trans for the part that I wanted he wouldn't sell me just what I wanted from it.
This engine and trans was originally from a 64 pickup.
While I had it strapped to the trailer I cleaned the points checked the oil, (which was quite watery and soot black) but between the marks on the stick so I went with it.with a jumper wire to the +on the coil, a screwdriver between the lugs on the starter and a splash of gas in the carb it fired up and ran.
I was both happy and surprised it was just that easy. I have no idea how long since this thing last ran. It did leak out the crimp on the sending unit pretty bad. Steady dribble the whole time I ran it. Which wasn't long at all because I didn't have a radiator connected.

Fast forward a couple of weeks and I seen a wanted post for that particular oil pan, It was a weird one/ id never seen a front sump pan on a a Mopar before. That's more of a Ford thing in my experience.
Anyway, I got that pan drained, and off the engine. It had at least a solid 1/2" if not more of sludge that came up about halfway between the top of the sump and the gasket flange. One thing that was for sure/ the whole oil pickup was completely submerged in this thick sludge. It was like brown mayonnaise. But I looked up into the engine and the walls of the crankcase were absolutely clean. I never did pull the valve cover.

The guy who wanted that pan swapped me for the pan that was wrong for him and I bolted that pan and pickup back onto the engine, to keep it sealed and clean inside.
 
ScampNYC said:
I couldn't get a socket to fit. 15/16 and 1" were both off. Any tips?
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There is a special sending unit socket, should be $10 or less, most are stepped because some were 1" and some 1-1/6. The socket will work for either. Sometimes a 12 point will work on them sometimes not. They're usually not a standard hex on a sending unit.
 
ScampNYC said:
I couldn't get a socket to fit. 15/16 and 1" were both off. Any tips?
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Yeah, an oil sending unit socket. I'm not bein funny either. They're made sorta weird. You can use an open end wrench, normally.....I just forget what size.
 
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