1990 Suburban Engine Knock

Well everyone I am new to this website so please bear with me and my "noobyness". I have searched this site and found it full of information. I have a question regarding a 1990 Suburban so here goes. My friend is the owner of this vehicle and his parents used it until the engine started to knock. They not too long ago replaced the tranny and he is in need of transportation, so he is kinda anxious to find out whats wrong. I realize there are probably many things that cause engine knock, so I intend to answer as many symptoms as i possibly can. All the information on the symptoms i have right now is the engine knocks, can be driven in drive and reverse and all gears, no obvious loss of power either. The engine just knocks, the sound kinda sounds like its not screwed in and its loose (just a description of the sound it makes). It is a half ton model, 350 engine, 4 wheel drive. I will be checking more out on it as soon as I get the chance, I was just wondering if anyone out there had any imediate ideas on what it could be, or what I could check. It has sat there for months and theres really nothing to lose as they are about to haul it off to a junkyard to get it off their yard. Due to sitting too long I will have to charge up the battery im sure, but has been started not too long ago, just knocks. Starts up on first try just knocks loudly. Any information or diagnosis from anyone would be greatly appreciated if they happen to have any immediate ideas or thoughts on the subject. I will get more information on it as soon as i can just thought i would put the bug out there and see if there are any ideas right off.

Thanks, ~Suburban Freak~

Any trouble codes?

What is the oil pressure at?

//2000CAYukon

Ok well we got out and got it running. Needs a new battery, the one in there is dead so we pulled the one from my car. Anyway I don't have a code scanner although I am thinking of getting one. I heard about $30 at checker auto for GM vehicles? Thats what the guy behind the counter said when I called him. Oil pressure is about 25-30, didn't change very much, consistent reading. The engine still knocks pretty bad but we got it out on the road and it seemed to sound better after we drove it around? Doesnt sound great but it sounded better. A buddy mentioned maybe a plug wire is bad? Or distributor? It leaks fluid really bad. It seems to be oil, but also seems to be coolant. Couldn't tell for sure but it looked like the fluid was coming out of the radiator hose where the thermostat is located. Where the hose bolts to the engine. Thinking of using some sealant and resealing it. It's been sitting a while and im sure it's pretty dried up. They said it always had a leak, but it was never as bad as it was today, and there was fluid sprayed all around in the engine compartment. It really looks like it's coming from the hose as i mentioned before. looks like its spraying almost out of there, seems to have got the alternator pretty good. Anyway Im going to try to reseal the hose and see if we get more fluid leaks. The thing was completely dried out of oil, took about 4 quarts would have taken more if we had more oil. Didn't seem to effect the engine knock, but like i said when we got the engine out into higher RPM's it sounded alot better than at first. No loss of power. Temperature was normal too never went beyond 150. My friend's parents told me they had the engine rebuilt about 60,000 miles ago. His dad said it always ran a little bit rough. Any ideas so far? Thanks for the replys and thanks to all those helping!

If you ran it out of oil, bearing damage most assuredly occured, yes it will run for now, but the " death" clock is ticking.

sounds like it may be a leaky head gasket which could be dangerous, especially if coolant is mixing in with the oil. If they are 2 seperate spots then it is 2 different leaks. Sometimes knock is caused by a bad EGR advancing or retarding the timing too much.
Also replace the upper radiator hose, thermostat and gasket.

another idea is a bad oil pump which has not been supplying enough oil to the engine for who knows how many miles and it may be time for a rebuild. Just some ideas and other will likely have other ideas as well

Thanks to all for interest and suggestions. I apologize for my ignorance in cars and also my lack of information on the vehicle at the moment (unable to get to vehicle to look more into the problem, due to lack of time). I just thought i would mention a suggestion made by my mother's friend, a long time mechanic, used to build engines and race cars. He suggests that it could be a stuck lifter or possibly an arm or rod striking something? Once again I apologize for lack of info, I was only able to ask question on the run with not much time to discuss. Just thought in the meantime i would mention this to you guys and see if it turns on a lightbulb in anyones head. Thanks for the interest!

~Suburban Freak~