Forums/Z31P/z31-performance-upgrade-forums engine-mechanical-aa/Oil Thickness/Rod Knock?
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MrwassmanNA2T: (2006-10-27 02:40:39)
So I switched to 15w-50 Mobil one synthetic last oil change from 10w-30 castrol synthetic.
Figured the car has a decent amount of mileage on it and maybe the tolerances aren't what they used to be, right?(~140K, ok not that much)
Well, after cruising for awhile (maybe 20 min+ in some warmish weather, 85+), I get a noise that sounds like knocking. This is from about 15 in/ vaccum all the way to boosting situations. So through out the 1000-3000rpm range pretty much. Then it goes away I think, then again i was fearing for the mains so i didn't boost to much.
Does it make sense in anyway that this could cause a lack of oil being able to get to the mains and rod journals? I am just trying to fit peices together.
I personnally think it kind of Does NOT make sense because it is after the oil gets hot, which in turn should make it thinner.
Input is gratefull.
BTW, i am dragging the car on saturday [archived image: biggrin.png] [archived image: biggrin.png]
SATAN: (2006-10-27 02:59:03)
um doesnt it get thicker after it gets hot. You need the thinner oil for the cold startin situations.
sounds like you are one your way to spinning a bearing. I'll put money that if you are spinning a bearing that it is a rod berring and not a main.
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MrwassmanNA2T: (2006-10-27 03:09:19)
ahh, yes, just kinda realized that, had my thinking backwards.
Um, lets hope not, for it to spin, it would have to be pretty dam thin.
Jason84NA2T: (2006-10-27 03:19:08)
What is your oil pressure reading cold/hot?
If it is indeed a rod knock (which is what you describe there) and you have good oil pressure, you can probably assume it was probably damaged due to starvation or contamination on the part of a previous owner. The reason I say this is because these engines don't seem to ever develop rod knocks easily. I drove one for 3-5 miles on the highway with NO oil pressure and it showed no substantial bearing damage when I tore it apart.
SATAN: (2006-10-27 03:19:09)
No, just wore out. that is always the first sign of a spinning bearing berring whatever. you can hear it "rattle" with slight load up to about 3k 3500 rpm? but under full load you hear nothing right? YUP :wink:
I heard mine start to do that and kept a VERY close eye on my oil. but still after a while it was done.
Have you ever changed the head gasket and not changed the oil afterwards maybe?
Andrevas: (2006-10-27 03:34:48)
[quote]SATAN wrote:
ahh, yes, just kinda realized that, had my thinking backwards.
Um, lets hope not, for it to spin, it would have to be pretty dam thin.
No, just wore out. that is always the first sign of a spinning bearing berring whatever. you can hear it "rattle" with slight load up to about 3k 3500 rpm? but under full load you hear nothing right? YUP :wink:
I heard mine start to do that and kept a VERY close eye on my oil. but still after a while it was done.
Have you ever changed the head gasket and not changed the oil afterwards maybe?
the only headgasket swap was with the ported heads added during the turbo conversion, and the oil was changed for that since he swapped pans for the turbo one.
SATAN: (2006-10-27 03:37:57)
Hmm, cause I know a lot of times people will do a head gasket and some coolant will get down in the oil sometimes, People dont really think anything of it but…
Dunno but I think we can all agree a rod rattle wont go away on its own.
Firehawk: (2006-10-27 07:29:41)
I never have had any problems using different viscosity oils, so you can rule out that problem.
jjewell: (2006-10-27 18:23:07)
castrol gtx high mileage 20-50. by far the best oil i have used in my z. i've had both mobil 1 and valveline full synth break down on me in just around 1500 miles to the point i would use up to 3 quarts in little time at all. now i do the normal 2500-3000 mile oil change and i can take out all 5 quarts that i put in. and no there are no massive leaks anywhere that 3 quarts of oil will go. the mobil 1 was in the 300 and the valveline was in my 350z which has 25,000 miles on it. 2 cars same problem. no more synthetics for me thanks.
ShamWow: (2006-10-27 23:44:38)
What are you talking about?
Are you saying that you ran synthetic in your 300zx and it lost three quarts, and you ran synthetic in your 350Z and it lost three quarts…But then you switched both to Castrol High Mileage, and now you dont ever lose any oil when you do your 3000 mile changes? So in your opinion MrwassmanNA2T's synthetic oil fried his bearings?
Im not trying to be a jerk, i just dont understand your post, or why its posted here.
On a side note, you lost 3 quarts of synthetic oil in 1500 miles once with your 300zx and once with your 350z? Something just doesnt seem right there…
-Mike
jjewell: (2006-10-28 01:49:31)
2 cars same problem and only with synthetics. the 300 happened with about 1500 miles on the oil in summer. the 350z with 25,000 miles on the engine did the same thing but after about 2000 miles . what i think happened was the heat broke the oil down and blew right past the rings and got burned in combustion. both cars only did it in the summer that i know of. i never gave it enough time to even make it to the winter without changing back to conventional oil. i only know what i have experienced first hand. alot of people will argue this because synthetics cost more so they must be better. i don't run the high mileage oil in the 350 just a good quility conventional oil because the engine doesn't have high mileage. when you pull a drain plug on a cold engine and the 2 quarts of oil that are left in the engine piss out of it thinner than water you know somethings wrong.
SATAN: (2006-10-28 03:33:51)
That............................ it is rediculous
Andrevas: (2006-10-28 04:20:26)
you're doing something really wrong to get that result with Mobil 1, especially in a Z33.
MrwassmanNA2T: (2006-10-28 05:05:48)
Well, since switching to the thicker oil i have a zero oil leak/burn now somehow. It has been 1000 miles and it is still slightly overfilled. Has yet to make the sound since that day....
SATAN: (2006-10-28 05:20:24)
Hmm, well just make sure you keep and ear on it.
Ive got rod rattle in my 240sx that I've had for over a year. The owner before me n2o'd it and fuxored it up I believe. but other than the rattle it does fine. rattle hasnt gotten worse, BUT, that doesnt mean it wont.
Maxmaxima91: (2006-10-28 05:30:24)
Um.. multi weight oil still gets thicker cold.. just not as thick.. thats why oil comes out so much faster when its hot. And thats why it takes me forever to empty my waste oil container in the winter.
just my $.02
Andrevas: (2006-10-28 05:35:59)
[quote]Maxmaxima91 wrote:
um doesnt it get thicker after it gets hot. You need the thinner oil for the cold startin situations.
Um.. multi weight oil still gets thicker cold.. just not as thick.. thats why oil comes out so much faster when its hot. And thats why it takes me forever to empty my waste oil container in the winter.
just my $.02
oil gets thicker as it gets hot
modern multigrade oils have wax crystal structures in them that expand as temperature rises, that's how it's able to maintain say 20 weight at freezing temps and 50 weight at operating temp
SATAN: (2006-10-28 05:37:22)
[quote]Maxmaxima91 wrote:
um doesnt it get thicker after it gets hot. You need the thinner oil for the cold startin situations.
Um.. multi weight oil still gets thicker cold.. just not as thick.. thats why oil comes out so much faster when its hot. And thats why it takes me forever to empty my waste oil container in the winter.
just my $.02
right, but as it heats up viscosity increases to fight the effects of it getting thin due to heat.
jjewell: (2006-10-28 12:10:46)
i don't see how i could do something wrong as far as an oil change. i check my oil every time i get gas and i know where my oil levels are. the synthetics i used where fine to a certain point and then all of a sudden it was gone. i drove the 350 on vaction this year which is a 250 mile drive. i checked everything before we left. and before we left to come home. by the time i got home i was down 3 quarts of oil. 250miles that is all.
Firehawk: (2006-10-28 14:37:22)
If you burned 3 quarts of oil in the cumbustion camber, your plugs would be fouled, badly. I run mobile 1 for 10k miles in my z, and it looks fine when it comes out, like any other oil. Something here just does not sound right.
Dan-TSS: (2006-10-28 14:47:36)
[quote]Firehawk wrote:
2 cars same problem and only with synthetics. the 300 happened with about 1500 miles on the oil in summer. the 350z with 25,000 miles on the engine did the same thing but after about 2000 miles . what i think happened was the heat broke the oil down and blew right past the rings and got burned in combustion. both cars only did it in the summer that i know of. i never gave it enough time to even make it to the winter without changing back to conventional oil. i only know what i have experienced first hand. alot of people will argue this because synthetics cost more so they must be better. i don't run the high mileage oil in the 350 just a good quility conventional oil because the engine doesn't have high mileage. when you pull a drain plug on a cold engine and the 2 quarts of oil that are left in the engine piss out of it thinner than water you know somethings wrong.
If you burned 3 quarts of oil in the cumbustion camber, your plugs would be fouled, badly. I run mobile 1 for 10k miles in my z, and it looks fine when it comes out, like any other oil. Something here just does not sound right.
- Not only would the plugs be fouled, He would be leaving such a smoke screen for the claimed 250 mile trip, that it would be DAMN OBVIOUS.
I'm not saying he didn't loose the three qts. I am merely saying, he didn't burn it off in combustion. It would have to SMOKE to the point where it is soooooooooooooo obvious to "burn" three qts. in that amount of mileage, even if it was doubled, or tripled with the mileage number.
- roll:
jjewell: (2006-10-28 15:33:02)
all i know is what happened to me personally. i don't try to explain these kinds of things anymore because i know it just supposed to happen to me. no fouled plugs no smoke screen just no oil. not mention both engines should have spun a bearing or something. like i said i don't even try to figure this shit out anymore because no matter what it is cars or other wise this shit seems to only happen to me and no one can explain it. i have had no problems with conventional oil and sure everyone hasn't as well as long as they do there 3000 mile oil changes. i don't beleive in the 10,000 mile oil change nor will i ever. regardless of what type of oil you use it's still going to get shitted up from just normal operation. if i had a dollar everytime someone told me synthetic oil was junk i'd have like $2.00 [archived image: biggrin.png] if you where here when it happened to me you would scratch your head just like i did. :? these things aren't supposed to happen in the real world but unfortunatly it happens to me. it hasn't happened since so i'll just keep doing what i'm doing and all seems happy with both of my engines.
Dan-TSS: (2006-10-28 16:07:52)
- shock:
- I know…that freak around the corner from you saw you dumping in the "Good Stuff", and before you left, he dropped out what he felt would have wouldn't have been obvious" Frelling thieves. (and with the price of things, no wonder!)
OR
You were hung over or feelin dandy…And could swore you put in 4 qts. or so.....but got distracted, misplaced the oil, got robbed, totally lost a moment in time with out realizing it, Hell,..you blacked out, or possibly there's an oil gremlin that doesn't like you.
- ?
- This is all weird stuff....this kind of stuff happens to you? Sounds silly, and there's a name for this…I just can't place it.
- lol:
Maxmaxima91: (2006-10-28 16:15:20)
[quote]SATAN wrote: [quote=Maxmaxima91]
um doesnt it get thicker after it gets hot. You need the thinner oil for the cold startin situations.
Um.. multi weight oil still gets thicker cold.. just not as thick.. thats why oil comes out so much faster when its hot. And thats why it takes me forever to empty my waste oil container in the winter.
just my $.02
right, but as it heats up viscosity increases to fight the effects of it getting thin due to heat.
Viscosity goes up but it stilll thins.. heres a Quote from a web site that sums it up pretty well. made me understand it much better..
"At cold temperatures, the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C, the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot. "
Maxmaxima91: (2006-10-28 16:15:55)
So it still thins.. just not as much.
SATAN: (2006-10-28 16:23:48)
Ah, that makes good sence