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Overheating, Did search but-

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by santana, Jun 7, 2003.

  1. santana

    santana 1/2 ton status

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    found no answer to my question,,,,, How do I tell what's causing it, water pump or t-stat???? How to test t-stat $ pump?? /forums/images/graemlins/1zhelp.gif
     
  2. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    Make sure your fan is totally engaging. If you have one with a bad ground, it can cause it to come on, but not fully work. I had that issue in my truck, and my car. Seems to be something fairly common. It's an easy thing to check out. If it doesn't work, then hey, you aren't out anything then maybe the cost of a new terminal...
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Why not help us help you. How about some details:
    When does it over heat?
    Temp it get's to?
    A/C on or off?
    Any mods like tranny cooler, electric fan etc?
    Other symptoms?
     
  4. santana

    santana 1/2 ton status

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    Sorry /forums/images/graemlins/confused.gif It overheats just idling , the temp gauge rises all the way to the top, I squeeze the top rad hose when it hot to feel for water pressure but I just feel air pressure, I removed the t-stat but I cant tell if its bad, I push down on the valve and it moves with little pressure. I guess I'll just go to the parts store and pick up a t-stat and water pump and try both, the water pump doesnt leak or make noise like the book says it does when its bad but hopefully either one will take care of this. Thanx for help. /forums/images/graemlins/ears.gif
     
  5. TorkDSR

    TorkDSR 1/2 ton status

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    boil the thermostat. water boils at 212...the stat should open at 195..

    water pumps cant go bad. if it doesnt weep or make noise, its still good.

    is it a thermal clutch, or electric fans? do the fans spin? is the clutch working? throw it in the oven and find out. is there water in the system? is the radiator cap bad?

    what kind of fans are
     
  6. fad2blk99

    fad2blk99 1/2 ton status

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    I've chased overheating and poor heater operation in our body-style Chevys since I got my first 77 K-10 over 8 years ago. With my current toy ('89 K-5), I used an Edelbrock water pump. Nothing worked like this pump!! It is well worth the extra money. It increases flow so that the heater works better and, in your case the truck stays cooler.
    With that being said.... start troubleshooting by making sure your fan works as previously stated (if the fan is spinning and pulling air as it should, you'll most likely need a new clutch). While checking your fan (provided the truck isn't too hot) pop off your radiator cap and look at the coolant flow. Verify that it has enough coolant and that you have descent flow through your heater core (it should be coming it through the small nipple below the filler neck provided it hasn't been rerouted by a previous owner). Also, while you are under the hood, listen to your water pump pulley. Do you hear the metallic sound of worn out bearings? Is water leaking out the weep hole just beneath the pulley? Next, shut off the truck and very carefully feel your radiator. Feel for cool spots. Cool spots may indicate stopped up water passages and a new radiator may be in your future (the flushes usually don't work in my experiences).
    If you have poor flow but no cool spot on the radiator, replace the thermostat.
    If the water pump is leaking and/or making noise replace the water pump (again, I prefer the Edelbrock)
    If you do need a new radiator, go ahead and replace the heater core, as what ever is stopping up your radiator is likely in your heater core as well(check out www.radiator.com if you need a new radiator... I think mine cost about $160.)
     
  7. wrathORC

    wrathORC 1/2 ton status

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    Just replace the thermostat. $4 + $1 for a new gasket and you're good to go. It's never worth testing a thermostat in my opinion.

    While you're there, purchase a new radiator cap. Make sure it's rated for 15-16psi. It'll cost you around $8.

    A water pump is a chore to replace. I only do it if the pump rumbles (contaminated and/or wore out bearings). If you don't have to, don't do it.

    Check to make sure it's got enough coolant too of course. Spray out the radiator with a garden hose, first backwards and then forwards through the radiator. If you can, get the hose between your condensor and ATF cooler (if you have them).


    If this doesn't do it then you've got an airflow problem, a coolant flow problem, or a clogged radiator problem.
     
  8. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Wrath has a good plan of action.
    Sounds like the system is not building pressure if the radiator hose is not firm once up to temp. Also make sure your catch tank is operational. The catch tank will help purge all air out of the system. Somewhere there is a loss of pressure and the cap is the usual culprit like Wrath pointed out..

    Before topping off the system, after you put in a new stat, look down in the radiator at the tubes and see how crusty it looks. If you see a lot of deposits and the holes looked closed over then it's probably time to take the radiator to a shop and have it rodded out.

    Also while flushig the radiator with the garden hose is fine, DO NOT USE TAP WATER IN THE COOLANT. Tap water is full of minerals and chemicals. They cause deposits, eat the inside of the cooling system. They also destroy the addatives in the antifreeze that are there to protect the cooling system from corrosion. Use DISTILLED water. less then a buck a gallon at your local food store. Get two gallons.

    On the side of the block just above the oil pan is a plug on both sides. This will let you drain the block. You may have a lot of deposits and when you remove the bolts you might have to break it free with a small screw driver.

    Check the clutched fan. if it spins very free when the truck is stone cold in the morning then it's proabaly bad. A good one will lock up for a couple minutes at start up first thing in the morning. You can hear it roar when it's locked.
     
  9. wrathORC

    wrathORC 1/2 ton status

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    I second the motion about the garden hose water. Even filtered (but not conditioned) tap water.

    I grew up in the country where our water was damn near pure. You could boil it and nothing was left behind in the pan. Put it in your radiator and no deposits. However, I have first hand experience as what happens when unpure water gets in a cooling system. First, it ruins the antifreeze and often makes it corrosive as or more corrosive than plain water (hello rustville). Next, calcified water does really uncool stuff to your radiator's tubes. It not only leaves the entrance built up with calcium but often in the tubes as well. I have found that not even CLR (yeah, the bathroom cleaner) will get rid of this calcium stuff. It does make the copper tanks pretty though...

    Anyway, if you're going to do a flush I'd retrieve as much coolant you can and dispose of it the right way (some cities let you dump it down the drain, call your city manager and find out). Next, pull the block plugs (1/4" NPT) which are just about right in the middle of the block and you can see them from underneath, especially the starter side. This will let you drain the rust and other sediment out. The driver's side of my 350 was full of black crud. Probably half a cup worth. I washed it out by squirting water down the intake at the thermostat. You can either put the plugs back in or you can buy all metal brass petcocks and go oldschool. In the 70s it was commonplace to put them in. I always do when I have a motor out. Don't use a rubber-sealing one because I don't trust them due to the heat involved.

    Put the system together and run the motor with all fresh garden hose water. Pull the lower radiator hose and let the water dump on the ground when no one is looking. I'd do this until you don't see any crud coming out. Don't forget to let the thermostat open.

    Put it back together and fill it with a 50/50 mix of distilled water and antifreeze. The block has about half a gallon of garden hose water in it still but that's not much. If you want to drain it go ahead. Fully drained it'll take 4 gallons of 50/50.


    Anyway, doing this, my beyond belief calcified 2 core radiator can now keep my truck at 170° with a single electric fan on an 70° day at idle. Before, it'd overheat (I consider 235° overheating) when it was 30° outside and I was on the expressway. If I had a 3 core or a 2 core aluminum radiator I think I could even keep it cool when driving in the woods on a hot day at high rpm in first gear and low range. Right now it will overheat because of the lack of airflow through the crappy radiator.
     
  10. santana

    santana 1/2 ton status

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    Thanks a lot guys you're great /forums/images/graemlins/thumb.gif I did the boiling water test on the t-stat and it turned out bad /forums/images/graemlins/rolleyes.gif saved me a lot of work in replacing the pump. I would've probably gotten reamed at the repair shop had I taken it in /forums/images/graemlins/thinking.gif I'll be becoming a member of this fine organization in the days to come thanks again for the /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
     

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