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Chevy C/K Series Maintenance and Repair

69flh69flh Posts: 10
edited March 2014 in Chevrolet
I have a 1990 K2500 Chevy pickup with RWAL.
I have had problems for quite sometime with the right rear wheel locking up when applying the brakes. I installed new rear shoes and it really compounded the problem. I then installed a new master cyl. & wheel cylinders and the problem still exists. Sometimes it feels as though the drum is warped as I get a vibration when applying the brakes but not always. I checked the drums and they are within .010 roundness. Is there any way to check the combination valve? This valve is pretty expensive and I hate to replace it and still have the same problem.


  • PF_FlyerPF_Flyer Pennsylvania Furnace, PAPosts: 7,966
    We were in need of a "problems & solutions" topic for C/K series trucks, so I'm going to rename this one to make it the general problems topic where ALL C/K problems and fixes can be discussed...

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  • catamcatam Posts: 331
    It actually sounds like your wheel speed sensor may be bad. This is the sensor that tells the ABS whether or not the wheel is actually turning. I would check that next.
  • dustykdustyk Posts: 2,926
    A bad speed sensor would be my first guess, too, but if I understand the problem correctly I would suspect the one that's bad is on the other side.

  • 69flh69flh Posts: 10
    From what I can find this truck has one speed sensor located on the tail shaft of the transmission. I have not been under the truck yet to look at it and was wondering if anyone knows what is involved to replace it?
  • akjbmwakjbmw Posts: 231
    Do you know that the left rear wheel brake is working correctly? Getting less pressure?
    If one wheel locks and the other doesn't, the drive shaft will turn twice as fast.
    If the sensor is on the drive shaft, it would see increased speed and apply some strange engineered logic control? It could be comparing front speed to rear speed and reduce braking to the slower of the two. If there was a weak/blocked pressure on one side, the problem could be exaggerated. How are those flex brake hoses?
  • 69flh69flh Posts: 10
    Lines look good. When I bled the brakes, the fluid coming out of the bleeders did not appear restricted. You are right about "strange logic control". Sometimes the brakes really act up, especially when wet. Other times they are fine.
    I am still wondering about the combination valve,
    (the proportioning part of it.
  • dustykdustyk Posts: 2,926
    I'm sorry, my brain was turned off when I sent that last message.

    Many manufacturers with RWAL Brakes only use one sensor. Dodge uses an encoder (they call it the exicter ring) made out of steel internal with the differential and mount a sensor on the rear axle housing.

    Since Dodge uses the GM-made American Axle on some of its trucks, I suspect yours is the same way.

    So, I take back what I said earlier. You could have a pinched brake line on the side that isn't over-applying. If you've inspected everything at the rear brakes on both sides and everything looks good and operates static, then I think you'll find you have a bad hydraulic control unit (HCU) or ABS Control Computer. Since it is a GM product I think this HCU high on the suspect list. I've seen quite a few of them fail.

    Good luck,
  • bassmanbassman Posts: 1
    I have developed a "bearing knock" when engine is cold. Noise goes away after warm up. These is a Tech. Service Bulleton on this problem. It is TSB #99-06-01-003 issued in April 1999. Does anyone have any information as to what the TSB says?
  • mcmike06mcmike06 Posts: 1
    Hey to everybody out there. I just recently (as in tonight) came across a problem with my 1990 Chevy C1500. This is what happened, I went outside to my truck & got in it started it up & moved it out of our driveway then I backed into our driveway except when i shut off the truck & got out my tail lights were still on. I have looked all around the truck for problems that I could see & I saw none. I was just wondering if anybody had any idea as to why they wont go off or what's causing this I would really be thankful for it.
  • rayt2rayt2 Posts: 1,208
    The TSB says it's normal and no fix required. Did'nt you always want a truck that sounds like a diesel when it first starts up ? It's not the bearing knock but rather "piston slap" do to poor design, tolerances are to loose when cold, when it warms up they expand and piston slap goes away (on 90% of them). My knocker has 48k so far and only makes the noise during cold startup. I had read of a fellow knocker turning over 100k on his with no ill effects other than embarrassment.

    MCMike: The tailights were known on the older trucks 1988 & up to corrode the curcuit board on lamp holder. I had same problem on my 88. You need to replace taillamp holder assembly with upgraded unit. The holder unscrews from the lense once you take the entire unit off truck. Another problem was that the lights would melt the lenses from the short which kept the lights on all the time.

    Ray T.
  • catamcatam Posts: 331
    Is it your tail lights or brake lights??
    If its your brake lights check the brake pedal sensor switch to see if its working properly, I had this problem once on a GM car.
    If its your tails lights see the previous post.
  • 69flh69flh Posts: 10
    I have a 1990 K2500 with the 4 speed, (granny gear), that is making a rather loud clicking noise in reverse while in 4 wheel drive. I do not notice it in 2 wheel drive. Any ideas??
  • rojo87rojo87 Posts: 2
    The temp gauge on my '87 silverado is stuck on max hot even when engine is cold and ignition off. The oil needle also fluctuates wildly but mostly stuck on max. Approximately 500 miles ago I had the heater core replaced and a/c switched over from freon to another type (can't remember the R#). All of this was done by my local Chevy dealer.

    Any idea what would cause these gauges to suddenly start acting act so strangely?
  • I have a 02 Chev Duramax w/ ALLISON, after 25000 miles suddendly @ startup no power brakes or steering, locked up for @ least 20 minutes , called dealer, checked out fine w) no codes, occured again & again, Dealer said no TSB on problem, finally bulletin came out & Chevy said there was no fix & would have to live with it,
  • xwesxxwesx Fairbanks, AlaskaPosts: 11,162
    You'd have to "live with it?!" That's one way of losing customers....

    While I'm here, can anyone tell me if the lug bolt pattern on the C20 has changed over the last 35 years? I have a 1969 C20 camper conversion w/ step side long bed that has 68K original miles and all original equipment. Having original rims and hubcaps is great, but it makes for expensive tires. Living in Fairbanks, AK, I have considered for many years to get a set of winter rims that were more up to today's standards. The 16.5 rims make it difficult to find tires and when I do, they are expensive. I don't typically haul too heavy of loads in the winter other than the 900 lbs of sand to give me enough traction to stay on the road, so a rim/tire set wouldn't need to be capable of the load rating 'D' I use now.

    Any suggestions?
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • xwesxxwesx Fairbanks, AlaskaPosts: 11,162
    Is it possibly a fuel filter issue? Not sure what year of truck so I'm just going with basics here.
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • This is a 1998 Chevy full size pickup. Would the fuel filter cause pressure to build up in the tank? Or could it be the evaporator box that one of the lines run to under the hood?
  • xwesxxwesx Fairbanks, AlaskaPosts: 11,162
    Admittedly, I am well out of my element with a '98. I was queing in more on the hesitation than the tank presssure. My '69 will hestitate when I punch the pedal to pass, etc, if the fuel filter gums up at all. I think the filter is either undersized for the vehicle or it is suffering some minor but continuing ill effects of having sat for 20+ years without use....

    Just thinking about it intuitively, it doesn't seem like tank pressure should negatively affect the flow of fuel to the engine - vacuum, yes, but pressure, no. But, with all the interconnected electronic gizmos and sensors on vehicles anymore, who can tell? You might check a repair manual for your rig's year to help figure out what systems are in place for evaporative control. I know that mine breathes through the gas cap, but newer ones probably try to internalize the evaporation to prevent fumes from escaping the vehicle. There's likely a block in the evaporative system somewhere and if you had some diagrams to help lead you through an inspection, you might find the culprit.

    Good luck!
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • xwesxxwesx Fairbanks, AlaskaPosts: 11,162
    Oh, and thinking about it a little more, if there WAS a block in the system and it was a negative feed system (meaning that vacuum draws the gases through the system), perhaps it IS causing the hesitation because the vacuum is too strong on the up-system side of the block. So, you're getting increased vacuum on one side and increased pressure on the other.

    Just some thoughts.
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • dustykdustyk Posts: 2,926
    >>>Would the fuel filter cause pressure to build up in the tank?<<<

    I'm not sure, but just for clarity is this a negative pressure (vacuum) or a positive pressure?

    All other things being correct, a clogged fuel filter will not cause the tank to "implode" because a clogged filter would stop the flow of fuel from going out of the tank.

  • hankwhankw Posts: 2
    I've got a "new" style '99 Z. xtcab short bed.
    The only problem that I've had is at 93K the
    autotrany trashed. Then at 103K the pump in the
    transfer case wore a hole in the case. The steel
    stop clip has since been enlarged.
    GM stated that after 100K their design
    fault was my problem.
  • xwesxxwesx Fairbanks, AlaskaPosts: 11,162
    Have you worked the rig hard? Such severe problems with both your transmission and transfer case after only 100K seems like perhaps design weaknesses (not necessarily problems) were exploited through prolonged intense use...
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • hankwhankw Posts: 2
    Mostly freeway driving. No off road stuff.

    The most that I've had on it is maybe 700lbs,

    once or twice. Chevy said that because I didn't take it to a dealer, and it had over 100k on it, it

    was my problem. My '91 s-15 has 135k on it and no trany problems.
  • xwesxxwesx Fairbanks, AlaskaPosts: 11,162
    Wow. That's about as easy as it gets, esp. if you aren't driving in 4wd much or at all. My truck doesn't get driven unless it's gonna get a workout!


    Do you live in a warm climate? If you had never changed the tranny or diff fluid, then I can see why Chevy wouldn't want to warranty the repair/replacement costs after 100K, but if you had and could document that you had, then it is poor service on the mfg's part. I've seen worse though....


    My father purchased an '01 Nissan Frontier new w/ all the goodies. He mostly uses it for commuting and as a tow-behind with his RV. at ~ 35,200 miles, one of the leaf springs on the rear left side broke, twisted about 10 degrees, and punctured the gas tank. While it was discovered almost immediately, they were on an RV trip about 1000 miles from home and headed home, so they decided just to move the spring back in place and duct tape in in position. They pulled the truck home and stopped at the dealer on their way to their house. When they pulled in at the dealer, the truck had 36,124 miles on it, but Nissan would NOT cover the nearly $1000 cost of replacing the tank and the leaf spring because it was out of warranty (3 year / 36K miles), even though the problem was almost assuredly a mfg defect, the part broke before the 36K mark, and it was far less than 3 years from the purchase date. Talk about cheap. That took the cake.
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • ryanbabryanbab Posts: 7,240
    Did you ever change the transfer case fluid? In 2000 they started using a new blue fluid (Autotrac II). I have drained mine twice in 51K miles.
  • We got our 2000 2500 a few weeks ago and noticed the fuel gauge goes flat to empty even when it's full. After a while, sometimes it registers actual tank fullness, but then for no explainable reason, flats out again. Help? Is it complicated to fix or expensive? We are thinking the sending unit and that the bed will have to be removed to fix it? Thanks.
  • I have a 1995 C1500 ext. cab with 200K miles. I have had to replace the battery every 2 months since July.The charging system checks out fine. The two month intervals has me puzzled. I am on my way to the parts store to pick up my 4th new Delco 6 yr battery since July. Anybody have a suggestion? Thanks,

  • xwesxxwesx Fairbanks, AlaskaPosts: 11,162
    Sounds to me like a problem with the voltage regulator. For some reason, your vehicle's alternator is allowed to charge your battery unchecked and it is causing the battery to overcharge, likely boiling away the water and causing the battery to fail. I had this happen in my '69 and it was caused by the (incorrectly installed) addition of a solenoid for a camper battery. I do not run maintenance-free batteries in my truck, so I was able to pop it open and noticed that the fluid was unusually low. I had to refill the battery once a week to keep the cells from warping, until my father suggested the regulator. No problems since and that was 5 years ago (I still have the same NAPA battery in it).


    Good luck! If nothing else, replacing the AC Delco with a non-maintenance free unit will allow you to monitor fluid levels in the battery. If the level drops rapidly, the battery is likely being over-charged.
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • Thanks for the tip! I'll check into it.

This discussion has been closed.