Chevy Silverado and GMC Sierra Radiator and Cooling Questions



  • obyoneobyone Member Posts: 7,841
    The recovery tank should be located on the passenger side under the hood against the fender. Fill both the tank and the radiator when cold, start it up and allow it to reach running temperature so that the thermostat opens.
  • huerohuero Member Posts: 5
  • keith76keith76 Member Posts: 1
    I drive a 2004 GMC Sierra. I have a small coolant leak that looks like it is coming from the water pump. Is there anything I can do without replacing it?
  • obyoneobyone Member Posts: 7,841
    You could try a stop leak type of product that you can find at the auto parts store. I've heard black pepper works well too. At most though these will be temporary fixes. Eventually you will have to replace the water pump.
  • opc167opc167 Member Posts: 14
  • opc167opc167 Member Posts: 14
    Need some help trouble-shooting. Every 400/500 miles I have to add coolant.

    Oil clean.
    No presure in Reservoir to suspect head leak.

    I added stop leak yesterday. I haven't taken the top cover off, but does this model have a radiator cap and should I flush it, add treatment and stopleak again or should I have a preasure test done on it? I don't know what to do at this point to trouble-shoot. It's not running hot at all. Someone suggested it may be evaperating but how can you tell? HELP.
  • hahhhahh Member Posts: 1
    I need to replace the thermostat on my 1995 GMC Sierra PU. Is the thermostat located on the top of the engine where the radiator hose connects to engine block?

    I haven't had to replace a thermostat on any vehicle for many years. The vehicles I used to work on had the thermostat on top and were easily identifide.

    Just looking for a little direction.
  • tomcatwillietomcatwillie Member Posts: 1
    I've got an 01 Silverado with the 5.3 and can smell antifreeze and am loosing a very small amount and like most others here - I have not been able to find the leak - yet. I went to our local GM dealer Parts Dept and inquired about the supposed "GM Magic Pills." The parts guy believes the way I do. Don't put that junk (any stop leak) in your cooling system as it will plug up the radiator and heater core and cause overheating problems down the line. A radiator repair shop owner told me the same thing. Fix the leak properly - once you find it. I am just beginning to check my system out. I've pulled all of the spark plugs out and there is no visible trace on the plugs that antifreeze is getting into the cylinders. Good news so far... I will run a compression test on it tomorrow. I bought a new water pump and serpentine belt (about $200 at O'Reilly's) and plan to install them. The GM Parts guy told me that some of the water pump gaskets that came out (on some years) from the factory were faulty and will start leaking in time. Not sure exactly what years. I should have asked. Even if it's not the water pump or it's gaskets, my Silverado is due for a new pump anyway. It's got close to 140,000 miles on it and the pump has never been replaced. It surely couldn't have lasted much longer. Same with the serpentine belt... It has cracks at 140 K. So time to replace it too. I'm also replacing the spark plugs and the plug wires. I ran a resistance test on two of the wires. One tested fine and the other has HIGH resistance. One bad one spoiled the whole barrel... I will up-date here - if and when I find where my antifreeze leak is/was. Good luck to all of the rest of you who are having the same problem with your Silverado 5.3. Whatever I find still beats driving a Dodge... LOL

  • jeb1870jeb1870 Member Posts: 1
    has anybody figured out were the anti freeze goes??I have an 04 with the 5.3 and cant find the leak??
  • dannykana67dannykana67 Member Posts: 1
    I have a 98 GMC Seirra 1/2 ton 4x4. How do I remove the fan clutch/fan from the water pump?
  • snydosaurussnydosaurus Member Posts: 1
    Here's something to consider. I have an '01 GMC Sierra w/ 5.3, and experience the same "phanton" coolant leak.
  • keonisierrakeonisierra Member Posts: 1
    Please help. I have a 98 z71 silverado. It has begun to overheat. I've filled the radiator, replaced the cap and the thermostat and it still gets warm. When the truck heats up it spills into the overflow container. The container actually sucks in like theres a vacuum till the cap pops and fluid spills from the cap. I have flushed the radiator and still no change. Does anyone have any ideas. Water pump next? I do not see any leaks. Any ideas will be appreciated
  • bowanabowana Member Posts: 9
    I would start out with a cold engine and take the rad cap off, start the engine and let it warm up. When the thermostat opens, you should be able to see the antifreeze circulate in the rad. If it does, I would then rule out the water pump unless it has very poor circulation.

    Nice thing about the water pumps is that they are inexpensive and relatively easy to change.

    Another thing to look at is the heater and if it blows hot air as it should. You could have a blocked heater hose or possibly a connection from the rad to the heater causing pressure.

    I am not certain that this would cause your problem, but it could be a head gasket but you should be able to see white smoke out the exhaust. Another thing is the rad hoses. They have wire in them to keep them from collapsing but you never know.

    A couple of google's should locate the problem as I am sure you are not the first with this issue. A call to a rad shop could also yield some answers.

    Nothing to say that the thermostat was good either and hopefully you did not put it in upside down.

    Good Luck.
  • byrd76byrd76 Member Posts: 1
    i have a leak in a 1/4 inch metal tube that goes from drivers side to pass side and y's off and runs under the intake manifold does anyone know what it goes to and what it is called it is a pinhole leak and coolant is coming out of it also would anyone know where i can get a diagram that shows where this is and where it goes any help is great thanks
  • squirtspopsquirtspop Member Posts: 3
    Had same problem. Was the intake manifold gasket leaking. Gasket only has a small bead of sealant around each port. Had gaskets changed and no more leaks
  • scotty_3998scotty_3998 Member Posts: 1
    I have a 2004 Silverado and my engine temperature keeps changing between 205 and 235. I had a problem a while back and it was found that I had a stuck thermostat and bad radiator. Both were replaced then a couple months later the temperature gauge started showing my truck running warmer. Took it in and I was a gallon low on coolant. That was fixed and the mechanics said that it might have been caused by air pockets. About a month later my truck started doing the same thing and so I took it back in and they said my coolant was a pint low so they added a pint. They couldn't seem to find any leaks, and I haven't seen any leaks or evidence of a leak. My truck is starting to do it again, but this time it will get to close to 235 and then while I'm driving and I get to about 50 then the temperature goes back down to around 205. Does anyone know or have any idea as to what it could be?
  • obyoneobyone Member Posts: 7,841
    You state that they couldn't find a leak? If the leak is internal it wouldn't show up on the exterior of the motor. Any white smoke on start up? During idling?

    If the coolant level remained the same and the temp goes down to 205 when driving on the freeway, it could be a bad fan clutch. At highway speeds the fan is less important to cool the truck.

    A blockage in the motor could also cause overheating. When the radiator and thermostat was changed was the motor back flushed?
  • akdrmrakdrmr Member Posts: 2
  • akdrmrakdrmr Member Posts: 2
    Does anyone know if my 2012 Sierra, 4 x 4, 5.3L has a drain or petcock on the bottom of the radiator? I have crawled underneath but cannot see one. Before I remove the plastic shield under radiator I'd like to know if there is a way to drain radiator w/o removing the hose. I just had my truck in the dealership to get free oil change and asked them to lower freeze protection to -60 from -30. (I'm in AK). The untrained service "advisor" in Wasilla wanted to charge me $140. I asked him why they couldn't just drain a gallon of 50% antifreeze out and add 1 gallon of undiluted antifreeze in. He didn't know if there was a drain or not and that they would have to make a "special" mix themselves. This isn't exactly higher math and you would think a dealer in AK would have run into this type of request before!
  • sierratrucksierratruck Member Posts: 3
    Hi, I have something goofy going on with my truck. When I turn on the heater, the windshield fogs up and I can smell the coolant. However, there is no water leaking on the floor inside the cab - as I would expect if there was a leak in the heater core. Water does, however, leak from the evaporator drain located on the other side of the firewall.

    Additionally, if I run the A\C, water leaks from the evaporator drain as well. It's more than condensation, as it will eventually drain all of my coolant.

    I have several questions running through my head:
    1) Could I have a bad heater core without it leaking inside the cab?
    2) Could a bad heater core result in a leak through the evap. core drain?
    3) Would a bad evap core cause the windows to steam up when running the heater or defroster without the A/C button on at the same time?
    4) Without having to take it to a shop and pay their $120 diagnosis fee, is there some way an average guy - like me - can figure out for sure if the heater core is bad? Same thing with the evaporator core?

    Thanks in advance. I've spent so much time looking for anyone that has these same issues online, but virtually everyone that has a bad heater core says it leaks inside the cab. Mine doesn't, but something definitely is going on...
  • KCRamKCRam Member Posts: 3,516
    Sounds like a combination of heater and evap cores. The heater core could be ruining the evap with a coolant leak into the A/C system instead of the floor.

    kcram - Pickups/Wagons/Vans+Minivans Host
  • sierratrucksierratruck Member Posts: 3
    edited March 2013
    Thank you for the reply. I was scared that that was what you would say.

    Naturally it couldn't be straight-forward and easy to determine. Is there any way I can test both of these cores?

    It's about $1,000 to replace the heater core, which I don't have laying around, so I was going to spend a long weekend doing it myself. The thing that scares me is that I tear everything down, replace the heater core, put it all back together and find out the evap core it bad too (or it wsa the only thing bad in the first place). And, although I might be wrong on this, I think the evap core is quite a bit more than the heater core.

    To test them, do I need to tear everything down, then pull each core and take it to a shop?

    Thanks for your help.
  • KCRamKCRam Member Posts: 3,516
    I would definitely recommend having them tested before you swap out. If you can, take pictures and/or video of the leaking water before you tear down so that the mechanic testing the cores has an idea of what you're experiencing.

    kcram - Pickups/Wagons/Vans+Minivans Host
  • sierratrucksierratruck Member Posts: 3
    Good idea, thanks for the help, I really appreciate it.
  • mtbouymtbouy Member Posts: 1
    my truck is doing the exact same thing did you ever figure out what was wrong with your. i have 2006 gmc sierra
  • ramnuttramnutt Member Posts: 3
    If I understand correctly you replaced these items, and now it stays cool and doesn't get up to temperature. If this correct, replace your thermostat. The failsafe thermostat is stuck open. I had the same problem, and when I removed and inspected the thermostat it was in fact stuck open. Replaced with a regular thermostat.
  • ramnuttramnutt Member Posts: 3
    I have a 94 K-1500 Suburban 350ci, that we just purchased, it had a crack in the tank of the radiator. So I replaced the radiator, water pump, and thermostat. The original radiator was a single core, was replaced with a 2 core, that's the only one AutoZone had in a 34'' core (between the tanks). Problem 1:The thermostat I had bought didn't fit in the seat in the intake manifold (it was smaller and moved around a lot, in fact you could slide it to one side and there would be a gap that would allow water to pass), I took it back thinking that they gave me the wrong one, I was assured it was the correct one. Has anyone ever run into this situation with a thermostat? As I have never in my 20+ years working on cars.Problem 2: The engine doesn't want to get up to temperature, 180 degree thermostat. My guess it that the thermostat had moved allowing a gap to allow water to pass. The gap guessing would be maybe a 1/4'' or less, that just doesn't seem like a big enough passage to keep it that cool, it barely get off of the 100 degree mark. The fact that the radiator is a 2 core instead of a 1 core entered my mind, but the thermostat basically keeps the water in the engine until it reaches the proper temp that would allow it to open exchanging hot water and for cool water. And my experiences with over sized radiators not matching water pump volume usually causes an over heating problem. Your Thoughts
  • ramnuttramnutt Member Posts: 3
    If your are constantly having to add coolant, then its the heater core. Newer style climate boxes houses both the evap and heat cores with using an exchange door that opens and closes to allow heat or to block the heat to the cab area. So the both being housed in the same box this would allow for any heater core coolant leak to exit in the same drain as the condensation. One easy way to test for coolant leak at the climate box, is to run the engine with A/C off, heat on. If you see liquid coming from the drain at the firewall it is coolant.
  • dadrummer77dadrummer77 Member Posts: 3
    Hey Guys, Need Some Help, Have A 99' Chevy Silverado 2500 LS Ext Cab 3 Door 4x4 6.0 Liter, I've Just Started To Notice My Temperature Gauge Going Past Normal 195F Is Normally Where It Would Register. I Took It To My Mechanic, I've Been Noticing @ First It Would Climd To 220F & 230F & While Driving It Would Cool Down & Somewhat Go Back To Normal Or At Least 210F, Which It Never Registered @ 210F Fully Warmed Up, Always 195F Since I Bought The Truck Used Last Year, Now A Week Has Gone Buy & The Temperature Outside Is 83F & Notice That While Driving It Started To Climb To 220F & 230F & The More I Was Driving It Stayed @ 230F & Stopped @ A Light It Went All The Way To Almost 260F & My Check Coolant Temp Light Came On, Started To Drivd & It Dropped A Little, But Soon As I Stopped Again & Idled, It Started To Go Back Up & Then Check Engine Coolant Temp Light Came Back On.It Has New Water Pump, & No Leaks, & My Heat Is Working. What Is Causing This? The Fan Appears To Be Working As Well, I Check Reservoir Last & Coolant Appeared To Be @ Full Level, Not Seeing Any Leaks Anywhere & Have Heat. Is It The Thermostat Or The Temperature Sending Unit Or Both? Anybody Thinks They Know What It Is, & Had Same Similiar Problem, Please Let Me Know. Thankyou, Donnie
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,482
    If it's getting hot while you are moving then it's some kind of circulation problem. The truck is almost 20 years old so you might want to examine that radiator carefully. The thermostat can be removed and test on a stove top in some hot water.
  • dadrummer77dadrummer77 Member Posts: 3
    Yes, It Warms Up To Normal Temperature, But The Longer Its Running, & I Drive, Its Starts To Climb, Yesterday It Climbed To Close To 260F, & My Light Came On Check Coolant Temperature, I Started To Drive After Being Stopped @ A Light, & Then It Would Cool Down A Little Bit & The Light Would Go Off, But Soon As I Was Stuck @ A Traffic Light, It Start Rising Again, I Got To Drop It Off Today @ My Mechanics, Their Is No Leaks, It Has A New Water Pump From Previous Owner That Had It Done, The Coolant Level Is Up In The Reservoir, The Fan Seems To Be Ok, & Im Getting Heat, 
  • dadrummer77dadrummer77 Member Posts: 3
    Also, Since I've Bought The Truck Last Year, I Also Been Noticing A Idling Problem, When I First Start It Up & Its Really Cold Out Side, My Idle Starts Fluncuating & Sounds Like Truck Wants To Stall, In The Extreme Heat To, It Does It In Drive & Reverse Or @ A Traffic Light, Out Of No Where The Idle Starts To Jump Up & Down, But It Don't Do It All The Time? I Was Told Possibly TPS, But The Code Don't Come Up For It, So When I First Bought The Truck Last Year, The Check Engine Light Would Come On & Scanned It & Scanner Said Back To Oxygen Sensors No Activity, Now They Are Brandnew & Replaced In The Rear .Both Sides With Bosch, & Check Engine Light Was Cleared, & Right After They Were Replaced An Hour Later Check Engine Came Back On, & Still Says No Activity & They Are Brandnew Oxygen Sensors In The Rear, & Apparently The 2 Front Ones Were Already Replaced, Now With It Been Over Heating, Notice With My Scanner Yesterday, That Now I Got More Codes P0161 Oxygen Sensor Heater Circuit Bank 2 Sensor 2 & P0141 Oxygen Sensor Heater Circuit Bank 1 Sensor 2 Popped Up Yesterday Which Never Popped Up Before, Until Its Been Going Over Normal Temperatures For The Last Week, Its Getting A New Thermostat & Temperature Sending Unit Now, & New Antifreeze, But No Leaks, New Water Pump & Never Had A Problem Until A Week Ago, Could A Bad System Ground Be Causing The 2 Oxygen Sensors In The Real That Are BrandNew Being Causing The No Activity After They Were Just Replaced?Its A 99' Chevy Silverado 2500 LS Ext Cab 4x4 6.0 Liter Long 8ft Bed. Anyone One That Had Or Is Having Same a Problem, Please Let Me Know Why My To Brandnew O2 Sensors In The Rear After They Came Up Originally On Scanner & Replaced Them But Still Causing Engine Light To Come On, Bad Ground Zoe Coroded Ground Underneath The Driver Side Cab Is All Full Of Rust On The Ground, Good This Be a Problem. Donnie R Longo
  • outerbanksboyouterbanksboy Member Posts: 1
    I have a 2005 silverado Z71 with 116,000 mi. this just started-engine warms to 110 deg. and normally I can turn on the fan and get heat, now all I get is cold air, especially if I am just idling. when I drive +35, I will get heat until I idle-then cold air. No visible leaks, belt changed at 110,000 mi.
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