04 silverado 117k temp'ing up then correcting itself.

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Bowtied, Mar 27, 2013.

  1. Bowtied

    Bowtied Epic Member 5+ Years 500 Posts

    Hi all,

    Typically my 04 silverado v8 5.3L with 117k miles usually warms up to about 210 (or slightly less than 1/2 the gauge) and holds the temp. Lately, it has been temping up to over 210, then falling back down and holding them temp. This worries me because its a-typical behavior and in the past i have heard from a mechanic (while i owned a diff car that had over heating probs) that you want your car to temp up and hold a temp. no fluctuations. This worries me as it has just started happening (with no other issue to blame) and i dont want it to persist.

    I should add that i have not had the vehicle's 100k mile service yet (plugs, wires, coolant flush, etc. have NOT been done, i cannot afford it and dont want to do a coolant flush myself lest i make the situation worse) but that made no difference in the 100k-115k interim, so why now would the truck begin to temp up then go back down and hold? God forbid it one day does not hold its temp and actually over heats. Are there any fail-safes in place that will save me from smoking the motor if it does decide not to hold its temp and actually over heat? I can only guess that it temp'ing up then going back down and holding is from the radiator kicking in but it never did this in the past.

    Also im going to be taking a closer look at this problem so that I can accurately describe it better. The over heat (if you can call it that) only appears to happen on the first start of the day, subsequent cold starts (like the 2nd start after an 8hr work day) do not seem to have this over-heat-then-steady problem as the 1st start of the day has. And it also only appears to happen on "colder" days, as hot days dont seem to affect it (this is only my hunch and i cannot confirm this 100%)

    Anyways, any help is gladly appreciated.
  2. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    It sounds like the thermostat is sticking. They are about $12 and take about 15 minutes and a gallon of antifreeze to replace. I just did one on my 2005 5.3L. It is literally two bolts. DO NOT buy a "fail safe" thermostat. Everyone I have had sticks open and the truck will not get to operating temp, damaging your MPG.
  3. Bowtied

    Bowtied Epic Member 5+ Years 500 Posts

    Thanks, how can I be sure if its only beginning to fail? or if it is 100% the culprit? Obviously i dont want to wait until it fails completely to replace but then again if its only 12 and the problem persists that would be a cheap way to rule out the thermie

    ETA: This is the TEK i'm following in the near future in case anyone else comes along this thread and needs info about how to replace their Thermie:


    2nd Edit: When you mentioned the fail-safe thermostats (180 degree?) I started to look into this and found out about those thermostats not allowing the truck to go into the closed loop (as you mentioned) and im wondering:

    is it possible [if my thermostat is still operational] that (as my hunch suggests) since this only happens on cold days, the truck is "forcing" a temp up, to get out of open loop and into closed then functioning as normal? That would explain why this happens on cold days and not hot days.
    Last edited: Mar 27, 2013
  4. j cat

    j cat Epic Member 5+ Years 1000 Posts

    I do not agree with your maintenance intervals. If the coolant is 9 yrs old along with the thermostat and the engine temp wanders then you could have more than a thermostat issue.

    since you do not have any funds to properly maintain the vehicle I guess you continue to operate it until it stops running then get another vehicle.

    the coolant requires replacing not so much for freezing protection . these engines corrode internally . when this begins with old coolant and contaminated coolant the aluminum gets eaten and all the gaskets start to leak it can be quite expensive. could even destroy the engine .

    any temp fluctuation can mean fluid loss and air in the coolant system this is how it starts. also poor heating from the heater.
  5. Bowtied

    Bowtied Epic Member 5+ Years 500 Posts

    thanks, obviously this is something i want to address. I am less than familiar with this truck but learning. I only drive it in the winter, when summer comes back along i'll park it for ~6 months and drive my motorcycle. Hopefully then i can find some time to adequately service this vehicle starting with the 100k service.
  6. Skippy

    Skippy Member 2 Years 100 Posts

  7. j cat

    j cat Epic Member 5+ Years 1000 Posts

    The problem is not just you . GM markets all their vehicles as being very low maintenance . the coolant is for 5yrs 150,ooomi. most replace after 3-4 yrs. this insures that the corrosion is kept to the minimum. the transmission fluid/filter should be replaced @40,ooo mi. this is because a new transmission generates alot of debris. plugs must be replaced at 50,ooomi. I found that sometimes the AC delco plug tips fall off. the irridium plugs appear to be better. plug wires need be checked for proper resistance .

    using synthetic oil and good quality oil filters all of these things will save you money in the long run. MPG improves and the other components like starter motor / O2 sensors /cat converters all have less stress and will operate longer before they fail.

    the owners manual is written with the vehicle life of 100,000mi. so if you follow the manual and you need a new engine and transmission @ 100,ooomi then that is what GM is expecting.

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