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Chevy S10 - GMC S15 and Sonoma Radiator and Cooling Issues



  • the_big_althe_big_al Posts: 1,079
    although I am not looking for a step by step process (I'm pretty good at reading a chilton :D), but what is the basic process to do this??
  • gonogogonogo Posts: 879
    Get a book, easiest way to have complete information.
    First you need to look closer, prove it is the intake gasket, don't want to tear it all apart for nothing.
  • I have a 2002 S-10, 4.3, A/T. I just change the thermostat to a 195 deg. The operating temp now stays at 210 deg.( mid range on the gage ). My question is will this be detrimental to the life of the engine, will I see any difference in mpg, any adverse effects in warmer outside temps? I live in Phx. Ariz. so the temps can get quite hot in the summer months. What is the recommended operating water temp? Thanks for any help.
  • the_big_althe_big_al Posts: 1,079
    As far as I can remember, my S-10, an '01 4.3 A/T has always read right at the 210 (midway) point once warmed up. In the summer it has been dead on mid-point and in winter it reads just a hair below. My truck also spent several summers in Phoenix and I had no problems. I have the standard 180 degree (I think it's 180) T-stat. I have changed it once and I stuck with an OEM one.

    You won't see any damage if the temps stay at 210. What you do need to worry about is that in the summer, you might see the temp range in the higher side rather than the low side because of the 195 degree t-stat. That is something that I would be careful of. Instead of operating between 100 and 210, you are now operating between 210 and 260, which can get dangerous on hot days. Especially in rush hour traffic traveling at only 10 MPH.

    In my opinion, I would switch back to the standard factory t-stat. Is there a reason you went to the 195 degree one? People make all sorts of claims pertaining to running one, but I haven't tested it to be sure and so I don't know. They all sound like hocus pocus to me.
  • You could be 180 degrees off? At # 1 cylinder both exhaust and intake should be loose if you want TDC ( top dead center)? This means that. both intake and exhaust valves should be loose upon inspection or both are closed. This is a common mistake and don't feel bad about it! When you turn the crank, the rotor should be pointing towards #1 on the cap or distributor? Wires for #1 should be located at front not back of engine. Hopefully, this will want you!
  • I have a 2003 Sonoma 4x4 ZR2 with 71,000+. The engine temperature heats to 190 and then Fluctuates between 190 and 210. When it get to 210 the heat inside the cab blows cold air. When it returns to 190 the heat returns. I have had the thermostat replaced at 55,000 and the heater control panel inside the cab was changed out due to transmission valve vacuum failure. Truck starts normal and idles normal. After about 25 minutes of running the engine stops the temperature swings. Any ideas? About every 9000 miles I have to add antifreeze.
  • the_big_althe_big_al Posts: 1,079
    (This is an old post, but maybe you are still searching for a solution?)

    Here are some things to check... You have a coolant leak somewhere. More than likely it is the intake gasket (see my next post on this very issue). The reason you have no heat, even at 210 is because you have low coolant. You do not have enough coolant to get into the heater core. Do you notice that after you add coolant that your heater works properly? This was happening to me. I would have a temp reading of 190-210 and no heat. I would then add coolant and I would have heat after a few minutes. I was losing coolant at the intake. This is common on these motors to do that (so I have heard)... With the truck running and with a full coolant level, check for drips under the truck. If you have an external leak, you might get lucky and it will be bad enough to see. If you have an external leak you are also lucky in that you won't have water in your oil. If you have an internal leak, check your oil. You should see a white milky film in the oil. You can also check the oil by parking the truck overnight, crawling under and cracking the oil plug. Since water is heavier than oil, it will sink to the lowest part of the pan (where the plug is) and be the first thing to come out when you pull off the plug. You won't have to pull the plug off all the way, just enough so that if there is water in the pan, it will start to come out. If there is water in the pan, more than likely you have an intake manifold that is leaking...

    Now see my next post on that...
  • the_big_althe_big_al Posts: 1,079
    A while back I posted about a coolant leak. I finally found and fixed it... (ya ya it took a while. Thanks gonogo for pointing me in the right direction).

    It was indeed the intake manifold. Boy oh boy was it bad. Okay - here's the short story. A while back, several months ago in fact I realized I had a coolant leak. My heater would quit working and so after doing research (on here mostly) I found it to be low coolant. I wasn't losing coolant rapidly enough for me to do much about it, plus funds were a bit short and it also wasn't or didn't seem to be an internal leak so I didn't worry TOO much about it. I should have and so I know I played a bit of a gamble here. I rolled the dice and luckily I seem to have come out okay, but not counting my chips yet. Anyway...

    Fast forward to a couple weeks ago. I am headed to work and my temperature shoots towards hot. I pull over and realized that I am REALLY low on coolant. Like almost out. That'd odd because I had just filled it. Literally like not even a week earlier. I was able to limp home after some cooling off and getting water into it, but while the truck was running, I could look under the truck and see coolant REALLY dripping off. It was coming from the front of the motor and dripping under the water pump area. A buddy comes over and looks at it and determines from what he can tell that the water pump appears to be bad. This is now in addition to the other leak that I know I have somewhere that I think is at the back of the motor, but more on that later. So I trot down to the parts house and get a water pump and tear into the truck and replace it.

    I get it all put back together and fire up the truck and...................................... it still leaks just as bad as before. Trouble is, I now have no clue where to look. My friend who originally diagnosed it is now on vacation for two weeks and since funds are short I also can't take it to a shop to have them look at it. He also has a cooling system pressurizer that will pressurize the system with the vehicle off to help in spotting leaks. This is something we should have done in the first place, but at first blush, it really did look like the water pump was bad. On later inspection of the old pump, it does indeed look like it was either getting ready to go bad, or was at least contributing to my loss of coolant so changing it out was not necesarally a bad thing to do. It has now eliminated once possible source. While funds were short, the pump itself was only $60 so it's not a total misstep.

    So not knowing where to go since I can't tell with out tearing down the whole thing again where the leak is coming from and with the truck running, I can't see it with everything in the way, I park it till my friend comes home and can help me tear it down and check it out. While talking to him and letting him know what happened, he then says it is probably the intake and confirms what seems to be common even on this thread. He says it is probably the intake. So today, we are able to finally work on it.

    I take it over to his house and we start tearing into it. We first put his pressurizer on it and we can see it bubbling and pushing a little bit of coolant out from the under the intake on the front passenger side of the motor. So we have confirmed what looks like a "minor" leak and could be my leak that I saw with coolant dripping from the back of the motor, in that the coolant would run down the valley between the valve cover and intake and off the back of the motor (in theory).

    So we start to tear everything off that is in the way so we can see the entire cooling system. Alternator, alternator brackets, power steering, A/C, clutch fan, idler pully, tensioner pulley, air box and mass air flow sensor and air tube. Anything that was in the way of looking at the cooling system that we could take off with out breaking into the cooling system we removed. Now we can see. We hook up our pressure tester and pressurize the system. Immediately we can see at the front of the motor where I had initially been looking water just pouring out. You couldn't see it before because the alternator was in the way. But there was a definite intake leak right there. It just poured out and ran down the front of the motor. Another concern I had was maybe I didn't get the new water pump sealed and mated properly to the block, but that checked out fine.

    On to part II
  • the_big_althe_big_al Posts: 1,079
    So that sealed it. Off to the parts store I went while my buddy started to tear down the rest of the motor. While we were in there we decided to go ahead and do valve cover gaskets as well since they were also leaking and they were covered dirty grime from the bolt gaskets seeping a bit and also they were leaking a little where they mated to the head. I got back and we finished pulling everything apart. Upon removal of the intake manifold, we could definitely see where it had been leaking. It was actually leaking in a couple of spots. The front of the motor was the worst. It had almost completely disintegrated (luckily it decided to leak externally only). We cleaned it all up, pulled the valve covers, cleaned them all up and put them back into place and then proceeded to get the new gaskets in place and the front and back of the motor siliconed. Back on with the intake and then back together everything we had torn apart.

    Before starting the truck though, we decided to pressure test it again to make sure there were no leaks. We hooked the pressure tester up and immediately we could hear it losing pressure somewhere. So we start poking around for the source and find it at the upper radiator hose where it mates with the T-stat housing tube. After hunting for a new hose clamp and finding one an hour later after going back to the parts house, we get that taken care. Pressure again and now we can see it dripping still. Another bad hose clamp (we should have just replaced ALL the spring loaded, but we didn't. We replaced that one and now all the clamps that we have removed are no longer the spring loaded ones, but the screw down type. We pressure again and FINALLY seem to be holding pressure and have no leaks, drips or hissing.

    We start the truck and AMAZINGLY it fires right up. I say amazingly because we had this thing ALL the way apart practically. Electrical connections were all unplugged, vacuum lines disconnected, distributor taken out and so to have it turn over on the first try as if it had never been apart was really quite amazing. We let it run and inspected for leaks all over. Let it get to operating temperature making sure we added coolant as it needed it. It pushed a lot of air out and finally after running several minutes the T-stat opened and began to draw coolant in and the heater got warm.

    We let it run several more minutes, making sure the coolant level stayed full and also checking for drips and leaks. After seeing none, we closed her down, and I came home! It appears that we have fixed it. (Hopefully)... I'll keep my eye on it for a few days and won't venture to far from home, but I think all will be well. Hopefully we took care of that minor oil leak I had too in the process. That would be nice.
  • gonogogonogo Posts: 879
    I think you got it too, great job.
  • Did you ever figure out what the name of this pipe is? I am having what sounds like the exact same problem and I can't seem to find any information about this. I know this post is like 2 years old but I really help. Thank you!
  • gonogogonogo Posts: 879
    I would ask for the thermostat housing assy, might be a dealer only part. If it was mine, which is not leaking yet, I would try to pull the tube out of the housing and reseal it.
  • I just recently replaced a water pump on my 1992 s-10 Chevy pickup. Before this coolant leaked everywhere. So I tore everything apart, put the new part on, new gaskets and put rubber gasket sealer on the gaskets. I got everything all put back together. I believed it to be fixed because it quit leaking. The next day I drove the truck to school and noticed it to be leaking again. I found it to be a pinhole in one of the lines and fixed that as well. So all said and done I finally believed I got it, but the next day I was driving down the road and my temp. gauge went wayyy up. I stopped on the side of the road and checked the coolant it was all up to specs. So I continued to drive home. The truck drove fine and acted fine, and while i was driving, the temp. went back to normal and the check gauges light went off. The temperature gauge now goes up for a few miles and then goes back to normal while i drive it. I'm really stumped on this one hopefully someone can help me out.

    Thanks... :confuse:
  • the_big_althe_big_al Posts: 1,079
    Did you change the thermostat?? That will make the temp gauge fluctuate if it's not working properly. The T-stat should be changed (or at least I did and would) when you change the water pump.

    You might also have air trapped in the system, especially since you broke it wide open changing the water pump. That air will cause the truck not to vacuum properly and won't push or pull water from the recovery tank. Try bleeding the system. Or taking it to a shop and having it flushed. They can do a pressure flush that will force any air out of the system...
  • i have a 94 s10 4.3 5spd i recently replaced the water pump due to over heating and its still leaking somewhere i've bubbled the system a few times then come out the next day and the coolant had leaked there a soft plug around the waterpump area??
  • the_big_althe_big_al Posts: 1,079
    I've been there done that with cooling issues on my 4.3 I had a while back. Do you have a pressure tester that you can use to pressurize the system with the motor off? IF not, can you rent one or borrow one from a store or friend. I would do this, even buy one, if it's not too expensive.

    Then pressurize the system with the motor off. You do this by replacing the cap with the pressure tester. It pressurizes the system and will expose any coolant leaks. You can then trace them with out fear of moving parts and fans and belts and pulleys and with out the noise of the motor running.

    Here are typical problem areas I experienced and found are typical of the 4.3. I did this on a later generation 4.3 (2001) so I am not sure how much will have changed, but the basic block configuration didn't change much. Heads and intakes changed, but not much else. My 4.3 had a lower intake gasket leak. It was spewing coolant into the valley where the valve covers, intake and heads came together. 4.3's are prone to this leak.

    Since you also state you overheated, you might have cracked or warped a head. Especially if you have aluminum vortec heads. If that's the case, you'll have to tear down and replace the affected head. The pressure test though will tell you where it's leaking, unless it's leaking internally into the block. If that's the case, your oil will be full of water.
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