How long can you drive without oil cap?

[ironhippy]

I once filled up some oil, closed my hood and didn't put my oil cap back on.

I then drove 100kms to my girlfriends house. I then thought "hrmm, did I put the oil cap back on?"
I opened the hood, there was a bit of an oil mess (not as bad as I was expecting) and the cap was still in the place I had left it.

I put the cap back on and tried to forget about my stupidity. I didn't lose enough oil to add any more.

 

[retrofive]

I will say, I once forgot to put the cap on my vw rabbit pickup. Driving down the freeway oil splash and caught fire. Complete smoke out looking out the hood and smoke screen for 1/2mi back. Somehow got the fire out and continued on.

 

[Sc0-]

Bought a $500 '93 that had severe piston slap due to the previous owner not having the oil cap on for i don't know how many miles... Not sure how long the incident took place prior to the engine noise appearing... When the engine was tore down, one piston looked like it tried to seize in the bore and two others were close to it.

 

[SmokingRocks]

Its funny the varying effect leaving the cap off has. On my '95, there is no change in idle or performance. Done it twice, made a mess both times, but other than the smell of the burning oil on the exhaust manifold, I had no other indication.

Check your PCV valve

 

[REKCUT]

I thought my post was pretty straight forward..

Two things occur when the cap is off:

1) your idle will be piss poor since the intake manifold won’t be able to pull vacuum on the crank case. And by piss poor I mean stumbling 350-450rpms and that’s if it doesn’t just stall out all together.

2) you will lose considerable amount of oil out the opening. More so during high load/rpm. And it will be all over the engine causing smoke and smells.

Your post is straight forward but that doesn't make it correct. The things I do know for a fact on my truck is that it rans smooth as silk all they way to parking lot where I turned it off and opened the hood and looked at the mess with no oil cap. So obviously mine ran perfect with no cap on.

 

[REKCUT]

I am not worried about any damage to my truck. Only added a little over a quart to bring back to full so I only lost a little more than a quart. I am more fascinated by the events and am curious as to how long the cap was off and why it decided to start blowing back out of the truck.

1. I didn't leave the truck unlocked anywhere that day so no-one messed with the truck.
2. With the picture i posted i can't believe there is any way it came loose, shot forward, worked its way past the fan, around the radiator, and throughout the grill and ended up perched up on the winch spool.

3. I have to believe that it sat there for the 5 days and 300 miles, however unlikely that is, as its the most believable of the crazy possibilities.

It has been well below zero with snow so its possible that the cap was slightly frozen to the cable.

In this scenario, I am curious what it was 4 days and a couple hundred miles later that it started expelling oil.

Several of you have expressed that it will blow out oil with no cap, but several others have told of experiences of running with no cap and not having leaks or running problems. Mine gave no indications whatsoever that the cap was off. No smell, No smoke, No codes, No idle issues. The amount of oil on top of the engine and no smell or smoke make me think it started leaking out at the very end of the run as it had not worked its way down to the manifold. Just all over the liner and top of engine and hoses.

 

[retrofive]

Just out of curiosity, now that your home (I presume) in a control environment so to speak in the driveway or whatever, if you remove the cap your idle doesn't change at all?

 

[SmokingRocks]

What he said ^ If it doesn't you have other problems. Likely with the PCV (Positive Crankcase Ventilation) Valve. Your crank case is designed to operate under normal engine vacuum at idle (about 17inHg).

If that's not happening you may have pressure building up in the crank case during idle, which with a loose cap could push it off. It also explains why there was such a mess since the case was 'ventilating' excess blow by out the cap hole.

You asked for advice, I and others who know every inch of these engines provided it. Perhaps you ought to ask clarifying questions when something doesn't make sense rather than writing off the advice as incorrect. It will help you get to the true issue faster, there is a ton of knowledge here.

Again if you open your oil cap or dip stick tube and there is no change to the idle quality or speed you need to check / replace your PCV valve.

 

[SmokingRocks]

PCV Valve Explained

Our rigs use a Modified Closed PCV system, the 1FZ-FE has a hose before the throttle plate that allows filtered air to enter the crank case for the PCV valve to suck into the intake manifold.

 

[REKCUT]

Just out of curiosity, now that your home (I presume) in a control environment so to speak in the driveway or whatever, if you remove the cap your idle doesn't change at all?

Using the ODP port and reader my truck will idle when warm around 640. The digital readout fluctuates form 620's to 650's. IF i remove the oil cap it will drop to about 50 rpm's. down to 580 range. You can hear the difference if you take it on and off but not enough of a difference to tell if you if it happens while you not listening for it.

 

[SmokingRocks]

50rpm drop indicates that there is an issue, your engine should be stumbling pretty hard or stalling out when you open the cap up. When you take the cap off you are essentially creating a vacuum leak for the intake manifold. The valve is designed to move enough air volume that the vacuum leak created by removing the oil cap should nearly or completely stall the engine.

How many miles are on the engine?

PCV valve Part Number 12204-35040............. $7.66 from toyota
PCV Grommet Part #: 90480-18001....... $6.32 from toyota

 

[shocktower]

I have done it once and I now have a Hood blanket I am going to try and clean if not I am tossing it, we are human and we make simple mistakes, mine was distraction from my kids

 

[REKCUT]

Just out of curiosity, now that your home (I presume) in a control environment so to speak in the driveway or whatever, if you remove the cap your idle doesn't change at all?

Removing oil cap or dipstick does nothing real noticeable, but pulling hose off pcv valve kills engine

 

[DirtScaresMe]

Schrödinger's oil cap.

hahah

 

[DirtScaresMe]

I totally did this once on an old ford, made a huge mess. Now I really remember to tighten that sucker on after that lesson.

 

[SmokingRocks]

Removing oil cap or dipstick does nothing real noticeable, but pulling hose off pcv valve kills engine

Smoking
Gun

 

[retrofive]

Smoking
Gun

 

[Tedward]

I'll say I looked under the hood on my OBDI '95 300 miles in on a fishing trip and the cap was missing. Not too much of an oil mess. Hadnt noticed any poor idle or other issues, just random under hood check. Added oil, stuffed a wad of foil in the hole and drove another 500 miles. Found the cap after I got home.

 

[half k cruiser]

I've done it before as well. Opened up the hood on the 94 one day and realized the cap had been riding on top of the valve cover for a week. I also had a 92 civic that the wife and I took on our first vacation together. About a 2400 mile round trip that I thought required an oil change before and after. When I was setting up to do the after one I couldn't find my filter wrench anywhere. When I finally poked my head up under the car it was right there, still attached to the old filter !

 

[bigredmachine]

didn't do that on the truck but on my old camry I left the dip stick out and it puked oil all over the hood pad, claned it and called it a day after topping off the oil.

I have to believe that it sat there for the 5 days and 300 miles, however unlikely that is, as its the most believable of the crazy possibilities.

id believe it, you would be surprised some of the things that ive found that ive left or someone else has left under, on or where ever on a car and it should have fallen off. I left a book on the front bumper if the fire engine, went on a call cross town, came back and it was still where I left it. I found a 1/4 ratchet with extension that someone left on the sub frame of a camry, also plenty of drop lights and wrenches