alright, so ive got a knocking noise coming from somewhere under the hood. i seems to be near the front of the engine, possibly down low...right around the radiator? itll speed up with the pace of the engine for a little while, then disapears after i reach a certain speed. sometimes its barely there at all, sometimes its very noticable. it sounds like an actual KNOCK. not like when you clothes-pinned a baseball card to your bike tire when you were little, thats what a typical rod knock sounds like right? i was told there is a bent pulley at the bottom of the engine that is causing this knocking.

heres some history on the truck;
1994 / 5.0l / 153K miles
its a known fact that the gasket is bad. ive had issues with the exhaust system quite a long time ago, maybe its an exhaust leak? i recently had an issue with gasoline in the engine oil (fine now). about 2 weeks ago i had a problem where the truck would not idle for crap, itd just stall out at every stop light and when you could actually get it to idle it was so, so rough...that is also fine now. the oil is changed religiously. i baby this truck like none other...cant imagine why at 153k miles the truck would have a rod knock.

thanks for any info

 

if it's a rod knock, put new rod bearings in it. as long as the crank is in good shape.

um, you had gas in the oil? and you fixed it how?

the only way to get gas in the oil is from blow by. "worn out rings" and the only way to fix that is to:

put new rings on the pistons and hone each cylinder. complete tare down. and if you had it tore down you should of put new bearings in it. gas in the oil will chew up you're bearings

if it's knocken really bad, put a good used motor in it or rebuild the one that's in it. if it's not to bad put new rod bearings in it

 

well i replaced the cap, roter and all spark plugs. apparently if you have a bad plug, it doesnt burn which allows too much gas to be dumped? i dont know...thats just what i was told by a former mechanic. so after i replaced all that, everything is fine. oil level is staying steady.

lol i understand i would need new bearings but how exactly can i determine if its a rod knock or not

 

The best way I've found to determine rod knock is while the engine is running and the knock is present. Start disconnecting one injector at a time as you move from cyl to cyl. Listen for the knock to stop or lessen when the problem cyl injector is disconnected. You can also (carefully) do the same thing while disabling the spark to one cyl at a time as well. Something else that can make a knock in an engine is a cracked/broken damper keyway.

 

i took a wooden broom handle, put it to my ear, and then touched like every possible part under the hood. i think ive got the source of the knocking.

http://tinypic.com/r/dh5p54/5

 

I've heard "rod knock" type sounds from several things looks like you've identified the A/C compressor as the possible source. could be the clutch is bad on it. Start off removing the serpentine belt start the engine for a few minutes only and see if the sound is gone. If it were me I'd get a new compressor out of a junk yard and fill the system with R134. Could also be your damper is bad. I've had them go bad and I was sure the motor was toast. could also be exhaust..

 

wow thats really interesting. WAY back when this knocking first started (when it was barely noticable) some one told me it had something to do with an AC part. now that ive figured out the knocking is coming from that, i researched AC compressor failiures. loud knocking is included in the symptoms along with improper cooling, both of which apply to my situation.
so a junk yard...how much you think theyll run there? i mean theyre around 250 new. are they a pain in the rear to replace? and whatll this do to my truck when it completely fails? could this have something to do with the massive amount of coolant i burn, or is that just a gasket issue?

 

I would think you oughta be able to find one in the junk yard for $75-150. A person with basic mechanical skills should be able to install one in an hour or 2. It would have nothing to do with your engines cooling system. The $225 quote you got for one was probably an autozone one and I've heard those ones are junk. Get a nice used one they last along time usually never fail..

 

When you replace a compressor, or open the refrigerant system, you need to replace the accumulator. In case of a bad compressor, you also need to replace the orifice tube, and blow the lines out with a compressed gas, that you can buy in an aerosol can.

When you are confident you have the system clean and sealed, you have to pull vacuum on the system to get moisture out of it. Then add the oil and refrigerant to the system.

If you don't get the moisture out of the system , it will combine with the refrigerant , and actually make little rocks inside the lines. they will clog the orifice tube.

I do recomend you get help with this procedure, because you will need a vacuum pump that will pull 28.6 to 30 hg of vacuum for at least 30 minutes.
More if you are in a humid climate. Some people say 30 hg , but 28.6 is enough to evaporate the water.

 

wow, sounds complex. yeah i definitely am not going to mess with this stuff myself. guess ill be headin to the scrap yard this weekend. is it really bad to drive it like this?

jethat- it was an autozone one lol

 

If you are burning a lot of coolant then I wouldn't call it "just a gasket issue" If you are getting a lot of coolant into the cyl's there is a serious potential for hydrolocking your engine. If that happens the last thing you'll be concerned with will be the A/C. as you can fix that when you have the engine out. I personally would revaluate what is going on here and prioritize.

 

well right, its not JUST a gasket issue...its a pretty big deal. man i dont even want to tell you the crazy stuff that goes on in that cooling system. its scary. but its an old truck, im not looking to put a ton of money into it...it never leaves me stranded and im happy with that. of course ill get the gaskets fixed and if that dont do it, then i dont know what to tell myself!