Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

temp problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Bross82, Jun 17, 2002.

  1. Bross82

    Bross82 1/2 ton status

    Joined:
    Feb 11, 2002
    Posts:
    215
    Likes Received:
    0
    Location:
    Spencer, MA
    hey, after i start driving and the engine warms up... it'll run at normal temp for a few minutes and then it'll go up about 10 degrees and after a about a minute it'll go back down... the only thing i've done recently is change the spark plugs.... just wondering what might cause this.

    thanks,
    matt
     
  2. slider

    slider 1/2 ton status

    Joined:
    May 7, 2001
    Posts:
    547
    Likes Received:
    0
    Location:
    Whidbey Is. Washington
    That surge in temp is when your thermostat opens. Mine does the same thing its normal
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    I'd say *not* normal, but if its only 10 degrees I wouldn't worry too much about it. Keep an eye on it, if its sticky now, it could very likely stick shut and spike a lot higher.

    AC Delco's are highly regarded as being "smooth" temp/opening wise. Robertshaws I've heard both ways, but the complaints are always temp spikes. FWIW, my cheapy Stants have/do work fine.
     
  4. Bross82

    Bross82 1/2 ton status

    Joined:
    Feb 11, 2002
    Posts:
    215
    Likes Received:
    0
    Location:
    Spencer, MA
    hey thanks... are you saying the plugs could be responsible for the temp spikes??

    thanks,
    matt
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    No, I'm saying AC Delco t-stats are great pieces from what everyone whos used them has said. They do make good plugs too lol.
     
  6. Bross82

    Bross82 1/2 ton status

    Joined:
    Feb 11, 2002
    Posts:
    215
    Likes Received:
    0
    Location:
    Spencer, MA
    oh, lol... didnt know they made thermostats too... thats why i got confused...

    thanks,
    matt

    if the thermostat does end up needing to be changed, how hard is it to do?
     
  7. Shaggy

    Shaggy 3/4 ton status

    Joined:
    Dec 15, 2000
    Posts:
    6,737
    Likes Received:
    0
    Location:
    Los Banos, CA
    <font color="green"> The t-stat is one of the easiest things to change on the truck. See where the hose goes from the radiator to the dealie-bopper with the two bolts, right in front of the carb? Take out the two bolts (after draining some coolant so you don't make a huge mess), and the t-stat sits right in there. Easy as pie.</font color>
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    It's a fairly straight forward process, kind of. As long as the bolts don't break off from corrosion, and the stuff attached to the t-stat housing (vacuum lines) doesn't get in the way (just disconnect if necessary for the change) its pretty easy.

    I siphon coolant out of the radiator with small vacuum hose (snake it down to base of radiator or as far as it will go) into a suitable container, if it doesn't need changing, so I can re-use it. When you do this, you don't have to worry about air bubbles in the system when refilling as much, nor do you have to remove as much coolant...just enough to get coolant level below the thermostat housing on the block. There will be some spill out anyways, but not so much. Pull off the fill neck end of the radiator hose, and move it out of the way.

    Just need a gasket and the t-stat, and thats about it. Unbolt the housing, pull out the old t-stat, clean the mating surfaces up if necessary, and bolt it back together. I use silicone on the gasket all the time, but most of the time, its probably not necessary. (please no comments on silicone here...my vehicles haven't complained for the last 8 years about my practice) Silicone is one of those "works for some, not others" deal, so if you want to use it, and know how (very thin, not even a bead) go for it, if not, or you don't want to, don't. No biggie, whatever works and doesn't leak.

    I would imagine, about a 30 minute job, cleaning up the surfaces, draining/refilling coolant, moving any stuff thats in the way. if a bolt breaks, its going to be considerably longer. As long as you don't burn yourself, it probably can't hurt to try and take the bolts out right after you get done driving it while its still warm...aluminum intakes are even worse by easily stripping threads, so keep that in mind if AL intake.
     
  9. Blazer_Boy

    Blazer_Boy 1/2 ton status

    Joined:
    Dec 16, 2000
    Posts:
    1,669
    Likes Received:
    0
    Location:
    Sioux City, IA, USA
    Stant makes a fancy pants Thermostat now thats a little under $6 and has a lifetime warranty. It gets a little beyond temp and BOOM, its open, comes down (like 10 degrees). I never see the gauge move after it opens. I had a 195 in there for a few months and went to 180. When I pulled the 195, it looked brand new. Good stuff.
     
  10. porboy

    porboy Registered Member

    Joined:
    May 7, 2002
    Posts:
    29
    Likes Received:
    0
    Location:
    Poway Ca.
    I have had nothing but problems with the stant t- stats. Most recently when I fired up my new crate motor and the damn thermostat refused to open. I almost overheated the first time firing the motor. I let it cool and tryed again with the same response. This was the third vehicle that i have had problems with the Stant. AC Delco from here on out!
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    I had one fail on me too, but not sure that I can blame it. Sat out in the weather for about 6 months lol. Upper radiator hose collapsed, and the guy at the auto parts store has the nerve to push on the moving portion and say "its fine, it moves". I agree, "cheap" (prolly as much as a Delco) t-stats are pretty weak, and as I recall, they shouldn't BE popping open, it shoould be a slow even process, so that you do NOT see temp spikes.
     
  12. slider

    slider 1/2 ton status

    Joined:
    May 7, 2001
    Posts:
    547
    Likes Received:
    0
    Location:
    Whidbey Is. Washington
    Gee and I thought that surge was normal, I learned something today. Looks like I will change mine tomorrow /forums/images/icons/grin.gif Thanks Dorian
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    Well don't do so just because I say so, but I don't see that kind of surge in either of my vehicles, admittedly both with Stants.

    It's my understanding that the opening should be gradual though...anyone else?
     
  14. Shaggy

    Shaggy 3/4 ton status

    Joined:
    Dec 15, 2000
    Posts:
    6,737
    Likes Received:
    0
    Location:
    Los Banos, CA
    <font color="green"> In my experience if your cooling system is very effecient you'll get the gauge fluctuation, since when the stat opens more coolant gets in and quickly cools the engine down, causing the stat to close a little bit, which makes the engine get warmer, causing the stat to open a little... It'a a vicious cycle. /forums/images/icons/wink.gif My truck fluctuates a little bit, maybe 5 degrees or so either way, I have a 4 core big block radiator on a 350, with a standard flow water pump so the water stays in the radiator long enough to cool down quite a bit. </font color>
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    If the water stays in the radiator for any amount of time, it just means the block is staying colder for a longer period of time...low water pump flow can't ever help, only hurt. The larger radiator increases the cooling effect by larger (or more) cores....if the t-stat is popping open, you get temperature fluctuation...if it was a smooth operating t-stat, and could meter water at a rate that maintained the temp the t-stat was rated for, there would be little to no fluctuation.

    You can either let the engine block overheat,(not overheat overheat, just get warmer than it needs to) flood it with cold coolant, and over and over, or keep the temperature/coolant flow entering the engine block fairly constant, and thus, achieve a constant block temperature. If your engine can maintain this cycle, it can also maintain a constant temp lower than the peak of the temp spikes.
     
  16. Bross82

    Bross82 1/2 ton status

    Joined:
    Feb 11, 2002
    Posts:
    215
    Likes Received:
    0
    Location:
    Spencer, MA
    thanks a lot, I'll probably check it out soon and change it.... just curious though... i noticed someone else has a 350 and mentioned origionally running at 195... i'll have to double check but i'm pretty sure my 305 only runs at about 145 normally... is there that much of a temp difference between a 305 and a 350???
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    All GM engines that I am aware of, since probably at least the late 60's, have run 195 t-stats. This includes Oldsmobiles for certain, but 305 and 350's Chev's got 195 t-stats since their inception AFAIK.
     

Share This Page