oil overfilled?

But, part of the question remains unanswered: will overfilling the oil sump harm the engine? I don't think so, but I am willing to be corrected. As far as I know, the extra oil may be dissipated, somehow, but I don't see how it could harm anything, except, maybe, the environment.

The story in the old days was that, if the level were high enough to be 'beat into foam' by the crankshaft the oil pump wouldn't be able to pump the foam and you'd have oil starvation. I suspect with newer oil formulations and having the pickup for the oil low in the sump, it might be difficult nowadays to get into that kinda trouble - not impossible - just unlikely if you're slightly overfilled.

Carl

snipped-for-privacy@worldnet.att.net wrote:

Hi,

Is that hot or cold? If hot, it sounds "just about perfect" (see Ed's description of "hot" mark) and if it's cold, it's a tiny bit overfilled, but not enough to worry about (see Carl's description of foaming--still potentially as much a problem as it ever was if grossly overfilled, but your description doesn't raise any red flags.) Overfilling by the dealers seems to be a common thing--I always do my own oil changes to maintain control over all aspects: brand, weight, amount, but looking thru the service records of my Toyota which was dealer maintained exclusively prior to its coming to live at my house, sometimes an oil change was charged by the quart, often at 5 qts in a 4.5 qt engine (did they keep a half qt, or just pour it in?), other times it was "one unit,

6 cyl" so they probably just dialed a figure on the dispensing hose and let 'er rip. Regardless, that car's at 227k miles right now with no known adverse effects. So I wouldn't worry about the Subie...

Rick

I did this when i changed the oil in my wrx. My issue was the car was not perfectly level when i changed it. So i added more. I had about that.. 1/4 over the full line ,i did drain mine down. To much oil can cause excess pressure in the crankcase. Damage gaskets and seals and cause leaks. Like the rear main seal, oil pan gaskets. And if its way to high the crankshaft will be turning in the oil and that will cause more load on the engine, poor milage and pre-mature wear.

Totally agree -- the extra pressure may not do damage you notice right now but in the future. I woulnd't take the risk - draining some of the oil is easy.

Michael,

I hate to be skeptical, but I've been spinning wrenches for a LOT of years (scary close to a half century), and nobody's ever been able to prove this "too much pressure" thing to me: the oil pump doesn't create more oil pressure just cuz there's a bit more oil, and any air pressure buildup is taken off by the PCV system (or the old road draft system for those who've been around long enough to remember.) The engine's crankcase is NOT a sealed system with no pressure relief designed in. If it were, your engine would probably last about 15 minutes before self-destruction. Methinks that "excess pressure" thing's an old wive's tale that needs to be put to rest.

And the crank turning in the oil isn't going to cause enough drag to make a difference. What CAN happen (assuming the oil level's grossly overfilled, which a quarter or even half quart in a car engine's NOT gonna be) is that the crank will churn the oil, causing foaming. "Foamy" oil doesn't lubricate well, causing lowered oil pressure and a lack of lubrication at critical points, including seals, which CAN cause the seal damage and engine wear you mentioned.

Maybe you can elaborate on what I've missed? I'm willing to learn something new.

Rick

Yup.

First wife blew the diaphragm in the oil send unit, by overfilling by less than a quart, on one of my cars.

I've never seen a baby born, but I'd be a fool to claim that proves it never happens ;-)

Maybe this makes sense.. if there is to much oil in the crankcase it takes up more space, leaving less space for the air. Same ammount of air being forced in a smaller space will make more pressure. The pvc, old breather system can only relieve so much. I rebuilt a chevy 327 and a Ford 302. The

327 was out of a 69 impala i put in a 71 nova. The 302 was a 72 in a Bronco. I remember a few times while working on them having the breathers blow out of the valve cover and the dipstick pop out.This has nothing to do with to much oil but to much pressure built up from turning it over alot and it couldn't relive it. So the system pcv is ok under normal conditions,but to much oil, to much pressure it cant relieve properly and could blow out seals, gaskets. The extra pressure has to go somewhere. And if you get in a pool and try to walk, how much more effort do you use then out of the water ? Any extra load on the rotating assembly will affect milage, wear and performance.

I think the whole point is "how overfilled"? Four ounces will make no difference. Do you keep exact track of how much oil isremoved? If not you may overfill. Four quarts probably will!!! Why are some of you so anal? Will the roof rack fail w 101 lbs?

Yes, I understand the concept. But did you blow things out of your engines cuz you overfilled them with oil? And if so, how far were you overfilled?

I've seen the same thing happen you've described, but there was a much more serious problem than a little too much oil! (And with all due respect to home garage builders, the problems I saw DIDN'T occur in professionally built engines. Hmmmm....) Small block Fords and Chevies can take a LOT of hotrodding before they start tearing themselves up, IF they're done right. Blowing a dipstick out sounds like an extreme case--blowby from improperly installed rings, clogged oil return galleries, something like that was creating an incredible amount of excess AND unrelieved crankcase pressure. Simple pumping pressures from the pistons are pretty unlikely to build the kind of pressure you've described if all the venting systems are operational (remember that as one piston comes down, adding pressure, another is going up, relieving it, so it's not quite as straightforward a system as a compressor dumping all its output to a holding tank.) I've seen such engines pulling close to 400 hp on a dyno when I used to hang with the racing crowd, which is close to double factory numbers (and they're capable of even more), and they didn't blow seals--everything else would break quickly, but that's from overstressing parts, not crankcase pressure.

And, as you said, your engines were far from stock, so I'm still open to seeing a current engine in good shape develop the kind of crankcase pressures required to blow seals without GROSSLY overfilling with oil. As another poster put it, the fact I haven't seen it doesn't mean it doesn't occur, but I've seen and been in too many discussions with engineering/builder types and busted enough knuckles getting up close and personal with engines to believe it's the problem people think it is.

Rick

Speaking from experience with '78 Honda Civic, working on a car with valve covers and oil pans off, over several weekends, possibly even outdoors, can cause a lot of 'gummy residue' to develop. In my case it cause the oil pressure releif valve to not do it's very descriptive title. It blew the through the oil filter gasket.

Again, given what we were told - which of course is all we have here on a usenet group, I feel (and Rick's opinion is probably worth at least

100 times mine) you're OK.

As for CAN bad things happen given COMPLETELY different circumstances? well - H3LL YEAH!!!

Carl

Rick Courtright wrote:

thanks Since the overfill is in ounces and not more, I'm just gonna leave it as is.

g

Carl 1 Lucky Texan wrote: