Over Heating.. "Sticky Stat?

I was driving in traffic for 20 minutes in 85 degree heat. Engine heated to the last hash mark before "red" on coolant gauge on inst. panel. I stopped the engine for 10 minutes and the temp was down to just above normal. Later while driving at 45 mph, it began to heat up again. The coolant was at proper level. Could I have a sticky thermostat?..and how to check/replace it. Any thoughts would be helpful. Thanks.

Use diagnostics to verify your fans are working.

agree with checking the fans.

10 minutes with the engine off doesn't sound like it would be enough time for the engine to cool down very much, if at all. a "old school" trick regarding overheating is turn the heater & fan on (turn off a/c & roll down the windows). that should take the coolant temp down a bit in a few minutes.

thermostat repair: http://reattaowner.com/roj/component/content/article/66-engine-a-drivetrain/cooling-system/176-thermostat-installation-instructions

as Padgett does, i also use a 180 degree thermostat.

another possibility is the water pump is going out. hope not!

Did you check the coolant level in the overflow tank, or in the radiator itself? Check the level in the actual radiator after it cools. If it's not completely full, have your system pressure tested at a competent radiator shop.

Could also be a collapsed lower radiator hose but if it cools down over 50 mph look to the fans.

Thanks to you all. Lots on my "to-do check list". I'll replace my thermostat and check all hoses(lower radiator hose),

check pressure of radiator, and fans operating properly.

Just drove 50 miles in 85 degree heat. Let it idle at home for 30 more minutes and temp. remained normal. Both fans working. Fluids are exact when hot and cold in overflow tank and radiator when cold. So I'm at a loss. Fortunately, my 91 has easy access to thermostat housing bolts if it needs changing.

Question: what is the adjustment type screw on top of the thermostat housing for?

It's an air bleed.

It's an air bleed.

Just got back from vacation. How and when should I use the air bleed? I'm assuming while it's running at temp. Also just noticed the upper hose is always hot and can't feel water flowing when I squeeze it. I'm thinking my thermostat might be stuck half open??

Air bleed should NOT be opened when the engine is hot. The air bleed should be opened while filling the radiator when the engine is cold. Slowly fill the radiator until you see water come out the air bleed valve then close it. Continue filling the radiator slowly until it is full. Then gently squeeze the top radiator hose while watching the opening in the radiator to see if air burps out. Refill the radiator if needed the put the cap in the radiator. It's OK to open the bleeder again to see if additional air come but don't open when the cooling system is hot or under pressure. You could get seriously burned by hot water spraying out.

BTW, If this is a Reatta you are working on I have never seen a air bleed valve on one.

Hi Ronnie. I have a '91 Reatta in question. Harry Yarnell mentioned the screw on top of the thermostat housing is an "Air Bleed" seen in picture. I opened it while engine was cold and let a little radiator fluid escape. Is this the valve you're referring too? If not an air bleed, what is it for?

It looks like an air bleed screw in the top of the water neck to me. That must be unique to a '91 model as it has a later series of 3800 that the older models.

Did any air escape when you removed the screw?

No air escaped, just a little antifreeze. Checked all other operations and it still overheats in traffic. Dial goes up to the 2 o'clock position on the temp. gauge.

Do you know the temperatures per light over the 12 o'clock position? I'm in the blind here.

here's a partial list provided by a fellow forum member some time back. Ronnie had a nice jpg showing the gauge segments and their corresponding temps, but I didn't find it.

The 2nd segment comes on at 115 degrees F.

The 3rd segment comes on at 131 degrees F.

The 4th segment comes on at 147 degrees F.

The 5th segment comes on at 167 degrees F.

The 6th segment comes on at 184 degrees F. (This is the 12 o?clock position).

The 7th segment comes on at 212 degrees F.

The 8th segment comes on at 217 degrees F.

The 9th segment comes on at 223 degrees F.

The 10th segment comes on at 230 degrees F

Here's the jpg from Ronnie

[h=2]Re: temperture[/h]

Thanks to all. This gives me piece of mind. Seems if I keep it under 230 in traffic for short periods of time, I won't blow my engine.