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Overheating when the a/c is on...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ChevyCaGal, Sep 1, 2002.

  1. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    Ok... like it says my truck over heats when the a/c is on. It doesn't do it when it's off, runs fine and dandy (well as far as overheating there's other issues we won't touch for now).... but anyhow where do I start? I'm not going to stop running my a/c when it's 102 outside like it's going to be today. I'm hoping it's a simple thing but I gotta feeling it's not... /forums/images/icons/tongue.gif
     
  2. 95 Silverado

    95 Silverado 1/2 ton status

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    if it runs hot "all" the time when using A/C, running at highway speeds or low speed, in traffic, I would suspect the radiator, poor flow, heat transfer. If it's more of a low speed, idling in traffic problem it could be a weak clutch fan that's not pulling air across the radiator as it should. It's normal for the engine to operate at a higher temperature when running the A/C as the heat out of the condensor is being pulled across the radiator, it will test the efficiency of your cooling system.
     
  3. sosamantx

    sosamantx 1/2 ton status

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    agrees whith 95silverado. what shape is your radiator in also? one small thing you can check, drain some coolant out of your system (not hot). pull off your radiator cap and look down inside (might need a flashlight), and see how much calcium buildup is in the tubes (holes) inside of your radiator. if there is alot (restricting flow)then you might just need to have it rodded out (about $45) here, not including R&R. you could also start up your truck till it's warm (thermostat opens up) and see how much it's flowing, it should flow decently, and if you give it a little gas it should be pretty much shooting out of the tubes. you could also tell what size radiator it is (2 row, 3 or 4), how many rows of tubes there are. if it's time for a new radiator, it might be cheaper to have it re-cored, if it's a 2 row radiator, you could make it a 3 row radiator (they should be the same tank size). anyway, hope this helps some.
     
  4. Ck1500

    Ck1500 1/2 ton status

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    how about the thermostat??? last time i had that issue i changed the t-stat, and added some coolant, and haven't had an issue yet, plus also i dropped the temp on my stock 200degree stat to a 180, and i haven't looked back since, but it could also be poor coolant flow in the radiator . welp hopefully some of this helps.

    Ck1500
     
  5. White Knight

    White Knight 1/2 ton status

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    If the radiator is plugged or clogged, you could try a old fashioned fix before you replace the old one, mind you I've never tryed this,,,but it may work....place some cascade dishwasher powder in your radiator, run the thing for 30-45 mins and drain and flush well, I've heard it will remove scale and build up. Might be worth a try if you're considering replacing the radiator....Good luck
     
  6. trailblazer87

    trailblazer87 1/2 ton status

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    If it a calcium based deposit you would want something acidic to dissolve it, I know a shot of vinegar works pretty well.
     
  7. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    My rad is newer, and in good shape (had it flushed last spring). Never has given me an issue before. It doesn't need to be replaced.... I'll check the thermostat.... it's been replaced recently but maybe I got a bad one? As for the when.... it really heats up when it hot outside and it's in stop and go traffic. It still does it when driving, but not as often. It's days when the heat is just nasty seems to affect it more. Like even the air when dirivng moving through is so hot it does nothing to cool. I'll see about cleaning the hoses out too see what it does. Thanks....

    Oh not to sound stupid, but I cannot my rad cap off now. I could until 2 weeks ago, now it's jammed on there. WTF did I do? I know it sounds stupid but even my friends dad who came by to drop off my pager I left at their house tried and it wouldn't budge? Am I retarded or did I manage to lock it somehow and there's some magic GM thing that I dunno about?
     
  8. trailblazer87

    trailblazer87 1/2 ton status

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    Sounds like that could be the problem right there.
    If you have a bad cap, it might not be letting the system pressurize and casuing it to heat up, or worse yet it could be letting water out and you don't notice it until it heats up. You may be low on water. I would try to get that thing off of there and replace it ASAP
     
  9. White Knight

    White Knight 1/2 ton status

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    Does it have the little red lever on top? lift it first then turn...if that doesn't work I'll sell you my K5 cheap....LOL good luck, be careful and don't use to much force, I've seen the flange twist loose on Radiators before.
     
  10. 77blazin

    77blazin 1 of a kine K5

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    White knight is right, those odd red levers, once you open them, it relieves pressure from your radiator, just like the turn types: press down with your palm of your hand and turn counter clockwise, it locks once to relieve pressure from the radiator, or so it doesn't blow up in you face, (Had it happen once with a 79 Scout, it wasn't a pretty site.).
    Once the pressure has subsided, you turn again counter clockwise to open the cap and look inside.
    Also check your coolant supply and see how the level is.
    Make sure that your rubber hoses are not damaged or defected, sometimes those little particles of rubber could be running around in your engine and radiator, but thats rare.
    Squeeze those rubber hoses, if they feel like they are cracking, replace them imediatly, I rather replace both for the just in case thing.
    And of course, the one thing we usually don't look at is the fan, I do not know if you have a flexfan or just one of those steel fans, you might have to upgrade to better sucking fan.
    And also the fan should, damage to the fan should could also cause a problem when you need to cool down your radiator.
    The one on my 78 shows a 4 core radiator, but the fan shroud was the wrong size, smaller, so I ordered the right size from LMC, A perfect fit.
    Steph, check those items, I know it sounds stupid, but maybe that could be the cause of your heating problem.
    Sincerely
    Michael W.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Tried the vinegar myself, didn't even get the radiator back to 50% of the recommended flow rate. Recore solved the problem entirely.

    Not that it won't work, but if its corroded (fairly heavily, a little won't hurt, but you can't see all the cores conditions, so you are guessing unless you ahve it flow tested) I'd replace it.

    A LITTLE corrosion won't hurt much, but again, you can't see the bottom half of the radiator, and it could be worse than what you CAN see. Flow test is the only true way to see how efficient the radiator still is.

    Less antifreeze, more water will help the system as well, if you can get away with just water and some water wetter or something that inhibits corrosion, your system will be more effective.

    However, GM designed these systems to work in all the climates of the US, so you are obviously having a problem, not seeing something "typical".
     
  12. 70~K5

    70~K5 1/2 ton status

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    What gauge are you going by? The stock one? Electric gauges lie. Hook up a mech. gauge and verfiy that it's realy overheating.
     
  13. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    I don't have a little red cap to flip up and it's jammed on there. I have had like 4 people try to get it off now and it's stuck. This is so lame its pathetic it won't come off. I wonder if that is what is causing the problems? Argh, always something stupid like this.... /forums/images/icons/tongue.gif
     
  14. trailblazer87

    trailblazer87 1/2 ton status

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    Has anybody tried a pipe wrench?
    Just be careful doing it, you could twist the radiator fill neck off /forums/images/icons/shocked.gif
    You can also try drilling out the CENTER of the cap, this should pretty much destroy the spring, do this only as a last ditch effort though.
     
  15. Cmoe

    Cmoe 1/2 ton status

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    ChevyCaGal, Go to your local Radator shop and have them pull the cap. You said that it's a new radiator, how many row is it? About overheating, Is your trany cooler still being used in the readiator? My want to change to an add on Trany Cooler. On the outside, it maybe the water pump. But that is the last steep.
     
  16. K5 NUTT

    K5 NUTT 1/2 ton status

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    I feel your pain steph...your problem is not unique...i firmly believe the ccot system was not field tested in thew extreme sw. Now that i'm in colorado and not phx i don't have the problem anymore...but here are some basic's....16 lb cap...for ever lb of psi on the cap = 3 degree's cooling...so a 16lb cap gives you 48 degree's....plus a proper mixture of coolant vs. H20 is critical... in diesel engines improper maint. can cost quite a bit....-35 degree's is the norm...and can be checked with a hydrometer...when someone forgets the maint on diesels's...it will pit the liners in the block...until it eats all the way thru and puts pin holes in them...then we have a hydro locked cyl...usually with bent valves...hehehe...or peanut butter for oil. Anyways if the core in the rad is good (metal does loose it ability to transfer heat) you would normally have a 10 to 12 degree drop across the radiator....less than this indicates the core is internally plugged...which is usually the case...and lets not forget the condensor....fan on...you should see a 40 degree drop across condensor in order for the a/c to function properly....one thing many people don't due is to remove the grille once a year and hose out the cores....dirt...bugs...misc. road debris account for over half of all the overheats i see at the shop....and last but not least...do we have waterpump psi? Harder yet to check...and i don't have a spec for a sbc...but an N14 cummins is around 5-7 psi at idle and 20ish around high idle...h20 impellers are sometimes made of plastic...improper maint can cause the fins to rot on the impeller which = less flow.

    Adding a aux cooloing fan to help out with idle and a/c will really help things out up front and your temp gauge...GM sells a newer low psi switch pigtail...it has 3 wires...i used the largest one to be the input VDC to the switch...one of the smallers wires went on to the a/c comp coil as intended...the 3rd wire i used to trigger a relay so that the aux condensor fan is on all the time with the a/c....made a huge diff in the temp gauge and the a/c duct temp...

    Sorry for rambling on...

    Azblazer
     
  17. ken

    ken 1/2 ton status

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    Get rid of the antifreeze, run straight distilled water with a bottle of Water Wetter and I will guarantee you your temps will go down. I was very skeptical of Water Wetter, but after using it in 4 of my rigs and seeing temps down by 20 degrees or so, I am a firm believer! Also, a 160° thermostat will help too.
     
  18. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    Cool I will try it... and since you live in land of traffic you would know if it works!
     
  19. 84_Chevy_K10

    84_Chevy_K10 Banned

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    A lower temperature thermostat will NOT keep your engine from overheating and with a fuel injected engine it will not allow it to run correctly and it will get horrible fuel mileage. Not to mention she's from California and it will possibly keep her from passing emissions. Come on guys, use your brains before you recommend something that could not only not be helpful, but could hurt as well. And don't ever tell someone to bypass a radiator transmission cooler!! That doesn't solve the cooling problem and it might cause transmission failure! Yes, auxilary coolers do work, but they're designed to work in conjunction with the one in your radiator, not as a replacement for the factory cooler.

    It sounds to me that the problem is that the fan is not pulling enough air through the radiator. She says that her truck overheats in traffic and she's pretty sure that the radiator is fine. I think the problem is definitely that the fan is not doing its job correctly. Possibly the fan clutch is worn out.

    More info is needed to correctly diagnose this, but I'll tell you for sure that a lower temp thermostat is not the answer.

    A low speed cooling problem is normally caused by a clogged radiator or not enough air coming across the radiator.

    I suggest an upgrade to a better radiator if it is decided that it is the problem. It can never hurt to have an oversized radiator. I'd get a 4 core.

    If you give us more info it'll be easier to help you.
     
  20. Cmoe

    Cmoe 1/2 ton status

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    84_Chevy_K10,

    You don't need to be such a jerk. I've heard both ways that you should leave the internal cooler hooked up and that if your rad. is to small or that it is old, clogged that you should bypass it. If you would have read my reply, I said to take it to a radiator shop, and also asked what size the core was. So pull your head out and remember that we are all here for the same reason. To keep our K-5's going strong. So keep that in mind when your write a reply too!!!! Disagreeing with someone is fine give your two cents and but keep the bagging to yourself.
     

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