Thermostat open temperature
Thread Starter
Instructor
Joined: Jun 2008
Posts: 233
Likes: 9
From: Marietta Ga
Thermostat open temperature
Thermostat question:
1973 350 L82.
I have a 180F thermostat and as the car warms up the temp goes up to 210F on the gauge then drops back to roughly between the 155 and 210 mark on the temp gauge (180F?) at idle when the thermostat is in control.
Holds there steady and never goes back up to 210F. 55 mph and up it sits at about 190F.
Question is this warm up to 210F normal with the sensor mounted in the head?
Doesn't seem to be air since my overflow increases in level when hot and drops back when cold.
I've shot the thermostat cover with an IR gun at idle and the temps match the gauge in the car fairly well. My sensor is new.
1973 350 L82.
I have a 180F thermostat and as the car warms up the temp goes up to 210F on the gauge then drops back to roughly between the 155 and 210 mark on the temp gauge (180F?) at idle when the thermostat is in control.
Holds there steady and never goes back up to 210F. 55 mph and up it sits at about 190F.
Question is this warm up to 210F normal with the sensor mounted in the head?
Doesn't seem to be air since my overflow increases in level when hot and drops back when cold.
I've shot the thermostat cover with an IR gun at idle and the temps match the gauge in the car fairly well. My sensor is new.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
? Has the OE water pump been swapped for a newer one ?
? If so, does the current pump have the small bypass-hole (adjacent to passenger side pump mount; Not visible with pump installed) ??
? If so, does the current pump have the small bypass-hole (adjacent to passenger side pump mount; Not visible with pump installed) ??
Burning Brakes
Joined: Sep 2009
Posts: 1,124
Likes: 140
From: Western New York
For a few bucks I'd put in a new 180* thermostat. What's probably happening with yours is when it's starting to open, it's doing so very slowly and that allows the water in the engine to go up above 180*. Then when it fully opens, the temperature levels out where it's supposed to be. There's a possibility your stat is on the way out. I'd just replace it for peace of mind. Easy job and cheap.
Duane
Duane
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
you can emulate the OE bypass by drilling two small holes (1/8" - 5/32") in the thermostat's flat mounting ring ... just inboard of the manifold's flange.
Last edited by jackson; Dec 1, 2019 at 08:51 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Your 'new' thermostat has a " hitch in its 'get-a-long' ". If you were to put that stat in a pot of boiling water, it might NEVER open. Your symptoms indicate that the mechanism is binding in some manner and requires "extra help" (more heat) to force it open. I would probably pull the stat out and test it on the stove. Take it back for a replacement if it doesn't open easily and smoothly.
P.S. You can add salt to the pot water to get the boiling point to increase.
P.S. You can add salt to the pot water to get the boiling point to increase.
Thread Starter
Instructor
Joined: Jun 2008
Posts: 233
Likes: 9
From: Marietta Ga
Following up on this.
Replaced the stat with a Stant Superstat 180F with a 1/8" hole drilled in the mounting plate of the thermostat. Problem solved, does not overshoot to 200F+ and really doesn't take long to warm up.
Was it the stat or the bleed hole?... dont know, but its fixed.
Replaced the stat with a Stant Superstat 180F with a 1/8" hole drilled in the mounting plate of the thermostat. Problem solved, does not overshoot to 200F+ and really doesn't take long to warm up.
Was it the stat or the bleed hole?... dont know, but its fixed.
Last edited by Joebrick; Dec 7, 2019 at 01:42 PM.
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Brett Foote
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
It was the stat....100%. If you still have it, throw it in a pot of water and heat it up on the stove. Watch the action of the valve as it starts to open.
My money says it will just begin to open, then hang up for a while, and finally just pop open all at once. But, that's just a guess....
My money says it will just begin to open, then hang up for a while, and finally just pop open all at once. But, that's just a guess....
Last edited by 7T1vette; Dec 8, 2019 at 01:37 AM.
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
I had the same problem with an 88 PU. Went to 210+ then came down to 180-190 and stayed there. Turned out it was air in the system. I could here water rushing through the heater core. Pulled the t-stat and drilled the 1/8" hole plus added a bleeder to the heater hose and bled out all the air. Problem solved.