Overheating help

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  #1  
Old 09-03-05, 02:46 PM
melon
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Overheating help

I have a 94 4runner with the 3.0. I have done everything to stop preasure building and overheating. Changed fan clutch, flush. I have a combustion leak getting into the cooling system. I have no water on the oil and no steam comes out of my tail pipe so I don't suspect blown head or head gasket.

Does anybody have any ideas?
 
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  #2  
Old 09-03-05, 03:14 PM
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When you say you have a combustion leak into the cooling system, you are describing a blown head gasket or a cracked head or block. I think you need to take a closer look starting with a compression check.

You could also have a bad thermostat, clogged radiator, or water pump.

You might pull your spark plugs and inspect them also. One of the telltale signs of a coolant leak into a cylinder is a nice clean, white porcelain on the spark plug center electrode instead of a slightly sooty appearanace that is normally seen.
 
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Old 09-03-05, 03:27 PM
melon
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I am not very mechanical. Will a compression check tell where the leak is coming from?
 
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Old 09-03-05, 03:39 PM
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Not necessarily, but it's a starting point. If you have one cylinder that is considerably lower than the others (the readings are in PSI) that would tend to point towards that cylinder. If two adjacent cylinders are low, that would indicate the gasket could be blown between the cylinders.

You can also have a cooling system pressure check done. What they do is attach a special adapter and pump to the radiator filler neck and pump it up to operating pressure to see if it will hold the pressure. If the pressure drops, you have a leak somewhere, either externally or internally.

Pulling the spark plugs and inspecting them, as I mentioned, is a fairly good way of looking for a cylinder that is burning coolant. It's like steam/pressure cleaning the plug which is why the interior porcelain would look nice and white like a brand new plug.

You might also remove the radiator cap (while it's cold) and start the engine. If the head gasket is bad enough, you may see some bubbles in the coolant while the engine is running. In some instances, when the head gasket is badly blown, you can even get a regular geyser out the radiator filler. Caution: As the engine warms up the coolant will overflow from normal expansion.

Check www.autozone.com, you may find some more general info that could be helpful. Check here: http://www.autozone.com/servlet/UiBr...3d8016087e.jsp

One final thought/question: Has the engine actually been overheated and how badly, i.e. how far/long did you drive it and how many times? Modern engines do not react well to being overheated and the result is often a warped cylinder head which creates the same symptoms as a blown head gasket even if the gasket is intact. Normally they go hand-in-hand.
 
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Old 09-03-05, 08:53 PM
melon
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Overheating 4 runner

Thanks. You have given me more info than any mechanic out here. I have no bubbles when the car is operating with the cap off, or no water spewing out. When the vehical gets hot it doesn't act hot. I have a lot of preasure in my hoses and you can feel the heat from the engine. I'm gonna try that bargs leak that is supposed to fix blown gaskets and heads. It's better than doing a head gasket repair right now. This is really starting to annoy me and if It's too much I'll just get rid of the car.
 
  #6  
Old 09-04-05, 02:50 PM
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Be aware that the Bars Leak (aka mechanic in a can) can do bad things inside your motor and cooling system including the radiator and the heater core. There is no instant fix for a blown head gasket (or most any other problem that the mechanic-in-a-can makers would have you think they can magically fix for three or four bucks worth of their product) if that is in fact the problem.

Additional question: This sounds pretty basic, but is the first Q I should have asked. Are you sure the engine is actually overheating and you don't possibly have an indication problem? Pressure in the hoses is normal; you have to remember that your system pressure is probably 14 or 15 psi which doesn't sound like a lot, but is enough to make a normally soft hose fairly rigid. And the external temperature of an engine is enough to fry an egg on any car when it reaches operating temperature.

You also need to make sure you radiator cap is holding the proper amount of pressure and you could also have a defective thermostat. The list of possible causes of overheating is practically endless.
 
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