Engine Knock

[jonnyincognito]

Hello everyone,

I blew the oil pressure sending line for my aftermarket gauge on my 76 Celica. I didn't notice at first, and it basically pumped all the oil out of the engine on the highway. When I finally heard the engine knocking, I pulled off the road. I don't think I could have gone more then ten minutes like that. I moved it to my garage, capped off the leak and filled it back up with oil. It now has a knock that starts at about 2500 rpm. It's not a tick like you'd expect to hear from the top end, but a knock. Is it safe to say I lost a main bearing? I've never done bottom end work myself, is this something that can be fixed or is it likely smoked? Take it to a mechanic or something I can reasonably handle myself?


Thanks,
Joshua

[Howieau]

If you have lost a main bearing, you can jack the car onto stands, drop the oil sump and remove the main caps to assess the damage. If you have damaged the crank journal though (the surface on the crank where the main bearing sits around) then you have to remove the crank and have it machined. Once machined you will need to buy oversized main bearings because once they machine material off of the crank the journal will become thinner so the oversized bearing will compensate for the extra clearance. I am unaware if there are any machining tools that operates can use to machine a crank while inside the engine. Pulling the crank out can be a big job because you need to free it of all components connected to the rotating assembly (connecting rods, flywheel, clutch, pressure plate, main pulleys(harmonic balancers).

You should pop your head under the car while you have someone rev the car until the knocking noise starts. Listen to whether it sounds like it is coming from near the sump (main bearings/connecting rods bearings) or if it sounds like its coming from the top of the engine (camshaft bearings perhaps).

[jeffro ra28]

big end........... usually the big end fails because it is the furthest location for the oil to travel. The oil has to travel through the main bearing to reach the big end. Plus a knock is definanty failed big end symptoms