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93 chevy 2500 engine "noise"
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93chevy
Novice
Oct 5, 2007, 8:10 AM
Post #1 of 7
(2280 views)
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93 chevy 2500 engine "noise"
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Hello, I am new here and like what I have seen so far. I am not anywhere near a gearhead, but do know some things. My problem - I have a 93 chevy 2500 with utility bed. It has about 86K on the 5.7 v8. The engine has been making a very light "knocky" type noise for about 3k miles. It runs great, has plenty of power, no oil leaking or pressure problems, or any other leaks and such for that matter. The noise is in the area of the AC compressor, but I can't seem to pinpoint exactly where it is coming from, even with a stethoscope. (probably because my ears aren't that good anymore, lol). I have taken it to a few mechanics, and have been diagnosed by one as having a rod knock and to replace the engine to the tune of about $2k (2 other mechs said that it was definitly not a rod knock) another said it could be something as simple as changing the oil filter and make sure it is one with check valve, or that it could be something in the AC compressor, and another said it could be piston slap or cam sensor. I had the oil changed, again, and made sure the filter was the right kind. The noise is still there. I am leary of putting a fortune into the truck without knowing what it actually is. There are no engine codes or anything either. What kind of noise would the AC comp make? And the cam sensor for that matter? Should I just put up with the noise since everything seems to be fine? I have been hearing about engine knock in the newer trucks, but can't seem to find much info on the older ones. All help is much appreciated, and thanks for the great site!!
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way2old
Veteran
/ Moderator
Oct 5, 2007, 8:37 AM
Post #2 of 7
(2279 views)
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Re: 93 chevy 2500 engine "noise"
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To eliminate any outside problems, remove the belt and run the truck for a little bit and see if noise is still thewre. If it is not, then the problem lies with one of the externally mounted parts. if it is still there, then it is internal. Let us know
Being way2old is why I need help from younger minds
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93chevy
Novice
Oct 5, 2007, 8:38 AM
Post #3 of 7
(2278 views)
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Re: 93 chevy 2500 engine "noise"
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Thanks! I will try that and let you know.
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93chevy
Novice
Oct 5, 2007, 10:14 AM
Post #4 of 7
(2273 views)
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Re: 93 chevy 2500 engine "noise"
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Hello again. Funny thing has happened- I put 2 new batteries in this truck about a month ago, and they were both dead when I went to start it. I charged them back up, and made sure no accessories were left on, none were. The problem with the batteries didn't start again until I used the wipers yesterday, which come to think of it, were a bit slow. Could the wiper motor or module be the source of the noise and such also? I haven't done the belt thing yet, since after this happened my main concern was the batteries and wipers. Now I am also wondering if maybe this was the problem in the first place, since I replaced the batteries for not staying charged, even though the wipers were not a problem at that time. I was unsure of the age of the batteries, so I erred on the side of caution. (I guess I overlooked the obvious, lol!) I am not sure where the wiper motor is located, so for all I know the two problems are unrelated. What do you think? Should I take care of the wiper problem and see if the noise goes away?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 5, 2007, 2:54 PM
Post #5 of 7
(2270 views)
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Re: 93 chevy 2500 engine "noise"
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Did you try taking the belt off yet? This was a noise complaint and now seems like a hard drain on the batteries. Adding up the symptoms I think that alternator is making the noise and causing the drain. That alt should say Delphi on the case I think and two of those have been silent but shorted out with no warning draining battery in no time. Again they didn't make noise in my cases. The wipers would be slow if the alt couldn't keep up or was the drain but I don't think motor can draw power when the key is off. Test for drain when everything is off with test light between battery and neg cable with cable disconnected. the light should stay off. Now if on leave bats disconnected and remove the large (I think red) wire to the back of alt and set it safely aside and see if the short is gone.
FYI: compressor noise is usually a rattling sound which is usually lack of lubrication and low on refrigerant can cause that. Common for compressor body to leak on these. If it's even medium noisy when on unplug it and prepare for fixing that when you are ready. If those crash out they take the condenser with them.
way2olds belt test would tell if the noise is the engine itself or an assesorie,
T
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93chevy
Novice
Oct 5, 2007, 4:15 PM
Post #6 of 7
(2268 views)
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Re: 93 chevy 2500 engine "noise"
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Thanks again. I just returned from the parts store, where they tested the alternator, which is fine. The parts guy (a former GM mech) said the noise sounded like it was coming from around the wiper motor. Since I am not that well educated lol, I am going to replace that motor and see what happens. He mentioned that the motor is electric on this one, and he has seen them drain the batteries before, so we will see I guess. He also mentioned that GM had a TSB out on the wiper motors at one time, so I will look into that too. He also did the belt thing, and the noise stopped, which confirms an external part like you said. You are great! Thanks for the wonderful help!!!
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way2old
Veteran
/ Moderator
Oct 5, 2007, 4:58 PM
Post #7 of 7
(2266 views)
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Re: 93 chevy 2500 engine "noise"
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We are glad to help. Keep us posted on the outcome. If it has a tensioner or idler for the belt, check those.
Being way2old is why I need help from younger minds
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