Mysterious Oil Comsumption? 1990 NA motor

[marcyprojects]

Recently encountered an issue with my motor. Had a noise which sounded like the typcial VTC or lifter tick. I thought great, only had the car for a few months and now this. Anyway, I decided to take a look at the oil and give it a change for good measure and I found that it was VERY low. I only drained out maybe a quart if that. This is really weird considering I changed the oil upon buying the car just a few months ago, may have about 1800 miles on it from the last oil change. This car was very well taken care of and has an exensive service record which came with it so again, weird? The oil that was used was just the cheap conventional stuff that the chain places use and the filter was a cheap STP brand. I use Mobil high mileage synthetic blend and Mobil filters in all my cars so I guess I upgraded the oil from what was used. I used 4.5 quarts, I replaced one of the quarts with a quart of MMO to clear up the tick which worked and now shes quiet again. Still not sure how I was able to burn through 3 quarts of oil in 1800 miles? The oil I drained was also black as night, some of the darkest ive seen. The only symtoms I saw leading up was an was the ticking and what looked like chronic low oil pressure readings but we all know how inacurate those can be (mine has been replaced already though). Anybody seen this or was it just a fluke?

[Ziggy1621]

Are you getting any smoke when running? Do you park on concrete so you can see if there is a drip spot? You can also do a leak down test to see if you are getting any oil past the seals or rings.

[marcyprojects]

Are you getting any smoke when running? Do you park on concrete so you can see if there is a drip spot? You can also do a leak down test to see if you are getting any oil past the seals or rings.

No smoke at all while running or at start up. I did have a leak when I first got the car but I wasnt able to narrow down exactly where it was coming from. Somewhere at the back of the motor, it was so gummed up back there the leak was hard to isolate. I'd get a little collection on the ground after a long drive, leaked kind of like a leaky faucet if you can imagine. Stopped once the motor completely cooled down though. This prompted me to go ahead and do my first oil change. Changed oil with 4 qts 10w-40 mobil synthetic blend and blue devil stop leak and it never came back.

[Ziggy1621]

Cool, put a reminder to check it in a week or two

[marcyprojects]

Cool, put a reminder to check it in a week or two

Ya, I did that first oil change back in july to stop that leak. I check it daily and seems to be fine. Still cant quite make sense of this oil consumption though. My oil pressure gauge is reading all kinds of weird numbers now. Has gone back to reading close to 0 when stopped, and then anywhere from what looks like 20 or as high as 60 psi while driving? Could just be a result of our crazy a** oil gauge and it may always do this I guess. I've read all the stickies and all about oil issues on the z32. All have been true for me with this but now that my gauge is reading like this again is making me paranoid.lol. I even topped off my oil with another half quart just to make sure, thinking that maybe the readings are result of the MMO I used starting to thin out. Dipstick reads full now with out question, though I couldnt get a clear reading last time either. While all this is happening the car is still VERY powerful and pulling strong. No ticking or noises. Soo confused right now...

[marcyprojects]

Reviving this thread as my original issue has come back. Still have no real answers on what it could be. Its been about 6 weeks since I changed the oil as mentioned before. Motor started ticking and loosing oil pressure again last night. Still "running" fine with enough power to spin the tires easily. Ive read some info about this whole VTC gear leak which might be whats happening here but I dont have any of the described symptoms besides the ticking. I topped up with another half quart of oil last night, drove it to work this morning and all is good. How can I loose a half quart of oil in 6 weeks with no visible leaks or obvious symptoms?

[McShanks]

I lost oil pressure, and chased a few ideas, none of which worked. At first I thought it was the sending unit, so I replaced that. Then I thought there was a clog. Then I blew a head gasket and so I pulled the motor.

I pulled everything apart, and there is no damage to anything (except the head gasket), thank goodness, but I did find that one of my oil check valves had popped loose. I do not know if you can check this with the engine in the car, and I did not come across this issue in my research until I started trying to figure out what these 2 little ball bearings were. To get to the check valves, you will need to pull your oil filter and remove its housing. There is a piece in the block that holds 2 ball bearings. The balls are held against the housing by springs, and you should be able to push the balls in and they should spring back into place. If a housing breaks and a ball pops out, you will lose oil pressure, which can lead to other bad things...

[marcyprojects]

I lost oil pressure, and chased a few ideas, none of which worked. At first I thought it was the sending unit, so I replaced that. Then I thought there was a clog. Then I blew a head gasket and so I pulled the motor.

I pulled everything apart, and there is no damage to anything (except the head gasket), thank goodness, but I did find that one of my oil check valves had popped loose. I do not know if you can check this with the engine in the car, and I did not come across this issue in my research until I started trying to figure out what these 2 little ball bearings were. To get to the check valves, you will need to pull your oil filter and remove its housing. There is a piece in the block that holds 2 ball bearings. The balls are held against the housing by springs, and you should be able to push the balls in and they should spring back into place. If a housing breaks and a ball pops out, you will lose oil pressure, which can lead to other bad things...

ok ill check it out. So how does this valve effect oil consumption though? is it a matter of lack of flow? I have reason to believe this has been going on for a while. The first time I changed the oil on this car it had next to nothing left in the pan, dont remember any ticking though. If I could get a good read on the dipstick I could track this a bit more accurately but we all know that goes.

[McShanks]

I would say that based on your symptoms, you may have more than 1 problem, unfortunately. Loss of oil pressure could be due to bad pump, bad check valve(s), bad seals, and a number of other issues. Since you have no visible signs of external leakage, you are probably burning oil. This could be due to bad piston rings, bad head gasket, maybe even bad valve seals or guides. When I pulled my engine, I found that there were a lot more issues than I was aware of. Never had codes, either. Basically, anything that could wear, did. Gaskets, o-rings, seals... These cars are pushing 25-years old (even though they don't look it). They have held up well for their age, but if your engine has never had a rebuild, now would be a good time if it is not your daily driver.

[McShanks]

And if it IS your daily driver, and you can get a friend to help you out for a long weekend, spring for a jdm engine and do a fast swap. It really is not as bad or difficult as it may seem, there are many good write-ups out there. You put the newer lower-mileage fresher engine in there, and you can sell your old engine for parts or rebuild it to your liking. Living in FL, there are a few importers down there (and also CA) that can get you a jdm engine, well under $1k for NA motor.

[marcyprojects]

I would say that based on your symptoms, you may have more than 1 problem, unfortunately. Loss of oil pressure could be due to bad pump, bad check valve(s), bad seals, and a number of other issues. Since you have no visible signs of external leakage, you are probably burning oil. This could be due to bad piston rings, bad head gasket, maybe even bad valve seals or guides. When I pulled my engine, I found that there were a lot more issues than I was aware of. Never had codes, either. Basically, anything that could wear, did. Gaskets, o-rings, seals... These cars are pushing 25-years old (even though they don't look it). They have held up well for their age, but if your engine has never had a rebuild, now would be a good time if it is not your daily driver.

I read this over the weekend and had to hold back tears.lol. Ive only had this car 3 months, took me double that to pry it away from the previous owner. Just crazy though because Ive dealt with other cars that had the issues that you mentioned and all of them had at least one symptom that I could see. Ive had 2 s chassis cars with bad seals and valve guides and those things would blow a cloud of smoke if left idle for too long. I had an S14 for about a month only to find out that its head gasket was bad, loss of power and it shook like a leaf. This Z doesnt display ANY of that which is what is making me crazy here. The car has an extensive service history from the original owner, ive checked through all the known issues, common fixes and they have all been addressed. The owner between me and the original didnt really care for it well but he only had it for 6 months. I dunno if that kind of damage could be done within that short period.

What I did find over the weekend was that there are some baby leaks around the rear valve cover, none of which I believe could cause this oil issue but cant be too sure. Dont judge me but, I have started to fill those in with RTV where I can. Mainly just to stop the leaking while I track this problem. I also looked into oil weights again, thinking maybe I have it wrong? I was using 10-40 over the summer, dropped down to 10-30 in light of cooler temps here now, and now the comsumption issue is more visible.

[marcyprojects]

UPDATE: Had to top up again. another half quart. Oil pressure has been reading kinda ok up to this point though which is good. Got to wondering though, if I upgraded oil again to a full synthetic would that help/solve my issues? I only think of this as I remember that I really had no way of verifying what kind of oil was used before I got the car. I have the service records from the orignal owner but he hasnt owned the car in nearly a year. Records show he was using cheap conventional oil from the chain shops. I feel like the car is ready to go full synthetic considering the mileage (167k) and the issues that ive been having. As mentioned before, i have been using mobil synthetic blend 10w-30.

[McShanks]

Hm, look up switching from dinosaur juice to synthetic. You might make more issues than it is worth. Have you done a compression test? That could give some indication of what is going on. Low compression means bad valve seating/seals or bad piston rings. Do you have any smoke coming from you exhaust or anywhere else? I am really thinking you should do a compression test. I would guess you have piston ring(s) leaking, causing you to burn oil. Do you have any oil in your coolant? You can drain your radiator into a clean bucket, and see if there is oil in the coolant, indicating a leaky head gasket (which may also cause low compression). There are so many things it could be on a 25 year old car... I am with ya man. It is maddening!

[NolimitZ32]

Oil comsumption could also be cause by bad valve guides, definitely do a compression and leak down for good measure. The more you know about the overall condition of your engine the better equiped you'll be to diagnose the issues.

[marcyprojects]

yea compression test is def a good idea. I think im going to give the synthetic a try still. I'd rather work with the potential leaks than continuing to burn through oil like this. If theres any chance that things internally are good, running the motor till it ticks cant be doing any good. Theres also plenty of evidence out there showing the synthetic oil leaks to be a myth. Ill be sure to post the results.

[NolimitZ32]

Synth wont solve your burning issues, it may very well create leaks though. The difference between "fossil" oil and "synthetic" is not that one is HC and the other is not. the difference is the level of processing and purification they go through. Synthetic as a result of more and better purification has on average, smaller molecules which may cause leaks when put into an older engine due to the fact the rubber seals have lost their elastisity and ability to swell with the introduction of heated oil. So you going between synthetic and non-synthetic should not by any means change a thing although wierder things have happened. Also as with any issue that arises, bandaids are the worst solution because they may only temporarily HIDE a problem, you should always get to the root of the issue.

[McShanks]

Yeah, a major concern with putting synthetic through a high mileage original engine is that there are all sorts of sludge deposits that have built up over time, and the synthetic can dislodge these rather suddenly. This can end up resulting in chunks of crap going through your oil passages and into your critical components.

Compression test is fast and easy, a basic kit is cheap at $20-40, don't need anything fancy. You could also check at a car parts store that loans tools. There are multiple write-ups/instructions for doing a compression test, and it shouldn't take more than 30 minutes start to finish.

That compression check is key. Most of your sources of oil leaks (and pretty much all the main sources of burning oil iirc) will also cause low compression: Piston rings, valve seals, and head gasket. If all cylinders test good on compression, you have narrowed your loss of oil down significantly, and most likely won't have to do any major engine work.

Sticky rings are pretty common and result in burning oil and low compression. If you have low compression in one or more cylinders, the oil test will indicate if it is a bad piston ring(s). If it's not sticky piston rings, valve seals can be replaced with the engine/heads in the car (and valve seals are cheap!). Piston rings and head gasket, not so much...

I am curious that you haven't seen any patches of oil in your driveway... If the compression test (which will give you an overall health assessment of the engine) looks good, you could drive the car up and down the driveway, forward and backwards AFTER you have driven the car around and the engine is up to temp. Look for any dripping spots of fresh oil on the pavement. Perhaps you have a leak that only occurs when things are warmed up and in motion, for example an oil pan gasket leak at the front of the engine that pours oil under breaking or something.

Also consider that people have had oil burn through the PCV system under heavy (read autocross-style) driving. I don't know the details about this, but it may be something to consider if you drive like a bat out of hell.

To sum it up: start with a compression test!

***Edited due to being tired and needing editing... and sleep***

***Edited again due to valve seats having nothing to do with oil leaks, and I need sleep!***

[marcyprojects]

Def appreciate all the advice. My guess is the compression test should check out. The pcv issue u mentioned sounds interesting to me too. I think youre on the right track with the oil. After reading what u said I think there's a chance the blended oil I been using could be at fault. The blended Mobil is advertised for its power to clean deposits which I like. I think I've definitely cleaned some stuff out since I been using it so now I feel the natural choice would be just to go ahead and go full synthetic. I think it will perform the same but hopefully keep the ticking under control for longer while I diagnose the rest. I was able to score some Mobil 1 today for cheap from this dude on craigslist so I figured just go ahead. 4 quarts for $20, can't beat that. I'll be sure to update the results if any.

[marcyprojects]

Def appreciate all the advice. My guess is the compression test should check out. The pcv issue u mentioned sounds interesting to me too. I think youre on the right track with the oil. After reading what u said I think there's a chance the blended oil I been using could be at fault. The blended Mobil is advertised for its power to clean deposits which I like. I think I've definitely cleaned some stuff out since I been using it so now I feel the natural choice would be just to go ahead and go full synthetic. I think it will perform the same but hopefully keep the ticking under control for longer while I diagnose the rest. I was able to score some Mobil 1 today for cheap from this dude on craigslist so I figured just go ahead. 4 quarts for $20, can't beat that. I'll be sure to update the results if any.

Changed oil over to mobil 1 full synthetic yesterday. Added along with lucas oil stabilizer on the reccommendation of a friend that I trust. We decided to see how this combo works since im in no place right now to rebuild the motor. Drained old oil out, including the filter I only had just over a quart in the car and it was quite dark. FML If I can get this combo to hold for a couple months or more ill be happy and just use it to change the oil quarterly like I usually do. I know synthetic is supposed to go much longer but like a lot of people I dont track mileage on this sort of thing. Running fine, and quiet as of now. Pressures reading correctly.

[veery]

What color is the oil now after you've run the car with the new synthetic?

I wonder if you are actually getting it all out.

[marcyprojects]

What color is the oil now after you've run the car with the new synthetic?

I wonder if you are actually getting it all out.

Ill have to check it when I get home on the dipstck. Every time ive changed it and drained so far its been pretty dark brown/black.

[NolimitZ32]

You are NA correct? If that doesnt work you could run some Marvel mystery oil (gooood stuff) or even some ATF through a wash cycle. It'll at least clean a lot of crap out and perhaps even show you where the leak is (if there is one) or make it a bit easier to diagnose. Once you've thorouthly flushed the engine you may want to try running a zinc additive or some delvac diesel oil.

[marcyprojects]

You are NA correct? If that doesnt work you could run some Marvel mystery oil (gooood stuff) or even some ATF through a wash cycle. It'll at least clean a lot of crap out and perhaps even show you where the leak is (if there is one) or make it a bit easier to diagnose. Once you've thorouthly flushed the engine you may want to try running a zinc additive or some delvac diesel oil.

I ran a bottle of marvel with the last oil change I did. Maybe that combined with the mobil blended might have cleaned some stuff out. Not sure but at this point I feel like the inside of my motor should be pretty clean. Ive also run marvel through my gas tank with good results to help unstick an injector. I also tried royal purple maxclean just to see if there were any differences between that and seafoam. I believe it was wayy too harsh as I started to have more injector/performance issues after using it. Marvel seems to be the safest and most consistent for the crankcase and the tank, just takes a little longer to work.

[Metacom]

Have you tried running a dye through the oil that responds to UV light to look for any leaks you may not see?

[marcyprojects]

Have you tried running a dye through the oil that responds to UV light to look for any leaks you may not see?

I havent. Any more detail on how to do it or where to get the dye?

[McShanks]

Do the compression test first!

As far as a UV leak test stuff, any local auto parts store will have it. The brand Tracer is common. You will need to buy or borrow a true UV light which aren't cheap, maybe $50-70 or so, but the dye is cheap at about $5 a bottle.

Do the compression test first!

Seriously, don't avoid the compression test, everyone recommends it for a reason. Multiple reasons, actually. You need definitive answers, and a compression test is a great place to start.

Do the compression test first!

[McShanks]

Any updates on your troubleshooting?

[marcyprojects]

Yes actually. Just been busy with thanksgiving and all. Had a buddy come run the compression test with me. All numbers test within spec for a car of this age. I have been running the 10-30w mobil 1 with lucas additive for about 2 weeks now and all seems to be good. Good pressure readings, no ticking. Need more time to get more conclusive information. Maybe check back in around 2 weeks from now which would make a month.

[McShanks]

Ok, glad to hear compression test was good, good luck!