Engine Knock Noise? help.... mk1

[mikeym]

hey guys,

i don't know anything about engines.... so i don't know exactly where to start. i bought this mk1 (1989) this weekend with the intention on fixing the engine with my dad. he is still going to work on it with me. but i'd like to have a clue whats up, so i can read on the problem online.

when i start this car the engine makes a very loud knocking noise... but then after its running a bit, it goes away....

what can this be?

please bear with me guys, i'm still learning

~mikeym

[91MR2quickNA]

Usually older cars start to experience rod knock or piston slap on start up.

Rod knock is when the rod bearings have slight to excessive play and creates a knocking sound which is the rod knocking against the piston or cylinder wall. Excessive play that is not used up under engine load can result in a spun bearing which damages the crankshaft or a thrown rod, which yeah, demolishes the bottom end (usually). I knew a guy that threw a rod through the top of his engine.

Piston slap generally occurs when the bore of the engine is slightly bigger than the piston itself. This usually happens with age as the engine wears. It normally stops after warm-up because the pistons' metal heats up and expands to fill the remaining space in the cylinders.

[mikeym]

91quickmr2na,

thanks a lot for the information....

ok i started the car up this afternoon and i believe i gave you a false statement...

it starts up and knocks a little bit... but not too much, then idles perfectly... when i give it gas not a lot of gas but a little gas i get a knocking noise... then when i give it a lot of gas this noise seems to get a little less loud...

right now, we're taking off the exaust, and then we're gonna take off the oil pan to see if the rods are bent.... but what do you think? its gonna be about 2 days until we get the oil pan off (just cause my dad and i don't have much time)...

think its the rods?

thanks a lot

[mikeym]

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