Tide in my radiator!

I noticed that the coolant level in my radiator rises and falls very rhythmically. It seems to be very consistent in it's tidal movements and appears to coincide with a fluctuating temp gauge.
This problem (?) first appeared when I had the heater hose fitting on the intake manifold replaced due to corrosion (damn thing fell off!). I tried bleeding any air out of the cooling system and replaced the thermostat, but it didn't help. That's when I noticed the radiator tidal action. The truck (95 K1500 5.7L auto with trans cooler) doesn't overheat. I've never had a vehicle with a constantly moving temp gauge. It goes up and down between 1/4 (guessing 160deg.) and 1/2 (210). When first warmed up, it spikes at something slightly over 210 and then drops down and up and down and..... With the summer heat soon upon us and increased towing (boat), I'm afraid it may overheat or worse. Otherwise, the truck seems to run fine. Thoughts? TIA TomC
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This is caused by the lack of a bleeder orifice in the thermostat. If you still have the original you'll see a ~3/16 - 1/8 hole in the thermostat.
Cheers

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that usually is a sign that the radiator is low on water. But you said you filled it with water, so i am not sure . make sure there are no air pockets trapped in the engine/radiator. old john
Hello, TomC! You wrote on Thu, 17 May 2007 19:35:03 -0500:
T> I noticed that the coolant level in my radiator rises and falls very T> rhythmically. It seems to be very consistent in it's tidal movements and T> appears to coincide with a fluctuating temp gauge. T> This problem (?) first appeared when I had the heater hose fitting on T> the intake manifold replaced due to corrosion (damn thing fell off!). I T> tried bleeding any air out of the cooling system and replaced the T> thermostat, but it didn't help. That's when I noticed the radiator tidal T> action. The truck (95 K1500 5.7L auto with trans cooler) doesn't T> overheat. I've never had a vehicle with a constantly moving temp gauge. T> It goes up and down between 1/4 (guessing 160deg.) and 1/2 (210). When T> first warmed up, it spikes at something slightly over 210 and then drops T> down and up and down and..... T> With the summer heat soon upon us and increased towing (boat), I'm T> afraid it may overheat or worse. T> Otherwise, the truck seems to run fine. Thoughts? TIA T> TomC
With best regards, snipped-for-privacy@comcast.net. E-mail: snipped-for-privacy@comcast.net
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I am not sure what the OP is calling "tidal action" but water does expand with heat so all things being equal it will rise some and if there is air or steam pockets it will rise even more. The water level will never be constant and that is the reason for the sealed coolant recovery system. ----------------- TheSnoMan.com
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