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Thermostat question... 89 k5 w/ 5.7 which one's you runnin?

Discussion in 'The Garage' started by rocko, Jul 1, 2004.

  1. rocko

    rocko 1/2 ton status

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    Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    I'm installing a new radiator.. while I'm at it, I was going to do the thermostat. Went to price them... I was looking for a 160-175 range thermostat, but no one lists one. The only one listed is for 195 degrees...
    What do you all run? what's best in summer? I've read 160 degrees...
    Help please... thanks in advance.
    Charles. /forums/images/graemlins/usaflag.gif
     
  2. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    Re: Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    I assume your truck is fuel injected with a computer so you should prolly run the factory spec'd 195 otherwise it may run a little rich as it thinks it hasnt warmed up yet. Sizewise you can fit any thermostat you want from a Chevy though..... 160-195. Especially with a new radiator a 195 thermostat should be fine, oh and buy the good one not the standard or less expensive one, the good one's are much more accurate /forums/images/graemlins/thumb.gif


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  3. HarryH3

    HarryH3 1 ton status Author

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    Re: Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    The computer wants to see a 195 in there.
     
  4. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Re: Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    The problem with a 160 is it will not allow the computer to go into closed loop mode because it will continue to try and warm up the engine. I would go with a 180-195.
     
  5. rocko

    rocko 1/2 ton status

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    Re: Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    Good info.. muchas grassyass fellas...
    I truely do appreciate this site.. and everyone on here..
     
  6. fortcollinsram

    fortcollinsram 1/2 ton status

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    Re: Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    I run a 180* in my TBI 454.

    Chris
     
  7. Hardcore

    Hardcore 1/2 ton status

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    Re: Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    I run a 180* in my 1990 with a Flowkooler pump (30% more flow) and my temp guage never gets over 1/4 of the way up. I'm going to swap a 195 back in because I know the computer isn't liking the motor being so cold /forums/images/graemlins/doah.gif
     
  8. Wingnutt

    Wingnutt 1/2 ton status

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    Re: Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    If you go below the factory setting, you will want to get yerself ALDL and monitor the ECM readings to see if your ECM does or does not go into closed loop mode. I'm running a GM 170 degree thermostat (PN:7503157) and my ECM DOES go into closed loop mode, even with a new fan clutch and 4 row raditator. Every vehicle is different so watch and see what yours does.
     
  9. b55baron

    b55baron Registered Member

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    Re: Thermostat question... 89 k5 w/ 5.7 which one\'s you runnin?

    I've been running a 180 degree in my '89 since it was new. That was 200,000 miles ago and I haven't any problems.
     
  10. simpleman83

    simpleman83 1/2 ton status

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    SUPER OLD THREAD - new question

    So I know this thread is ridiculously old, but I've been trying to figure out about how the computer fits into the whole TBI/thermostat setup and I've been searching around to try and get an explanation. I have found that most people say that the TBI engines with computers should definitely have the 195*F thermostat. But my understanding is that the thermostat is what actually controls whether the loop to the radiator is closed or not. My question is; what does the computer have to do with checking over the temp? If anyone can explain this to me I'd appreciate it. Thanks.
     
  11. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    On a FI truck you have a temp sender for your temp guage then you have a coolant temp sender for the ECM. If you go installing a lower temp T-stat the coolant temp sensor tells the ECM that the engine isn't hot enough yet so the ECM stays in open loop mode which allows the engine to run on a set of pre-calibrated parameters. This mode the engine runs richer than normal and all other sensors no longer come into play. You fuel mileage will suffer drastically because of this as well. With that being said there is no reason to install anything other than the factory 195* T-stat.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    ECM uses engine temp as ONE input as to whether or not it will go closed loop. I think on most it's actually pretty low, like 120*. Thermostat is what sets the engine temp (assuming cooling system is up to par) the ECM simply looks at the coolant temp sensor readings.

    It really doesn't matter, there is absolutely no reason to run anything other than a 195* t-stat EFI or not. Tests I've seen even on all out race motors don't hold up to the colder/more power theory. It doesn't do anything but cost you mileage and heat. Why people try to re-think what GM has been doing since before emissions, even on the most outrageous factory motors made, baffles me.
     
  13. simpleman83

    simpleman83 1/2 ton status

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    so where in the loop is the "coolant temp sender for the ECM" located at? How would this read a different temperature than the thermostat? I think I'm just not connecting the dots on this one but, I'm just confused as to the fact that some of the threads about thermostats have said running a lower temp rated tstat it continues to warm the engine by not "closing the loop" Basically, what I'm thinking is that a lower tstat would open at a lower temp and continue running and never "close the loop" which could in turn, cause the engine to overheat. So, why would a 195 gauge stop this from happening? like I said, total noob when it comes to this apparently... thanks for the help.
     
  14. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Let me start by explaining how the t-stat works. Think of the t-stat as a switch. Lets say this switch is 195*. When the engine is cold this "switch" (t-stat) is closed. Once the engine warms up to the 195* then the "switch" (t-stat) opens and lets the hot water (now 195*) out of the engine and as it's leaving the engine it is pushing the cold water from the radiator into the engine. Once the "switch" (t-stat) senses this cold water the "switch" (t-stat) closes. Now the hot water in the radiator has a chance to cool off as the water in the engine is now being heated until it reaches 195* and the "switch" (t-stat) opens again to allow this cycle to continue.

    Open and closed loop is being refered to in the ECM and not the cooling system. Assuming you have the correct temp t-stat installed (195*) when the coolant temp sensor sees the proper temp then the ECM will go closed loop and ALL sensors come into play. The 02 sensor also has a role in the ECM going closed loop. If the 02 sensor does not see 600* then the ECM also will not go into closed loop operation.

    The coolant temp sensor is located in the intake manifold near the thermostat housing in the water passage that goes from head to head.
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    Perhaps part of what you aren't understanding is that a thermostats job is solely to get and keep an engine up to the determined operating temperature. So a 195* t-stat will not be "fully" open until the engine coolant is 195*. (they are actually a bit progressive, but nonetheless)

    As 4x4high said, it's a switch essentially. There is nothing hooked up to it. It opens/closes as needed to keep the coolant temperature at 195*.

    The temperature *sender* is an actual sender...it "measures" the coolant temp in the engine, and this is what the ECM sees. So while a t-stat is dumb you might say because it is simply on/off, a switch, the ECM is actually watching the coolant temp as it increases and decreases. This allows the manufacturer to do things like try to keep the engine cooler as it starts to overheat (by increasing idle speed, cutting out AC, etc) richen mixture for startup, run electric fans, etc. All depends on the application, but these are some of the things that can be done.

    If the manufacturer for instance, says that under 120* the engine needs X amount of extra fuel, much like a choke on a carburetor, they can do so. You can actually read/edit all of the stuff that is put in the PROM with a program like TunerproRT.
     
  16. simpleman83

    simpleman83 1/2 ton status

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    Thanks guys, that makes a lot more sense now, I was thinking that somehow the thermostat actually controlled how the ECM read by having the the sensor close to it and that was what the idea was. Now, I see that they both serve two separete jobs, the tstat to regulate the temp, and the ECM uses the fluid temp that the tstat controls to control fuel/air control etc to make the engine run correctly. Thanks for the help.
     

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