Short background: Bought the car a couple months ago. Previous owner said the car had a 160 thermostat in it when he bought the car, which he removed because the engine temp barely went past the 1st line. He replaced the therm with a "stock" unit. When I test drove the car, it never approached what I consider to be a "normal" operating temp...I attributed this to the fans running non-stop due to an SES light. Now the SES light is remedied, but I am still looking at the same issues. I will add visuals to the story:

Driving down the road:



Imediately after pulling in to my driveway



Over the next 2 minutes at idle:






Once it reaches this temp, it cools back down to about 200, and then instantly starts to climb again:



I know the temp gauge is not an exact representation of temp, but the fluctuations are just bizarrare to me. I have used an IR gauge, and the car gets up to about 225 when it is peaked out at idle, and then cools back off to 205ish, which for the most part seems normal to me. When going down the road, however, the car barely gets warm enough to put out any heat from the heater, regardless of ambient temp.

Any thoughts on what I may have going on would be greatly appreciated. I know the temps aren't out of line now, but my primary concern is keeping it cool in the summer with the a/c going. Thanks in advance for any suggestions.

 

Threads like this is why GM turned the coolant gauge into a dummy gauge. What you are seeing is normal since the stock high speed fans don't come on until almost 230 degrees.

 

Its actually not normal for it to get that hot, IIrc the stock thermostat opens at about 210. I have owned 6 different 4th gen firebirds, and have never had the temp go that high when there wasnt an underlying issue.

If I were in your shoes, I would replace the thermostat with a new stock one or a 160 if you believe the car was programmed for one (lt1 thermostats are different from gen 1 350 fyi) that way you know what is in there. And i would bleed the coolant system (this is my guess at the issue) cause it sounds like you have air pockets in the cooling system.

also check the front of the radiator and ac condenser for any blockages (shopping bags and such)

Those are the 3 steps i would do in your shoes.


Good luck

 

either you have an airpocket, or a sticking thermostat.



test the thermostat in a pot of water.


properly bleed coolant.


problem may go away

 

Stock thermostat is 180 degrees. And the coolant gauge on the cluster is not remotely accurate. If it was a coolant pocket the temp wouldn't come back down when the fans come on and it would instantly shoot into the red and stay there until he revved the motor.

 

The pictures of operation look absolutely normal for a stock system to me. Your lack of heat from the heater would likely be remedied by a heater hose/core flush. Your fans are obviously working fine and when you run the a/c the fans come on, so there should be no problem in the summer.

The 225° temp you gunned was spot on. Fans are programmed to come on at 226°. I don't see anything to worry about, here.

 

Agreed with Rob. What you're describing (and showing) is perfectly normal.

 

Were all of those 4th gen Firebirds LT1 cars with stock tunes and stats? The thermostat opens at 180*F and the fans come on at 226 for low speed and 235 for high speed. The car should yoyo between 210 and 230 while stationary. This is completely normal.

 

I'll say this is not normal. Once the engine stabilizes, it's temperature should be pretty steady.

While the stock gauge may not be very accurate to the numbers on it, it still shows a cold to hot range.

I agree with everybody else here, replace the thermostat, do a good flush and make sure the air is purged. Check the PCM fan on settings. Perhaps also the radiator is bad-meaning clogged with junk. You'd be surprised how many issues people have that are cured by a new radiator.

 

An engine with an electric fan is not going to stay at a steady temp when sitting at idle. It's going to heat up somewhat. They all do it.

 

4 of them were lt1 cars and all were stock at one point, I never had a car get that close to the 3/4 mark without an inherrent issue.

typically the cars all ran 200-210ish. (and that was both in washington and a few years in arizona)

 

Agreed. However, this huge swing from cold to hot then back is not normal. The swing looks to be 50-60 degrees.

Sumpthin ain't right!

 

It's more normal than abnormal to me. A swing from 180-226 is 46. Hard to tell without an accurate gauge that might not even be reading linearly.

 

Lets be fair, how many of the other gauges really work correctly lol

 

This sounds like classic clogs since you have no heat. To be honest if the fans are set to factory on and off temps in the pcm it is fairly normal. I will say it might be changing a little to fast though. It sounds like clogs and a small air bubble.
There is a restrictor on the heater core lines that slows how much water flows through the heater core and causes slow water circulation and allows for crap to build up in the heater core. You need to flush the heater core lines. Do not allow for your garden hose to build up a lot of pressure on it when you flush them though. The clog should come out. If you cant run water through it and the clog wont come out then it's time for a new heater core.

The second spot that clogs is the steam pipe on the back of the heads. Not as easy to deal with if it's really clogged and not easy to get to. The temp may be spiking in both directions due to a clogged steam pipe that would allow an air pocket in the head. the sensor is located on the driver side head and the steam pipe on that side loves to get clogged up. if there is air or steam in the head and it reaches the sensor the sensor will go up and down as it looses contact with the water. This is very rare that the sensor will actually loos contact with the water. Still any air in there can still cause the change you see on the gauge.
One way to test would be let the car cool way down. Open the radiator cap. Track where the steam pipe runs along the intake on the passenger side to the throttle body and from there back into the radiator just below were the cap is. You can drain a bit of water to below where this port is on the radiator. Start the car and see if water is flowing out of it. When the steam pipe is clogged it moves very little like a trickle if any at all. most of the time the passenger side stays open a little and this wont tell you crap. But if the heater core is clogged my bet is the steam pipe may need to be checked as well. This will require 4 special rubber gaskets and possibly even the 2 banjo bolts. Might want to read up on making your own steam pipe/ crossover before attempting this just so it wont leave you stranded with out a car.

 

Thank you all for the replies. And a special thanks to Speed Demon24 for giving me partial credit for the invention of the dummy gauge...your input was GREATLY appreciated.

I guess there are still a couple things that are confusing to me:

1) Despite all the discussion about fan operation, I sort of feel as though this is a moot point...the car behaved exactly the same with the SES light on, which I believe means the fans would have been running basically from start-up.
2) Last time I checked, I had heat when the car would start migrating up towards the 200 degree mark after idling for a bit. When moving and at the cooler temp, I have mildly warm air coming out, but definitely not HOT air. I will reverify that I have good heat when the car actually warms up, and if this is the case, that would seem to nullify the clogged heater core theory.

Regarless, I will go ahead and flush the system...this will give me new coolant (although the previous owner said he had just done this), as well as take care of any clogged this or that and air pocket theories. Won't be this week, but I'll get everyone an update on that when it happens. In the mean time, any further thoughts are welcomed.

 

Flushing the system is great, but you must specifically flush the heater core and it's hoses. A general flush does not always clear the heater core and hoses.

You now mention that it acted the same way when you thought the fans were already on all the time because of the SES. That scenario doesn't really fly, because the temp would not reach a certain point, then come back down repeatedly. It was more likely because the fans were coming on at that time. Before it gets any more confusing, do the flushes and see how it shakes out.

 

Agreed. When I had my '93 Formula, I was shocked how much crap was in the heater core. Then I had heat for days.

 

This explains why my temp guage is exactly at the point in the pic and I'm barely getting any heat.

Don't know if this has anything to do with the engine temp but the temp guage was lower initially after the rebuild but I guess with the fact that the car sat for 14 years the heater core got stopped up.

 

Ment to add this the other day, here is a picture of me driving my camaro with 160 tstat in 40* weather.

Dosnt even uncover the 160 #s lol



And it will still blow heat so long as temps don't go below 40ish

So you def need to clean out the heater core!