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Post by tomtina3 on Feb 14, 2008 17:54:41 GMT -5
1995 Pontiac Transport 3.8L, 195k mi., Oil pressure gauge reads normal when cold, goes down to almost zero as it warms up. Engine runs smooth when cold, but knocks like hell when it heats up, especially under torque. Leaks oil dripping fairly fast when cold (but not once it warms up) around the crankshaft. so.... mechanic thinks the engine is shot, thinks oil is leaking internally, engine bearings etc, and thats why the oil pressure is low. Could it be the oil pump? rebuild is about $250, pump is internal (in engine, not in the oil pan). How can you test whether its the oil pump, or if the engine is shot? i hate to put another $2-300 if its not the problem, and mechanic is skeptical. Any advice?
Also, would a thicker oil buy me some time? What viscosity?? Thanks!
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Post by idol on Mar 18, 2008 10:05:47 GMT -5
Hi tomtina,
Sounds like your oil pump and /or bearings are shot. Normal or high pressure when the engine is cold and then dropping slightly after the engine warms or becomes hot is pretty standard. BUT, dropping below normal or down to almost zero, is a sure sign that either your pump is worn or your crankshaft main bearings and possibly your piston bearings are leaking and worn. HENCE the knock when the engine is hot.
I recommend you rent a pressure gauge, install it where the current sending unit is installed, run your engine and write down the readings. Check cold, then warm then hot all at idle. Then rev the engine to about 2000-2500rpm and check those readings. Go to a library, (unless you have access to a manual) and look up what the oil pressure readings should be.
This test will help you identify the problem fast.
Additionally, a leak around the crankshaft is an indication that the engine main seal(s) are leaking.
Let us know what you find. IDOL
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