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Smoke Under The Hood


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#1
Vornskr

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I really don't know much about cars, so I'll try to be as detailed as possible describing the situation:

Got my '97 626lx 2 years ago almost exactly from Carmax. Love it. About a year ago, CEL came on. Took it to a Firestone or Goodyear (forget), and the guy who looked it over said there was some sort of loose sensor there, he readjusted it and the CEL shouldn't come on anymore. I smile-nodded and went on as usual, the next time the CEL came on (maybe a month max) I thought it was the same problem, so I ignored it...

Well maybe a few months after I started losing rpms while driving, thought I needed a transmission filter change so I took it in and that made the problem less frequent for about a month, and then it came back. Well last June heading to a concert 2hrs away the car died on me, it was losing furious rpms on the way up and then just stalled while I was going 70ish. After that incident I went online to look over problems with the 626, and first learned about the common problem with the transmission.

CEL still on the whole time btw.

So after a grand and 3 days I got a brand new transmission, but after a month or so I started losing RPMs driving again.. Coming home to Miami from Orlando one weekend, the car stalled out on me again, only this time it was also blowing out smoke under the hood. Not oil smoke for sure, was rather clear but a lot of it. After a tow back to the same transmission place (leaked some trany fluid on bed of tower), I was told it wasn't the 2 month old transmission, but that something was causing the car to overheat (making his case with pot of burned but clean transmission fluid he had just drained and replaced). The car was running again, so I took it to a "Friend of a friend's" place who worked on japanese imports who told me it was the air flow sensor. He also mentioned the silicone for the oil pan and transmission were bad and needed to be replaced.

CEL still on.

I got the air flow sensor replaced as soon as I could save up the $200 to buy it (little over a month ago) and the CEL finally turned off, leading me to the conclusion that all along the problem was with the Air Flow Sensor, and that I've been running this long with a bad one which has caused (or further agravated) problems with my transmission.

Early in the AM on Holloween, this drunk lady backs into my 626 while I'm pumping gas at a 7-11. The damage seems to be cosmetic, she didnt really hit me that hard, just enough for the hood to bend, bust up a headlight and the grill.. and as I found out later bust the catch on the hood cause it flew up while I was driving around. Got the body work fixed asap, but afterwards the car seemed to run a lot warmer. I never drive with the A/C on, all windows down music up etc.. so I noticed a slight burning smell.. not like oil but more like the metal was heating up too much. No CEL, no increase on engine temp indicator. Plenty of oil, antifreeze, water in resevoir. I asked a mechanic at work (U.P.S.) and a guy who has a 626 he works on, both said not to worry about it.

Sorry for the small novel, but I thought I would include everything that had happened to the car so far just in case, since I know squat really about how the automobile works.

Just today I got the silicone replaced on the oil pan (part procrastination, part lack of time to wait on car) and as I'm driving home, im noticing the same smoke coming out from under the hood that I saw the 2nd time my car broke down. Only much much less, I only notice it when im idling sometimes. When I get home I park the car and open the hood and I see that its coming from the front of the engine, metal part that has "HOT" with an "X" covering a hand on it indicating not to touch. I think this is the part that leads from the engine to the oil pan, but like I said no idea about cars... and it didn't come with a manual. Every so often one of the fans behind the radiator would kick in for a little bit, the wind would be enough to elimate any of this "smoke," so that's how light its. Doesn't really smell like anything in particular is burning, esp. oil. There are some stains on the part I mentiond the smoke seems to come off of, white though. I dont remember spilling anything on there. All the essential fluids are there and full up and nothing on the dashboard is lighting up, engine temp is same as always it says, but the hood feels much warmer after I get out of the car than it used to.

At this point I don't even know what it could be. It seems to me like the car is overheating, and its getting worse but slowly. This faint smoke (steam maybe?) is really bothering me though. Even if its harmless (which i doubt) it's embarassing. Like I said, it seems to be rising off that one part in the front of the engine, right behind the two fans behind the radiator. I'm wondering if its an after-effect of having a bad air flow sensor, if this lady who backed into my front actually damaged the radiator, or if its something else altogether.

I just hope the car gets me to work and back when I have to leave in 2 hours :(

Any suggestions would be massively appreciated.

#2
NickR

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as I'm driving home, im noticing the same smoke coming out from under the hood that I saw the 2nd time my car broke down.  Only much much less, I only notice it when im idling sometimes.  When I get home I park the car and open the hood and I see that its coming from the front of the engine, metal part that has "HOT" with an "X" covering a hand on it indicating not to touch.

Welcome to the board!

Let's concentrate on the bit I have quoted above. My car is the V6, so it's a bit different from your's, but from the picture in the Haynes manual, that metal part with an 'X' and "HOT" on it looks like the metal plate that shields the exhaust manifold. (It's curved, thin unpainted, non-shiny metal, and about one foot long, right?)

I can think of two possibilities:

1. There is a pinhole leak in your radiator (or one of the rubber radiator hoses), (caused by the drunk lady backing into you?) which is spraying a tiny jet of coolant (water plus antifreeze) onto the shield, where it is immediately evaporating as steam.

2. There is a slight oil leak, probably from your valve cover gasket, which is dripping oil down onto that shield (or possibly onto the exhaust manifold underneath it), and the oil is burning off.

Neither problem is a big deal.

I lean towards the first possibility. If it were oil it would smell like burning oil. If it is coolant, it will have only a slightly sweet smell.

Do you notice that you have to add coolant occasionally?

Get the car engine warm, then open the hood and look carefully for any leak. It will probably only leak when the engine is hot, because only then will the coolant be under pressure. (Keep your hands clear of the fans, especially if the engine is running).

Don't worry about the Mass Air Flow sensor. You had it replaced, the CEL has gone out, so it's fixed, and I can't think it could have caused any permanent damage.

By the way, most people with the 2.0 litre automatic transmission have found it desirable to change the transmission fluid very frequently (annually?) and to install a transmission fluid cooler, to prevent the transmission from failing. You should check out some of the posts on this subject. But this is unlikely to be related to your current problem.

Edit: I notice that the radiator thermostat housing is underneath that shield, at the end of the rubber hose (the bottom hose), where it joins to the engine. It's possible that the gasket there has a slight leak. That would be a good place to check (and if that's where the problem is, it's a very simple fix).

#3
AwGeez

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  • Car: 1996 Mazda 626 DX 2L Manual
Nick gave some excellent suggestions.

As far as a transmission cooler, get one. The number one failure of auto trannies is over heated tranny fluid. You need to get a plate and fin, not tube and fin. the Hayden Rapid Cool is real good and mounts in the flow of the A/C condenser by the radiator, so the A/C condenser fan will help it cool the oil.

With the engine running hot, does the temp gauge seem to be higher than usual? The white smoke could definitely be from the coolant escaping and steaming off the exhaust manifold heat shield. The trick is to find out where it is leaking. If it from the radiator, you will need to get that repaired. I wouldn't use Stop Leak or other additives since the leak seems minor and you're not noticing significant coolant leak. Those additives only add gunk to the cooling system and can potentially cause blockages.

When you last get the coolant flushed? Another recommendation would be to get your coolant system "power" flushed, not just a drain and refill. You could have some blockages in the engine that is causing the motor to run hotter than usual. Another potential issue could be a stuck thermostat. If you get a power flush, they usually remove the thermostat to get a good flow when flushing the system...

So if you get your coolant system power flushed with a new thermostat and gasket, have them check/fix the radiator and other parts of the system for coolant leaks, and get a tranny fluid cooler (have them change the tranny fluid again), you should be good to go.

If you plan on keeping the car, since you already popped for a new transmission, you might want to check levelten.com for their "bullet proof" tranny upgrade. It's not cheap but their upgrade will make up for the deficiencies in your auto tranny.

Good Luck and let us know how it turned out. B)




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