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Thermostat sticks until I relieve pressure from the radiator
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Author:  ppsi [ Wed Apr 22, 2009 6:20 pm ]
Post subject:  Thermostat sticks until I relieve pressure from the radiator
My troublesome slant has a new issue. It heats up and the thermostat sticks closed but will open if I open the radiator cap and relieve the pressure.
I see the dash gauge go up but my Autometer gauge stays cool and I feel the top hose and it is very hard. After opening the cap the hose is soft and the flow starts through the radiator.
It is a new radiator, a new 160 degree thermostat and a 13 lb radiator cap. This one really has me baffled. I thought it was the thermostat so I changed it. Could it have anything to do with the heater hoses being just a loop? My heater core leaks so I just fed the in to the out. I was thinking maybe it is some trapped air or something?
Thanks-Howard
Author:  SlantSixDan [ Wed Apr 22, 2009 6:28 pm ]
Post subject: 
Nothing the matter with heater hose loop, that's not it.

160° thermostat is wrong, you want a good quality 180° unit, preferably Stant SuperStat #45358.

Make sure thermostat is installed right way around.

Where is the sensor for your Autometer temp gauge?
Author:  wjajr [ Thu Apr 23, 2009 3:55 am ]
Post subject: 
Voice of Experience Son, Department:

Easter weekend I installed a new radiator and all the fixen's that go with it. I installed the thermostat in the top hose housing and bolted it up. Same thing hard hose, high gage reading, and a lot of over flow...

Next day I realize the I installed the thermostat backwards. Took it apart, pan tested the opening temperature, it was good, put it back in the hose housing, and fired it back up. Same thing again; hard hose, high gage, and cold radiator.... WTF????

Took the damn thing apart a third time after cool down. Had a massive what a dope moment, as palm of hand aggressively lands squarely on forehead, and this time with no distractions reversed direction of the thermostat so the spring end is placed into the head. To quote young Frankenstein; "It's alive,... it's alive!!"
Author:  ppsi [ Thu Apr 23, 2009 7:46 am ]
Post subject: 
Quote:
Voice of Experience Son, Department:

Easter weekend I installed a new radiator and all the fixen's that go with it. I installed the thermostat in the top hose housing and bolted it up. Same thing hard hose, high gage reading, and a lot of over flow...

Next day I realize the I installed the thermostat backwards. Took it apart, pan tested the opening temperature, it was good, put it back in the hose housing, and fired it back up. Same thing again; hard hose, high gage, and cold radiator.... WTF????

Took the damn thing apart a third time after cool down. Had a massive what a dope moment, as palm of hand aggressively lands squarely on forehead, and this time with no distractions reversed direction of the thermostat so the spring end is placed into the head. To quote young Frankenstein; "It's alive,... it's alive!!"
You placed the thermostat in your head!? D@mn that is hardcore.
I'll check again to see about the orientation of the stat but if it in backwards I won't admit it.
I have the sending unit for the autometer gauge in the head just past the thermostat housing and the sending unit for the dash gauge is on the flat part of the head a little to the rear of the stat housing. I suppose the electric dash gauge is more sensitive than the mechanical dash gauge?
If I go to a 180 stat what is the difference since the motor-w-a 160 stat still runs 180-190?
OOps-almost forgot-there is a spot on the top of the radiator that will accept my autometer gauge. This will give me true water temp yes?
Thanks-Howard
Author:  SlantSixDan [ Thu Apr 23, 2009 10:14 am ]
Post subject: 
Quote:
I have the sending unit for the autometer gauge in the head just past the thermostat housing
Make sure it's not physically interfering with the thermostat opening.
Quote:
I suppose the electric dash gauge is more sensitive than the mechanical dash gauge?
Not necessarily.
Quote:
If I go to a 180 stat what is the difference since the motor-w-a 160 stat
Compared to a 180° stat, a 160° unit causes your engine to use more gasoline, contaminate the oil faster, and wear more quickly.
Author:  wjajr [ Thu Apr 23, 2009 1:09 pm ]
Post subject: 
Quote:
OOps-almost forgot-there is a spot on the top of the radiator that will accept my autometer gauge. This will give me true water temp yes?
That placement will give you temperature of coolant in the top radiator tank.

Temperature of the head water jacket would be better indicator, that is why the factory placed the gage sensor where it did.
Quote:
I'll check again to see about the orientation of the stat but if it in backwards I won't admit it.
Well we can assume that if you don't pursue the over pressure topic after this we will all know that indeed you installed the thermostat backwards.
Author:  ppsi [ Thu Apr 23, 2009 4:43 pm ]
Post subject: 
I ordered the Stant 180 degree stat today and will get it in this weekend.
Thanks for the clarification in the 180 vs 160 stats. Point well taken.
I don't imagine the location of the sending unit could interfere-w-the operation of the stat because it is a bung that was in the head originally and I had to use a reducing bushing so the device I am using for my gauge is smaller but I will check it out regardless. The bung may have been for something like a hose connection but I really don't have any idea.
Thanks-Howard
Author:  Mister_Perkins [ Thu Apr 23, 2009 4:51 pm ]
Post subject: 
im actually having this same problem.. I'm going to try this too. Its a new thermostat, but its only 160* also
Author:  ppsi [ Fri Apr 24, 2009 9:54 am ]
Post subject: 
I installed the Stant 180 degree stat and still have the same issue.
One thing I noticed was when I shut the car off after about 5 mins I heard a gulp sound so I started the car again and sure enough the water was flowing. The Autometer gauge read 190 and my dash gauge read about 80% high so I'd say the dash gauge is way off.
How long should this take to warm up enough to open the stat? It was 80 degrees out and, as I said the car was running for at least 5 minutes. I'm wondering if it was a coincidence that the gulp was heard when I shut off the car and the thermostat opened at the same time I turned off the car. I didn't have time to let it cool off and recheck it until Sat.
Any other ideas? The radiator is full and I have a cheezy aftermarket overflow tank.
Thanks-Howard
BTW I took a pic of the stat that was in the car and it was hanging off the end of the top radiator hose and it showed it to be correctly installed but the picture got dumped as I was loading it to photobucket so no proof :(
Author:  Joshie225 [ Fri Apr 24, 2009 12:05 pm ]
Post subject: 
Sounds like you had air trapped at the thermostat. Very easy to do. Happened to me not long ago on my '67 after having the radiator out.
Author:  Pierre [ Fri Apr 24, 2009 2:42 pm ]
Post subject: 
And easy to prevent too. Drill a small hole into the inner part (1/16 or so, maybe even less) of the flange, and make sure the hole is pointing skyward when installing. The amount of water flowing through it will be negligible and will allow any trapped air to pass.
Author:  emsvitil [ Fri Apr 24, 2009 3:30 pm ]
Post subject: 
The stant's have a little notch in poppit valve for the air to pass thru.

You want the notch up.........


(look from the spring side, sometimes it's hard to spot)
Author:  wjajr [ Fri Apr 24, 2009 6:11 pm ]
Post subject: 
I had a problem with slow drain down. Just drilled a small hole maybe 3/32", can't remember exactly, about an 1/8" from the edge of the thermostat, and mounted so hole was at 12 o'clock. She drains, and fills nicely now.
Author:  ppsi [ Sat Apr 25, 2009 6:48 am ]
Post subject: 
I always drilled holes in the stats I installed EXCEPT in these last two. I have no idea why I fofgot to do this. The one I took out originally had a hole I drilled in it and I remembered saying to myself that I needed to do this before I put in the new one yet I still forgot. Same thing-w-the new Stant-no hole.
Hopefully the belch took car of it. It circulated the coolant this AM so I'll keep an eye on it.
Now for the Autometer gauges & speedo instrument cluster retrofit. I'm making a polished aluminum plate to mount this cluster in ADN I'm going on Sun to look at an 8 1/4" rear I finally got a line on-I hope it is good. I'm batting 0 for 2 on "good" BBP 7 1/4" rear ends I've bought thus far.
Thanks for the help.
Howard
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