GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER

Coolant not circulating!?

Discussion in 'Chevy C/K Truck Forum' started by GMANs95, Oct 31, 2013.

  1. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    Just replaced the thermostat and temp sensor on my 95 350 c/1500. Getting proper temp reading on gauge, but the rad hose is hard (dont go there) as a rock.
    New coolant blah blah blah. It is inserted correctly (spring down) and it is the OEM temp rating.

    What am i missing? :grrrrrr:
    #1
  2. JTWard

    JTWard New Member

    Joined:
    May 29, 2013
    Messages:
    223
    Likes Received:
    0
    Is the upper or lower radiator hose as Hard as a rock ? If you remover the radiator cap when the engine is cold, then start it and watch to see if your coolant begins to flow across the radiator. But I'd say you have a clog somewhere, and i'd doubt the sending unit is telling the truth.
    #2
  3. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    Upper.....it's a new radiator too. Sending unit is brand new.
    #3
  4. j cat

    j cat Active Member

    Joined:
    Sep 28, 2010
    Messages:
    1,522
    Likes Received:
    3
    what was the problem before you changed these parts ?

    thermostat could be defective. sender could be the wrong one .

    what is the operating temp when heated up ?
    #4
  5. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    As far as I know there was no problem. (see my introductory post) When I got the truck the engine was shot. (spun bearings) I put a "new" reman 350 in it. Thermo is new...sensor is new, radiator is new. Thermostat is a 190.....and the temp reading is 2 notches below the printed 210 on the gauge.
    #5
  6. RayVoy

    RayVoy Active Member

    Joined:
    Apr 18, 2012
    Messages:
    2,122
    Likes Received:
    5
    What's the condition of the water pump?

    Did you reuse the old one?
    #6
  7. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    Good question......it visually checked ok......didn't see any sign of leakage at the weep hole....and there is no sign now. Have about 300 miles since the motor swap.
    #7
  8. JTWard

    JTWard New Member

    Joined:
    May 29, 2013
    Messages:
    223
    Likes Received:
    0
    I know it's a new engine, but if you pour water into the top of the radiator, does it come out of the bottom ? The reason I ask, is if the thermostat is working, (And I have no reason to think it's not) then it seems the upper radiator is pressurized, but it's not flowing through the radiator ? And I don't mean any disrespect, but there wasn't any plugs left in the cooling system anywhere right ?????
    #8
  9. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    No disrespect taken. I too am originally from a small town north of philly.......so skin is thicker than most. I am going to take the lower hose off in the morning to see if it indeed drains. which way does the fliud flow? Top to bottom thru motor or bottom to top thru the radiator?

    When I get in it in the morning there is no pressure in the hose....when i get to my destination it is pressurized. What about taking out thermostat and seeing what happens? Recommended or not......
    #9
  10. JTWard

    JTWard New Member

    Joined:
    May 29, 2013
    Messages:
    223
    Likes Received:
    0
    Well the Corvette is the only 1995 GM vehicle that had reverse cooling that I know of, so I'm going to say it a conventional system in the top and out the bottom and up thru the engine again. But never the less, the radiator in your truck seems to me to be the biggest unknown here. For all intensive purposes I can't keep thinking it's working and the new engine has super clean coolant cavities so that leaves us at the thermostat, which seems to be working as the upper radiator hose gets hard, (I'm guessing it's pressurized which is why it's stiff) so that leaves only the radiator as the culprit. It's got plastic tanks on both ends, but it might be clogged and the only way to find out is drain the cooling system and see what kind of flow you have ?
    #10
  11. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    Seems logical......guess I'll be doing just that first thing in the morning. Damn thing is new as well.........
    I will get back with you/forum tomorrow. Thanx JT
    #11
  12. RayVoy

    RayVoy Active Member

    Joined:
    Apr 18, 2012
    Messages:
    2,122
    Likes Received:
    5
    I just re-read your original post and your post which is #9. What you describe is a working system.

    Why do you think you have a circulation problem?
    #12
  13. j cat

    j cat Active Member

    Joined:
    Sep 28, 2010
    Messages:
    1,522
    Likes Received:
    3
    if the coolant temp is normal then you have flow thru the radiator. temp reads just below 210 deg f is dead on correct.

    so the issue is the hard hose. this is normal the hose when the engine is hot should have about 10-15 psi of pressure in it. more pressure as the temp increases / or ac on........

    if the hose was soft you would have no pressure then the coolant5 boils. when that happens your temp will spike up ward...water pump will not pump air bubbles..
    #13
  14. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    Sorry for the late reply Ray.....Well if what I am described is a "normal system" then it makes me curious why I have no hot air in the cab.....my son put in a new heater core when he owned it, and the blower motor is blowin air..(not hot) the 2 hoses to the core are warm.......whats next?

    - - - Updated - - -

    I am just trying to sort things out......as I said in my introductory post I have a laundry list to sort out...I found out from my son that he had scavenged parts from this (my 95) to put on his 91 Chevy lowrider, so there is no telling what I am actually dealing with. I wasn't expecting much for 500.00. The 4 biggest issues at present are the wipers, heater, brake lights, and fixing whatever is killing the battery if i don't disco it. I think the wiper issue is the multi-function switch as I have no hazards or cruise either.
    #14
  15. j cat

    j cat Active Member

    Joined:
    Sep 28, 2010
    Messages:
    1,522
    Likes Received:
    3

    if the heater is not putting out heat then this should have been in post #1.

    the heater core hoses should both be hot. if warm then the heater core needs to be blown out / reversed flushed. after that run engine with pressure cap off so as to remove air bubbles. with a new engine this air bubble effect can cause the heater core not to flow properly. since the temp is correct on the gauge I would suspect the heater core is restricted...
    #15
  16. RayVoy

    RayVoy Active Member

    Joined:
    Apr 18, 2012
    Messages:
    2,122
    Likes Received:
    5
    You probably have air trapped in the heater core. Sometimes it can be hard to get out. Look at the hose fittings, can one be removed to let the air out? I've had luck parking on a steep hill (nose up), sometimes the air will move upward, into the rad.
    #16
  17. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    I probably would have had I known it at the time.... I'll be sure to check it.
    #17
  18. j cat

    j cat Active Member

    Joined:
    Sep 28, 2010
    Messages:
    1,522
    Likes Received:
    3
    with a new engine/complete coolant removal this then increases the trapped air issues . this will create a poor heater temp ...could also be debris in engine gunked up heater core.
    #18
  19. JTWard

    JTWard New Member

    Joined:
    May 29, 2013
    Messages:
    223
    Likes Received:
    0
    Hay Ray, I wonder if the heater hoses are hooked up backwards ???? The upper heater hose coming out of the thermostat area of the intake manifold is the one that carries the hot coolant to the core, then in exits out the lower hose to the water pump , Am I right ? I always thought the lower heater core hose was the exit hose, ? been awhile since I put in a heater core ? Although I know from my Corvette, that GM coolant systems need to be burped before you close up the coolant system. If there's air in there the system will act like it's blocked ? :rolleyes:
    #19
  20. GMANs95

    GMANs95 New Member

    Joined:
    Oct 21, 2013
    Messages:
    54
    Likes Received:
    0
    Both of the hoses to the core are HOT. What about environmental control panel? Since everything is damn near electronic. I have also just found that "cold air blows out the floor vent only. When I turn the temp dial to hot....and the selector knob to defrost (or any other position).... it still blows out the bottom (cold). Ideas?

    - - - Updated - - -

    I have to look but the one coming out of the intake area is the rightmost hose and the one to the wp is leftmost. Right? I will check this at lunchtime.
    - - - Updated - - -

    A side note....the blower doesn't work on high either. Resistor or relay?

    - - - Updated - - -

    I checked at lunch and the hose going to the water pump is the left most hose, and the one on the intake (rear) is the right hose.
    #20

Share This Page