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SUVs Chevrolet Suburban & Tahoe Chevy Suburban Maintenance and Repair
511 messages, Last post on Nov 24, 2009 at 5:42 PM
You are in the Chevrolet Suburban & Tahoe Forum. Your Hosts are steve_ & tidester
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I have an 01 Tahoe. The abs and brake warning lights are on together and have been for months. The brakes seem to work fine. Any suggestions on the problem? Thanks
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Replying to: mike123 (May 09, 2009 6:27 am) ____________________________________________________________________ Your problem could be the computer that controls the ABS system....when the computer fails your brakes will still work but the anti-skid feature will not work. You might test the vehicle in an empty parking lot by getting up to speed then applying full brake pressure. If the ABS system is working you will feel it automatically "pump" your brakes as you come to a stop. If the wheel locks up upon braking your ABS in not working. The computer is not a cheap fix...over $1K at the dealer....you might find one cheaper online. |
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Replying to: mike123 (May 09, 2009 6:27 am) Your problem could be with the ABS control module but you could also have a problem with a much lower cost part. For the ABS each wheel has a speed sensor. These sensors tell the ABS control module the speed of each wheel and ABS control is based on these speed readings. If you are just a little bit of a mechanic you could trouble shoot this yourself. This would require buying one of the speed sensors, which cost I do not know as I have not had problems with my ABS in my Tahoe but I would think the sensor cost less than $100. Rotating the new sensor from wheel to wheel might reveal which sensor, if any, is faulty. You can also take your car to the dealer to find out what the problem is but just diagnosing it will cost about the same as a new sensor. You can also have a sensor knocked out of alignment. This actually happened to my old Lincoln that I used to have. The sensor needs to be at certain distance from the notched wheel that it reads for it to work. If sensor distance to the wheel gets too big it cannot sense the rotation of the wheel and the ABS system is disabled. Arrie |
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I have a 2003 Suburban with 123K on it I've had since 2005. I just had the belts and tensioner replaced last month; now it is making noise when you accelerate above 2000 rpm. If you turn off the A/C at that point- there is no noise. Shop is wanting to replace the A/C compressor- does this sound right? I trust the shop- but geez- I keep soaking more and more into this thing. Air works fine regardless. Thanks for any help here- I love this vehicle, so I always fix whatever is needed (and its the wife's car)- but I just wanted to shop this diagnosis. (and I work extra at night just to pay my mechanic off!) Should have bought the Sequoyah....
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Replying to: ecarlclay (Jun 03, 2009 8:01 am) Personally, I would pop the serpentine belt back off, and manually turn each of the accessories to feel whether there is a bearing going bad in one of those accessories. Turning the A/C switch on energizes the clutch which then turns the compressor....so that 'could' be the source of the bad bearing and noise. But, compressors also place a significant load on the belt and engine, that perhaps the belt load is causing one of the other pulleys to get a load on it and make a grinding noise. If their diagnosis is just based on the noise going away when you turn the a/c off, I'd have them check it closer before replacing the compressor. If they already checked everything else, and they are okay, then it could very well be the compressor is bad (which you are going to want to replace before it disintegrates and messes up your whole a/c system with metal filings). |
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Replying to: ecarlclay (Jun 03, 2009 8:01 am) So stay on top of this issue and invest whatever time you need to, to make sure you have the right diagnosis. "Wait and see" while often good advice, is not the best course in this case, IMO. |
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Replying to: ecarlclay (Jun 03, 2009 8:01 am) If your A/C compressor is making dry grinding noise then you need to lubricate it. A lot of A/C compressors are lost due to inadequate lubrication. This is internal lubrication, i.e. mixed in A/C refrigerant. This is a very easy fix to do. Go to auto part store and buy an A/C system service kit that includes fill hose and pressure gauge. Some kits also include a bottle of refrigerant and some come with lubricant also. You can buy all these separate too. If your A/C system works, i.e. you get cold air from it when needed then the system has enough refrigerant charge but what you can be missing is lubrication. If your A/C system has never been serviced the lubricant oil in the system can be broken down, i.e. the oil that was added in the system at factory has lost its lubrication properties and your compressor now could be running with marginal lubrication. This can generate grinding noise, which precedes the moment when the compressor locks up and is completely ruined (= high $). So, go buy a fill hose, pressure gauge and a bottle of A/C oil lubricant. First run the A/C on full cooling for 5 minutes with engine on idle and then add the oil charge in the system but if compressor really makes noise don't wait 5 minutes and start adding oil immediately. After this measure the pressure in the system. If pressure is too high after adding oil, which it should not be, let some refrigerant out using the fill hose, i.e. shut off the needle valve at the end of the hose and connect it to the service port. Then open needle valve and let refrigerant out. Make sure you don't spray it on painted surfaces as it could corrode paint. If the noise you are hearing does not come from the compressor itself but disappears when A/C is turned off it can be coming from the belt tensioner. You had it and the belt replaced. Was this noise present before these parts were replaced or did you have them replaced just because they were old? Belt tensioner can make the kind of "rattling" noise but it also is caused by the compressor. This noise is generated by the moving tensioner arm that can in bad case even bottom out its travel. Arm movement is caused by changing belt tension. Changing belt tension comes from the A/C compressor from its piston strikes, i.e. every piston strike causes more load to compressor shaft, which translates to more tension in the belt. Apparently belt tensioner should have been designed to be able to handle normal belt tension changes from A/C compressor. This is why rattling belt tensioner is an indication of abnormal condition, which translates to compressor problems. Compressor problem can be the above explained lubrication issue, i.e. marginal lubrication increases friction in the pistons. Another way compressor can cause higher than normal belt tension pulsing is if A/C system refrigerant charge is too high. Too high charge can cause refrigerant to enter in the compressor in liquid form. Liquid cannot be compressed so it could cause very high load on the belt each time liquid is pressed in the compressor cylinder. This condition is not very likely as over charge would need to be quite big but that is why you need that pressure gauge. With that you can verify that the system is not over charged. A good gauge comes with instructions and chart for pressure reading as the correct reading depends on the ambient temperature. If you have a compressor issue it could be a very simple "lack of lubrication" issue and I highly recommend adding a small bottle of oil lubricant in the system in any case. If your A/C system has never been serviced that oil from car's manufacturing 6 years ago is worn down and new lubricant is needed. A/C oil breaks down just as any lubrication oil. That is why we change engine oil too, correct? Arrie |
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Hi all !! Hoping you can help...We just purchased an 09 Suburban LT have had it for a wk...noticed when accel at low speeds around 20mph to 40mph the vehicle shakes...reading in manual that vibration can occur in 4WD mode but this is in 2WD is this a transmission glitch it's very frustrating having to bring it back to dealership...anyone else having this problem and any thoughts on what it could be...hoping we didn't make a $30,000 mistake... Thanks...
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Replying to: zookpr46 (Jun 07, 2009 8:19 am)
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We were advised to change the rear bearings but found that it is the wheel axle that is worn down and the bearings are not too bad. Our mechanic advises us to buy new and not rebuild. He says rebuit axles are not strong enough for this type of v;ehicle. What do you think? The Suburban is 10 years old and we have already spent a lot on repairs.
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