flushing coolant and changing thermostat ? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 10-29-2006, 10:17 PM   #1
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Default flushing coolant and changing thermostat ?

Helping a neighbor do a coolant flush and refill ( 1999 3800 ) should we chg the thermostat too ? Rad cap too ? If so do they only offer one heat range thermo ? His digital temp says 183 when hot I thought these ran more like 195 ? Do you suggest we install a flush T also if so which heater hose do you put it on ? Thanks fellas !
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Old 10-29-2006, 10:39 PM   #2
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It is possible that the thermostat has been changed with a 180 degree one.
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Old 10-29-2006, 11:05 PM   #3
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Rad cap is a definite yes.

I would change the thermostat simply because this is a great time to change it, winter is starting, and its a good 7 years old now.

I would install the flush T, I buy the Prestone Flush-n-fill kit from Walmart for under $4.oo, the directions tell which hose to put it in.
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Old 10-30-2006, 12:12 AM   #4
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any clue which hose the T goes in ? They both seem to go into an aluinum block thing by the alternator ?
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Old 10-30-2006, 12:47 AM   #5
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It goes in the hose that runs from the firewall to the top of the engine,
not in the one that comes from the waterpump to the firewall.

I hope that helps. I don't have a Bonne but I suspect my Olds will be close if you need a pic. The hose actually runs along near the top of the firewall for a bit and thats the place I cut in.
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Old 10-30-2006, 09:54 AM   #6
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It won't hurt anything to reverse flush, if you refill the system and bleed it carefully. IIRC, the flush tee is usually installed in the hose to the heater core, but check the instructions on the flush tee package. On the Series II 3800, locate the hose to the heater core from the engine by finding the arrow indicating direction of flow cast into the nipple where the heater hoses connect to the tensioner assembly. (I'll try to find a pic.)

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If the gauge is accurate, 183 is a good temperature to run. If you doubt the accuracy of the gauge, buy a 180F thermostat, drill it, and install it. The drilled hole allows air to bleed from the engine to the radiator gooseneck where it can be purged at the bleeder screw. Locate the hole at the high point because air bubbles will rise to the top of the coolant under the flange, and that way you get most of the air out.

New cap is a good idea, too. I think the standard pressure is 15 or 16 psi. Also, check the condition of the hoses for softness or oil damage.

If you haven't already done so, read this techinfo article about how to refill your cooling system before you open it up. http://www.bonnevilleclub.com/forum/...=article&k=100
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Old 10-30-2006, 09:58 AM   #7
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put the t in the red arrow hose ?
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Old 10-30-2006, 10:00 AM   #8
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Yes, the red arrow hose is the outflow. See the arrow cast into the aluminum underneath the steel elbow fitting?
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Old 10-30-2006, 10:03 AM   #9
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yup,thansk
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