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Help with cooling problem?

Discussion in 'Chevy Trucks' started by red2500, Dec 31, 2007.

  1. red2500

    red2500 Junior Member
    Messages: 23

    Hi, this is my first post. I have a 1991 GMC K2500 with a new motor (355, hydraulic roller cam, headers, TBI mods, and a custom tune by me.) It now has about 6,000 miles on the new motor and since the I got the truck (even with old engine and radiator) the coolant temp soars to almost 240F before settling down. I have read that my engine needs a reverse rotation water pump. I verified this by tracing the serpentine belt and indeed it does rotate in reverse (counter-clockwise). Wait it gets better....I had replaced the water pump on the old engine when I first got the truck and the parts guy said he only had one listing for my truck.
    It was the same part# as the normal rotation cars? So, for lack of wanting to go to the dealer,
    I bought it. Does anyone think this could be my problem? Or does it even matter?
    I have changed the thermostat twice to make sure, and even the radiator was new when the motor was changed!
    Thanks in advance for any help, Randy
  2. nicksplowing

    nicksplowing PlowSite.com Addict
    Messages: 1,226

  3. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If it has a standard rotation pump on it now I can pretty much guarantee you that's your heating problem....as they are not one size fits all...

    If it's serpentine it needs the reverse rotation pump no questions asked.

    When you spin the pump in the wrong direction, they will move water but not nearly enough to do the job...which will cause it to overheat.
  4. nicksplowing

    nicksplowing PlowSite.com Addict
    Messages: 1,226

  5. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Definately put a proper water pump on that motor!!! Dont want to destroy that nice 355. That would just make for a bad day:mad:
  6. red2500

    red2500 Junior Member
    Messages: 23

    Thanks for all the responses

    Believe it or not I have been running it for 2 years like that. If you let it warm up til the t-stat opens it is fine. The real problem is when enroute to my accounts driving 45-50 mph the temp rises to about 220 and even sometimes 240! Not good for prolonged operation, but it only lasts 2-3 minutes and the will come down. If the engine cools down during breaks, t-stat closes and then temp will rise to 230 again if I dont let it warm up before driving. I guess the motto is don't buy from autozone, good quality, they just don't list the proper part for my truck. Now, I want to take it back cause it has a lifetime warranty which I paid a premium for, and say "make it right". But, the pump hasn't actually failed and after 2 years they will look at me like why didn't you bring it back right away? Well because the pump was replaced for that reason, and I thought after it did not go away it was not the pump. What are the chances the previous owner got a wrong pump too? pretty good. I am sorry for the long stories but none of my mechanic friends care to help (I also build and dynotune racecars) and they think I should be able to find it on my own.
    Thanks again ,
  7. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    Im glad to hear it isnt a prolonged thing. You should look into a high flow pump to really help with all of that motor work done and plowing. Never hurts to keep that thing nice and cool!!!!:nod: Good luck:waving:
  8. red2500

    red2500 Junior Member
    Messages: 23

    Oh well

    Look at this......

    Duralast New / Water Pump CWP-715HD
    Reverse rotation
    HD pumps utilize roller bearings, ceramic seals and larger diameter shafts.

    direct from their site guess they figured out that problem already.....
  9. Sydenstricker Landscaping

    Sydenstricker Landscaping PlowSite Veteran
    Messages: 3,882

    I never trust the parts counter guys from autozone. They should give them a how not to be a dumba$$ course too
  10. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    i work auto repair every day. i wouldnt buy any real parts from auto junk zone. the only things i will buy from them are name brand like timkin/acdelco plugs/ and so on. there house brands are garbage. even at the premium level.

    and yes get a good reverse flow pump and a high flow tstat with propor 50/50 mix green coolent. and we can go from there.

    on a note: my 87 tbi 350 truck it goes to 220ish at first warmup open of tstat. been doing it for years no problems.
  11. nicksplowing

    nicksplowing PlowSite.com Addict
    Messages: 1,226

    Any Updates Did Ya Get Er Done ???????
  12. doh

    doh Senior Member
    Messages: 253

    so is 220 degress half way up your gauge? Mine is in Celsius here, and adding a plow bring my gauge to 100 degress celsius everytime I travel.

    It is middle of the gauge. 100 degres. It is normally 1/4 of the way up the Gauge.
  13. 04HDBoss

    04HDBoss Junior Member
    Messages: 19

    I have NEVER went to Autozone and got the right part the first time it. It always takes at least 2 trips.. AUTOZONE SUCKS!!!
  14. red2500

    red2500 Junior Member
    Messages: 23

    Sunday is the day! It is going to be so warm I am breaking out the pressure washer and some ZEP TNT after that dries a bit on to the pump. I already replaced the factory engine driven fan with a unit from a 2003 Nissan Maxima (my truck has no A/C) that I got from a crashed one for free. I used a variable thermostat to control what temp it comes on and also an override switch on the dash. When I installed the new motor I upgraded the radiator to the next size up (my stock one for a stripped 2500 was the same size as the V-6) 28" core I believe. By replacing the clutch fan I gained over 5 MPG, so with my custom tune(chip) I am now getting 27 MPG highway and 20 city making around 330 HP and 410 FTLB's of torque!
    If I can just get it cool...........:mad:
  15. red2500

    red2500 Junior Member
    Messages: 23


    Well it wasn't the waterpump. I replaced it anyways, it was a free replacement.
    The funny thing I noticed is that the new thermostat is different. Same part number
    but is has a little poppet valve that lets air by, but shuts if water goes through.
    My guess is that valve prevents steam pockets behind the thermostat. Air will cause the thermostat to not open at the right temp. I also learned that drilling two 1/16" holes, one at 12 and one at 6 o'clock, in the outside ring of the thermostat.
    Works great so far! Temp. comes up to 195 and stays there. I put the plow on for the big nor easter and drove around tonight the temp never went over 215 even with the plow all the way up! We will see what happens tomorrow in the storm.
    Thanks to everyone for the suggestions.