I work on cars. AMA
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Anonymous
Ok, so there’s “warmed up” according to the light on the dash or the temp gauge, and there’s “warm” as defined by other things. When the temp light goes out or the gauge shows warm, that’s the coolant temperature. That’s important for things like mixture control, emissions stuff, and various other things that the ECU controls and needs a warm engine to operate efficiently. But there’s some other stuff that requires a warm engine, stuff related to the oil and keeping the oil clean. So basically, every time a cylinder fires while the engine is running, there is a thin film of burned gasoline residue on the side of the cylinder wall. As the piston comes up to complete the exhaust stroke, the piston rings are scraping this microscopic residue off, and it gets caught on the rings. And then during the next intake stroke, as the piston bottoms out in the crankcase, the oil bath coats the rings and washes off this residue. Over time, this is what makes the engine oil turn from clear golden to opaque black. All the burned carbon residue from the firing cycles, scraped off by the rings, and washed into the oil. But it’s also got other stuff in it too. Mostly hydrocarbon chemical liquid compounds that didn’t burn in the firing cycle. This stuff is accumulated in the oil, too. Unlike carbon, it’s a volatile chemical, and can evaporate into a gas over sufficient time and temp. Which is good, because the stuff is sometimes corrosive to some components in the engine, can cause varnish to form, or gun up oil passages. So it’s good this stuff evaporates and cooks out of the oil. But the oil has to be hot to do this. Hot, for a while. And the engine has to be running to route to these gases produced by the evaporating nastiness into the PCV system, which sends them into the engine fuel air charge, into the cylinder, where it is burned and eliminated. So that’s why you need things to get warm, and stay that way for a while like on a long drive. It helps clean the oil As for the exhaust system... sometimes in winter, you can literally see streams of water pouring out of the exhausts on some cars. Ever see police cars that are sitting in one spot for a long time in the winter? Sometimes they’ll actually have icesickles hanging off the exhaust tip. In cases like that, low rpm or idling, the exhaust is never going to get hot enough to dry out. On a high speed drive, like a highway, it will. But neighborhood driving or crawling along in traffic, won’t get the engine to work hard enough to burn enough fuel to get the exhaust temps up all the way to the tailpipe. |
Anonymous
At ten years old, you’re on borrowed time already, even though it doesn’t get much use. At the very least, check the electrolyte levels (assuming it’s not a sealed battery like an AGM style) and make sure the tops of the plates are covered. Being on a tender all the time can slowly cook off the electrolyte, even though it never gets anywhere near the boiling point. Something to do with ionic bonding or such. I don’t really understand the chemistry completely, but that what happens. So check the level, add distilled water if needed. You won’t be able to tell if the plates are sulfated or not, but at ten years, I’d suspect they’re at least partially sulfated. And carry some cables, or one of those neat new little charge booster packs that are all over Amazon for like $80 now. Because it’ll fail at some point, and then you’ll know it’s time. |
Anonymous
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In the winter, my subaru (2004) emits a burnt oil smell coming through the vents, and I can see smoke coming out of the hood, but this only happens when the engine has been cold and I drive it long enough for the engine to get pretty warm. This doesn't happen when it's warmer.
I have taken it to my mechanic twice now, and as great as he is, he can't figure it out. I've googled it, and can't figure it out. If you can point me to the right direction, you are a god in my eyes. |
Anonymous
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My RAV-4 is approaching the need for an oil change, but based on mileage and on estimated date of change given to me by Jiffy Lube, it's a few hundred miles away from actually having the light on, etc.
My car wouldn't start today; it took several tries over 10 minutes to start. I think it's the heat. Are these two things related? Thank you! |
Anonymous
Lol North Dakota. The record difference (this is real) was 181 in 1936, 60 below in February and 121 above in July. According to the tourism people, ND is typically the last state people visit who make a point of visiting all 50. |
Anonymous
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How worried should I be that our 2018 Hyundai Santa Fe has had the following issues (all now repaired; car under warranty) since we bought it in Dec 2017?
-Bolt loose in the suspension, so every time we put the breaks on it made a loud creaking noise - hinge on back of tailgate wasn’t coated in the right material, so it rusted. -recently a fuse blew, so the car locking from the keys and switches wasn’t working. But the lights still blinked so looked like it was working. -the latch on the back of the car to shut the trunk stopped working. so if we shut / locked the back, we couldn’t unlock it (unless we crawled inside), and if it was unlocked, door wouldn’t stay shut. Car has 10,500 miles on it, mostly city driving, no accidents. |
Anonymous
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Another question about my 2009 Ford Escape.
A few months ago on a trip of about 100 miles the engine seemed to run a little rough for about 5-10 seconds several times. Then later that day on the way back the check engine light came on. That was a Saturday. On Monday I was going to take it to my mechanic after work to see what was up, even though it was running fine with the light on, but in the middle of the day the light went off so I didn't take it to the shop. Do you think I should find out what the code was? Or should I just be satisfied that the light has been off and it has been running fine for the last few months? |
Anonymous
I’m betting you have a very small leak in one of the cylinder head gaskets that is allowing oil to seep out in cold temps when the engine, which is made of metal, is at its maximum point of cold contraction. Metal expands and contracts as it gets warmer or colder. (Unrelated- did you know the SR-71 spyplane, which flew at almost 2,200 mph, got so hot from friction with the air around it that it “grew” 11 inches during flight? That’s how much metal can expand with heat) in the winter, the engine will contract more that it does in the summer. We’re not thing much here , just .0001, one then thousandth of an inch, is enough to let oil wick out past a seal and drip onto the exhaust manifold. In the summer, the engine doesn’t get cold enough to contract that much. What to do? Unless you also have a leak in the cyclinder head gasket that is mixing coolant into the water or vice versa (cyclinder head gasket issues are common on Subaru H-4 enginess, btw) I’d let it ride. Live with it. Eventually it’ll get worse, and the leak WILL be easier to spot then. Same cost to fix it now or later. I’d wait until I couldn’t stand it anymore. But that’s just me. Lastly, I’m NOT a god. Definitely not. But you’re very kind to say that. |
Anonymous
I’d be seriously annoyed. And I fix a lot of Hyundais, too. Not because they’re unreliable, just because there’s a lot of them, and I work on popular vehicles. I remember working on a 2009 Santa Fe that had a similar electrical gremlin, and it was maddening. The interior light would NOT work, no matter what we did. Ended up replacing the entire ground block and fuse assemblies. I’d be irritated at having that many issues in a new car, especially the corrosion issue. I’d probably trade that car to be honest. I wanna like Hyundai, because of all the automakers out there, they and Kia have made the biggest strides in the last decade. And in so doing, they threatened Toyota and Honda so much that they’ve each had to raise their own game in return. And that benefited everyone. |
Anonymous
My bet would be an O2 sensor. I had a 2011 Escape Hybrid 2wd that would run like a top all day long just driving around town, but after a couple hours at highway speed, especially if I was really hauling ass, I’d get an engine light. It wouldn’t run any different, it would just have a code. So I’d check the code, and it was always the O2 sensor. But then it would clear itself within a day or two after going back to normal around town driving. If you have a code reader, see what code it’s throwing. If the running rough happens again, and corresponds to another light, check it right then while it’s still on, before it resets itself again. Ford ECUs are supposed to store codes, but mine didn’t. Go figure. Code readers are fairly inexpensive now, you can get a decent one for under $100 now. And knowing those codes can really help narrow down the diagnosis for what could be causing the running rough. Because it could be at least half a dozen things, and you don’t want to just start blindly fixing stuff without knowing the specifics. |
Anonymous
I don't have a code reader myself but my mechanic would check it for free. I have actually driven it on a 2500 mile trip since then with no issues so maybe it's nothing to worry about? |
Anonymous
The hard start today had nothing to do with your oil. That said., let’s ponder what it might be in the order of greater improbability Maybe you possibly had a vapor bubble somewhere in your fuel line. Do you park the car outside? Because it’s possible the pavement was warm enough, long enough, to radiate enough heat up under your car to get your fuel temp warm enough to evaporate enough fuel to form a bubble in the fuel line. And that’s pretty improbable! Or... It could be that the engine temp sensor thinks the car is already “warm”, because it’s hot as hell outside, and even when you shut the engine off let it sit for hours, it really doesn’t cool off as fast or as much as it would in lower temps, and the ECU is trying to start the engine with a lean fuel-air mixture because it thinks it’s alreaf been running because it’s so warm. I had a 2005 Toyota Matrix that used to be VERY hard to start when it was warm. Or... You didn’t describe the starting attempts, but it could also be a dying battery if it seemed like it wasn’t cranking fast. And hot weather kills batteries that are already in marginal condition. But what I do know is that the oil condition had nothing to do with it. And Jiify Lube sucks. I’d be remiss if I didn’t say that. |
Anonymous
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[quote=Anonymous][quote=Anonymous][quote=Anonymous]Another question about my 2009 Ford Escape.
A few months ago on a trip of about 100 miles the engine seemed to run a little rough for about 5-10 seconds several times. Then later that day on the way back the check engine light came on. That was a Saturday. On Monday I was going to take it to my mechanic after work to see what was up, even though it was running fine with the light on, but in the middle of the day the light went off so I didn't take it to the shop. Do you think I should find out what the code was? Or should I just be satisfied that the light has been off and it has been running fine for the last few months?[/quote] My bet would be an O2 sensor. I had a 2011 Escape Hybrid 2wd that would run like a top all day long just driving around town, but after a couple hours at highway speed, especially if I was really hauling ass, I’d get an engine light. It wouldn’t run any different, it would just have a code. So I’d check the code, and it was always the O2 sensor. But then it would clear itself within a day or two after going back to normal around town driving. If you have a code reader, see what code it’s throwing. If the running rough happens again, and corresponds to another light, check it right then while it’s still on, before it resets itself again. Ford ECUs are supposed to store codes, but mine didn’t. Go figure. Code readers are fairly inexpensive now, you can get a decent one for under $100 now. And knowing those codes can really help narrow down the diagnosis for what could be causing the running rough. Because it could be at least half a dozen things, and you don’t want to just start blindly fixing stuff without knowing the specifics. [/quote] I don't have a code reader myself but my mechanic would check it for free. I have actually driven it on a 2500 mile trip since then with no issues so maybe it's nothing to worry about?[/quote] Most of the time, the amber/yellow check eng light is emissions related codes. The red lights are the scary lights, lol. |
Anonymous
This is what we all guessed, too, but no one can seem to find where the leak is. No traces of oil anywhere, and I'm guessing that's because it's being burned off. I know replacing the head gaskets is $$$$. Thanks.. you are still a god ... with a small g. |
Anonymous
Thank you!!! 
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