Hey everyone,
Unfortunately I haven't been active on here a while because of EMT school and my starting as an EMT.

So just recently I took my 86 305 trans am home. I noticed halfway that the temp was two ticks past half way. So I turned on the heat for a few minutes to get it down. Kept driving and had to pull over at a station to let it cool. I did have ac running but stopped when it got hot. The rest of the way home it pretended the two ticks passed half was actually half way. In town it was completely fine. Even when idling. I thought it was one off because it was hot that day.

Coming back today with it cloudy and around 70 it did the same thing.

It got a little warm a few weeks ago and went past half in town going pretty quick but didn't happen again until this trip.

In the past year the radiator, hoses, water pump, belts, ac system (complete), thermostat, heater core, and trans cooler have all been replaced. Never had an issue until now? Air dam looks intact. Car also see excessive fuel because of it not running as efficient.

Let me know of things to check. Unfortunately due to my work, I need to my car ready to go always and have very little days off so I need to get it done when I can.

 

Here's a list of the things I would start checking:

1. Thermostat. Put the factory recommended thermostat in. Be sure that it opens or closes by putting it in a pot of boiling water on the stove. Or by aiming a temperature gun at the upper hose. can use a lower temp thermostat if you want, but I would not go below 180*.

2. Air dam under car. Check to see that the air dam is on the car. It is the lower spoiler in front. Sometimes these get damaged by tow trucks and parking blocks. Make sure it is pushing air upwards toward radiator.

3. Check to see front of radiator has no obstructions. Look for the plastic components that direct the air to the radiator behind the front bumper above air dam. It should look like a giant vent or air passageway directly to radiator.

4. Fill car up with coolant while running with cap for radiator off. Do this when car is cold and warming up to ensure all air bubbles are out.

5. Watch to see if fans come on when warmed up. If not, start checking for for electrical problem, switches, wires, or sensor. (on passenger side of engine on head).

Common sense things need to be checked like coolant level in radiator not just overflow bottle, and the color of the coolant. It should be bright green. Your car is an 86 and I am not sure if you have a manual fan on that or not... If so, disregard #5.

Also check your waterpump and could also be because your radiator is not the best quality

 

Thanks for the feedback!

The current thermostat is a 180 but I will check operation.

Air damn is straight and attached

There is a slight ubstroction with a bottom piece of fender sagging. Its hard to explain. Just need to TAC it up. Didn't mention because its been like that since I owned it

Fans are new and functional

And its full of the green stuff I will post back with thermostat findings. Thanks for the help!

 

Might be as simple as a bad connection to or temp sensor going bad, I've had new thermostats fail in the past, also, double check your lower radiator hose, should have a nice firm feel with the spring installed inside, without, it can suck closed at higher rpms slowing coolant flow. Back in the days of quality builds, found casting slag in a cooling port of a 1965 head that would intermitantly block fluid flow..

 

temp switch..made my car seem as it was going way past halfway..i replaced it..only goes halfway if im in tempe Az, running AC..but i never overheat.. so in short..replace it..or check plug wire for dmg..move it ever so slightly n see if temp changes..

and like Camaror86IrocZ said..all good info here..

good luck bud

 

Thanks for all the help! Thermostat opened properly! Air damn is in good shape as well. However I do believe the temp sensor is correct. My reasoning for this is the very poor gas mileage I got on the road, the bits of bubbled over coolant on the bottle and its general sluggish behavior when that hot :/ I'm going to drive today and check

 

You need to buy one of these, it's absolutely a must for our 3rd. gens.
It will put your mind at rest knowing that the real nuisance is the Gauge.
http://www.harborfreight.com/automot...ing-60725.html

 

yeah i bet your gauge is off. mine was reading 220 on the gauge but the water neck was only reading 170 with a temp gun.

 

I see you are working with a '86 LB9. Seems I tell everyone else with one to check there prom # against this TSB - so here ya go -- http://www.gmtips.com/3rd-degree/dox/tips/ecm/prom.htm

Hope yours isn't on the list...

I've installed new temp sensors that were off right out of the box..