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How did my car go this long with no oil filler cap?

This is a sad story, first of all. Please withhold any judgment on me until you read the entire post too! Jumping right in: I made the mistake of borrowing a car to a friend. Given it was my best friend but still I went against the advice of nearly everyone I asked. My friend took the car from Wisconsin to Colorado. About a 2000mi round trip. Before I handed the keys over I was cautious and did some preventative maintenance to ensure a safe trip for my friend and the car. I replaced the air filter, cleaned out the cabin, and checked all the fluid levels. In addition, I also brought the car to a friend recommended garage to get the oil changed and the tire pressure right (I don’t have the ramps to elevate my car, or else I would have certainly done the oil change myself).
The car was returned a week later with a growling engine and oil splattered everywhere under the hood. In addition to that there was a thin layer of oil around nearly every part of the car on the outside. Disaster right? I opened the hood and there was no oil filler cap. How is it this vehicle was driven for this long (1000mi one way!) and the car did not completely seize up, break, break down, etc? I am in amazement of both the garage and my friend. Both have fault, as well as I do for borrowing it out in the first place.
One other thing: my friend did not call me or even stop to see what was wrong after the car started to sound gravely on the way back. He simply drove through it. The next morning I went to the garage. Fresh oil, cleanup under the hood, and a new oil filler cap. Somehow the car sounds/runs okay. The clutch feels very loose from when I last drove it. So does the shifter. What is everyone’s opinion on a)what I should do b)the extent of the damage to the car c)any other thoughts/experience you might have with this situation ( I realize it’s probably unique…). Thank you so much for the help.

Your engine doesn;t need an oil cap to operate. The pump draws the oil from the pool in the oil pan and pressurizes it in the channels to lube the parts, then it drains through return channels back into the pan. It only needs a cap to keep from splashing out all over and to con tain hydrocarbons from escaping into the air. When I was young, oil caps were vented to the outside world. However, if enough blows out to let the oil level drop too low for the pump to draw from the pool, if the pool drops below the pickup. that’s when the engine starts to self-destruct.

Since the clutch may be going out (has he driven a manual before?) and the engine seems to be running okay, I’m going to take the optimistic view. The gravelly sound may have been from the clutch assembly. The cap may be missing because he topped off the level at some point and forgot to replace it. I’m going to optimistically assume that there was no engine damage.

So, how many miles are on this vehicle?
What year is it?
What engine?

How much damage? You’ll know once you get the clutch checked out. Whatever the cost, I think you’re going to end up eating this one. Consider it the cost of an education.

As I usually do, I am in agreement with mountainbike, but I want to add that it is possible that the local garage left the oil cap off, rather than the person who was driving the car. At this point, I suppose that it is going to be difficult to figure that one out. Is the garage eating the cost of the oil cap and the clean-up? If so, it sounds like they are admitting fault for the cap.

However, I have to say that I found the post confusing. Based on the circumstances, it sounds to me as if the OP loaned his car to a friend, but twice in the post, we are told that the OP borrowed the car, so it is a bit difficult to figure out whose car this is, as well as who was driving it.

Gustywinz–Did you loan your car to someone?
Or, did you borrow someone else’s car?

???

@VDCdriver…I was struck by that too. It seems just an incorrect word choice. Such things are perhaps not so rare these days, but in this case it leads to confusion.

From context, I read this as he loaned his car to a friend. He says his friend took the car from Wisconsin to Colorado, and then says before he “handed over the keys” etc…so it seems as you suggested that he allowed someone else to use his car (and returned it in much worse condition).

I suppose that this may have been an incorrect way of describing the situation, but since we were told twice that the OP “borrowed” the car…

The car was returned a week later with a growling engine…

A noisy engine might indicate that it was out of oil. How low was the oil level?

The story is a bit convoluted and it does sound like the garage made a mistake by omitting the oil filler cap. The person who borrowed the car also made a mistake by operating it with an engine noise and apparently not raising the hood for a looksee.
The allegedly looser clutch and shifter could also possibly be an indication someone drove the car a bit aggressively to put it polite terms.

This leads to the point that the OP apparently drove the car to the garage the next morning with oil splattered all over, a noisy engine, and possibly not even checking the oil level before doing so.
In a nutshell, mistakes all around.

Just because the engine sounds fine now does not mean that it is fine.

Nevada asked the key question: How much oil remained in the engine when the car was returned to you?
Your friend drove the car 2000 miles and never even opened the hood? I wouldn’t loan this person my bicycle…

It seems unlikely low engine oil would affect the clutch. My guess in that the clutch problem – if there is one – is not related to the missing oil filler cap.

The key question here is what was the reading on the oil dipstick when the car was returned to the owner. Without that info, it’s hard to voice an opinion.

I used to get that from my dad too. He’d always say borrowed instead of loaned. Its a little confusing but I’m sure the OP loaned the car to a friend who 1) rode the clutch in Colorado hills and may soon need replacement and 2) was oblivious to oil squirting around the car and what to do about it. I suspect if the friend didn’t know what to look for with oil spraying over the car, he/she wouldn’t have known how or thought of checking the oil. I think the place that changed the oil just left the cap off.

Lots of lessons. Loan your car to a friend? Make sure they are competent. Have someone else change your oil? Always check their work afterwards for tight drain plug, filter, and any missing parts. No good deed goes unpunished. That’s why rental companies charge so much.

There’s one other thing which might have created a problem: The PCV system on most cars requires the valve cover not leak air. Otherwise the suction which brings crankcase gases back into the engine doesn’t work. If the oil filler cap is off, that might well cause the PCV venting to fail. Seems an unlikleyh cause of the noises being heard, but worth consideration at least.

The car was loaned. He’s my best friend and I decided after a few days of contemplation to let him use the car for Colorado.
When the car was returned and we had hung out for a little while it was basically like a mystery unfolding. First being made aware of the problem, looking under the hood for the first time, seeing the dipstick, etc. I was more mad at the garage, but as I think about it more I am amazed my friend, even with the ability to throw a football (like Aaron Rodgers), still has complete inability to resolve car problems spontaneosly.
75k on the car. 2003 Corolla, 1.8L Engine (just look up '03 Corolla).

So let me get this straight- the shifter feels “looser” (much looser, I would say more like 20k mi was driven rather than the 2k) is due to driving style? Such as accelerating with clutch still engaged/using it often (Colorado hills)/ etc.? I just don’t understand how my car can feel different, is this a wear issue? Of course this is a learing lesson for me, and I am thankful to have everyone who has replyed and for being my professor on this one.

Re the looser shifter:
Some people have the bad habit of holding the shifter in a death grip as they drive along and/or manhandling it when shifting instead of feeling for the spring action (aligns itself in the 3-4 channel) and gates.

I seem to find whenever I loan a car out it does not feel the same when I get it back. Of course after the last 40 years I am more selective about who can borrow a car, but barring a major mechanical failure I think most of the time when I got the car back I was hypersensitive to things I had ignored before.

Some of the regulars who have been around here for quite a while may remember the lady who posted some years back about the clutch in her just purchased VW New Beetle. She had taken her daughter out to instruct her in using a manual transmission and said daughter wiped the brand new clutch out in 2 days time. Much depends on the left foot of the person behind the wheel.

What I would be most concerned about would be the engine noise and oil, or lack of, issue.

Neither a borrow nor a lender be. Hamlet Act I, scene 3. Still seems to make sense. Rocketman

Is funny how big a mess a little oil can make. I have seen this situation a couple of times after a quicky oil change and one on a brand new car (26 miles). The oil loss was insignificant in each case, but they were caught in short order, not a 1000 miles later, but it looked like a gallon of oil had been thrown under the hood.

But in each case, some of that oil landed on the exhaust manifold and that generated a LOT of smoke. How did your friend miss this, it should have choked him out during the trip. Surprised he wasn’t stopped for excessive smoke, especially in Colorado. He must not have gone through Loveland.

Yes, loaning things can be a big mistake. Years ago, we had a big old tent we used. Friends asked to borrow it for a two week trip. We showed them how to set it up, and how to pack it.

When they brought it back, I asked them if it was dry when they packed it. They assured me it was, and like an idiot I took their word. Fie on me.

A few months later, we took it out to use it, and it was half eaten with mold. Their idea of dry apparently meant the flood water was below the floor of the tent and it clearly had been packed when wet with dew.

I said not a word to them, because I was the idiot who took their word that it was dry. In 15 minutes, I would have known it was not. My stupidity.

George, all that does is allow hydrocarbon fumes to waft up into the air. It has no affect on engine operation. The PCV valve is just a check valve, like if you put a little free-flooating valve in a valvebody. It would cause ni noise and not affect engine operation.

It may help to know that the purpose of a PCV valve is to allow the crankcase to vent fumes without allowing a backfire to ignite fumes that might exist under the valvecover. When an engine gets old, and if it’s misfiring, the fumes blown past the rings and into the crankcase can contain unburned aerated gasoline, and it can be volatile. The same fumes that are in the crankcase also are in the space under the valvecover.

4 cylinder engines tend to pulse air out of the oil filler hole when the cap is left off, and that will make a growling noise. Don’t ask how I know this;-)