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Overheating...PLEASE HELP!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Bowtied, Aug 8, 2001.

  1. Bowtied

    Bowtied Registered Member

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    Dudes, sorry about the shouting in the title, I just really need some help on this one fast.
    I have (I think) a bad thermostat on my 87 (5.7 TBI) The temp has been slowly getting higher and higher the past week or so. I've flushed it twice with the chemical stuff and she appears to be totally cleaned out.
    So, tonight I set out to change the thermostat. After I was done, and filled it up, I cranked her up...The temp went even higher than before! It was going up to about 235, now she's slipping past that.
    Here's where my question comes in. The stock thermo temp rating is 195. I found, after a lot of headscratching, that the one I just took out tonight is rated at 180. Can someone PLEASE tell me how low of a temp rating I should go?
    I have heard that you have to obtain a "certain" temp to get the computer to go into closed loop. Does anyone know what that temp is and should I go with a thermo rated just above that temp?
    I appreciate, in advance, any replys to this.
    Thanks
    Bowtied
     
  2. CaptCrunch

    CaptCrunch 1/2 ton status

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    First off you should make sure you don't have any air bubbles in there.... a 195 stat does just fine in my beast... which is a well worn in 87. Was 99 degrees and humid today and mine never ever goes over 210.... runs around 190 almost always.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://www.geocities.com/milnerlives_2000/blazer.htm>http://www.geocities.com/milnerlives_2000/blazer.htm</a>
     
  3. thatK30guy

    thatK30guy 1 ton status Premium Member

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    This is just a suggestion:

    Even though you used the chemical to flush the system, did you or have someone BACKFLUSH the system? Doing this will loosen up the crud that could be built up inside the radiator, block, hoses, etc.

    Just an idea.

    <font color=blue>Daddy told me while learning to pee......"if you shake it more than twice, then you are playing with it!!!"</font color=blue>
     
  4. Bowtied

    Bowtied Registered Member

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    Cap'n
    How do I remove air bubbles?

    K30
    I used the flush kit where you cut your heater hose and hook up to a garden hose. Is this the same thing?
     
  5. Storm Trooper

    Storm Trooper 1/2 ton status GMOTM Winner

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    Don't forget to check your fan clutch. If it's slipping all the time it won't keep the motor cool. Even if you have a lower temp. range t-stat it still shouldn't overheat. Does it heat up when just sitting there or when you drive it?

    [​IMG]<font color=red>[/b]"Rid'in HigH in my K5"[​IMG]
    ....[​IMG]<font color=blue>[/b]"8" Lift -<font color=purple>38.5's"[​IMG]....
     
  6. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I need to take my K30 back to the tractor repair shop and watch the guys do it again. I'm having problems now with this hot weather! Mine seems to stay at least 210 degrees or slightly warmer during this hot crappy weather! [​IMG]

    If I remember right, they took some hose that was custom made to fit from the neck of the radiator to an air hose fitting and blew it backwards. This broke the "stuff" loose inside the radiator. Then they took the same gizmo and hooked it to the water neck (without the thermostat) and backflushed it thru the motor. It worked pretty good, even though it was a "home made" set up.

    <font color=blue>Daddy told me while learning to pee......"if you shake it more than twice, then you are playing with it!!!"</font color=blue>
     
  7. BlueBlazer

    BlueBlazer 1/2 ton status

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    Are you sure your temp guage is accurate? Did the temp go up about 15 degrees after the thermostat swap. If so, you need to get your guage and sending unit checked out to see if they are accurate. It sounds like it really isnt overheating, its just the guage says it is. I may be wrong though.

    82 K5, 6.2L Diesel, sm465, np205, 14 bolt welded, 8 lug 10 bolt lock right, 410 gears, 35" Mud Kings
    SPEAK SOFTLY AND DRIVE A BIG TRUCK
     
  8. Itali83

    Itali83 1/2 ton status

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    Ok, sounds like my type of cooling prob. Did you just have any intake/head work??? when I got my truck it had no thermostat in it, When I tried putting one in, it would never open and the truck would overheat into infinity if I let it. Well after about 8 thermostats, brand new(not rebuilt) water pump. flushed cooling system, new radiator I found out it was my intake manifold gaskets. Believe it or not, the slap nuts that worked on the truck before I bought it put the intake gaskets on backwards. So just a thought, if you have had any head/intake work involving new intake gaskets. that could be it. If not, when the truck is hot, or over the rated temp of thermostat, grab top radatior hose and see if the thermostat is even opening, that'll tell ya a lot right there, if it isn't opening, then you have a blockage of some sort, If it is opening and the top hose is hot, than the radiator isn't doing it's job. I hope some of this helps ya out!
    Ben 87 Jimmy
    <font color=blue>Rust=Bad</font color=blue>
     
  9. Rockjunkies

    Rockjunkies 1/2 ton status

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    Not positive, but I believe that you should have a 210 thermostat if it computer. That is what my 88 pickup had to have. But I think your overheating problems my lay in your fan.

    Keep it simple!
     
  10. DMK

    DMK 1/2 ton status

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    I would also check gage. Factory gages are not that good. Buy a nice set of auto meter gages. If temp is only high while you are sitting still fan clutch is more than likely bad. If temp gets high while moving you have a resriction in your cooling system. Make sure lower hose is not collapsing while engine is running.
     
  11. scrapmetal

    scrapmetal 1/2 ton status

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    hooking up to the lower heater hose with a garden hose and blowing it backwards will help blow it out, and also heres a wacky idea, water pump?? mine was only two years old, wasnt leaking or making noise, but it was still bad, put in a new one and presto,, I use a 195 thermo and I never go above that, except while pulling a heavy trailer, it might go to 200 on a hill, then it'll go back to 195, course i got a four row in the Blazer too,,

    Never been stuck, just temporarily delayed.
    <a target="_blank" href=http://hometown.aol.com/bcscrapper/myhomepage/index.html>hometown.aol.com/bcscrapper/myhomepage/index.html</a>
     
  12. 90idahoblazer

    90idahoblazer 1/2 ton status

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    Ok guys, I had the sme problem...did the exact same things and it still over heated...The solution was so simple I was embarassed. My buddy owns a radiator shop and all he did was clean between the fins and it ran cool as could be....I had bugs and crap all over the place...If the fins are not clean no air circulation can happen....I wish I would have thought about that before I had the neck and the thermo out about five times to include a new water pump.....check the fins out its worth a shot....good luck
     
  13. CaptCrunch

    CaptCrunch 1/2 ton status

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    Well the best thing in tn terms of trying to refill a cooling system is to go to the local parts store and get what is called a flushing T. I know Prestone has one they sell at any CSK store and is like $2. You slice into the top (smaller) hose that leads out of the heater core and into the radiator (the other hose goes to the block or manifold). Cut the hose in half, install the T ... while we are at this spot this makes an excellent spot to backflus the system... just before you put in the T shoot water back into the heater core w/ the heater on and truck running. Once the T is installed I open the radiator cap and turn on the hose... unscrew the cap on the flushing T and start the truck w. the heater on... let the sucker flush till the fluid coming out is ultra clear. Then remove the hose and pour anti freeze in (keeping the flushing T cap open... clear water will come out) When you start seeing green coming out of the flushing T cap it off tight. and fill the truck up to the normal level.... continue to let the truck run and reach normal operating temperature. You can then unscrew the flushing T a bit and let any air vent out and let out a loittle bit of fluid... then cap it and you should be good. Keep an eye on the fluid in the radiator, are there air bubbles coming up? If so you have air getting in somewhere's... double check all the hos connections and look for leaks... if it is still there you may have a leak in a head or manifold gasket.

    A 180 stat should have you running no more then 210 if your guage is accurate. What did your truck run at before? Even one that is 195 should be in about that area.... if the coolant system is ok air wise then I would look into the fan and/or try to have any crude around the radiator blown out. Between the radiator and condenser is a common crude holder. Overall if things don't improve you will probably need to look into replacing the fan if it is bad or radiator.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://www.geocities.com/milnerlives_2000/blazer.htm>http://www.geocities.com/milnerlives_2000/blazer.htm</a>
     
  14. Pookster

    Pookster 1/2 ton status

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    My Obvious question is going to be does it overheat when on the highway? My theory is that if it cools down on the highway (no matter what the outside temp) its probably just a busted fan.
     
  15. WhiteWhomper

    WhiteWhomper 1/2 ton status

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    A little trick to getting out the air bubbles when filling up your system. Take a 1/8" drill bit and drill a hole over to the side of the thermostat. This will allow air to pass through to the radiator. Your '87 will run fine with a 180 degree t-stat. I didn't catch where you live, but if freezing isn't a problem for you, run plain distilled water with a corrosion inhibiter only. Plain water dissipates heat better than coolant. Next thing I would check is if your clutch fan is working properly, and always run a full fan shroud.
     
  16. WakeBoard&4X4er

    WakeBoard&4X4er 1/2 ton status

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    Here is what I would so. Pull the thermostat, reinstall housing with NO thermostat, drain radiator, radiator fill with just water, run for 5 mis, open pit-cock, till just steam is coming out the sure off motor, (repeat) radiator fill with just water, run for 5 mis, open pit-cock, till just steam is coming out the sure off motor, both hoses, install new thermostat, make sure your radiator is good (pressure check), new radiator cap, 60/40 mix coolant/water.
     
  17. muddin4fun

    muddin4fun 3/4 ton status

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    The best thermostat in my opinion is a 195.

    Is it overheating while ideling or going down the highway or both?

    Make sure there isn't a bunch of bugs, mud, etc on the radiator to block air from going thru it. I wonder if when you flushed it you knocked some crud loose and it partially clogged something else.

    I've got a mind like a . . . a . . . what's that thing called?

    <a target="_blank" href=http://www.geocities.com/muddin4fun79blazer/>http://www.geocities.com/muddin4fun79blazer/</a>
     
  18. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    Wake,
    Do you mean 60 water/40 coolant....?

    Dave

    Saw It... Wanted It... Had A Fit... Got It
    91 K5 - in the process of 4" lift with D60/14FF plus LOTS of extras. ETF August 1.
     
  19. newyorkin

    newyorkin 1 ton status

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    A quick test you can try would be to run it up to op temp, the shut down, and feel around the radiator for cold spots. That might help locate a blockage in it if you have one.

    I agree with Muddin, and 90idahoblazer, and just about all the other suggestions here. I especially think it's a good idea and easy as pie to pull out the radiator and blow air and water through the fins (without enough force to bend them) to increase airflow. If you have any bent fins, carefully straighten them out too. Same thing with the condenser and tranny cooler, but they're a bit of a hassle to remove, so clean them in the truck (easy enough if the radiator's out). I did this in early July, and the guage hasn't moved over 200 since (well, once, but I was very low on coolant). Before I did it, I was literally watching the guage rise if I was in stopped traffic, and had to shut the engine off when it hit 210. Heck, even if it doesn't help with the current problem, it'll be nice and clean for when the problem solved.

    Also, on the water pump idea; I've seen a couple pumps go bad by the impellor actually seperating from the shaft, without making a sound or leaking. Another good way to see if it's flowing on these trucks is to lower the coolant amount enough to look into the radiator and see where the heater hose returns, then start it and see if anything is flowing through there.

    How does the oil look? I'm wondering if you possibly have a bad head gasket?

    Ratch
    <a target="_blank" href=http://k5.8m.com>k5.8m.com</a>
    **Your ad here**
     
  20. Fish

    Fish Registered Member

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    Bowtied,

    To get the air bubbles out, (after replacing t-stat), take the radiator cap off and start your truck. Let it warm up to a normal operating temperature. The air should vent out of the radiator, and you can add more antifreeze/water as needed.
     

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