Hello all,

I have a 85' Trans Am with an LG4 and according to my temp gauge the engine never goes past 150*. I just put in a new 180* t-stat in the hope that my problem would be resolved but nothing has changed. Is there a chance that my new t-stat is defective? It came fresh out of the box but I hear that sometimes they can be faulty. If it is in fact working then could my temp gauge possibly be messing up?

The old t-stat I took out was a 195* stat but was really easy to open with my fingers so my guess is that it was no good. I tried to open the new 180* t-stat I just put in and it seemed prett firm but I'm not sure if it is good.

Any thought is greatly appreciated.

 

Was it a "fail safe" brand name thermostat? Because if it's faulty and made by them then it is going to fail in the open position.

Are you in a climate controlled garage or just outside?

My general thoughts are that if you are in Philadelphia, PA in the winter it's going to be hard to get near 180 with cold temps outside, much more so going down the road.

 

I also own an '85 T/A and just went through this with my car. I installed the 180 "failsafe" t-stat and it seemed to take a long time for the engine to warm up. Even more annoying, it took the trans a real long time to kick in to overdrive. I decided to go back to a 195 t-stat. When I pulled the 180, I noticed that the mechanism was slightly cocked to one side which wasn't allowing it to close. And this was a brand new part! I have had no issues with the 195 t-stat from Motorad. The heater warms up nicely again and I believe my fuel mileage is a bit better also. There was only one week between the t-stat changes. I just didn't care for the lower temp. My temp gauge when at operating temperature was just slightly below the 1/4 mark. With the 195, the needle is slightly above 1/4 mark. You wouldn't think 15 degrees could make such a difference but it certainly does.

 

Its a good idea to call around to find a shop that will put an infrared temp. gun on the engine. You need to know if your gage is right on .The shop I used put the gun on different parts of the engine but where the temp sensor was is the reading we used.
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It only takes them under 1 min. to do it so I doubt they would charge you .I was not charged and luckily the gage is right on.

 

You should check with a lazer temp gun. I had my temp sending unit give me false readings. In a pinch you can hold a meat thermometer on the upper radiator hose and get a pretty close reading. Also the gagues on are cars are known to give false readings too. You can use a potentiometer to check if your gauges are reading right.

 

I put a 180 Stant "Superstat" in my T/A and have been pleased with it. Seems to warm up quick and maintains a very steady temperature, no huge swings of the gauge like you get with those cheap t-stats.

 

My Iroc (305) stays cool, but steady 180, if I let it run eventually it reaches 227 and kicks the fan on, but almost would take 25 minutes.
On the GTA (350) heats up to 227 in 15 minutes at idle, but cools down on cruise over the road and stays at 180 ...

Can get a laser temp gun at Horror Freight for $37 .... great tool to own.

 

Plus, it is the middle of the winter. Things take a LOT longer to warm up.

 

Like everyone said, its freezing cold out right now, your temp gaughe may be wrong, and your t stat may be a bad one.

All are easy things to check without just randomly buying and swapping parts.

 

Thanks for all of the responses. The stat I put in was a Stant Superstat, not one of the failsafe ones. I'll see how the heater is after cruising around for a bit so I can get an idea of whether or not the stat isn't letting the engine warm up. If the heating is good, then I guess my gauge isn't giving me a good reading and I'll get that checked out. If the heating isn't good, then I'll get a new 195* stat and see how that works. Once again, thanks for all the input people

 

 

Okay so I ended up getting a new 195* thermostat and it seemed to do the trick. My temp gauge goes up past the 160* mark now and my heating actually feels like heat. I guess since the engine was made with a 195* that that is what it needs in stock configuration. Maybe a 180* would work nicely in the Summer, but as for Winter temps the 195* is the way to go. I'm still going to hold on to the 180* stat since it's a perfectly good part and who knows maybe I'll need it in the future. Hopefully now that my engine can get closer to an ideal operating temp I'll see some increase in fuel economy because for the last few weeks I've only been getting 11-12 mpg . Keep in mind that this is an LG4, the "Economy" V8. And no I'm not flooring it every chance I get. I've been trying to be as gentle with the gas as I can in the hopes of getting closer to the 17 mpg city rating.

 

I've had really good results using my MrGasket radiator cap. I trust my temp gauge but come on, it's 25 years old. Stone

 

Running around in open loop will kill
mpg.

I would test the 180 stat you just pulled out.

You should also verify the temps as suggested before.

Diagnosing a problem the right way is much better then randomly replacing parts.

 

Your bad fuel consumption has got to be carburetor related. The higher water temps are only supposed to help achieve more complete combustion. I recently rebuilt my E4ME carb and even though the mileage didn't change much it was good to replace all the old rubber parts like the accelerator pump. I am typically getting 21 mpg in mixed city/highway driving. I keep the rpm around 2000 on the freeway which puts me just under 70 mph. Perhaps your trans isn't shifting into overdrive. Or if you don't drive it far enough to get the engine fully warmed up that could also account for poor mileage. I hope you get it sorted out.

 

check that the ECM system is working-if the ECM is not working,car will run but carb will be full rich and there will be no distributor advance.

 

If on an OBD1 equipped vehicle the ecm reads too cold of a temperature via the sensor, doesn't the engine run slightly rich until it reaches operating temperature? The change can be indicated by the response of the mixture control solenoid. Once warmed up, less fuel is required so the ecm leans out the fuel delivery by reducing the mixture solenoid pulses. So in a sense, running too cold will kill mpg. Keep the 195 t-stat in year around is my advice.

The O2 sensor also needs to warm up properly too which means its in open loop for about 10 min before the ecm takes its reading.....basically just a ground reference but it too can cause a running rich condition.

 

^ that's what the "open loop" I refereed to is.

Yes it will run rich until it reaches operating temp.