Diagnosis Help Requested: 2002 Suburban
May 30th, 2016, 11:09 AM
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Diagnosis Help Requested: 2002 Suburban
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!
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!
May 30th, 2016, 11:38 AM
#2
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So this only occurs when the a/c clutch engages - with all new tensioner & pulleys I would be looking at the compressor more. I'm just a back yard dyi guy, but I would start by unhooking belt, engage clutch and see if I can spin it by hand and feel for binding that would set up that oscillation. Since your ps pump is leaking give that pulley a good spin too to see if it is binding.
Congrats on 330k and original tranny too. Curious how's your oil pressure these days? My 93 with same mileage drops to 5-10 at idle when hot but continues to run like a champ.
BTW welcome to the forum and thanks for the excellent 1st write up. Lots of very knowledgeable friendly folks here and I'm sure someone will get you fixed. Please make sure you follow up with a final post when solved!
Good luck, RTed
Congrats on 330k and original tranny too. Curious how's your oil pressure these days? My 93 with same mileage drops to 5-10 at idle when hot but continues to run like a champ.
BTW welcome to the forum and thanks for the excellent 1st write up. Lots of very knowledgeable friendly folks here and I'm sure someone will get you fixed. Please make sure you follow up with a final post when solved!
Good luck, RTed
May 30th, 2016, 11:42 AM
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The A/C tensioner is bad, I never do just the pulley on those. If its getting an A/C belt its getting the tensioner assembly also and with that mileage its very likely as those A/C belt tensioners seem to last about 1/4 of the time a normal tensioner does.
May 31st, 2016, 9:17 PM
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Thanks all, yes, I changed the A/C tensioner pulley twice now, two brand new tensioner pulleys in three weeks, same result. So, I like the idea of testing to see how the A/C spins. The Power Steering Pump is on the Serpintine Belt system and I guess binding on that pump could find it's way through the harmonic balancer to the A/C accessory belt and eventually the A/C tensioner pulley. I have to replace the power steering pump anyway so let's hope.
When at idle, my oil pressure is about 25 - 30. It runs about 55 - 60 pounds at 70 mph.
When at idle, my oil pressure is about 25 - 30. It runs about 55 - 60 pounds at 70 mph.
May 31st, 2016, 10:19 PM
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Thanks all, yes, I changed the A/C tensioner pulley twice now, two brand new tensioner pulleys in three weeks, same result. So, I like the idea of testing to see how the A/C spins. The Power Steering Pump is on the Serpintine Belt system and I guess binding on that pump could find it's way through the harmonic balancer to the A/C accessory belt and eventually the A/C tensioner pulley. I have to replace the power steering pump anyway so let's hope.
When at idle, my oil pressure is about 25 - 30. It runs about 55 - 60 pounds at 70 mph.
When at idle, my oil pressure is about 25 - 30. It runs about 55 - 60 pounds at 70 mph.
June 1st, 2016, 7:57 AM
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I read it that way then watched the video and read it again before I caught it ha.
Changing the pulley won't change anything at this point the tensioner is weak. The A/C belt only touches 3 things and if the dampener or compressor had issues you'd likely have more symptoms, when the compressor engages it puts a jolt of pressure onto the belt that the tensioner can't handle causing the bouncing and your noise. If I remember right there used to be some kind of bulletin on the tensioner assemblies for them wearing out quickly.