1993 Chevy Suburban engine knock? |

[norcalitrader]

Ok I got a 1993 Chevy Suburban with the 5.7L 350.

When i first start my truck theres knock sound for like 5 seconds then it stops.

After the truck warms up its ok...

But lately the knocking noise appears on and off at a stop light at idle?

Oil pressure at idle is at 20psi? is that low?

I was told by a friend that it may have something to do with the rockers?
Is there and adjustment I should check on the rockers (like you do valves?)

[Fireplug]

20 psi is got idle pressure.
The sound does it sound like its deep down in the engine or up top?? Rocker arm /valve adj are 1 in the same thing.

[Larry Derouin]

When was the last time u changed the oil.

The knock on startup is due to longer than normal time for the oil getting to the rod bearings, and the valve train. Sounds like the anti-drainback valve in the oil filter might be bad. Use a Purolator, Wix, or AC-DELCO filter(stay away from Fram!!!) and whatever oil you choose to use.

the 20# reading at idle is ok. However the dash gauges are not known for being totally accurate. Get a remote gauge and "T" it off and leave it on permanently. The "off and on" knocking is indicative of the lifters, and valve train not getting enough oil.

A couple of things to look at.

1.) Oil Pump. (rebuild kit or new pump).
2.) blocked passages or oil pump pickup. (crud buildup)
3.) OUT of spec bearing clearances.
4.) too thin oil

A.) Get some Engine flush(SEAFOAM), 7qts of oil, new filter.
b.) get the engine warm. Pour the SEAFOAM in the crankcase, start the engine and run for 20 minutes.
c.) drain, change filter and pour 1 qt oil in the right valve cover and 1 qt in the left. This will help flush the remains of the Seafoam and any residual crud in to the oil pan. Let drain.
d.) install the pan plug, and add 5 qts oil. Start engine and run for 3 minutes, turn off and check for leaks.

During the next week or so check the oil pressure under all conditions. If no change then proceed to next step.

Next step is pump check/change. Lift engine, and remove pan, Clean, check for rust and repair/replace as necessary. Check oil pump pickup for blockage and reverse flow clean with solvent as needed or replace. Replace pump if normal pressures are not met.

Anything more will require a teardown of the engine and a rebuild.

Do the cheap and easy stuff 1st. You don't say how many miles on the Engine. It's probably got over 100-150,000. Change the oil and filter religiously. These engines will last a very long time if maintenance is done from the get-go and the engine is NOT abused.


Larry