engine knock

[rush1981]

1996 3.8 liter is quiet at startup until it warms up then knocking and oil light comes on and blinks with the knock. worst at idle, oil light goes out and knock gets quiet upon acceleration. cruises down highway quietly and no oil light. mechanic said I should check oil pump, 128000 miles. also wiper delay does not work right, wipers just move an inch then stop. I see3 a relay under dash that says DELAY ACC but don't know what it is for

[tempfixit]

Originally Posted by rush1981

1996 3.8 liter is quiet at startup until it warms up then knocking and oil light comes on and blinks with the knock. worst at idle, oil light goes out and knock gets quiet upon acceleration. cruises down highway quietly and no oil light. mechanic said I should check oil pump, 128000 miles. also wiper delay does not work right, wipers just move an inch then stop. I see3 a relay under dash that says DELAY ACC but don't know what it is for

I would start by hooking up a mechanical oil pressure gauge where the idiot light sending unit is and observe the oil pressure from start up to warm.

What weight oil are you suing and oil filter??

Can you record the knock and post on you tube for the group??

[rush1981]

I changed oil and filter right away, 10-40 and added stp treatment and marvel mystery oil but no change. i'm in florida

[tempfixit]

Can you tell where the knock is located???

I am wondering if this could be a camshaft sensor problem, hopefully will chime in on this thought.

Have you checked for any codes even tho the check engine lite is not on??? Look for a P0340 code.

[rush1981]

knock sounds loudest on the right side closer to the drivebelts and more towards the back of the engine, towards the firewall. No I have not checked for any troublecodes

[jefelex]

mine sounds like it has dropped a valve - engine is ruined. smokes, will not idle sounds like it is going to blow up - I am disappointed, because it is a nice van, just junk motor - off to the wrecker with it

[tomj76]

Most likely there is a clearance issue in the engine oil path. When the engine is cold and the oil is thick pressure is maintained, but as the engine heats the clearances degrade, the oil thins and pressure is lost. The knock is mostly the connecting rods knocking on the crankshaft.

The primary places to check are: Main Bearings, Rod Bearings, camshaft bearing, wrist pins. The first two can be checked just by dropping the oil pan (requires removal of the y-pipe first). However, the other two are only accessible with a much more dramatic tear down of the engine.

It could also be your oil pump clearances.

When I rebuilt my '96, the main bearing clearances were about 0.003", and the rod bearing clearances were a bit less 0.002". However the wrist pins were at least 0.006" (spec is 0.0005"). I replaced the pistons and wrist pins, main and rod bearings.

You can replace the main and rod bearings without removing the engine and for a reasonable price, so since this might be the cause of your oil pressure it may be a worthwhile attempt to repair. I'd say its worth it, because your engine won't last long running with low pressure.

[jefelex]

Originally Posted by tomj76

Most likely there is a clearance issue in the engine oil path. When the engine is cold and the oil is thick pressure is maintained, but as the engine heats the clearances degrade, the oil thins and pressure is lost. The knock is mostly the connecting rods knocking on the crankshaft.

The primary places to check are: Main Bearings, Rod Bearings, camshaft bearing, wrist pins. The first two can be checked just by dropping the oil pan (requires removal of the y-pipe first). However, the other two are only accessible with a much more dramatic tear down of the engine.

It could also be your oil pump clearances.

When I rebuilt my '96, the main bearing clearances were about 0.003", and the rod bearing clearances were a bit less 0.002". However the wrist pins were at least 0.006" (spec is 0.0005"). I replaced the pistons and wrist pins, main and rod bearings.

You can replace the main and rod bearings without removing the engine and for a reasonable price, so since this might be the cause of your oil pressure it may be a worthwhile attempt to repair. I'd say its worth it, because your engine won't last long running with low pressure.

Way too much work for me - no garage, no hoist, hardly any tools, the thing is crap, off to the wrecker - couldn't even get my full tank of gas out of it because of the anti siphon features of the gas tank, just annoyed that it barfed on my when I was beginning to trust it - only had it a few months, and babyed it all the time, never once had it full throttle. oh well