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I am committed to my 2002 Suburban LS 2WD. She has over 330,000 miles, original engine, transmission, etc.
In trying to keep her in good shape I need a hand. Something happened recently that has me perplexed. On May 6, 2016 on my way back from Houston to Dallas, as I slowed down and entered local stop and go traffic I began to hear a noise when I would accelerate from a stop to normal speed. The noise would occur about 1200 to 1500 rpm and would fade or cease when I let off the accelerator. As I got to cruise speed (40mph or higher) the noise would completely disappear. Essentially, I would have to nurse the accelerator until I hit about 40 mph to keep the noise from happening.
Also, when I was sitting idle at a traffic light the engine seemed to be running rough. At over 300,000 miles, I know my truck and this was not normal. It was enough that the hood bounced a bit and it felt like a bad spark plug or in same way that the engine was missing. The funny thing was that when I turned off the A/C then engine ran smooth like it always has and the hood stopped bouncing.
The following Sunday I began to troubleshoot. I began with vent fan off and the A/C off. I drove and drove and no duplication. So, I turned the fan on but still no A/C. Again, I could not duplicate. And then I turned on the A/C and sure enough the noise returned and so did the rough “idle”. The sound, to me, was if a pulley was bouncing around.
About a week or so later I was able to shoot a GoPro of the situation. And, sure enough, as I suspected, the sound was coming from the A/C tensioner pulley. Please see the video on YouTube at the following link. The video has starts and stops, turns, idles (see the tensioner bounce) and I turn on and off the A/C. Oh yeah, plus it SHOWS where the noise is happening!
So now we know the symptom but I still do not the root cause. Before I get into what I have done you need to know that I changed all the belts, tensioner pulleys, idler pulleys, water pump at 307,122 miles back in June 2015. I only had little over 20,000 miles on the new A/C Tensioner Pulley and A/C Belt when this issue began. Both ran perfectly fine until May 6th. And, by the way, it is a Gates Pulley which I have had very good service with Gates products on my other vehicles. And this has NEVER happened before.
The first attempt at fixing was easy. I replaced the A/C tensioner pulley. But, I also wondered if my A/C compressor might have caused part of the issue as it too is over 300,000 miles. So, I replaced the clutch complete with a new bearing. The first day I was impressed with myself. The next day I was reminded Pride is not necessarily a virtue. Yes, the darned noise was back.
The work week went on and the following weekend I once again replaced the A/C Tensioner Pulley with another brand new pulley. And, this time, I put on a new A/C drive belt just in case the belt was the issue. You guessed it. I still have the problem.
Is it the A/C compressor itself? It is the OEM Denso unit and it still produces good cold air…. I know my Power Steering Pump is shot, is leaking, and needs replaced. Could power steering fluid be getting on the belt and causing slippage? I cleaned all the pulleys really well and none of the belt installations gave any indication fluid was on the belts. Could the Gates A/C belt be too long? I kept the belt from the change done in June 2015. It was purchased from AutoZone and is a Duralast 378K4 (4PK0960) with an effective length of 960mm. The more recent two belts were from OReilly and are Gates belts K040378 (outside circumference 978mm) with an effective length of 962mm. I find it hard to believe that 2mm would make a difference. The two A/C tensioner pulley bolts are torqued to specifications so it is a solid installation (not my first rodeo). I checked the harmonic balancer. It is still on good and tight and the video I believe shows that it is still in good balance and condition. I haven’t checked my engine mounts yet. Could mushy mounts throw the tensioner into the dynamic?
Can anyone think of things that it could be or that I can check? This is driving me crazy!! Help!
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I would wager the tensioner itself is the issue. It almost sounds like the internal spring isn’t dampening the vibrations enough so the tensioner maxes out or something to that effect.
I would still fix the power steering leak first and see if anything changes, just to properly rule it out.
Thanks! I guess I find it hard to believe that after 3 tensioner pulleys it still remains the pulley. I guess I’ll go to the Chevy dealership and get an OEM part and try that. Thanks.
Can’t say for sure but I know of a couple cases with this exact scenario (it was a Chevy Silverado in both cases) and eventually the compressors locked up and died. Seemed it was putting a bizarre load pattern on the belt which made the tensioner go mental.
Mental is a good way to put it. I am beginning to become resigned to the fact that I will have to replace the compressor. I just don’t want to do so unless I can absolutely prove it is the compressor. Why spend the money if I don’t have to, right? Thanks again.
Hello RG, you do not say but my first step is checking for technical service bulletins. It is pretty embarrassing to have been beating your head against the wall when there exists a factory fix,have you looked? By the way as soon as you let it known you are having the least little trouble at the Dealership someone will ask “did you check for bulletins” and even worse announce “there is a bulletin on that”.
All I usually get online are the titles of tsb’s like this:
http://www.carcomplaints.com/Chevrolet/Suburban/2002/tsbs/But for what it’s worth, check it out.
Appreciate the link. I have been teaching myself to work on vehicles over the last couple of years out of necessity and for some odd reason for enjoyment. I was never around anyone who did this sort of thing and so I had no idea about TSB. What a nice find! Thanks.
And, btw, while inspecting the A/C system I took the caps off the Hi and Lo side valves. Guess what, the High Side valve is leaking.
It probably just needs a new Schrader valve e core. There’s a special tool to change them without recovering the refrigerant , but try tightening it up with a tire valve core tool first. Maybe you can get it fixed without buying all that refrigerant. Just be sure to do it when the vehicle has sat for a while so the pressure won’t be as high.
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