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Chevy S10 - GMC S15 and Sonoma Radiator and Cooling Issues

sn4ck0sn4ck0 Posts: 8
Recently replaced the head, and while doing so, I had broke off the Plug in for the Coolant Temp Switch below the Thermostat, so, I didn't pay it any mind drove it, then a bit later, I broke down and replaced it, (temp gauge before didn't work until I replaced it) so now it works, after ignition and idling about 5-10 mins or so, it would readout 260^, when stated with the new Switch it would idle at 1k RPM, before without it it would idle at about 1400 RPM then Idle down to 1k RPM (guessing when the Thermo opened etc), anyways, I've replaced the thermostat, and thinking it might be the h20 Pump I took that off, and it's in good order, and even reverse flushed the Radiator.

Any Ideas on what else to do, or what the problem might be?


  • gonogogonogo Posts: 879
    Did you bleed all the air out? Will it overheat going down the road, or just when idling.

    You have a clutch fan on a 95 I assume, will it roar when it gets hot, it should.

    260 F is getting ready to boil over. What temp is the coolant in the radiator, I use a candy thermometer, wife doesn't know.
  • sn4ck0sn4ck0 Posts: 8
    I'm Not Quite for sure what you mean bleed the air out, as in out of the Radiator?

    Overheat doing both, and yes it'll engage not all the time, but I checked the spin of it, and it's seemingly stout, and no cracks.

    With the New Temp Switch, it's like there is no water moving anywhere, remains stagnant, and is cool/cold (top and bottom hoses are cool as well) with the Switch unplugged water is exceedingly warm, and I can view h20 moving. top hose it hot to touch.

    Note, there is a metal tubing going from below the thermostat housing toward the back of the engine, (assume to the Heater core) and it is HOT with both scenarios.

    Another thing I tried, was the have the heater on with the new switch, and it seemed like it would take longer to Overheat, but in both cases the Heater was ...doing it's job, nice and hot :).
  • gonogogonogo Posts: 879
    Puzzled, you say with the temp sensor unplugged, it makes a difference?
    I reread your posts, it did not appear to overheat until you got the gauge working. I don't think your gauge is accurate, check actual water temp .
  • sn4ck0sn4ck0 Posts: 8
    Strange I know,

    I did so, had to take off the Thermostat housing, and saw that it was hot, steam, extremely hot to touch.

    The problem is, with the thing plugged in, seems like the Thermo is not opening, so I removed the thermostat, and replaced it all together, and it seemed to have worked.

    and if that is indeed the case, (Bad thermo) that would make two in a row.

    One thing I saw, after taking the housing off, was one time there wasn't enough h20 to fill up to the sensor. (I think that is what you refered to as Airlocked, so I made adjustments and tried to fix that (Jacked up one side, and started with the heater on)

    has to be one of two three things

    Thermostat (again)
    Waterpump (doesn't seem likely, as it was pumping with out the thermo in)
    Sensor, that's the only thing I haven't replaced (after the initial replacement)

    Any Ideas on what to do/check?
  • rrt1441rrt1441 Posts: 2
    My 95 S10 engine light comes on and temperature on gauge is higher than normal. Light comes on after driving a few miles and engine is hot. Have not noticed if the fan comes on. Could this be a sensor, or thermostat?
  • gonogogonogo Posts: 879
    I still think it is a gauge problem, not the right sensor, try a Delco sensor. Or gauge wiring problem, or bad gauge.
  • jae5jae5 Posts: 1,206
    When you replaced the original thermostat did you install the new one in the same position as the old. On the 4.3s you have to have the thermostat clocked in the right position or you can have issues. You can also check thermostat operation really easy by placing the thermostat in a pot and bring the water to a boil and see when it opens (should be 195 as stated).

    Are you using dex-cool (orange) coolant or the regular green? If using Dex-Cool you have to use a flushing agent / kit to get all of the old crap out; if not you can run into the problems you're having as well.

    You still may be having an air problem. You definitely have to have the heater on, blower on high, when your topping off or you can get air trapped in the system. You can do the initial system fill with everything shut off but after that you need to have the engine running and the the heater on to get the air out to finish topping it off. And what do you mean you jacked up one side? Did you jack up the truck so that water / coolant would fill up to the sensor? And you are using water / coolant right, not straight water.

    As stated the sensor may be out of spec, not sending out the right signal or is the wrong one. But it wouldn't cause an "real" overheating issue as it shouldn't be blocking a main coolant passage.
  • cachevycachevy Posts: 1
    I just purchased a 2000 S-10, with a 4.3 V-6, I am being told by my mechanic that this product eats up the inside of engine & I already have a intake leak.
    Also that it is better to flush coolant out & replace with green anti-freeze.
    Any suggestions out there? :confuse:
    I did not expect this appox. $700 repair B-4 I've driven truck more than 200 miles.
    Any thing else to look for? :surprise:
  • littleoscolittleosco Posts: 11
    We have the same vehicle, same engine. We were told that the Dex Cool needs to be replaced fairly often or it gets thick and gums up your engine. Come to think of it, we've only changed it a couple times and it's probably due again. I've not heard of replacing it with regular anti freeze but just being aware that the Dex Cool can cause these problems.
  • My cooling fan isn't kicking on. The temp. guage seems to be working fine since it reads normal while the vehicle is moving. I tried free-spinning the fan blades with the engine off and there is plenty of resistance. I checked all the fuses, both under the hood and in the dashboard, and they are all okay. Not quite sure where to go from here. No other symptoms other than overheating at idle or after the engine has been shutoff. Any suggestions would be appreciated.
  • My 1995 S-10 is leaking from the backside of the engine. I can't see any visual signs on the top, but underneath a steady stream is coming down between the starter and oil pan. I was wondering if there are freeze plugs back there that I can't see. The oil is clear of water, so I'm hoping it's not a cracked head. Just wondering if anyone else has had this problem.
  • jpfjpf Posts: 496
    What size engine is it?
  • 4.3 vortec
  • jpfjpf Posts: 496
    I had a 2000 S10 extended cab with the same engime. It had a leak from the intake manifold gasket. The truck never overheated but did lose coolant. Cost like $300 to $400 to fix if I recall correctly. Good luck.
  • I've got some issues with my sonoma its a 2000 with 185,000 miles. its been in one crash(not my fault). had some body work and new chip(registers E-brake and ABS gauge). But now im getting overheating issues within the first couple minutes of driving. spikes to (260). I thought it was leaking and replaced the hose/valve running rome radiator to engine. today when i turned it off i smelt anti-freeze and heard a sizzling sound? any thoughts? :mad:
  • hey i have a 2000 GMC sonoma and everytime I drive it. The temperature guage is spiking up into the 260 range? once I stopped and popped the hood i could smell anti-freeze and heard a sizzling sound. As if something is leaking and the engine is so hot it fry's the liquid. I've replaced the hose going from radiator to engine. Also checked the valve that connects the hose to the engine. that fixed the problem for a while now the problem has returned. (2nd time with the sizzling-1st without) Sny suggestions?? :mad:
  • I have a 1998 Chevy S-10 with a 2.2L Engine. There is a steel pipe on the top of the engine towards the drivers side. It is mounted down with one bolt on the back side and held into the thermostat housing on the front. It also contains the Coolant Temperature Sensor right before the thermostat housing. And on the back side of the pipe there is a rubber hose that has engine labeled on it. This steel pipe is leaking and i need to buy a new one to replace it. What exactly is the name for this pipe so the guys at the auto parts store can look it up for me. Any help is greatly appreciated.
  • This sounds identical to the problems I have had with my 2000 s10. The dexcool stuff is terrible and GM recently settled a class action lawsuit giving most truck owners 50 to 300 hundred for repairs. Did you fix your intake leak or?? Just curious as I now have one as well.
  • gonogogonogo Posts: 879
    That leak happens now and then, not yet on my 99, but only 55K. Just buy a new pipe and housing assy, it should be available after market.
  • I flushed the cooling system and replaced thermostate on my 2002 GMC Sonoma with79,000 miles on it.
    I've had nothing but probems after that. Service engine light came on, did diagnostic - water temp below engine temp. Replaced temprature sending unit. Same thing? I have to drive 10 miles before engine reaches operating temp?
  • gonogogonogo Posts: 879
    Bad thermostat.
  • bcrawf53bcrawf53 Posts: 4
    I'll try it and let you know!
  • peter931peter931 Posts: 13
    After [email protected] radiator and water pump on GMC Sonoma 4.3L coolant is leaking to oil pan. Truck is not smoking and compression is good on each cylinder. What could be the problem?
  • bcrawf53bcrawf53 Posts: 4
    I change the thermostate and it is working fine so far. I'll have to wait for cooler weather for a real test. It seems to work better when the outside temp is higher than +40 degrees. Fuel mileage is up to thank goodness.
  • bcrawf53bcrawf53 Posts: 4
    4.3L 's have an issue with intake manifold's leaking. I had the same problem on my 94 GMC Safari. Changing the gasket took care of the problem!
  • peter931peter931 Posts: 13
    It is a 3.0L SOHC engine. No engine interference. After R&R timnig belt , engine is not running on 6 cylinders. All the marks on cams and cranc are in position , distributor rotor is on #1 . Piston #1 is in the TDC . I am in dead end.
    Any one know where could be the problem?
  • I have a '95 GMC Sonoma 2.2L that's getting hot. The temp gauge only goes to about 210. But smoke is coming into the car through the heater. I thought it was the thermostat because I smell that radiator smell, but obviously that's not it. Any suggestions?
  • gonogogonogo Posts: 879
    Your heater core is leaking, not an easy job.
  • the_big_althe_big_al Posts: 1,079
    Truck: 2001 Ex-cab 2wd s-10

    Drivetrain: 4.3 V6 with Auto trans

    I seem to have a coolant leak somewheres. It comes from the back of the motor. When the coolant level gets low enough the leak seems to stop, as well as the heater. When I fill the coolant back up, I can park the truck and after a few minutes (a run into the gas station to pay is long enough), I come back and it is dripping from the back of the motor at a pretty good rate.

    When I run the heater, I dont get any odd smells into the cabin, but the heater will quit working once the coolant level gets low enough. I also do not have oil int he coolant or coolant in the oil. No smoking out the back of the tail pipe. The truck runs just fine. The only time it goes wonky is when the coolant level gets low. When the coolant is full, the temp gauge runs just below halfway (210 I think) and stays there. It also gets there quite quickly and always has. I know there is a couple of different places the leak could be, but I was wondering if there is a most likely culprit.
  • gonogogonogo Posts: 879
    Low coolant will effect heater operation. Seeing you have a V6, I would suspect the infamous intake manifold coolant leak, most times they will leak external. That's good news for you, get it repaired ASAP.
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