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Hatchbacks Chevrolet Metro/Geo Metro Chevrolet/Geo Metro
1696 messages, Last post on Dec 06, 2009 at 11:26 PM
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Zaken1: I got lucky. A local salvage yard had a used starter on the shelf which I got for $35.00. I put it in and it works great. The car starts right up now and runs great EXCEPT....... that knocking noise is definitely a rod bearing issue. My plan is to drop the pan and install 3 new rod bearings. There is hardly anything in the way, so access should be easy. Here is my question please: the car has 120,000 miles on it. Do you know what bearings I should get. Would you know the part number, etc. Thanks so much for your kind assistance and help.
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Replying to: annielulu (Aug 13, 2009 9:27 pm) 1> it does not make any sense to me that fuel dilution during a long period of cranking or local driving will take out rod bearings. This is because gasoline has some lubricating properties, and the loads and speeds which the engine was subjected to during the time when the injector was leaking were very low. So I just don't believe that this treatment would be anywhere near severe enough to take out the bearings. I have seen many engines run on diluted oil, and I have NEVER seen bearings become damaged as a result. It is only when an engine runs out of oil that this happens. 2> Furthermore (and perhaps even more significantly) any combination of load and lack of lubrication which would be sufficient to take out the bearings would probably also score the crank journals. So if your bearings are really wiped out; you probably need to have the crank reground, in order to keep from repeating the same scene. If you insist on replacing the bearings; please inspect the crank journals for scoring or bluing before you install new bearings. If the crank is scored or discolored from heat; then you'll need to have the crank remachined, in order for the new bearings to last anywhere near a normal length of time. 3> The knocking created by loose rod bearings is directly proportional to the amount of load on the motor. It is quietest at idle, and becomes louder the harder you accelerate. But you said that your engine's noise is loudest at idle; and becomes quieter as you accelerate. And this is just NOT what bad bearings sound like. 4> There is another type of knock which sounds totally ominous, and which DOES sound like what you described. It once convinced me that a 3 month old Toyota Celica had something major broken inside its motor. This noise was loudest at idle. It sounded to me like a heavy metal bar was banging around inside the motor. When I first heard it on my client's nearly new Celica, I told her to not drive the car one block more; and to have it towed to the dealership for warranty repair of an obviously defective motor. And she did so. Some time later, I encountered her again, and asked her what the problem turned out to be with her car. And she told me that the dealership had just run some carbon solvent through the combustion chambers, and that had completely cleared up the noise!!! They then told her that the noise, which is referred to as a "carbon knock," was caused by her use of cheap fuel that had insufficient quantities of engine cleaning additives in it. And that had led to the build up of carbon in the combustion chambers to such a degree that it effectively increased the compression ratio to the point where the engine went into uncontrolled detonation at idle. The dealership then told her to NEVER use any fuel except Chevron (which contains adequate quantities of carbon solvents). And the problem never came back. Some years before that, I had the same experience with a Honda motorcycle which I had bought new and lovingly maintained for 80,000 miles (except for always using cheap fuel). And I naively misdiagnosed that sound as a broken piston skirt; and as a result literally gave the machine away. I later learned that the person who bought it never did anything to the motor, and it gave him no problems afterward. Carbon knock is something that we old timers never encountered in the past. It is a unique consequence of a glitch in the chemistry of modern reformulated fuels; in which the additives which are used to replace lead turned out to produce heavy carbon deposits in combustion chambers. Some fuel manufacturers (Chevron, Shell, and Texaco) have developed additives which counteract this carbon build up. But those additives are expensive; so the cheaper fuels don't contain them. And that's where the carbon knock comes from. But it's your car, and your life. You can do what you want with it. Since I've been down that road before, I am just trying to save you a bunch of time, money, and frustration. But you can override my advice, (at your own risk) if you want. If you log on to Rock Auto's website, and select your car and engine model; scroll down to the "engine" category, click on "connecting rod bearing" and you can use any of the brands listed there. I personally would not use the Clevite/Perfect Circle bearing, because it is made of aluminum; which has poorer anti friction properties than the other brands. But the caveat in selecting bearing sizes is that some engines are manufactured with undersize crankshaft journals (as a result of a machining error when the crank was first manufactured). So those cranks would require a thicker bearing to achieve the proper clearances. Some connecting rods are remachined to a larger ID during overhaul, which also would require a thicker bearing. The situation is compounded because some manufacturers (namely Beck Arnley) call thicker bearings "oversize" (which is literally what they are); while all the other listed manufacturers call thicker bearings "undersize" (because they are made to match an undersize crankshaft). This is just a difference in semantics. All bearings which differ from stock dimensions are thicker bearings. Nobody makes a bearing which is thinner than the stock part; regardless of what they call it. But, since some new crankshafts have undersize journals, and some used engines have had their crankshaft remachined during an overhaul; you cannot assume any crankshaft has stock diameter journals. The journals must be accurately measured with a micrometer or dial caliper before you can know what size bearing will fit properly. Wear on the journal is not an issue in bearing selection (unless you have a Model T Ford). The journal will either be stock, or smaller than stock in .010"; 020"; or .030" increments. And the connecting rod inside diameter will either be stock; or larger than stock in .010"; or 020" increments. If your crank journals are stock diameter, while the con rod ID is .010" larger than stock; then you'd need a .010" thicker bearing. If the crank journals are .010" smaller than stock, and the con rod ID is stock; then you'd also need a .010" thicker bearing. Rod bearings for the Metro are made in stock thickness, and in steps of .010" (.25mm); .020 (.50mm); and .030" (.75mm) thicker than stock. If you look at the part image for the Sealed Power # 31140RA bearing, there is a handy chart which lists the stock crank journal diameter as 1.6530-1.6535". This chart also lists the ID of the stock con rod as 1.7716-1.7721". Wear on journals is less than .001-.002" so it is not a factor in bearing selection. And the oil clearance is also not pertinent to this operation. Just measure the crank journal and rod ID, compare the numbers to stock; and you'll know what size bearing to buy.
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Replying to: zaken1 (Aug 14, 2009 1:38 am) Thanks a million for taking all this time. It started my day with a bang!
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Replying to: vanillalatte (Aug 14, 2009 2:58 am) |
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Replying to: zaken1 (Jun 19, 2009 2:44 pm)
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Replying to: jessegeo (Aug 16, 2009 1:45 pm) It is absolutely essential that both the head and the valve cover be surgically clean and free of all traces of old gasket material and sealer along the entire sealing surface, before installing a new gasket. This cleaning should include the recesses in the curved part of the valve cover. You can use an inspection light and a screwdriver, solvent, an Exacto knife, dental probes, or similar tools to reach into the corners of the cover and remove fragments. It just takes one tiny chunk of debris to keep the valve cover from seating completely. And after the parts are cleaned; thoroughly check the entire sealing surface for cracks or gouges. The gray formula Permatex RTV is preferable to the high temp red formula; because it is more resistant to being squeezed out of place when the cover is tightened. And that cover does not get hot enough to require high temperature sealer. It is also important to only apply only a thin, even coat of the sealer to the top and bottom faces of the gasket (not to the metal parts); and then wait about ten minutes after applying the sealer to allow it to set up, before installing the gasket in the valve cover. The sealer should still be tacky enough to hold the gasket in the cover without it drooping out of position. And the valve cover nuts should be tightened in a criss cross pattern, going back and forth in several steps between nuts on opposite ends; so the cover can come down evenly. The final tightening should be done with a torque wrench, to 15 foot lbs. Some brands of gaskets may be made of cork, fiber or cardboard. These are inferior quality, and should not be used on this motor. If that is the type of gasket you've been using; find a store that sells a rubber gasket. And be sure they sell you the right gasket for this motor. It should match the shape of the cover, and fit snugly in the cover without needing to be cut or shortened. Also note that there is only one way the gasket will fit; there should be one curved end that matches the curve of the valve cover and the cylinder head. And the gasket definitely has a top and a bottom side. Some gaskets also come with grommets. These grommets go on top of the valve cover, under the cap nuts. If your gasket came with grommets, and they were placed underneath the cover; they would prevent the cover from seating. |
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Replying to: jessegeo (Aug 16, 2009 1:45 pm) |
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1996 1.0 5 spd Been on this one for months- starts fine but can't give any throttle before it warms up, or it floods out. Checked the voltage at the Coolant Temperature Sensor by backprobing. It has three wires: Light Green/Black, which is common and goes to the MAP, TPS, and IAT. Gray/White, which is the signal to the ECM. Yellow/White, which is not shown on wiring diagram, but I assume is the input from the ECM. LtGr/Bk is ground- no voltage. Gy/Wt reads 2.34V when cold, decreases with rising engine temp and finally goes to 0.5V when hot, at which point the cooling fan kicks on and takes it back up to around 0.65V. (With two different CTS units- same within .2V) At anything over 1.0V, the engine will flood and stall if the throttle is opened even slightly. These values seem reasonable if the temperature was around zero- but it's 80. What does not seem reasonable is the voltage on the Yellow/White wire which I believe should be the standard 5V input from the ECM, but reads a steady 9.2V, regardless of temperature and even when not running with the ignition on. If the input voltage is nearly twice what it should be, then the CTS could have exactly the correct impedence, but the output signal would be much higher than the ECM expects, and it would compensate with a mixture richer than Bill Gates. Is it possible that something is creating a field that the wire is having additional current induced in it somehow? My DMM read nearly a volt with the positive probe held in the air near (2 inches) the sensor wires. I hope this is the gremlin I have been looking for since April, but I don't have a clue how it could get 9.2V. Maybe something a little over 12v, yes- but not 9. Anyone see this before? Hints? My crystal ball keeps saying to try again later....
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Replying to: shaggyman1 (Aug 17, 2009 10:20 pm) But there is one other factor here which proves this point: The CTS resistance is highest when it is cold, and drops as the engine warms up. This means that the voltage signal the computer "sees" from the sensor is LOWEST when the engine is cold; and becomes higher as the engine warms up. So if your supply voltage was too high, the computer would get a signal that the engine was hotter than it really is. And under that condition, the engine would not go rich when throttle was applied. Instead, it would go too lean. But you claim the engine is flooding. Actually, I believe you are confusing the behavior of a flooding engine with one that is going too lean and starving for fuel. An engine which is too rich is typically insensitive to small changes in throttle opening; and will easily accept sudden openings in throttle position. A rich engine will also run much better when it is cold than it does when it is warmed up. On the other hand; an engine which is too lean will stall out if the throttle is opened when cold; but will run much better after the engine temperature comes up to normal. So I believe this is what your engine has been doing. Hopefully this will give you a better sense of where to look for the source of the problem. Here's a simple test you can do to prove this: Disconnect the plug to the IAT sensor, and then try running the motor. I bet you'll find that the cold stalling is gone. The IAT sensor is just like the CTS. Its resistance is highest when the air temperature is cold. So when you disconnect the IAT plug; the computer thinks the air temperature is below zero; and richens up the mixture.
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Replying to: jessegeo (Aug 16, 2009 1:45 pm) |
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