What happens when you use a rag in place of an oil cap? Hint: it's not pretty.

Dear Car Talk

Dear Car Talk | Dec 01, 2006

Dear Tom and Ray:

Oh brother. I lost my oil cap last time I changed my oil. While I searched for a new oil cap, I stuck a rag in the opening as a temporary fix. While driving on the highway, my car started making an awful noise. When I stopped to look, I saw that the rag was sucked halfway into the engine. I turned off the car and pulled the rag out, but the end was already very frayed. Now I've got bits of rag in my engine, and not only does my car sound terrible, but it loses acceleration on the highway and feels close to a breakdown. Is there any way to clean the rag fragments out of the engine of my 1998 Isuzu Rodeo without having someone take the whole thing apart? What are my options here? -- Ryan

TOM: Well, the 2007 Honda Pilot is a nice option, Ryan.

RAY: Actually, it's possible that some bits of rag got wrapped up between the cams and the valves, and are somehow preventing the valves from closing all the way.

TOM: That's odd, because normally the steel rotating cam shaft and the steel valves would just chew up the rag pieces and destroy them. But I suppose it's possible.

RAY: Preventing the valves from closing WOULD cause noise and poor performance. In any case, it's easy enough to check. Have a mechanic remove the valve cover -- which isn't a big job -- clean out whatever's in there, put it back together, and hope for the best.

TOM: And by "hope for the best," I mean hope that either (A) bits of rag didn't get chewed up and sent down the oil-return holes into the oil pan. Or (B) that you didn't just run the truck out of oil.

RAY: If rag fragments managed to get down into the oil pan, they could be clogging up the pickup screen on the oil pump's intake tube. That can lead to oil starvation, which can also create noise and poor performance. Then you'd need to remove the oil pan -- which is a pretty big job -- and clean off the screen, since a simple oil change is unlikely to get it done.

TOM: The worst-case scenario is that by driving without an oil cap, you ran the truck out of or very low on oil.

RAY: Right. The rag could have acted like a wick, and soaked up a bunch of oil. And then you removed the remnants of the rag and kept driving without an oil cap. While you were driving, oil could have splashed out of the valve cover -- further depleting your supply of oil.

TOM: If you run the engine out of -- or very low on -- oil, you can do serious damage to the bearings, which can result in knocking, poor performance and, pretty quickly, complete engine failure.

RAY: In fact, you already might have experienced complete engine failure by the time you read this, Ryan. If you did, congratulations! You no longer need our help.

TOM: I'd start by checking the oil level. Then, assuming it's good, remove the valve cover and see if there's stuff preventing the valves from closing. If there is, clean it out and then change the oil and filter.

RAY: And if there's nothing in the way of the valves, it's time to give yourself a dope slap, Ryan, for using a rag as an oil cap. Think about it. Do you think the manufacturer ever would have spent 3 dollars on an oil cap if a 10-cent rag would have sufficed?

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