I noticed when the outside temperature dropped the last few days here in Vancouver (-10C) that it was taking quite awhile for my GT to warm up. It never really did warm up properly and my gas mileage, as bad as it always is, was even worse than usual.

So, I decided to pull the thermostat and have a look...



The thermostat looked fine so I put it back in. Any other suggestions what might be wrong?

LMAO!!! I've heard that's actually a little known trick; bending the thermostat gives you like an extra 10hp.

Thats what Autozone T-stats do everytime. They are very flimsy compared to better brands.

I'm swapping mine as soon as my new thermostat cap comes in. It takes ages for my car to warm up, and even then it never really does...

quote Originally posted by Mike Gonzalez: Thats what Autozone T-stats do everytime. They are very flimsy compared to better brands.

I guess I've learned my lesson, although it is somewhat comforting to know that I'm not the only Fiero owner this has happened to!

I listened to the wise words of the late Don Gage and bought what he recommened Here as a replacement. Thanks Don.

ya that happened to me for the longest time i thought i had a sensor problem!

I had a Cutlass with a 2.5 that ran poorly and I couldn't figure out why. The heater didn't work very well either so I gave up on the engine and decided to fix the heat. I bought it a new thermostat and surprise surprise the engine ran well again. The moral of the story is the thermostat is there to keep the engine warm and the engine must be warm to burn fuel efficiently.

You also have to watch if the stat is old. Last winter my temp started running lower and fuel econ dropped off.
The stat was beine forced open from the coolant flow and engine would only get to around 150*. New stat and all is well.

Now I noticed my daughters GP is doing the same thing again. Stat was replaced 3 years ago and is already running low.

Seems stats are just not made well anymore. The springs must get weak over time.
Figure I'll be changing it tomorrow. This time I'm getting one with a lifetime Warr. so I can take it back since they don't seem to last more than a couple year in the GP. To bad it's such a pain to change. Wish it was like the Fiero.

quote Originally posted by Mad Mike: I had a Cutlass with a 2.5 that ran poorly and I couldn't figure out why. The heater didn't work very well either so I gave up on the engine and decided to fix the heat. I bought it a new thermostat and surprise surprise the engine ran well again. The moral of the story is the thermostat is there to keep the engine warm and the engine must be warm to burn fuel efficiently.

LOL Sounds like my old V6 Beretta. Unbeknownst to me, the thermostat was stuck wide open and the engine never reached operating temperature. It did OK around town but at highway speeds the TCC lockup wouldn't lock and my RPMs would run high, and I'd have NO heat in the car. After one particularly cold below-zero drive I was about half frozen there behind the wheel. On a whim I tried a new thermostat and all the problems were fixed.

quote Originally posted by Patrick: The thermostat looked fine so I put it back in. Any other suggestions what might be wrong?

Likely Your heater and/or line to heater is F'ed.
or
You have weak coolant and it froze some, blocking heater.

See cave. Tstat in coolant section

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

[This message has been edited by theogre (edited 11-24-2010).]

quote Originally posted by Patrick: Any other suggestions what might be wrong?

As theogre suggested, the most likely suspect is lack of flow in the heater loop. In a stock Fiero, the heater loop provides the only bypass (and thus the only pressure relief) circuit when the thermostat is fully closed. Of course, high-rpm engine operation before it is warm enough for the thermostat to begin to open will also cause a high pressure differential across the thermostat.

[This message has been edited by Marvin McInnis (edited 11-27-2010).]

ln addition to the heater, there's also the throttle body heat that provides a relief. I have actually had the bent thermostat happen on my car, but I assumed that I just probably didn't seat the thermostat properly in the housing.

quote Originally posted by pmbrunelle: ln addition to the heater, there's also the throttle body heat that provides a relief.

Of course, you are correct about the TB heater circuit ... but I don't think it has enough flow to provide any significant pressure relief.

A feasible theory about another possible cause of bent thermostats in Fieros is that enough air in the block could result in a "water hammer" effect at the thermostat every time the engine is started.

Coat the O-ring of your thermostat with faucet grease (as used for washerless faucet O-rings). This will make it slip in easily and not bend.

I'm much for water hammer than for heater loop. Anyone who has worked on the plumbing at their house knows what happens when you turn the water back on. You get nasty water hammer when the air passes through the valve and water gets blown out of the faucet at high speed. That seems like a whole lot more force than you will get from a blocked off centrifical waterpump. GM designed the engine to operate with the thermostat closed at warm up.

Oh, you are not suppose to use a hammer to install the thermostat.

I had this problem before. I looked in the shops around town for a more sturdy Stant thermostat but i couldnt find one! Maybe I should look again because that was a while back.
I solved the problem by (very carefully) welding thin strips of steel to the legs of the stat. Turned a flimsy thermostat into a beefcake.

quote Originally posted by theogre: Likely Your heater and/or line to heater is F'ed.

quote Originally posted by Marvin McInnis: As theogre suggested, the most likely suspect is lack of flow in the heater loop. In a stock Fiero, the heater loop provides the only bypass (and thus the only pressure relief) circuit when the thermostat is fully closed.

Both you fellas nailed it. Let me explain...

Back in the summertime, my heater core started leaking. I didn't need the heater at the time, so while I was tracking down a new core, I bypassed the leaking heater core by disconnecting the two rubber hoses from the core and re-connecting them to each other. However, between the two hoses I used a fitting which had a very small passageway for the coolant to go through. When I got the new heater core, I flushed out my system and I was very surprised at that time to discover my thermostat looked much like it does in the picture above. I didn't understand at the time what the heck had happened to the thermostat, so I just bent it back into shape and re-installed it. Unknown to me until the cold snap here revealed a problem, the thermostat arms bent again from "normal" water pressure in the system (because the thermostat "arms" were now weak from being previously bent).

So in retrospect it's now easy to figure out what happened. The fitting I used to temporarily connect the two heater hoses to each other restricted the coolant flow way too much and this resulted in higher than normal coolant pressure pushing against the thermostat. The long thermostat "arms" therefore bent.

Lesson learned!

Had this problem on the 88 and from what I personally determind was cheaply built parts. I discovered that they bend when you put the cap back on (not sure if they are catching something or not) - but I had bent 2 new ones, put them in, put the cap on and then removed the cap only to find it bent (never started the car). Went out and bought another new one and made sure the arms where of a heavier material and all was good (no more problems).

...anyways...