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any shade tree mechanics help with chevy

Discussion in 'Truck & Equipment Repair' started by cincy snowdog, Dec 24, 2006.

  1. cincy snowdog

    cincy snowdog Senior Member
    Messages: 262

    :help: One of my trucks is acting up,it is a 1998 k2500 with small block vortec,(4x4).
    it just hit 59050 miles and is overheating.
    when you start it and run for five mins or so it climbs to 210 ,at that time it has no heat inside the cab.
    what is the issue:
    1. intake gasket bad? dont spit out where it is visible.(a problem with these motors)
    2. bad thermostat?
    3. bad waterpump?(no noises ,maybe impeller broke inside?)

    it was overheated while it was being driven before it was noticed.(heads damaged now?

    where do you think i should start,waterpump then thermostat,then if no results intake gaskets.
    any help will be greatly appreciated .
    HAPPY HOLIDAYS to all
     
  2. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,878

    first check to see if you have any antifreeze. when the water pump goes bad it leaks all the antifreeze out from a weephole. second i would replace the thermostat which from what you describe is what it sounds like it is, the thermostat is not opening to let the coolant circulate which is why the heatercore is not getting any heat

    plus the thermostat is much cheaper than a waterpump so if you are trying to rule things out i would start from the bottom. it probably wouldnt hurt to put in a slightly cooler one, yours is a 195 id go with a 185 if you can find one but youll probably get the 180. if it runs the same as it did before you let it over heat than you are probably very lucky and you didnt do any damage. just cross your fingers and dont drive it unless you really have to.
     
    Last edited: Dec 24, 2006
  3. TenOfClubs

    TenOfClubs Junior Member
    Messages: 22

    probably a thermostat, but of course make sure the coolant level is up. avoid any colder thermostats with FI vehicles. If the coolant temp is lower than what its supposed to be, the PCM will enrich the fuel mixture (like a choke would with a cold engine) and this rich mixture will make quick work of your catalytic converter.

    Im not sure if 98 has the "expensive" thermostat or not. (I dont think so) but the newer ones come complete with the housing, and come in a box the size of a heater core! those are expensive.
     
  4. Robhollar

    Robhollar Senior Member
    Messages: 766

    To Start with Id do a coolant pressure test while it was running and lets see if it holds 15 lbs of pressure. Also see while under pressure if its blowing out the tell tail white steam out of the exhaust. If its not holding pressure or its blowing steam your prob looking at a bad head.

    Now we have to think why did it overheat in the first place? It will be my bet you prob will find your water pump has taking a dump. Or you may have a stuck thermostat. How I find if the thermo is stuck Ill use a non contact inferred thermometer. While its running Ill check the temp difference between both sides of the thermostat housing.

    The are other things that can be causing your probs. You could be air locked or your radiator maybe plugged. Last but not least anytime I do any coolant service I always change the rad cap. It my not need it but I feel better be safe then sorry. Im a bit of a freak when it comes to the maintenance of cars and trucks. When it comes down to it change the water pump, thermostat, and rad cap. While everything is all apart completely flush the coolant system with fresh water but be careful with the heater core. You can easily damage it with to much pressure. Do this and ill bet your coolant trouble will be min...Rob
     
  5. poncho62

    poncho62 Senior Member
    Messages: 431

    They about covered it in the above posts......Do not go with a cooler thermostat.
     
  6. terrapro

    terrapro PlowSite Veteran
    from MI
    Messages: 3,878

    i dont know if you guys are speaking from experience but i am. i have replaced the thermostat in 3 chevy vehicles with colder ones. 2 1990 trucks w/5.7TBI and an 89 S10 blazer w/4.3TBI all of them had a better idle after warmed up and got 1-2 mpg better gas milage afterwards. im pretty sure that 160 is the temp when the comp goes into closed loop mode so having a 180 stat will not effect the gas milage the way you guys are saying it will. i guess you dont have to take my advice but i have only had positive consequences from replacing my thermostat.
     
    Last edited: Dec 24, 2006
  7. TenOfClubs

    TenOfClubs Junior Member
    Messages: 22

    the vehicle goes into closed loop as soon as possible. that usually means as soon as the O2 sensor comes online. That requires heat from the exhaust in those old chevys, as they only had single wire sensors, the newer ones are heated sensors, and are operational much sooner.

    the early Chevs were about the only manufacturer that was too cheap to have an O2 without a heater, thus they programed their pcms to operate as such, and put less dependency on the 02 than other vehicles.

    the old Chevys you listed are speed density systems, and are prehistoric in the auto motive industry. I still wouldnt use a lower temp stat in that vehicle though. Along with melting down your cat, you contaminate your o2, contaminate the oil with excess gasoline, and usually get poorer performance.

    the extra gasoline may lower combustion chamber temps, and prevent pinging which may allow the vehicle to run with more spark lead, thus giving it more power, but still contaminating the oil, and the atmosphere.


    as much as we like to think we're smarter than the manufacturers, we're not.
     
  8. PDQ Pete

    PDQ Pete Senior Member
    Messages: 139

    If your loosing coolent out of reservior when it gets hot, possible head gasket or cracked head.
     
  9. cincy snowdog

    cincy snowdog Senior Member
    Messages: 262

    ok,worked on it for few today,thermostat changed(only had 195 degree) and water pump was circulating but it is losing a/f .
    it is internal-burning out the exhaust and a/f in oil.
    head ?
    head gasket ?
    intake gasket?
    looks like the news years project .
    Now would you rip the whole motor and get a jasper rebuild or just rip the heads off and rebuild it .(i can rebuild it but i was concerned as far as over heating the block)
    thanks to all for the help and Happy Holidays.
     
  10. cincy snowdog

    cincy snowdog Senior Member
    Messages: 262

    or the intake gasket first?
     
  11. Robhollar

    Robhollar Senior Member
    Messages: 766

    Youve got head probs. Ya it could be just a gasket but theres no way im gonna tear it down and put it back together only to find the heads blown. Heads dont blow for no reason id still suspect the waterpump is bad. If it was me Id change the heads, waterpump thermostat and flush the coolant system to be safe. After all if your gonna be that far into it you might as well change the pump too. Better be safe then sorry...Rob
     
  12. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    I agree! While the Vortec heads are an outstanding head as far as their efficiency to make power, they will crack in a hurry when subjected to an overheat condition due to their thin wall castings.I'd pull the head's too.
     
  13. cincy snowdog

    cincy snowdog Senior Member
    Messages: 262

    The initial cause was the thermostat i believe.
    Would you feel safe keeping the block?
    Also would you scrap the heads or magnaflux them first?Buy new or junk yard?
    I have heard of the intake gasket causing this,any thoughts?
    This is still a clean truck,so its worth fixing.
     
  14. poncho62

    poncho62 Senior Member
    Messages: 431

    If you have antifreeze in the oil, there is a possibility of bearing damage. Best to check that out too.
     
  15. Ding

    Ding Member
    Messages: 62

    If you find the heads are bad you can get new heads with valves already in them, yes new (not rebuilt) with complete valves for $250 a piece. Or just go with a crate motor (exact replacement) for around $2000. I use Pace or Scoggins-Dickey. Of course you have to supply the labor or have someone else do the work. I usually go with an entire engine unless it is minor damage.
     
  16. cincy snowdog

    cincy snowdog Senior Member
    Messages: 262

    yeh we will start pulling it apart this week ,i will find out which way i will go.
    thanks to all for your input.
     
  17. figure out how the antifreze is getting out first by looking at the plugs and doing a leakdown test figure it out before you start just throughing new parts at it could be intake manifold gasket the spark plugs should tell you where its coming from if its on top did the problem start with a plow on the truck ? my 94 chevy overheats on highway if your not watching the guage!! just courious? i went to a 180 thermostat with no ill effects so far 4 years and 30 0000 mi
     
  18. WetChicken

    WetChicken Senior Member
    Messages: 132

    Wow, I am surprised that no one said to check plugs until now!

    If changing pump, thermostat, heads, etc you might as well do the radiator (if it is in question and the budget allows), hoses, and belt(s). Nothing like that warm fuzzy feeling of security when you're out at 2AM. :)
     
  19. cincy snowdog

    cincy snowdog Senior Member
    Messages: 262

     
  20. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If it's burning the coolant you should be able to see it on the plug's. They'll usually have a heavy white "crusty" build up on them,