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Oil cap blown away?

This 1996, 145 k, 3.0 Dodge Caravan of mine never stops me from be thinking of him. I’ve just arrived from work 11.3 miles regular roads. Everything seemingly was ok. As a routine, every 3 or 4 days I use to raise the hood from time to time due an oil leakage. But to my surprise this time I found that the engine oil fill cap was not there, and everything around, everywhere had a huge bath of hot oil. Checking the oil dipstick revealed no trace of oil in the engine. I know how bas this is. My question is: Was I careless thighting the oil cap the last time or was there a kind of burst, explotion or cap tearing?.

Should I refill with oil and just buy a new cap? Or is there something else going on?

Give me a piece of advice please! I want to learn this one!

You probably have something very nasty going on. Just leaving the cap off will not spray oil all over your engine compartment. The fact there was little oil left in the crankcase proves it was forced out by severe pressure in the crankcase. This can be cause by a plugged PCV sytem, or more likely severe blowby, where combustion gasses blow the oil out of the crakcase and up to the valve covers. This could be cause by broken rings or severe wear.

I would not drive the car, have it towed to a good mechanic who can do compression tests and other inspections to determine the problem.

If you have severe blowby, an engine swap might be your best course of action, but find out first what the problem is.

Leaving the oil filler cap loose could have led to it falling out. Runing the engine with the oil filler cap off can lead to oil spraying all over the place. Fill it with oil and replace the filler cap. When was the last time the PVC valve was replaced? Replacing it might be a good idea. They are cheap.

Is there oil on the air filter or in the air filter housing? That is a sign of blow-by.

I’m with Doc on this one. A cap left loose can pop off and cause some spray, but yours sounds like something more serious is going on. Like that blowby Doc mentioned, possibly even in combination with a gummed up PCV valve (which severe blowby can cause).

OUch! What Docnick tells me is scary… I drove the car till home without noticing any change in the engine sound or car behavior.
Jeremy there is no signs of oil nither in the air filter nor in the filter housing and the PCV valve was changed just a month ago.
I had Valvoline oil 10W-30 in the car now… but I ran out of it. Is it ok to refill with Shell oil 10W-30???.. Any problem mixing them a little bit?

I’ve always thought there was enough crankcase pressure in most engines to slowly but surely blow oil out of the oil fill if the cap was missing. It’s happened on my Chevy 350 CID where I accidently left off the oil fill cap, Julio. I lost 3 Qts over 100 miles. Over the years I’ve seen what I thought were engines in good condition that had lost quite a bit of oil over say, a period of a few days that had the cap

missing for whatever reason. Recently in our shop a mechanic left the dipstick out and about a week later the car came back with oil spray around the engine compartment area near the dipstick tube but only a minimal amount of oil was lost. On the other hand Docnic and mountainbike are quite knowledgable so I could be wrong. I guess the crux of it is; if the cap actually blew off you’ve got a real problem

like they say. Is there evidence of damage from the cap blowing off? I would think there would have to be.
If you left the cap off, one would think that the open oil filler would be a nice place for oil to exit during say, acelleration when blowby gases are high and manifold vacuum, which the PCV system utilizes, is low. You should have your crankcase pressure checked at a garage you trust ASAP. OK to mix different brands of oil nowadays. Let us know what happens, Julio.

You get lots of oil on the engine when you drive with the oil cap off. You need a new 710 cap. It says OIL when you turn it over.

Thank you Karl for your wise comment. For sure I’ll let you know about the decision taken. I’ve just bought another oil cap. I also checked if there was any evidence of damage due to the cap blowing off and I found none… And I tell you, unfortunatelly I am always suspicious about this old car of mine. There is always something going on with it. I am also familiar to the roar of my engine and I think I would have heard any kind of explotion if there was any. Of course “I am not sure”… I’ll refill and try again… crossed figers!

My best regards guys!

I left my oil filler cap sitting nicely beside the fill a year or two ago. I drove about 100 highway miles before realizing it, but my oil level was normal and I saw no splatters of oil in the engine compartment when I checked. Just leaving the cap off doesn’t necessarily lead to oil on the engine. I’m sure it is possible, though.

And yes, Julio, you can mix different brands of oil. You can even mix different weights if you need or want to.

Julio, I once had an old Mitsubishi Colt with a lot of blowby. The PCV sytem froze up because of all the water vapor (for every gallon gas burned, you get a gallon of water) and the screwed oil cap stayed on tight. The result was that the CRANKSHAFT SEAL BLEW!!, and it cost $400 to fix it. In retrospect I should have scrapped the car.

So, I stand by my assessment; get a cylinder compression test and other inspections done. My father once drove his tractor for weeks with the oil cap off, and very little oil sprayed over the engine. But that engine was tight, with very little blowby. All engines have some blowby, but the PCV sytem is supposed to handle it.

It is okay to mix brands of oil as long as you use the right viscosity (10W-30). With some cars, there are moving parts right under the oil cap that can lead to spraying if you run them with the oil cap off. With other cars, that leaving the oil cap off doesn’t expose any moving parts and oil is unlikely to spray out. Is that the case with your Caravan? What do you see when you remove the oil filler cap (with the engine off)?

It sure is possible, depends on the vehicle. My daughter had a Ford Aspire that a quicky oil change place forgot to put the oil cap back on. I found the cap sitting on the valve cover and no oil escaped (through the cap anyway). I once rented a car, a brand new Chevy Nova, Toyota version, had 24 miles on it. I got about a half mile from the place and was engulfed in oil smoke. I pulled over and found the oil cap just sitting on top of the valve cover. Oil was everywhere, but the engine only lost about a 1/4 quart. I put the cap back on and finished my trip, although it took a few miles for the smoking to stop.

Jeremy about 2 1/2 inches from the oil opening I can see son stuff and I can asure you that they spin.

Well guys I put the almos 2 quarters of oil the the car lost. Put the new oil fill cap and went for a 13 mile rides, freeway included and everything seems to be fine… Till the next chapter… I know that there will be more chpaters!!

Thanks to you all dear fellows!

Funny you mentioned that. On a trip to see family, I had left the oil cap off on my wife’s 1990 Mazda Protege after adding a quart during a fill-up. A couple of hundred miles later, we stopped at a rest area, and I noticed an oil burning smell and wisps of smoke from under the hood. When I opened it, the top of the engine was an oily mess. It was then I noticed the oil cap off. The cap was still on the radiator support under the hood, luckily. I checked the oil level, and was surprised to find that I was down about a 1/4 of a quart. It was full when I topped off at the fuel stop. I put the cap back on, and drove the rest of the way.

Julio- I think you dodged a bullet. I hope the next chapter is way off, but you liven up the board anyway! Happy motoring!

Yup, definitely a similar experience, BustedKnuckles. I added a bit of oil before a trip home from visiting family and must have left the cap sitting on the valve cover. On the highway, I noticed my hood wasn’t latched all the way down so it was bouncing a bit - scary at 65 mph! I pulled over, popped the hood, and panicked when I didn’t immediately see the cap anywhere. So happened to glance down, and there it was sitting on the metal frame right next to the hood latch.

Ever since then, and one time when I dropped the cap to a bottle of oil into my radiator fan assembly and it took me a half hour to get it out, I’m a lot more careful about setting things on the ground and replacing them when I’m finished. :slight_smile:

The 3.0L is an overhead cam engine so oil is going to be driven out when you drive with a missing oil cap. As you can see from your replacement cap, they seal pretty positively when turned all the way, so I think we have to chalk this up to “user error.” Fortunately, the dipstick doesn’t measure the entire amount of oil in the engine, only the top 2 or 3 quarts. Driving with it down that much isn’t good for the engine, but probably not fatal in the short run. If you truly had no oil, you would have seen the oil light and heard the engine chewing itself to pieces.

Got you! NYBo… I read about similar events to mine above… They were lucky that they found the oil fill cap…At the beginning when I saw the dry dipstick I panic…but then common sense came to the rescue.
Thanks to you for placing your comment.

Julio; you may have just escaped some serious damage. I would keep a close eye on the oil level from now on, and make sure the cap is on tight. No se preocupe!

Muchas gracias Docnick!! :slight_smile: