Cobra consuming oil?

Jzepp300 · 06-01-2006

I have a 98 cobra with 60,000 miles on it.........i just bought it 6 months ago...........i have done 2 oil changes on it putting in 6 quarts of mobil 5W30 oil........i have noticed that at maybe 1500 miles or so the dipstick starts reading low and by the 3000 mile mark i have to add 1 -1.5 quarts of oil between changes. The car is not blowing smoke or leaking and oil.........Is this normal to be adding this much oil? Is it burning or what? The car runs fine otherwise.

JDHayes · 06-01-2006

I had the same issue on my 96 GT, there should be a PVC pipe somewhere on the top of the engine near the manifold....not sure exactly it was the right side on mine, but we took it off and it was clogged up so I went to Ford and got a new one, problem solved. Check your pressure too by taking out your dipstick and put a small piece of tissue paper on the hole where the dipstick would be, if it stays put your good to go, if it blows off...not good

BlueStreak03 · 06-01-2006

That would be the PCV valve. 1-1.5 quarts between oil changes isn't abnormal oil consumption for a vehicle with 60K on the clock. Just make sure you keep a close eye on the amount of oil it uses and don't forget to check it weekly incase it starts using more.

Monkey Boy · 06-01-2006

Quote:

Originally Posted by BlueStreak03

That would be the PCV valve. 1-1.5 quarts between oil changes isn't abnormal oil consumption for a vehicle with 60K on the clock. Just make sure you keep a close eye on the amount of oil it uses and don't forget to check it weekly incase it starts using more.

I've got almost 70,000 on my car and it doesn't burn a drop. I suspect the previous owner didn't care for the car as well as he/she should have.

Jzepp300 · 06-02-2006

Actually the previous owner didnt drive it much........its a 98 with 60,000 on it......i just changed the PCV valve for this oil change so i am gonna watch the oil this time and see what happens.......so far i am at 900 miles and its still reading full. Should it always read full in between oil changes or would it drop down or does it depend? Whats this that people are telling me to do a compression test........what will that do?

Monkey Boy · 06-02-2006

A compression test will tell you if your rings are bad and the oil is blowing by into the combustion chamber.

GTRaptor · 06-02-2006

Try other W rating, i had oil consumption problems with 5W40, i changed to 15W40, problem solved.
I have seen this in 2 friends Mustangs, both used 5W50 Mobil1, they swaped and all is ok now.

BlueStreak03 · 06-02-2006

Yes, in an ideal world, every drop of oil you put in the car would stay there. This is not an ideal world though. A bit of oil use is not unheard of nor anything to be alarmed about on an engine with that number of miles on it. I would do the compression test, just for general informative use. If the oil consumption gets abot 2 quarts between oil changes, then start planning to have the engine torn down and worked over.

Jzepp300 · 06-02-2006

thanks for your help everybody.......Should i be waiting until the dipstick is close to the minimum reading before adding oil or can i just add when i check it to make sure its always topped off to the maximum? I havent gone over 1.5 quarts between changes so is that ok? Is the correct dipstick the one with the thin rope like dipstick........my owners manual says the 4.6 liter is the flat dipstick that reads max. and min. and the 3.8 is the rope like dipstick that reads full and empty....its backwards from what i have.

BlueStreak03 · 06-02-2006

You can add oil before it gets to the minimum level, just don't go adding 1.5 quarts unless it's below the minimum mark. Good question about the dipstick. I honestly don't know the answer of that question though. Might want to talk to a Ford service tech and find out what he thinks about it.

markwondi · 06-04-2006

Don't bother with a compression test, it gives you no real information. Get yourself a leakdown test, it will pinpoint exactly what is going on inside that motor, from valve seals to rings.

My reasoning behind saying forget the compression test, is because in my years of testing/diagnosing motors, i've had numerous motors that have shown perfect compression in each cylinder, with no variation that had MAJOR internal damage, making my job harder to diagnose. A compression test is only good, in my opinion, to get a general perspective of what shape the motor is in, that's all.

Blow by, nitrogen leak down, and cylinder leakdown are the tests to perform to diagnose a motor. Nitrogen leakdown is one of the rarest tests, as most diagnostics don't get far enough to require such a test. In this test, we shoot ~500psi of nitrogen into a cylinder, and test at BDC. We'll know exactly what's going on as we push the motor through it's compression pulses.

Another good tool, is to use a borescope. Here we can check rings, ringlands, pistons and valves. Again, not needed unless leakdown and other tests show inconclusive results.

All of these tests "should" be able to be performed at most real shops.

BlueStreak03 · 06-04-2006

yeah boroscopes are awesome. too bad they're so freakin exspensive, I'd have one of my own.

Jzepp300 · 06-05-2006

Markwondi..........thanks for your advice.....i will get a leakdown test performed........like i said there is no oil on the ground or blue or white smoke at start up or driving.........i did look underneath and see some light oil coating on the starter.........i replaced the PCV valve and have just put on 1000 miles and my dipstick reads 3/4 full now instead of at the maximum mark 1000 miles ago.....so i have no clue what could be happening......the car runs strong otherwise..........do the 4.6 cobra/mustangs have a low oil light?

BlueStreak03 · 06-05-2006

Just out of curiosity, how much oil did you put in when you changed the oil?

Jzepp300 · 06-05-2006

6 quarts at every oil change