stuck thermostat?
Thread Starter
Instructor
Joined: Jul 2009
Posts: 213
Likes: 13
From: Jefferson City Missouri
stuck thermostat?
Yesterday I drove my 81 vette to work in the morning. It was about 25 degrees outside and the temp gauge did not get much above 100 and the heater was blowing as hot as it should be. My commute is about 8 miles and in the past the car would have warmed up plenty 1/2 way to work. Had the same problem on the way home with outside temps about 35 degrees. My RPM's seamed fine and the car ran fine. It had been about two months since the last time I drove the car and everything was fine with it then. I am thinking and hoping it is just a stuck thermostat. Am I right?
Thanks,
Darren
Thanks,
Darren
Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
It might be your temperature gauge or the sending unit for it. You said the heater was blowing as hot as it should be. If the thermostat was stuck open then the heater wouldn't heat as fast as normal. If the thermostat was stuck closed then you would have probably overheated.
Thread Starter
Instructor
Joined: Jul 2009
Posts: 213
Likes: 13
From: Jefferson City Missouri
Thermostat
It might be your temperature gauge or the sending unit for it. You said the heater was blowing as hot as it should be. If the thermostat was stuck open then the heater wouldn't heat as fast as normal. If the thermostat was stuck closed then you would have probably overheated.
I even prof read my post.
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Melting Slicks
Joined: Feb 2006
Posts: 3,105
Likes: 96
From: Sunrise FL
Responding to above..its not stuck closed...could be low coolant level or air in the system. If the level is low the thermo has to wait to get hot, then opens late..once the water is flowing it works properly
Melting Slicks
Joined: Mar 2006
Posts: 2,248
Likes: 67
From: Warrington PA
Finalist 2020 C4 of the Year - Unmodified
Just a logical thought here....after the engine has been running for awhile, turn off, open the hood and feel the top radiator hose. Be careful as it can get very hot to the touch. If it is cold or cool to the touch, then I would say you have a stuck thermo. If it is real hot to the touch, then your thermo is opening and flowing. Another way is to remove the radiator cap when engine is COLD, start engine and then watch the water movement inside the radiator, if no movement after engine is supposed to be warmed up, then you probably have a stuck thermo. Hope you get the problem solved.
Melting Slicks
Joined: Mar 2006
Posts: 2,248
Likes: 67
From: Warrington PA
Finalist 2020 C4 of the Year - Unmodified
I would correct that ASAP, as that is not the best thing for the temp to rise like that, then drop. What happens if it rises to that temp and stays there, or goes higher and stays there??? Then you have big problems.....
Melting Slicks
Joined: Mar 2006
Posts: 2,248
Likes: 67
From: Warrington PA
Finalist 2020 C4 of the Year - Unmodified
Not trying to break your stones, but I don't think that is necessary. Even though the 82 calls for a 195 degree unit like the 81, I run a 180 degree unit in mine with a stock ECM and it works great. Your heat won't be as hot as the higher thermo, but the engine performs better and is great for the AC.....just another thought.....
Melting Slicks
Joined: Mar 2006
Posts: 2,248
Likes: 67
From: Warrington PA
Finalist 2020 C4 of the Year - Unmodified
Thanks for pointing that out, never gave it any thought. Just was looking at another forum, which mentioned that with a change in TP, along with other conditions, that the ECM will go back into Open Loop.
this is what I found on another forum....again not trying to be a SA, always learning myself, along with getting a better understanding of what I am learning......
which always makes for good conversation
"What are the criteria the ECU looks for in order to go into closed loop?
Coolant temp is one of them correct?
Re: Definition of Closed Loop vs Open Loop
"No, many people used to think that though.
I remember years ago, the magazines said that too cold of a thermostat would cause the computer to not enter closed loop.
Its basically on a timer as to how long the car stays in open loop before going into closed loop at startup."
this is what I found on another forum....again not trying to be a SA, always learning myself, along with getting a better understanding of what I am learning......
which always makes for good conversation"What are the criteria the ECU looks for in order to go into closed loop?
Coolant temp is one of them correct?
Re: Definition of Closed Loop vs Open Loop
"No, many people used to think that though.
I remember years ago, the magazines said that too cold of a thermostat would cause the computer to not enter closed loop.
Its basically on a timer as to how long the car stays in open loop before going into closed loop at startup."
Race Director
Joined: Jul 2004
Posts: 12,706
Likes: 329
From: Scottsdale Arizona
Could be, but I don't really think so. I have a couple of small holes drilled to prevent bubbles from accumulating behind it. Makes it easier to fill te system as well.