overheating issues

98 s10 i swapped a 100k mile 2000 silverado 5.3 into.

using the stock silvy clutch fan and the stock s10 4.3 radiator, I am having major overheating issues.
BUT, i think the fan/radiator have nothing to do with it, as the symptoms appear to be a stuck closed thermostat.

symptoms were. cold upper rad hose. boiling noises.

so i replaced the t stat with a brand new one.


same issue.

cold upper rad hose, boiling noises, but the rad hoses are definitly pressurized.

watching my aftermarket temp gauge (not tested to see if it is good or not, but assuming it is good) the temp stays pretty steady at 180 until it suddenly starts to climb all the way up past 220 until i shut it down.



so, why is it doing this?
how do i fix it?

Sounds like the system has air in it and needs to be purged. It could also be air trapped in the heater core doing it as well...

does the t-stat have a small valve on it to allow air to escape? 



if not, you can drill a small hole in it to help let the air out. 

Is the water pump making any noise/wobbling and is it turning in the right direction? (idk if you messed with the belt routing)

did you flush out the 4.3 rad before hand?  what kind of coolant are you running? 

Sounds like air to me too.

Sounds like the system has air in it and needs to be purged. It could also be air trapped in the heater core doing it as well...

heater core is gone so its not that at least.
how do i purge the system more?

does the t-stat have a small valve on it to allow air to escape? 




if not, you can drill a small hole in it to help let the air out. 

Is the water pump making any noise/wobbling and is it turning in the right direction? (idk if you messed with the belt routing)

did you flush out the 4.3 rad before hand?  what kind of coolant are you running? 

yea, it was pretty small but it definitly did
truck'd damn loud now so i cant really tell but no noticable noise from the pump. and it's pressurizing the system pretty good so i dont think its shot. stock belt routing so i dont think thats it.
yes, flushed with a hose at least till only clear water came out.
im running meijer special non-dexcrap coolant (green)

Sounds like air to me too.

ok, so air gets a lotta votes. what's the best way to purge it?

Jack the front end up a few inches and make sure it's secure, start it up and let it run up to temperature, and pump the upper radiator hose by hand. Shouldn't need to run for long to get the air worked into the upper rad hose if there is an air hole in the thermostat, and pumping it by hand will usually help get it down into the radiator, if you're doing it with the cap off you can fill and continue, if not you'll have to stop and re-fill and start it back up. It's always worked well for me.

Jack the front end up a few inches and make sure it's secure, start it up and let it run up to temperature, and pump the upper radiator hose by hand. Shouldn't need to run for long to get the air worked into the upper rad hose if there is an air hole in the thermostat, and pumping it by hand will usually help get it down into the radiator, if you're doing it with the cap off you can fill and continue, if not you'll have to stop and re-fill and start it back up. It's always worked well for me.

on gen 3s t stat is on the exit of the rad,
so far i let it idle for like 20 min and it didnt get up to temp (according to the gauge sender in the t-stat...)

ive heard of filling till the crossover has fluid coming out, gonna try that sometime when i get the chance.

maybe you need this:

http://www.jagsthatrun.com/Pages/Parts_Cooling_LSI-tee.html

We copied wicked mayhem on the steam vent

http://www.s10forum.com/forum/f30/project-feel-the-luv-388243/index38.html#post7102907

Sounds like most people run it on the upper hose, but the steam connection on the 5.3 radiator was next to the lower hose, so that seemed like the best side to do it on.  Couldn't hurt to check if the steam lines and tubes are clogged.

Motor was definitely making "bubbling" noises after Ryo shut it down on our test ride.  The overflow was overflowing, but again the upper hose was not warm.  Seems like a circulation issue to me if the upper is cold.

If it was overflowing it was trying to purge air out of the system. Do as ArtosDragon said and jack the frontend up. Run the motor with the cap off, it'll probably spill out a few times but once it gets up to temperature you'll start noticing it burping alot of air out of it. Once you feel it's out of air, top the rad off, put the cap on, fill the resevoir almost full and drive it around. It'll burp any remaining air and also refill itself from the overflow tank.

Of course some systems create their own airpockets (airation from water pump) You might want to back-track any cooling issues with those motors.

ive confirmed on ls1tech that the steam vent going to the t-stat is okay,

i think next chance i get i'll drill a few more holes in the tstat, and jack the front end up and do everything i can think of to bleed tghe system of air.

ok, so after finally getting to drive it hard, water temps at t-stat (where my sender is) never got over 120F

does this mean the t-stat is now stuck open?

upper rad hose got warm, and lower got lukewarm/cool.

gah.
the 4.3 definitly would have been getting pretty hot with the driving i did today.

at least i think i might not have too much cooling issues in the summer?

Could be too many holes in the T-stat. How many and what size did you drill?

Could be too many holes in the T-stat. How many and what size did you drill?

i actually never got around to doing that yet
sooo there is still only the small hole that came in it when i bought it...

It has to be stuck...

It has to be stuck...

it was brand new.... i can try to put in the old one again....
can overheating an engine damage a t-stat?

nothing was changed. water, etc all the same as last time i posted....

Well here is what a GM tech would do for the two problems.

Overheating
1. Inspect for loss of system pressure

• Inspect connections for leaks
• Repair as required
• With pressure tester pressurize system to 20 PSI throught the overflow tank
• System should hold pressure for 2 minutes.  If not there is a leak.
• Pressure test the overflow cap
• Inspect for damage or debris on the gasket in the cap and the inner sealing surface of the filler neck.

2. Test Coolant Concentration
3. Inspect the drive belt for excessive wear or low tension.
4. Inspect the water pump for correct operation.
5. Inspect the radiator fins for obstruction.
6. Inspect the cooling system passage for obstruction.
7. Inspect the fan clutch

• In order to ensure complete fan blade clutch disengagement, begin testing with a cool engine.
  If the fan blade clutch assembly free wheels with no drag, (revolves more than 5 times when spun by hand), replace the fan blade clutch. For the 4.3L, 4.8L, 5.3L, and 6.0L engines, refer to Fan Clutch Replacement . If the clutch performs properly with a slight drag, refer to step 3. Testing a fan blade clutch by holding the small hub with 1 hand, and rotating the aluminum housing in a clockwise/counterclockwise motion, causes the clutch to free wheel. Consider this operation normal and this test should not determine replacement.
• Perform the following steps:
  1.  Sufficiently cover the radiator grille in order to induce a high engine temperature.
  2.  Start the engine.
  3.  Turn on the air conditioning (A/C) if equipped.
  4.  Operate the engine at 2000 RPM.
• Inspect the coolant temperature when the clutch engages. Allow about 5 to 10 minutes for the temperature to become high enough in order to engage the fan blade clutch. This will be indicated by an increase, or roar, in fan air noise and by a drop in the coolant temperature reading of about 3-10°C (5-15°F).
  -If the clutch did not engage between 110-121°C (230-250°F), replace the assembly. Ensure that the fan blade clutch was disengaged at the beginning of the test.
  -If you did not observe a sharp increase in the fan noise or a temperature drop, and the fan noise level was constantly high from the start of the test , replace the assembly. Do not continue this test past a thermometer reading of 121°C (250°F) in order to prevent engine overheating.
• When the clutch engages, do the following steps:
  1.  Remove the radiator grille cover.
  2.  Turn off the A/C in order to assist in engine cooling.
  3.  Operate the engine at about 2500 RPM.
• After several minutes, the fan blade clutch should disengage as indicated by a reduction in fan speed and roar. If the fan blade clutch fails to function as described, replace the fan blade clutch.

8. Verify the thermostat operation

• Place the thermostat and a thermometer in a container with a 50/50 solution of water and DEX-COOL antifreeze.
• Place the container over a heater.
• Important: While heating, do not rest the thermostat or the thermometer on the bottom of the container. This causes the thermostat and the thermometer to be at a higher temperature than the solution.
• Agitate the solution in order to maintain a uniform temperature of the solution, the thermostat, and the thermometer.
• The thermostat valve should start to open at the rated temperature. The thermostat should be fully open after the temperature has increased 15°C (27°F).
• A used thermostat can be about 6°C (10°F) above or below these settings without adversely affecting the thermostat. You do not need to replace the thermostat. If the thermostat does not operate at the temperatures specified, replace the thermostat.

9. Other factors, such as the following, may be causing the engine to overheat:

• heavy vehicle payload
• The A/C system
• Excess engine oil
• Restricted air flow through the radiator
• Extreme air temperature

Underheating....
1. Check the level of the coolant in the surge tank.
2. Check to see if the correct type of thermostat was installed, or if the thermostat sticks (or is stuck) in the open position.

And that's it for the second.... 

when testing the tstat in a boiling fluid, is the open/close obviously visible?
i tried once (with a steel cup and an OA torch) so it wasnt very controlled, but i didnt see any movement....

Yeah, I don't know about an LS stat, but first gen and LT1s usually move between a quarter and 3/8ths.