Oil overfill

subaru
forester

#1

Had the oil changed in 2006 forester. They put 6 qts of oil in. The car was driven for 1 day, less than 50 miles and was blowing white smoke. Had the oil changed again with the right amount. The dealer is saying the car needs a head gasket. Did the oil overfill cause this?


#2

Is it still smoking?


#3

It’s not stated what kind of process, if any, was used in coming up with a failed head gasket diagnosis. Another opinion should be gotten if they based it on a blowing smoke situation only.

Overfilling the oil should not cause a head gasket to give up. However, it could force some oil into the engine upper end and cause smoke. This can also come across as white in color.

If the engine is not overheating and no coolant is being lost then I’d drive it a few miles to see if the smoke starts abating.

With the engine completely cold you might loosen the radiator cap and retighten it. Start the engine, run it for 20 seconds or so, and shut it off. Very quickly loosen the radiator cap and note if you hear any hiss sound. If you do, that could point to a head gasket breach. That homebrew test is not the final word in diagnosis but could point that way.


#4

@ok4450 wouldn’t one expect to hear pressure being released if one were to loosen the radiator cap on a warm engine? I’d be more concerned if I didn’t hear hissing after loosening the cap.


#5

“wouldn’t one expect to hear pressure being released if one were to loosen the radiator cap on a warm engine?”

That is true, but…ok4450 did specify doing this very basic test after running the engine, “for 20 seconds or so”.
I haven’t seen any engines that were warm after running for less than a minute.


#6

No two separate issues. If you continue to see white smoke it means coolant is getting into the combustion chamber and needs to be taken care of asap.


#7

How many quarts of oil does your Forester normally take? 5? If so, a quart overfull shouldn’t be enough to cause any significant problem in a healthy engine, especially as little as it was apparently driven. If the head gasket is blown, it sounds like an unlucky coincidence, or perhaps it was “hanging by a thread”, since Subarus are notorious for blowing head gaskets.

If the problem proves to be the head gasket, and you can have the dealer put in writing that they believe this was caused by overfilling the oil, I’d take that document to the place that changed the oil and see if they will make good on it.


#8

That’s why I asked if it was still smoking. If it was oil, it should clear after the level is back to normal. Also, is it really smoke, or is it steam? Smoke hangs around, steam disappears fast. And, if the OP is still out there, an answer here would be nice.


#9

I agree with @bing. If there is a bad head gasket, it just gets worse till the worse happens to your entire motor. I would be tempted to get a price from another garage for a fix. But, if the price is close enough ( which I doubt) , I would be more tempted to let the dealer do it. Over filling by a quart causing the head gasket to blow would be a first I have heard of.


#10

Well, I would drive it and see if changing the oil stopped the smoking. Why did they change the oil instead of removing about a quart. I bet it is not harmed.


#11

Shouldn’t have hurt it-Kevin