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Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BlazerWheels, Sep 8, 2003.

  1. BlazerWheels

    BlazerWheels 1/2 ton status

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    How do I check to see if my water pump is failing?? /forums/images/graemlins/confused.gif Last night my truck was running a WHOLE lot hotter than it normally does/should. It was cool out so there was no explanation as to why. I checked the oil, up to the full mark, I checked the coolant, plenty, radiator is about 1 year old, tranny was rebuilt about 1 year ago and it has a cooler...If it is not the water pump, what else should I look at? /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif
     
  2. rcpilot

    rcpilot 1/2 ton status

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    To check pump, remove radiator cap and run engine up to temp..look into the radiator and take note of the flow out of the tubes.. it should flow rather rapidly and smooth... if it looks good then you should check the fan clutch (do you have one) if ya do then while its hot shut down the engine and spin the fan by hand.. it should not rotate more than ONE revolution (mark/watch one blade).. does it run cooler while moving (not a few deg, but loke 5 or more)? If so than the clutch would be suspect.
    Hope this helps..
     
  3. heavy4x4

    heavy4x4 1/2 ton status

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    Replace your thermostat with a new one. For $5 and 5 minutes, it's the cheapest easiest thing to fix.
     
  4. Stoopalini

    Stoopalini 1/2 ton status

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    If the water pump is failing, there's a good chance the weep hole will be leaking.

    If you look underneath the water pump, there will be a small hole almost direct center. Look around it to see if it has been leaking, if so, replace the water pump.

    If not, I agree to check the thermostat and fan next.

    Thomas.
     
  5. BlazerWheels

    BlazerWheels 1/2 ton status

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    I replaced the fan clutch and thermostat about a year ago, same time as I had the radiator replaced...would they be bad already??? I will check the fan and the water flow today when I get home. /forums/images/graemlins/thumb.gif
     
  6. rcpilot

    rcpilot 1/2 ton status

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    Not likely... check water pump flow first.. also if the water is flowing as soon as you start it up (cold) then you could have a stuck thermostat
     
  7. heavy4x4

    heavy4x4 1/2 ton status

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    That would mean the thermostat is stuck open though, which wouldn't explain his overheating problems.
     
  8. rcpilot

    rcpilot 1/2 ton status

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    An open thermostat would cause the vehicle to overheat by not allowing the water to remain in the radiator long enough to cool down...
     
  9. sled_dog

    sled_dog 1 ton status

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    thats why if you run without a thermostat you have to make like a piece of sheetmetal with a hole in it to restrict flow.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    No, apparently that piece is to induce turbulence into the coolant. You guys should read some of the stuff other people post.
     
  11. heavy4x4

    heavy4x4 1/2 ton status

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    [ QUOTE ]
    An open thermostat would cause the vehicle to overheat by not allowing the water to remain in the radiator long enough to cool down...

    [/ QUOTE ]

    Hmmm, let's see. At operating temperatures, the thermostat allows coolant to flow out of the block, up through the hose, and into the top of the radiator. The fluid then makes it's way all the way to the bottom, opposite corner. Tell me why that isn't enough time for the coolant to be cooled. /forums/images/graemlins/deal.gif
    Think about this; the thermostat, in order to keep your truck at 195, 210, or whatever, opens and closes at various points while you're driving. When it's open and free-flowing, the radiator actually does such a good cooling job that the thermostat has to close a bit so that the engine stays as high as it's supposed to.
     
  12. NerdBoy

    NerdBoy 1/2 ton status

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    Ok, before this debate goes too far, I would like to share some information.

    From http://www.grapeaperacing.com/GrapeApeRacing/tech/coolingmods.cfm I give you the following:
    The pressure in the block is higher than the radiator pressure, this is because the pump is building pressure due to the thermostat being a restriction. This pressure raises the boiling point of the coolant and reduces the chance of steam pockets, so never run with out a thermostat (or some form of restriction). The radiator cap will usually hold 15-18 psi, if the radiator holds the system at 15 psi, the boiling point of plain water will be raised to 250° F. The water pump can then make an additional 40-45 psi in the engine and bring that boiling point close to 300° F. So as you can see, pressure is important.

    From http://www.off-road.com/rick/thermo.html :
    Heat is generated inside a running engine. The harder you run it, the hotter it gets.
    The higher the rpm you turn, the faster the water moves through the cooling system.
    The radiator is designed to get rid of most of the heat. Your engine oil and the metal parts in the block will get rid of some heat through dissipation.
    In a race truck, most do not run a thermostat. It's just one more thing to go wrong.
    However, all savvy racers run a restructure plate. It's nothing more than a flat piece of metal with a hole drilled in it. In my experience, I have never had a "hole" fail. I have had thermostats fail.
    What size hole, you ask?
    While this varies, most racers who run V8s eventually settle on a 5/8th inch hole. Of course, you must experiment, but I've found this to work on most everything from a 302 to a 505 inch Ford.
    You must run some sort of restriction. Failure to do so lets the water pass through the block too quickly, preventing it from extracting heat properly.That's right, bubba. Your temp gauge will read OK and your block will be cooking!
    Engines that are heavily affected by a "no thermostat" condition are small block Chevys and big block Fords. Both will develop air pockets in the water flow when the engines are revved hard with no thermostat, or restructure.
    Water does, indeed, run cooler than anti-freeze/water mix. However, anti freeze is an excellent lubricant for your water pump and does prevent corrosion in your cooling system.
    In my race vehicles, I ran water only and then drained it out after the race and added some anti-freeze for the storage time between races. Naturally, I started the engine on the mix to allow it to circulate.

    I'm not saying that you shouldn't take the thermostat out, just make sure you run some sort of restriction. The cooling system depends on that restriction.
    There are many more people that say the same thing.
    http://www.woodyg.com/fairlane/finfo/coolingsystem4.html for example

    It seems that the experts agree that it is the pressure the thermostat creates inside the block, not the fact that it slows the coolant through the radiator. They also agree that you need some sort of restriction.

    The opening and closing to regulate temperature is important to help get the engine up to operating temperature as fast as it can, so that it is more efficient.

    Just wanted to stop a heated argument before it got started.
     
  13. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    Good info /forums/images/graemlins/thumb.gif
     
  14. rcpilot

    rcpilot 1/2 ton status

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    [ QUOTE ]
    Just wanted to stop a heated argument before it got started.

    [/ QUOTE ]

    No heated argument here...I know here in the desert a low temp thermostat (ie 160) or no thermostat will cause a engine to overheat.. outside temps normally in the 110's.
    I'm sure alot depends on your specific location and i welcome new info for me/us to learn from... /forums/images/graemlins/ears.gif thats what this is all about right? /forums/images/graemlins/thumb.gif
     
  15. heavy4x4

    heavy4x4 1/2 ton status

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    [ QUOTE ]
    i welcome new info for me/us to learn from... thats what this is all about right?

    [/ QUOTE ]

    ABSOLUTELY! I'm not trying to start an argument either...just simply stating what I know from experience or have heard in the past and seeing what other people have to contradict or add on. /forums/images/graemlins/thumb.gif
     
  16. NerdBoy

    NerdBoy 1/2 ton status

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    "heated" was a play on words, maybe I was a little too subtle. /forums/images/graemlins/grin.gif

    Truthfully, I'm a little paranoid about this particular subject becoming a huge debate. Everyone with experience seems to agree that running without a thermostat is detrimental to the cooling system efficiency, I just wanted to share the real reason behind why it has the effects that it does. I have listened to arguments about the reasons for hours between people that thought they knew, and, until now, I have always kept my mouth shut, being afraid that what I had learned in school was wrong.

    I hate people thinking that I think that I am a know-it-all, so I am generally quiet when it comes to things like this. This time, I was thinking that there are enough people here that might have an influence on the next generation of mechanics, and maybe they could pass this information along, so I didn't have to sit in my local parts shop and listen to another debate on the subject.
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    cummins spec sheet

    Agrees with the "pressurizing the block" info, but the laws of physics do not agree with water passing through the block so fast it doesn't cool properly.

    Until someone proves how water can somehow be more efficient at absorbing more heat the hotter it gets, it isn't true. The "hot pocket" theory is plausible, but at what coolant speed? Did these folks actually study the flow characteristics inside the block, or are they only speculating that magically all water pumps move the same amount of water at the same velocity?

    I obviously don't know exactly how coolant velocity affects pockets inside the engine, but I put forth the notion that no one short of GM and some top level racers do, either. So no slam on any information people find, but the speculation and assumptions from both sides really leave a lot to be desired. There are some hard facts, but there is some hard core speculation too. /forums/images/graemlins/smile.gif
     

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