When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi all, Im here with my '82 and a low oil pressure situation...
My first thought was a gauge/electrical issue, so I hooked up a manual gauge and still read nothing on a warm engine. even when taking out the oil pressure sender, there was very little oil in the hole where it sits.
So now I am doing my research and finding little in the way of what might be my issue, since most people have problems with the sending unit itself. I have no indication of leakage, at least not currently, so I think it might be my oil pump, or maybe the pressure regulator?
Being that I have never torn down a rotary, I would like to know if this diagram is also the same for this type of engine (sorry if this is a dumb question):
I have not started the car and then taken off the oil filter to see if any is getting up there.. If it is safe to do so I will, but I would like some input from you all.
EDIT: also to note is there is no indication of oil/coolant mixing anywhere, or any indication that oil is leaving through combustion.
Last edited by Gehmabandon; 09-15-21 at 01:30 PM.
Reason: Additional info
The front cover oil line is the output for the engine to the oil cooler. That's where I'd start. Remove either the line from the top of the oil cooler (input) or the lower one (output from cooler to rear iron).
Where and how did you manually check the oil pressure?
I don't think you would normally find much oil in block where the oil pressure sender is located, since it would all drain away pretty quickly with the engine off.
I have accidentally started my engine with the oil filter off and as you would expect it will make a mess. I don't think it will really hurt anything though if you turn it off again immediately. As noted above, you could also check the flow by disconnecting one of the hoses at the oil cooler. Probably easier to contain the mess, but harder to see quickly (so you can immediately shut the engine down) if you are doing the check yourself.
A year or so ago, I had very low (and erratic) oil pressure on a newly rebuilt engine. Turned out to be a bad sender.
The front cover oil line is the output for the engine to the oil cooler. That's where I'd start. Remove either the line from the top of the oil cooler (input) or the lower one (output from cooler to rear iron).
So essentially the flow is of the pattern PUMP>>COOLER>>REAR HOUSING ?
I assume I should disconnect a line and crank the engine and hope for flowing oil?
Originally Posted by Carl
Where and how did you manually check the oil pressure?
I don't think you would normally find much oil in block where the oil pressure sender is located, since it would all drain away pretty quickly with the engine off.
I have accidentally started my engine with the oil filter off and as you would expect it will make a mess. I don't think it will really hurt anything though if you turn it off again immediately. As noted above, you could also check the flow by disconnecting one of the hoses at the oil cooler. Probably easier to contain the mess, but harder to see quickly (so you can immediately shut the engine down) if you are doing the check yourself.
A year or so ago, I had very low (and erratic) oil pressure on a newly rebuilt engine. Turned out to be a bad sender.
Carl
I assumed (against the judgement of Haynes Manual) that I could just plug a manual tester into where the sender sits under the oil filter. I made sure to use a BPT adapter. I did this because I didn't want to drain and refill oil and also because I figured that's where oil pressure would be. The manual says to pop a testing gauge down low on the end of an oil line.
Yes, flow is front cover-cooler top fitting-cooler bottom fitting-rear iron.
The factory front mount oil cooler has an internal bypass thermostat. Once the oil gets to I think 165* the oil t-stat opens. There is a big "bolt" on the bottom of the cooler that contains the t-stat.
If you remove the line at the cooler be darn careful not to over tighten and use a new copper crush washer. You might get away without a new one. If you do a test, I'd disconnect the coils so it does not start.
Also, just to clarify where you put the fitting for the manual oil pressure garage. You removed the mushroom shaped factory sending unit?
Last edited by KansasCityREPU; 09-15-21 at 09:30 PM.
Yes, flow is front cover-cooler top fitting-cooler bottom fitting-rear iron.
The factory front mount oil cooler has an internal bypass thermostat. Once the oil gets to I think 165* the oil t-stat opens. There is a big "bolt" on the bottom of the cooler that contains the t-stat.
If you remove the line at the cooler be darn careful not to over tighten and use a new copper crush washer. You might get away without a new one. If you do a test, I'd disconnect the coils so it does not start.
Also, just to clarify where you put the fitting for the manual oil pressure garage. You removed the mushroom shaped factory sending unit?
Yes that is where I put the gauge. When I do the test, how much pressure should I be expecting when cranking?
40 to 60 pounds depending on condition of engine. Should be closer to 60. This is just an observation from my engine. Not sure if the factory service manual has this spec. The manual gauges us capillary action to push oil down the line.
40 to 60 pounds depending on condition of engine. Should be closer to 60. This is just an observation from my engine. Not sure if the factory service manual has this spec. The manual gauges us capillary action to push oil down the line.
Sorry I did know that, I guess what I am asking is should I expect to be completely covered in oil when I start cranking? Lol
Also the manual I have doesn't describe this troubleshooting guide so in depth like the one you posted does. Thank you!
From my one experience, if you are just cranking the engine I am pretty sure you will not be completely covered in oil immediately. Looking up the pump capacity in the FSM shows about 6 quarts per minute at 1000 rpm. That ends up being about a tenth of a quart per second, so not a big deal if you have something to catch it. (edit: referring to the comments below, at cranking speed the oil flow should actually be about 1/3 of that at 1000rpm)
If you are just cranking the engine, the engine speed will be pretty low, so you might not get a lot of pressure. FSM spec is just under 40 psi at 1000 rpm. I suspect that cranking speed is more like 300 rpm. Since the oil pump is positive displacement, the flow is approximately directly proportional to the speed of the pump. The pressure drop through the system is approximately proportional to the square of the flow. Thus I would expect the oil pressure while just cranking the engine to be about 40psi x (300/1000)^2 = 4.5 psi. Seems awfully low huh? I guess I will have to check that next time I have the car off the trailer and have a low range pressure gauge available. ;-) Anyway, the point is that if you are just cranking the engine I am pretty sure the oil pressure will be low.
What was the oil pressure when you were running the engine using the separate pressure gauge?
I hope some of this useless information is helpful.
From my one experience, if you are just cranking the engine I am pretty sure you will not be completely covered in oil immediately. Looking up the pump capacity in the FSM shows about 6 quarts per minute at 1000 rpm. That ends up being about a tenth of a quart per second, so not a big deal if you have something to catch it. (edit: referring to the comments below, at cranking speed the oil flow should actually be about 1/3 of that at 1000rpm)
If you are just cranking the engine, the engine speed will be pretty low, so you might not get a lot of pressure. FSM spec is just under 40 psi at 1000 rpm. I suspect that cranking speed is more like 300 rpm. Since the oil pump is positive displacement, the flow is approximately directly proportional to the speed of the pump. The pressure drop through the system is approximately proportional to the square of the flow. Thus I would expect the oil pressure while just cranking the engine to be about 40psi x (300/1000)^2 = 4.5 psi. Seems awfully low huh? I guess I will have to check that next time I have the car off the trailer and have a low range pressure gauge available. ;-) Anyway, the point is that if you are just cranking the engine I am pretty sure the oil pressure will be low.
What was the oil pressure when you were running the engine using the separate pressure gauge?
I hope some of this useless information is helpful.
Carl
So at that rate doing this test will only tell me if my pump is completely and utterly failed or not, I take it.
When I put the gauge in the sender's hole it read 0. Warm, Idle, and 3000rpm. Would I get a different reading if I put it where the manual wants, down on the long hose?
I would definitely rather replace a pressure regulator or a pressure control valve before I have to get all the way into the front cover, but I guess there is no real way of testing which is the problem without pulling them out and measuring.
With 0psi at idle and 3000rpm, that sounds like a problem, as long as your gauge is good. I assume you are looking at the FSM for the 80 RX7 when you are seeing the oil pressure test at the rear hose. My 83 and 85 FSM's both show taking the pressure measurement just like you did. The attached photos show that there should be no practical difference in the two locations. So assuming you gauge is good, there is a problem.
You might try testing for oil flow from the oil sender port when cranking the engine. That should be easy to control the mess. If the pump is moving anything you should see some flow from the port unless one or both of the pressure control valves is stuck open. I think you should be fine allowing the car to start during this test to ensure that the pump is moving enough oil to see anything fairly quickly. I would not let it run for more than a few seconds though. If you don't get any flow through the oil pressure sender port, then you could move backwards and see if anything is coming through or into the cooler.
Did this whole problem come on suddenly or slowly over a period of time?
It wasn't all too sudden, but I took a long ride over a 2 day span and the car started to get hot, and that's when I saw the gauge fail. Very very bad, I know, but I finished the drive, assuming it might be a gauge problem. I attributed the overheat to the stop leak all over the top, and likely clogging the inside of the radiator. It didn't have any problems the rest of the journey, and has been fine starting up since. When I have some free time this week I'll try unplugging the sender and see what happens. Thank you for those pictures, btw.
UPDATE: I ended up having to pull the engine. After trying to diagnose it in the car, it was time to take off the front cover and oil pan to further diagnose, and you will not believe what the problem was. I would never have guessed it.
Here's an Image of what it looks like. The sump is COMPLETELY covered, not a bit of room for oil to pass through.
At first it looks like the oil hadn't been changed in a long time, started gunking up, but as I took a closer look...
It looks like fabric? It all came off in one piece. I put it into a bag to look closer later. Was there a rag left in the oil pan somehow? Any ideas? Obviously this happened before I got the car, if so.
Thank you Carl and KanCity for all the help, maybe you two have some thoughts on this? I'm probably gonna have to rebuild completely now, but at least I found the problem!
Was the engine running well when you pulled it? Given the obvious cause of the low oil pressure, along with the lack of overheating (*which you diagnosed as partly due to Stop Leak and a clogged radiator), I would probably leave the engine core alone, slap the Oil Pan back on it and put it back in. But that's me,...
Was the engine running well when you pulled it? Given the obvious cause of the low oil pressure, along with the lack of overheating (*which you diagnosed as partly due to Stop Leak and a clogged radiator), I would probably leave the engine core alone, slap the Oil Pan back on it and put it back in. But that's me,...
I'm still deciding what to do since I want to build a solid engine in the future with some aftermarket seals and studs and all, but yes it was running fine. I have never run compression numbers on it though.
I blew a very strong/built NA 13b because my oil pressure light came on. I thought, eh loose wire and drove it home only to hear the dreaded tingle about a mile from my house. that sucked. live and learn.
I'm still deciding what to do since I want to build a solid engine in the future with some aftermarket seals and studs and all, but yes it was running fine. I have never run compression numbers on it though.
it sounds like it was starting and running fine up to the point where this problem started, so compression-wise, my opinion is the engine should be fine. if anything, maybe pull the rear stationary gear (or maybe the front since you already pulled the pan) and check the bearing(s) before you put it back in or decide to keep it out to build it.
I blew a very strong/built NA 13b because my oil pressure light came on. I thought, eh loose wire and drove it home only to hear the dreaded tingle about a mile from my house. that sucked. live and learn.
Very well could be. I'll try and stay optimistic since I don't hear anything out of the ordinary.
Originally Posted by diabolical1
it sounds like it was starting and running fine up to the point where this problem started, so compression-wise, my opinion is the engine should be fine. if anything, maybe pull the rear stationary gear (or maybe the front since you already pulled the pan) and check the bearing(s) before you put it back in or decide to keep it out to build it.
That's definitely a good starting point, I wanted to get a good look at my oil pump and see if it's okay so the front stat is another thing I can do without opening the keg.
since its out, you might pull the rear stationary gear and have a look at the bearing. if its showing signs of oil starvation, then maybe you pull the engine apart now. if it looks mint, you're lucky, put it back together and enjoy
since its out, you might pull the rear stationary gear and have a look at the bearing. if its showing signs of oil starvation, then maybe you pull the engine apart now. if it looks mint, you're lucky, put it back together and enjoy
I'd Like to get your opinion on this, as its my first time really tearing into an engine. Is this too far gone? I pulled the front since I wanted to get a look at the oil pump and other stuff too.
looks ok to me! the bearing is made as a flat piece, and then rolled into a circle, coated, and then its finished round, which is why they show that stripe of copper
My concern would be with the copper that is showing to the right of the seam in the picture. Seeing copper at the seam is ok, but not in other areas of the bearing. The front bearing receives oil last and it is hot because it ran through both rotors before it gets there. In addition the front bearing gets some side loading from the accessory belt (especially if it is too tight). I would replace this bearing for find another front stationary gear with a better bearing,
I would also pull the rear and see what it look like. If it looks better and is only wiped where the seam is then you could assume that the rotor bearings are probably acceptable because the rotors spin at 1/3 the speed of the front and rear stationary gear bearings. Only way to know for sure is to pull everything apart......
Make sure you take a look at the pump. If it has any scoring or wear, replace it.
The front bearing receives oil last and it is hot because it ran through both rotors before it gets there.
This was another reason Why I wanted to pull the front and not the rear. The Pump looks to be in pretty good shape but I didn't get any pictures.
I may end up putting things back together as is, because I'll be pulling the engine at some point again to do some bigger structural stuff and fully rebuilding.
What would be the best way to clean the rotors without taking them out? All the overheating seems to have put a thick coating of carbon on them but I cant get my phone to get a good pic inside for you guys.
This was another reason Why I wanted to pull the front and not the rear. The Pump looks to be in pretty good shape but I didn't get any pictures.
I may end up putting things back together as is, because I'll be pulling the engine at some point again to do some bigger structural stuff and fully rebuilding.
What would be the best way to clean the rotors without taking them out? All the overheating seems to have put a thick coating of carbon on them but I cant get my phone to get a good pic inside for you guys.
Seafoam will clean up the carbon. Just drizzle it down the carb and keep the RPMs up. It will make a hell of a cloud so do it outside.
09-15-21, 12:45 PM
Oil Pressure Issues
