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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / December 2005Thermostat Question
My 96 chevy truck was running cool according to the temp gauge so when I replaced the water pump, I flushed out the cooling system and put in a new 195 degree thermostat along with Dex-Cool antifreeze. Now it runs even cooler! It is my understanding that the engine runs more effeciently at the design temp, 195. If this is true, how in the heck do I get it to run hotter? It used to run hotter when new... Maybe the gauge is lying to me? Maybe the thermostat (a Thompson from NAPA) is no good? Would you guys please advise me on what to do? thanks, Libby >My 96 chevy truck was running cool according to the temp gauge so when >I replaced the water pump, I flushed out the cooling system and put in [quoted text clipped - 6 lines] > >Would you guys please advise me on what to do? The thermostat is the only thing that can cause the problem (other than a bad temperature gauge or sensor). A bad water pump or bad coolant will cause it to run hot because it's not cooling _enough_. Your problem is that it is cooling _too much_. Do the thermostat. It is a _lot_ easier than swapping the water pump. --scott  Signature"C'est un Nagra. C'est suisse, et tres, tres precis." : ) I had already replaced the water pump because the bearing failed. At the same time I replaced the thermostat and the coolant. Now it runs at about 160 with a new 195 thermostat, which is the problem I am currently trying to solve. Thanks, Libby "una mas cervaza, por favor, señorita." >: ) > I had already replaced the water pump because the bearing failed. At > the same time I replaced the thermostat and the coolant. Now it runs at > about 160 with a new 195 thermostat, which is the problem I am > currently trying to solve. If you've got a 195 thermostat in and it never runs above 160, then either your temp gauge is off or the thermostat is bad. I don't believe your engine would be able to stay at 160 with the thermostat closed. John. How are you determining your engine's temperature? I doubt the dash gauge is particularly accurate - especially on a 10 year old truck. Ed Temperature gauges are notoriously inaccurate. Most thermostats open at the correct temperature, but some do not. About a year ago I replaced an old thermostat that opened at about 185 degF with a new one that opened at about 205 degF. Both were rated for 195 degF. The rated temperature is the temperature at which the thermostat is supposed to start opening. If you put a 195 degF thermostat in a pan of water and heat it, it should start to open at 195 deg and be fully opened at about 210 deg. When my new thermostat was only half open with the water boiling I new it was out of specs. > My 96 chevy truck was running cool according to the temp gauge so when > I replaced the water pump, I flushed out the cooling system and put in [quoted text clipped - 9 lines] > thanks, > Libby SignatureMike Walsh West Palm Beach, Florida, U.S.A. How is the interior heat level? If it is the same or not noticeably different, then I would suspect the connection on the sender or just a crappie sender. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 http://www.imagestation.com/album/index.html?id=2120343242 (More Off Road album links at bottom of the view page) > My 96 chevy truck was running cool according to the temp gauge so when > I replaced the water pump, I flushed out the cooling system and put in [quoted text clipped - 9 lines] > thanks, > Libby Interior heat is not noticeably different. Heater is not as hot as it used to be when truck was new. Would this work: get it to operating temp then stick a cookie thermometer into the water and read the temp accurately, in order to verify thermostat? If it is really 160 it shouldn't spew out when I open the cap, right? If it does I can put the thermometer into the overflow cannister and check it that way. Thanks, Libby > Interior heat is not noticeably different. Heater is not as hot as it > used to be when truck was new. [quoted text clipped - 7 lines] > Thanks, > Libby none of that is a good idea, best is to use a aftermarket gauge to check the temp. second is use a touchless remote sensor (infrared thermoter) the block and tstat housing, it has worked pretty good for me. and you can check the rad and rest of the system for poor performance. KB SignatureThunderSnake #9 Warn once, shoot twice 460 in the pkup, 460 on the stand for another pkup and one in the shed for a fun project to yet be decided on You can open the cap and then heat it up with a thermometer in it, but it can overflow easily when doing this if the rad is full to the top cold.... There is a big difference in internal heat if you have a colder t-stat in. Even a 180 used to be a summer one only and you needed a 195 for winter heat. 160 would have it chilly inside if it was cold outside. You can verify the thermostat is working by carefully holding on to the top rad hose while the engine is warming up. It should stay cold, then suddenly get warm fast. If it slowly heats up, the thermostat is likely a bad one. Have you tried to clean or reseat the plug on the sender? If doing that changes anything, you have likely found the trouble. You also said you changed the pump. Did you overheat it? If so, that can kill the sensor. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Aug./05 http://www.imagestation.com/album/index.html?id=2120343242 (More Off Road album links at bottom of the view page) > Interior heat is not noticeably different. Heater is not as hot as it > used to be when truck was new. [quoted text clipped - 7 lines] > Thanks, > Libby >Interior heat is not noticeably different. Heater is not as hot as it >used to be when truck was new. [quoted text clipped - 4 lines] >open the cap, right? If it does I can put the thermometer into the >overflow cannister and check it that way. Not a good idea. What you do is pull the thermostat and test it out of the car. Put it in a pot of water with a thermometer. then watch the thermostat to see at what temperature it opens up. --------------- Alex >>Interior heat is not noticeably different. Heater is not as hot as it >>used to be when truck was new. [quoted text clipped - 10 lines] > thermostat > to see at what temperature it opens up. If the 195 thermostat you have in there is what the mfg calls for, then it may or may not be faulty....if it isn't faulty, then the other thing you might want to check is the check valve ( i think thats what its called) for the heater.... it may be no good anymore depriving you of good heat....I believe it is located on the firewall and has a cable hooked to it. The cable is the one that you adjust the temp with on the dashboard... make sure it is working properly and is not broken. Good Luck, Fwed I had the same damn question about my truck. I went to the parts section of my walmart and found an add on aftermarket temperature guage for $5.00. It's mechanical and screws into the temp probe port on the engine where the dashboard guage probe screws in. Took about 30 seconds to take the probe that goes to my real gauge out and put the new temp one in. The mechanical one told a different story. Turned out I had a grounding issue from the firewall to the engine block and the current for the dashboard guage was coming back threw the speedo cable (thanks mike romain). Check your firewall to engine block cable. It should be a braided cable. I also rain one from the post of the battery to the frame. > My 96 chevy truck was running cool according to the temp gauge so when I just drove back from Houston today during a cool snap, and have noticed the same apparent lack of engine heat. I think it is really only due to a very inaccurate dash temperature gauge, since the car ran fine and got reasonable mileage. I have seen people put cardboard or other in front of the radiator to partially block the airflow. That would be an easy solution, but I wouldnt do it unless I were darn sure about the actual temperature. > My 96 chevy truck was running cool according to the temp gauge so when > I replaced the water pump, I flushed out the cooling system and put in [quoted text clipped - 9 lines] > thanks, > Libby what kind of stat are you using? >My 96 chevy truck was running cool according to the temp gauge so when >I replaced the water pump, I flushed out the cooling system and put in [quoted text clipped - 6 lines] > >Would you guys please advise me on what to do? I would pull the thermostat and test it. ---------------- Alex Gonna pull the thermostat this weekend and test it. Is there also a way to test the temp guage sensor - if so where exactly is it on the 96 4.2 chev V6 block? thanks, Libby > Gonna pull the thermostat this weekend and test it. Is there also a way > to test the temp guage sensor - if so where exactly is it on the 96 4.2 > chev V6 block? > > thanks, > Libby I believe there is a wire (or two) that is above where the thermostat sits. that will give you your temperature... Fwed yeah, there is a whole bundle of them. > yeah, there is a whole bundle of them. There should be only one that wil connect to the sending unit. the sending unit should be right next to or on top of the thermostat housing... Fwed |
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