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Chevy Silverado and GMC Sierra Radiator and Cooling Questions



  • bowanabowana Posts: 9
    I don't know if the 4.3 is the same as the 5.7 but I have a 99 350 and I have just been chasing a problem with the guage fluctuating as well. I did change the sending unit on the water thermostat housing but have found out that particular sensor runs to the computer (2 wires). Look at the side of the engine heads between the plugs for another sending unit. It will be the unit with 1 wire and it will send the information to the guage. Hope this helps.
  • edw6edw6 Posts: 2
    Hi, I have recently purchased a 1993 Chev truck with a 6.2L diesel motor and I am fixing a few problems on it, the current fix I am addressing is a coolant leak between the timing gear cover and the engine block. I have removed the water pump and mounting plate and I see that the water pump pumps water through two passages in the timing gear cover into the block and it is at the joint between the back of the timing gear cover and the block where I have some leakage, I don't see a lot of leakage there but there will always be some coolant on the steering parts underneath. I will replace the water pump and install new gaskets and hope that retorquing will fix the problem because to remove the timing gear cover requires considerable work beyond what I would care to do.I am wondering if anyone else dealt with sort of a problem and how they resolved it. Would a stop leak product be a successfull resolve? Thanks for any feedback in this matter.
  • Hey folks, new here, with an issue. I've owned my 1998 Silverado since Thanksgiving, 2007. It has a Vortec 4.3L, 5-speed. For about a month I have been smelling antifreeze, but haven't seen any signs of a leak anywhere. Interior heat is good, temp gauge is good. Today while out and about I noticed when getting back in the truck, leaking from the back of the engine. It's dripping down from above the oil filter on the driver's side. I would think it's a freeze plug issue; possible? Is it something I can do in the backyard myself, how many freeze plugs are there, where are they, does the motor need to come out, can a freeze plug corrode and develop a small hole that could be fixed with Barr's leaks? Any comments would be appreciated! It's a 2-wheel drive. Thanks.
  • 3 hours after my last post, I started my truck, turned the heat on. It's still leaking somewhere, dripping down from above the oil filter. I noticed a little coolant on the intake manifold next to the valve cover on the driver's side. After idling for 15 min., still warm in the interior, but now it smells faintly of coolant. Water pump, rad, hoses, heater core all look dry, no milky foamy stuff in oil/dipstick. With rad cap removed, coolant wasn't visibly moving. Temp reading about 125-130. Ideas?
  • srtttusrtttu Posts: 1
    I have a 97 Sierra 1500 with 126,000 miles. I have a somewhat loud sound of water running through the passenger side of my dash. This is nothing new. It's done this for over 2 years. There has never been a problem until now...maybe? Now, the truck will randomly overheat until the sound of the water rushes through the dash and then the temp will drop to normal operating temp. Also, I would like to add that when the truck overheats and there is no water sound, the heater does not work. Then as if some type of magic, you'll hear the sound of water, the truck drops in temp and the heater works. The mechanic changed the thermostat and flushed the radiator and this clearly did nothing. The theory I have developed is that when I hear the water, things are normal and all is good, when there is no water, all is not good. Help.
  • srtttu
    I had a similar problem in my 2002 Altima. The sound of swishing water was quite loud. It turns out there was a very small leak in the radiator. The leak was so small the radiator fluid would evaporate before dripping onto the ground, so there was never a puddle underneath to tip me off to the problem. Apparently, when there is a leak, the cooling system wouldn't hold pressure and an air bubble would form in the system. The bubble wants to rise to the top of the system, which is the heater core inside the pasenger cabin. The bubble would create a condition like vapor lock that can occur in a fuel system. Anyway, long story short, once the radiator was replaced no more swishing sound and all is well.

    I'd have a pressure test run on the cooling system.

  • 57bob57bob Posts: 2
    Thanks for the information on the other sending unit on the engine head. I finally got it replaced and fixed the problem. I had a hard time finding it at the auto parts places and even the dealer parts department because they call it a temperature switch for some reason but it looks like a sending unit.
    Thanks again
  • whats involved with the replacement of thermostat on 2000 gmc z\71 5.3 litter: maybe someone can help me with this.on regular days with outside temps 70 are above,I get average mileage,as average as you can get with a 4x4,but on the way to the lease with temps in the 30's and below,I pass everything but the gas station,I use twice the fuel there and back,but gauge is in the normal range,if i make a stop for any amount of time the gauge drops below normal range,,way below.thats while it has been idling ,I have 275 thousand on her and have never changed the stat,could that be the problem.THANKS
  • my friend had the simular problem,is the smell more apparent inside or outside the vehical, his was outside,turned out it was the intake manifold,
  • hi again,
    been awhile since i last posted..silverado 1500
    5.3, 4wd just ovrheated..pulled over to check things out and added some water and it seems to be pouring out the backside of the engine..not dripping put a gallon in and its out in less then 30 seconds.....both sides,passenger and drivers side..tough to see but either its on the heads or just below on the block....havent done a freeze plug in 15 they still have them on the back of the block ,,2 at once tho???
    even if its a head gasket..both at once??
    and my big question here is do blown head gaskets always leak into the oil to show that white filmy telltale sign...engine runs skips or stalls..was only 2 miles from home so i filled it and drove away and the temp gauge went up then down and then blew warm heat then back to cold..
    i'm an old timer and just like tinkering with 70's and pre 70's engines,would there be any other coolant lines on the backside of the engine that might cause the leak?
    thanks for any help!!
  • obyoneobyone Posts: 8,054
    Heater hose.
  • doesnt seem to be leaking by the heater hoses that goes to the heater core if thats what you a better look today..seem to be coming in and all around the tranny bell housing..another post told me the block heater near the oil filter housing..dont have a block heater..are the freeze plugs on the block behind the bell housing? meaning the tranny has to come out?
  • obyoneobyone Posts: 8,054
    There are two block drain plugs toward the left and right rear of the block that you could check. These are the plugs used when draining coolant from the block or to back flush.
  • I have a 1999 Yukon 2WD with the 5.7 lt engine. There is cooloant leaking out of the intake manifold just behind the alternator. It is coming out of the gasket where the manifold mounts to the engine block. How hard of a project am I getting myself into? I am fairly competant and have worked on a lot of engines in the past when I used to buy/sell used cars. That was 15 years ago and now it looks very complicated. Could I be biting off more than i can chew? Are there any big "pit falls" I need to be aware of? I will not do it myslef if I have to disconnect A/C lines.
    Thank you!
  • whantonwhanton Posts: 1
    I have no pressure at the expasion tank lid after driving till temp gauge reaches normal reading. I had to add about 3 quarts of Dex Coolant the other day. The level is still the same. I can't find any trace of a leak except slight smell at exhaust pipe. What are the pills someone mentioned sold by GM to stop leak? I don't want to pull intake gasket then both heads.
  • The truck is a 5.7L 2WD with only 137K on it and I hope to keep it forever.

    I recently disconnected and bypassed the oil cooler hoses from the radiator while troubleshooting a curious high oil pressure indication. When I went to reconnect the hoses I found the lower fitting on the radiator stripped (the radiator was replaced several years ago, too late to raise a warranty/installation issue).

    The nut that threads into the radiator is fine.

    My question the female thread in the radiator an insert, sort of like a helicoil, or is the thread milled into the radiator body?

    I'd really prefer to not have to put in another new radiator.

    Any ideas?

  • I have a 1999 Sierra,small block v-8.
    For several months,I have been smelling antifreeze,ever now and then seeing a small amount on the driveway.
    Just the other day saw a leak from the heater core area by the hoses.
    Not the hoses;but a small 90 ell shaped rubber hose.I think maybe a drain to release coolant mix if the heater core was leaking.
    Has anyone seen this?Is there a way to stop a small leak?
    Maybe some type of stop leak?
  • pwryanpwryan Posts: 1
    I have an '04 Silverado 5.3L with the same coolant leak mentioned in the forums. Pressure testing, both at cool and hot, revealed nothing. No visible leaks. Not a huge loss. The thought was a seeping head gasket. Coolant would just burn before showing up on the ground. Was going to try the GM pills referenced in the forums but cannot find anyplace to add them to the radiator. Any suggestions?
  • obyoneobyone Posts: 8,054
    Add them to the recovery tank. Not while the engine is hot though as it's under pressure.
  • I have the same problem with the '04 Chevy Silverado 5.3L. Where is the recovery tank located? and you add them when the truck is turned off? Thanks.
  • obyoneobyone Posts: 8,054
    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 Posts: 5
  • 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 Posts: 8,054
    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 Posts: 14
  • opc167opc167 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 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.
  • 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 Posts: 1
    has anybody figured out were the anti freeze goes??I have an 04 with the 5.3 and cant find the leak??
  • I have a 98 GMC Seirra 1/2 ton 4x4. How do I remove the fan clutch/fan from the water pump?
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