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MrKarst's avatar

Why does dip stick show overfull but no oil will drain?

Asked by MrKarst (95 points ) November 26th, 2010

I changed the oil in my 2002 Toyota Sienna yesterday. When I was done, I checked the levels and the dip stick showed it to be overfull. I should have stopped before adding the 5th quart, but I didn’t.

So this morning I pulled the drain plug out to reduce the oil level and hardly any oil came out. After maybe ¼ of a quart, it went to a steady drip. I put everything back together and ran the engine for five minutes to warm things up, then when I pulled the plug out, NO oil came out! However, the dip stick stills shows it to be overfull!

Did the oil get pulled into a part of the engine where it’s not supposed to be and now it’s being held there by vacuum? I admit that I only understand the basics of combustion engines, but I’ve changed my own oil before and never seen anything like this. I was just trying to avoid any problems associated with overfilling the oil.

Any help would be very much appreciated.

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6 Answers

RealEyesRealizeRealLies's avatar

are you parked on a hill?

You need to give it a couple of minutes between turning your engine off and pulling the drain plug, and or checking the oil level. All that oil is still dripping down from the engine compartment. You won’t get accurate readings until all the oil has had time to pool in the pan.

Paradox's avatar

I’m guessing you’ve changed the oil on this same vehicle before. Usually by experience you will have an idea when to start checking your oil levels before you overfill. If I’ve changed the oil in my truck several times then by experience I would know to add at least 4 quarts without a need to check. When I would get to the fifth quart then I would add a little bit of oil from that quart at a time checking the dipstick each time until the oil level was within range. It always helps to warm your engine for about 5 to 10 minutes before draining the old oil. Make sure you are cleaning your dipstick with a towel before each check as well to avoid a false reading. Just trying to cover the basics here so you didn’t miss something.

If you did everything I said (again make sure you clear the dipstick with each check) and you did overfill the engine with oil (yes I’ve made this mistake myself) do not run the engine. In fact you shouldn’t even run your engine before verifying you have the correct amount of oil in the engine to begin with. Leave your engine off and wait a around 10 minutes and then check your oil again, you should now get an accurate reading. If you did overfill then the oil should drain easily. Sometimes gunk can keep the oil from flowing out of the drain plug hole freely so you may have to warm the engine again for a few minutes to help loosen any gunk, turn the engine off, take the drain plug bolt off and just wait for the oil to come out but be ready to cap it quickly again and repeat the dipstick check/s.

jerv's avatar

Most times I’ve ever had oil“stick” like that were when I forgot to undo the oil cap on the valve cover. Other times were when the car was not level, and within a couple of minutes of shutting it off. That last one makes a difference of about ½ a quart on my car. I also tend to give it a couple of minutes between pouring and checking since it takes a while for the oil to trickle through my old engine to the pan.

@Paradox You are correct that it helps to know the car. With mine, I add 3 quarts, run it for about 30 second to refill the filter and prime the pump, and then add most of the 4th quart slowly. If I don’t do that then I wind up almost a quart low after my first drive.
And I also keep a paper towel or something handy (often jammed behind my battery) to wipe the dipstick every time. Few things suck more than thinking you’re okay and finding out that you are actually so low that you need to add a full quart to even touch the bottom of the dipstick :P

Paradox's avatar

@jerv Yeah I forgot about mentioning the filter and pump. Its been a while since I’ve done stuff like that. I just take my vehicle to my mechanic to do this stuff anymore. Usually I would fill the oil right around the max because I always knew that by the time the pump and filter was filled with the oil I would still be well above the minimum. Again this was just from experience with my own vehicles from changing the oil so many times by instinct.

That was good advice you mentioned however which I forgot to mention.

UScitizen's avatar

No one can answer your question. There are many possibilities. The oil should drain when the plug is removed. Something is preventing it from draining, gunk, garbage, crap. Call it what you want. It could even be paraffin, if you have been using a high paraffin (cheap) oil. Warm the engine. Remove the oil fill cap so air can get in. Pull the drain plug. If no flow, use a small screw driver in the drain hole. GENTLY wiggle it around to see if you can remove the blockage. If this doesn’t work, buy a can of seafoam at the parts store. Pour it in the oil fill hole. Run the engine for an hour or so. Try again to drain the oil. Only use top quality oils. Cheap oils will leave deposits in your engine.

jerv's avatar

@Paradox I try to keep mine near the top as it tends to drink oil (about a quart every 2 weeks/600 miles or so) and I need enough to be able to keep running if I forget to check it for a few days. That is a quirk of my old Corolla, and the nearly-identical one I had 12 years ago. The Toyota 4A-LC engine has many great qualities, but it also has a few oddities, like oil consumption and overcooling.

@UScitizen Good advice. Personally, I go for Valvoline Maxlife. My father-in-law prefers the $1.79/qt no-name stuff, and he blows engines almost yearly :P

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