OT: Very Stupid Car Question

[Nooch]

That I feel like I should know the answer to, but am blanking.

I noticed after changing my oil the other day that I was losing a bit, presumably at the drain plug (I replaced it and the washer when I was doing the change, as the one that was there was cross threaded and not very happy).

The question is, when the car was hot, I checked the stick and showed it was at the lower limit. The next morning, when the car was cold, I checked the stick and it still showed it was hitting the upper limit.

Which oil level is more accurate, the hot or the cold?

Now, I know there's oil escaping, but have no concrete way at the moment of measuring how much. Hopefully resolving the issue this evening..

[gemship]

Go with the measurement when it's cold. You still have to start the engine when it's cold:p Anyways you should always wait several minutes after running to let the oil settle prior to checking. So long as the oil level is between the high and min marks that's good. Above/at min mark maybe arguably ideal as there is less oil pressure and less chance to blow seals.

[christian]

Hot.

Do this:


Run the car for 30 minutes or so (driving around). Let the engine temp and oil temp get up to warm.
Then let the car sit for 15 minutes for all the oil to drain from the heads into the pan.
Then check the oil level.

Realistically, this won't be any different from the cold measure, but that's how you're supposed to do it.

[AngryScientist]

Hot.

Do this:


Run the car for 30 minutes or so (driving around). Let the engine temp and oil temp get up to warm.
Then let the car sit for 15 minutes for all the oil to drain from the heads into the pan.
Then check the oil level.

Realistically, this won't be any different from the cold measure, but that's how you're supposed to do it.

this is it. though the hot should be a little higher, the coefficient of expansion of oil is pretty large, hot oil should be a little bigger than cold oil.

[AngryScientist]

by the way, if your drain plug was "cross threaded", and your oil sump pan happens to be aluminum and the drain plug happens to be steel, you've got a problem...

[Nooch]

I'll roll with that method after lunch -- have some running around to do (including picking up a new pan gasket, just in case it's not the drain plug), and will run back out and check it after the 15 minutes..

just baffled me that the cold level was near perfect when I know it's been losing (though don't know how much has been leaking, admittedly).

If it's the drain plug, planning the cheap approach of the oversized, self-tapping plug before going all out and getting a new pan..

but otherwise, after a tune-up this weekend (plugs, wires, distributor cap and rotor) and an amazon local deal for new front brakes, I'm loving my 13 year old, 164k mile CR-V...

[Dave]

The oil level has nothing to do with oil pressure unless it's so low that the pump is pulling in air. Now there's a recipe for disaster.

I can't even think of any oil seals that are exposed to the engine's oil pressure.

[Nooch]

by the way, if your drain plug was "cross threaded", and your oil sump pan happens to be aluminum and the drain plug happens to be steel, you've got a problem...

by cross threaded -- it was apparent that the quick-lube place that the previous owner went to cranked down on it to keep it in -- the threads closest to the head of the bolt were stripped.. the new plug went in by hand fine til about half way, at which point I threw the socket wrench on it -- did not give me too much resistance in continuing to thread.

[christian]

I noticed after changing my oil the other day that I was losing a bit, presumably at the drain plug (I replaced it and the washer when I was doing the change, as the one that was there was cross threaded and not very happy).

The question is, when the car was hot, I checked the stick and showed it was at the lower limit. The next morning, when the car was cold, I checked the stick and it still showed it was hitting the upper limit.

STOP. Don't buy anything yet. If you checked the hot oil just after the car was running, you could have had a quart of oil hanging out in the rafters by the valve train.

How do you know you're actually losing oil? Is she marking her territory?

Take a couple of consistent measurements using my method over 2 weeks. Otherwise, we're ordering remedies before the diagnoses. And that's something we leave to Congress!

[gemship]

this is it. though the hot should be a little higher, the coefficient of expansion of oil is pretty large, hot oil should be a little bigger than cold oil.

yep, Christian's procedure is the ticket but like you explain the expansion from hot to cold...I tend to check it several times. Once when hot upon oil change, again when add oil at change, run the engine for a couple of minutes then check again at least fifteen minutes after killing the engine and add if necessary. I may even check it first thing in the morning the next day and look for oil spots being a worry wort. I also like to use a torque wrench set at 20/ft. pounds to fasten the drain plug. So long at the oil mark is in the middle of the min/high marks that's good.

[Nooch]

STOP. Don't buy anything yet. If you checked the hot oil just after the car was running, you could have had a quart of oil hanging out in the rafters by the valve train.

How do you know you're actually losing oil? Is she marking her territory?

Take a couple of consistent measurements using my method over 2 weeks. Otherwise, we're ordering remedies before the diagnoses. And that's something we leave to Congress!

yes, marking her territory.

when I got under the car on Monday night, to put an extra half turn on the drain plug, it seemed that there might be oil on the pan bolts as well (raising the question of the gasket), though the leak appears to be coming from the drain plug, leaking forward a few inches, and dropping in two little tear drops. I also haven't gotten up to the filter to put another half turn on that, but the old filter came off with just a finger's touch, maybe there's oil sitting around from previous issues..

My wife's cousin is a tech, so we'll have the car up in the air tonight to see exactly what we're working with. Picking up the gasket just in case we need it, and will happily return it tomorrow when we don't.

[gemship]

By the way I have a chevy silverado with the vortec v6. The way the oil settles on the dipstick it will be far above the dipstick high mark maybe as much as several inches half the width of the dipstick. It's odd but the other half will settle halfway between the min/high marks as it should be. I get a better reading when it's cold and the oil has cooled/settled. When I change my oil I also consult the manual for capacity, it's a good reference/ballpark but I do read the dipstick as far as getting it right goes. My engine doesn't leak oil, not sure you have this problem but mine does leave a drip/wetness that just stays put on the face of the drain plug. I replaced the washer and my mechanic said to do what you did and replace the bolt itself but being a cheap skate knowing that I didn't over tighten it and no crossthreading I just don't worry. I would take notice if you see some tell tale drips. Sometimes it's hard to just say it's coming from the drain plug as that is the bottom of the engine.

[gemship]

yes, marking her territory.

Good luck hopefully it's nothing serious. If it is coming from your drain plug and the threads were cross threaded then I am not sure what to say. Maybe able to fix the threads/helicoil or maybe better to replace the drain pan. Of course I am just assuming things.

[gemship]

The oil level has nothing to do with oil pressure unless it's so low that the pump is pulling in air. Now there's a recipe for disaster.

I can't even think of any oil seals that are exposed to the engine's oil pressure.

Maybe true, I was told this repeatedly by folks working in the automotive business. That the more oil in the engine then the more pressure is in it. I do tend to believe these things are made to be pretty resilient for example even if someone added four ounces more oil over the high mark then that isn't enough to matter. However I listen to enough old wive's tales and backyard coaching blah,blah...heed the sayings and try to avoid inviting trouble.

btw- My father just for the heck of being a handy husband to my mom went and checked the oil in her subaru impressa and said the oil was so low he had to add two quarts to it! The thing was still running good of course with there patent pending click sounds.

[Chance]

this is it. though the hot should be a little higher, the coefficient of expansion of oil is pretty large, hot oil should be a little bigger than cold oil.

Define pretty large.:confused:

Liquids don't change that much, including oil, over a small temperature range. And for what it's worth, operating versus ambient temperature isn't that much. Not when calculating volumetric expansion. Add to this the fact that the engine's oil pan will also get larger due to any temperature increase just like the oil and the difference isn't worth mentioning.

If there is a significant difference it's because of air entrainment which changes the density, and or because the person doesn't wait enough time for all the oil to drain back to the pan. For the average Joe the simplest way to measure engine oil is when the engine is cold and hasn't been started in quite a while. Like hours. And of course the car should be parked on level ground because that can make a big difference.

[Nooch]

alright, 15 mins from engine off, and it's sitting between the high and low.. plenty to get to where I need to go, less than the full measurement from yesterday morning..

[rice rocket]

Jam some cardboard under your car, check each day for drips.

[Hank Scorpio]

If it is the drain plug and the threads are stripped they make self tapping drain plus with a removable center bolt for draining. Probably not the greatest long term solution but definitely cheaper than a new pan.

[shovelhd]

Hondas, at least all of the modern ones that I have owned and own today, use an aluminum sealing washer under the drain plug, and a hardened drain socket in the pan. The drain bolt is designed to strip and save the pan. A replacement drain bolt is under $10 at your dealer. You are supposed to replace the sealing washer at every oil change. If you don't, it will eventually leak.

[Nooch]

Hondas, at least all of the modern ones that I have owned and own today, use an aluminum sealing washer under the drain plug, and a hardened drain socket in the pan. The drain bolt is designed to strip and save the pan. A replacement drain bolt is under $10 at your dealer. You are supposed to replace the sealing washer at every oil change. If you don't, it will eventually leak.

and I did, when I did the oil change on Saturday. Replaced the bolt and washer -- hell, maybe in my caution I just didn't go tight enough, because having seen the other one stripped out (nearest threads to the head of the bolt) I didn't want to crank down on it.

it could be nothing, and I'm hoping it is.. if it's that the threads on the pan are too stripped out to prevent the leak, then it's time for an oversized plug, or eventually a new pan..

[shovelhd]

If you torque it to 35 ft-lbs it should be tight, not leak, and never strip out. Another thing to think about. If it was leaking, there may be a mess at the rear of the pan that is dripping back onto the plug.

[mister]

alright, 15 mins from engine off, and it's sitting between the high and low.. plenty to get to where I need to go, less than the full measurement from yesterday morning..

a half quart loss in a day is big leak
anymore than a couple drops on the pavement after the car has sit for a time is something to fix asap

as far as oil lever effecting pressure...perhaps the word he meant to use was crankcase windage...

i always pay attention to spots on the ground under my car
and try to park on clean pavement

also check yr oil every day or every other day or some type of interval like that to figure out how much oil you are actually using
you could have a seal leaking, bad drain plug, leaky oil filter, leaky oil filter housing, leaky oil pan gasket...so many things.
you have to clean it up real good then look at it shortly after to see where it's actually leaking from, some leaks will only leak while or right after the car has run

[martinrjensen]

What I always did when looking for the source of a leak like this was to take some spray Gunk and clean the underside of the engine, mainly the pan. Start up the engine to dry it off, check that it's dry and clean, then check it again the following day or two.

[Nooch]

stupid answer to my stupid questions -- the oil drain plug wasn't tight enough. in my caution not to over torque/strip the pan, I just didn't tighten it nearly enough.

thanks all!

[bargainguy]

One more thought.

There is something called a Fumoto valve or quick valve.

The idea is that rather than risk buggering your drain plug threads every time the oil is changed (and avoiding a costly oil pan replacement), you have a spout that's actuated by lifting a small lever and giving it a quarter turn. No threading or unthreading at each oil change and you only have to install once. Much, much easier if you do your own oil changes.

http://www.qwikvalve.com/