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Unknown overheating problems. Any advice?

Discussion in 'Truck & Equipment Repair' started by Duncan90si, Mar 8, 2008.

  1. Duncan90si

    Duncan90si Senior Member
    Messages: 602

    I just rebuilt the 454 complete from the headgaskets up in my 1990 K3500. Ran 110% perfect yesterday. I couldn't have been happier. I start plowing today and it is overheating. It has a brand new thermostat, water pump, coolant hoses and an electric fan. Coolant is flowing really well when I look into the rad. So I figured maybe the thermo is sticking a little bit.

    I installed a new thermo, no difference. So I stick another fan on it. I now have two fans that are as tall and combined as wide as the entire rad. They are both pulling air through from the backside of the rad. At first its running normal temps and I'm content. About 10 minutes later it begins to overheat again.

    I limp it home, stopping along the way to let it cool, get it into my driveway and shut it off. I start it a couple minutes later and its at 210*. I climb into the throttle and the temps fall down to around 170*. WTF!!!

    This is how its sitting right now. I have eliminated about all variables. I tried driving with the plow dropped. No difference. I know I installed all the gaskets correct such as head and IM gaskets, so they're not blocking any water jackets. Besides, the truck is flowing coolant through the rad well. The coolant hoses are not collapsing when it overheats. Upper hose is hot, lower hose is warm, like normal, so it SHOULD not be overheating.

    Does anyone have any suggestions? What am I missing?
  2. Green Grass

    Green Grass PlowSite Fanatic
    Messages: 9,568

    are you sure the temp sensor is good? Maybe the truck is not overheating and the sensor just thinks that it is
  3. Firebird

    Firebird Junior Member
    Messages: 2

    Hey, my truck overheats all the time, I just drop the blade a little to get air flow through to the front of the rad, If the radiator is old the front of the radiator is probaly plugged up with bugs,dirt,sand,salt, that sort of thing. I don't know if this helps any.
  4. wild bill

    wild bill PlowSite.com Addict
    Messages: 1,239


    why did you pull the heads ,was it over heating before ? pull a pressure test on the rad to see if it building pressure to see if the block or head's are cracked . eliminate the obvious first .
  5. Duncan90si

    Duncan90si Senior Member
    Messages: 602

    The gauge is accurate. I checked the temp with an digital meter and the gauge dead on. It started boiling at one point so I know that its overheating for sure.

    I think by some cold chance in he!! there might be one little piece of something getting stuck in a water jacket or something. Ex: It restricts flow in the head enough to over heat, but not enough to stop the coolant flow completely. (sounds highly unlikely, I know) The rad is in good shape so I doubt it, but it might be possible but is kinda hard to confirm. It seems like a stretch but I've seen weirder stuff.

    The timing chain decided to retire the valves into the pistons. :D Pressure test checked out, A+.

    Im ready to start punching my teeth out. I need a case of beer. :drinkup: (maybe 2) Keep the advice coming guys. Lord only knows I need it on this one!
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Does it only get hot if you actually drive it, or will it get hot just by allowing it to idle for a long period of time?
  7. Duncan90si

    Duncan90si Senior Member
    Messages: 602

    It usually overheats when driving but it would get warmer from time to time sitting or going slow.

    I think its a combination of problems. The plow blocking air, and the e fans not cooling as quickly and/or efficiently as the mechanical fan.

    I adjusted the fans to turn on at a lower temp and now its fine when plowing and idling (about 180*-190*). It warms up to about 235* going down the highway but doesn't usually get hotter now. It plowed all night and up until an hour ago without over heating. (no highway driving) I'll see what I can do to improve the cooling later this week.

    For now I'm going to bed. :sleeping: I've been plowing most of yesterday, all last night and this morning.
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    So this was an issue before you did the top end?
  9. Snowpower

    Snowpower Senior Member
    Messages: 636

    Are these fans shrouded? And you absolutely have to run the plow blade as low as possible when driving. Especially if its above, well...like 30 degrees for me. Even just a few inches lower can sometimes make a big difference.

    We do have the right head gaskets on this thing, right?

    Just thinkin out loud.
    Last edited: Mar 9, 2008
  10. jbrow1

    jbrow1 Member
    Messages: 76

    I'd pull the thermostat right out and see what it does. You can block the radiator with some cardboard to let it build some heat up. Could be the thermostat isn't working properly even though it's new. Two electric fans should pull plenty of air thru I would think.
  11. Duncan90si

    Duncan90si Senior Member
    Messages: 602

    No it was fine prior to the rebuild. I didn't have the e fans before either. <-- They are the problem, not the rebuilt top end.

    They are mounted directly onto the backside of the rad. I tried running the blade within an inch off of the ground and it would still get warm. The head gaskets are 110% correct.

    I tried a second new thermo when it first started doing this and it made no difference. You would think that 2 would be enough but obviously with the plow on its not.

    I took the plow off and ran down the highway and it never got above 160*. So, tomorrow I have adjust the e fans to turn on at a higher temp because 160* is a little too cold. Then I'll have to turn them down to a lower turn on temp when plowing. Its a little bit of a nuisance but I can live with it I guess.

    Other than this little issue the motor runs great. With a bigger cam, completely rebuilt heads with roller rockers and no heavy fan to spin, it was quite an improvement. Spring time will bring a new IM, 4 barrel carb, HEI dist, headers and a bigger cam yet. I might throw some higher comp pistons and new main and rod bearing if I'm feeling really frisky.

    I just wish I was able to make highway runs with the blade like before. I'm a little dissappointed in the fans, but winter is almost over so the plow won't be on for much longer.
  12. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Your correct, the electric fans are your problem. You wont find an electric fan(s) that will cool a 454 with a plow on it in a TBI truck (been there done that several years ago). The plow creates too much of a pressure drop behind the blade for the fans to pull the air through the rad.

    Ditch the electric fan idea and reinstall the factory clutch fan with a HD clutch. Your cooling problems will be solved. You can remove the mech fan in the spring and use the electrics for the other three seasons. Thats what I did for years.
  13. Duncan90si

    Duncan90si Senior Member
    Messages: 602

    Well I would reinstall it but its kinda already at the scrap yard from cleaning up the garage after I was done with the motor. DOH! :D Oh well.

    Thats what I will probably do next winter. Its already March and I don't have to drive it on any public roads with the plow on. It plows at one large shopping plaza of mine, thats it. If I decide to drive it I'll just drop the plow, for the rest of the season.
  14. AHammen

    AHammen Member
    Messages: 47

    just a thought

    If you think that when the plow is up you can't get enough air for the fans to pull in I've seen people put a small sheet of plexi glass on top of their lifting arm. This catches a lot of air for the radiator. Depending on what type of plow you have this may help.
  15. ken75ranger

    ken75ranger Junior Member
    Messages: 7

    Here a few things to check.

    Timing. If it is off it can raise temps quite a bit.

    The electric fans. You really need to know how many CFM's they pull. I wouldn't go less than 1100 cfm. Aftermarket fans are often rated pulling those numbers but it's not with a radiator in front of it.:angry: (I'm leaning toward this one.)
    Ford Taurus 2 speed fans will do the job but they pull around 60 amps.

    Check your air fuel ratio. If your running too rich or too lean both will make it run hotter.

    Last is a long shot but you could have an air bubble in coolant in the motor.
  16. abbert55

    abbert55 Senior Member
    Messages: 170

    B&B is correct, just had a similar problem on my 96 K2500HD. After installing a new 860SW, there just wasn't enough air moving to keep the engine cool. I suspected the fan clutch as it wouldn't kick in as the temp started to rise. Went to Autozone and picked up an extreme duty clutch for about $80.00. Problem solved. The temp just starts to get to 210 and voila, the silicone gets tight and the fan pulls the much needed air thru. The stock fan clutch's are known for going bad. JMHO;)