I think the engine bay temp argument is not valid. We're talking about a difference of 30°. There's any number of engine issues that result in the "glowing exhaust manifold" problem. These issues will cause FAR more increases in engine bay temps than 30°. Also, running too cold will not allow the engine to run at peak efficiency, which will result in increased carbon deposits, richer A/F ratio (which results in worse economy and more contaminants in the oil), and reduced burnoff of the contaminants from the oil. If you run too cold, it won't even go into closed loop. Unless you're racing, the engine won't really care whether it runs at 210° or 240°, but you might care when your fan goes out at 100K instead of 200K. If you're really concerned about engine bay temps (and I DO agree that the Fiero engine bay temps run high), I'd first make sure you're not running lean or rich (i.e., no vacuum leaks, good timing, good EGR, good sensors, air filter not clogged, etc). And then, if you want more temp reduction, wrap or coat the exhaust manifolds.

Personally, if I'm shopping for a car and I find one that has low temp stats, I tick that off in the negative column. Not a BIG negative, but still a negative.

quote Originally posted by SCCAFiero: Not having a thermostat can also sometimes allow the coolant to flow through the radiator fast enough that it does not have enough time in the radiator to dissipate heat through the fins making the vehicle overheat quicker.

I hear this often but this doesn't make sense to me. As long as the radiator is full of hot fluid, it will dissapate heat at a given rate, which is the function of the temperature difference between the radiator and ambient. This is, of course, for any given airflow. A faster flowing coolant is not going to reduce the heat transfer through the radiator unless the flow is so high that the fluid is cavitating.

quote Originally posted by Kevin87FieroGT: Here's a question. With the fan switch you have, does your fan run while driving down the road in summer temps. with the a/c off??

No. I run a 195 F thermostat and a 210 F fan switch, and even with an ambient temperature of 100 F, at a steady 20 mph or higher the fan will never come on. If the engine cooling system is healthy, the radiator fan should never come on (with the AC off) except when stopped or in slow, stop-and-go traffic.

FWIW, I prefer the 210 F fan switch to help keep the oil (not coolant) temperature within a slightly narrower range than the stock setup ... but that's just me.

quote Originally posted by masospaghetti: ... an engine at 195 degrees will radiate less heat than one a 235 leading to a cooler engine bay. Which, IMO, isn't a bad thing with 25 year old electronics and plastics around.

The dominant source of heat in the Fiero engine compartment is the exhaust system. The difference in heat dissipated by the engine block itself at 235 F vs. 195 F is comparatively insignificant.

quote A faster flowing coolant is not going to reduce the heat transfer through the radiator unless the flow is so high that the fluid is cavitating.

100% correct ... and for the right reasons.

[This message has been edited by Marvin McInnis (edited 11-29-2010).]

okay my fiero the fan never comes on because it never gets to 235 lol and its in the upper 30's out side

quote Originally posted by masospaghetti: I hear this often but this doesn't make sense to me. As long as the radiator is full of hot fluid, it will dissipate heat at a given rate, which is the function of the temperature difference between the radiator and ambient. This is, of course, for any given airflow. A faster flowing coolant is not going to reduce the heat transfer through the radiator unless the flow is so high that the fluid is cavitating.

I can't say it makes sense to me either but I have tried it on several occasions in multiple vehicles and have ended up with very similar results. On my (track only) Fiero, I removed the center section of the thermostat and only run the outer sheet metal as a restriction in the system. When I tried to run without it, it would always overheat, and under lower stress (running 90% or so, shifting around 6k) conditions, with the fan running constantly. It may not be a thermal efficiency per square inch issue as much as a fluid travel path issue. It may even be an airflow issue as well. Next time I take the car on track I might remove it again to see what effect it has now that my cooling system is no longer stock and I have a supplemental oil/water cooler with a secondary water/air core for that tied into the main system.

My old Plymouth is very similar, without a thermostat/restriction, it will overheat in traffic much quicker than running with none at all.

quote Originally posted by Marvin McInnis: The dominant source of heat in the Fiero engine compartment is the exhaust system. The difference in heat dissipated by the engine block itself at 235 F vs. 195 F is comparatively insignificant.

Yes... Think Catalyst... Fiero engine bay have the cat and the rest of exhaust system too. Catalyst operate 1000+ F all the time.

------------------
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...)

My car's fan never comes on (with ac off) except for extended idling. If it gets to 220 or so,
I turn on the ac to keep the temp from going higher. Could put in a fan switch, but just keep
an eye on it. The thing I would be concerned about with letting the temp go to 235 is say I
lose a hose and don't notice right away. 235 to the red zone isn't much.

quote Originally posted by theogre: You want engine to last? Oil temp and condition matter more than Coolant temp. What Oil temp measure? What? You didn't measure Oil Temp Max and Oil temp warm-up time? Most people don't... Oil Temp is more important then Coolant Temp.... Low Coolant temp likely mean low Oil Temp and takes longer to get to normal oil Temp. Oil needs some heat to work right. Low oil temp mean you Can't dry out gas, moisture, etc, fast enough. Gas? All engine has some Blow By. (Why you need a PCV too.)

I use synthetic oil, oil temp (because Corvettes do have a gauge) was usually 175-185* if I remember right. And yes I noted oil warm up was longer than coolant.

[This message has been edited by rogergarrison (edited 11-29-2010).]

Your Fiero does have a TEMP light that will come on when the engine is actually overheating.
The light will come on at 257.
50/50 will boil at 265

You have 8 degrees of 'safety'

quote Originally posted by fiamma: My car's fan never comes on (with ac off) except for extended idling. If it gets to 220 or so, I turn on the ac to keep the temp from going higher. Could put in a fan switch, but just keep an eye on it. The thing I would be concerned about with letting the temp go to 235 is say I lose a hose and don't notice right away. 235 to the red zone isn't much.

To be honest, I never have trust the accuracy of stock auto guages. True some are very close to the temp. sensed by fan switches, thermostats and the like, but there is guage error built in and I suspect it can vary allot. No so sure a basic 3% would apply to all vehicles including our Fiero's.

Great discussion guys. For me though I want to play on the safe side with a 210* switch. Our 87GT is for summer fun rather than a daily driver so I'm not too worried about the fan relay, fan or battery wear. I would rather have things a little cooler while in the "stop and go" of the Woodward Cruise next summer.

By the way, if you haven't done the "Woodward Cruise" through the Detroit burbs you have missed a true experience of everything auto out there and running!!!