Engine too cold, changed T-stat, now too HOT

[Matt J]

Awesome!

Use whatever thermostat is called for in the car, assuming everything else is stock. A lower temp thermostat won't necessarily run the engine cooler once it gets hot (once mine got to 195 and opened, it pretty much stayed between 195-205 the whole time so the tstat just stayed open). If the air outside is cold enough, it's possible that a lower tstat will keep the engine a bit cooler than the engine is designed to run, but in reality it just means it opens sooner, which will make it harder for the engine to get up to it's correct operating temp when starting cold. That can mess a bit with your cold idle and mixture. Remember, this is old school computer control, it uses things like the engine temp to determine when to turn things on and off, so if it thinks the engine is too cold , it adjusts things to make it get up to its correct operating temp. It's smart for 1986...works pretty well, but well, 1986. Think of Space Invaders and Frogger being the best games of that time...

Also, while overheating an engine is very bad, engines like running as hot as they safely can. Hot is good, as long as it's not overheating!

Look for a thermostat that has a little hole at the top to allow the air bubbles to bleed past it, if you do end up with air sucked into the system in the future, that bleed hole will allow the air bubble to move past the thermostat and get the hot coolant up against it to allow it to open. The air gets pushed back into the radiator, and the high point there is the cap. When the pressure builds, it pushes the air out into the overflow tank first, then it sucks coolant in when it cools off. Helps keep the air out of the block, and you can tell by looking at the "cold" level in the tank if you're losing coolant. That and the puddle under the car. Most good thermostats will have that bleed hole.

I'm glad you're getting it figured out!

[mdula]

If the core is not hot, that doesn't mean it's bad. It shouldn't get hot to the touch. Sounds fine to me. You also said that it was an 86 FI car. Do you know if it has a chip plugged into the back end of the computer?, You can only run a 160 stat with a chip. The stock program will not run right with a stat that cool.

You know, good point. I havent even looked at this thing for a chip yet. I'll check tonight,

-Mike

[mdula]

Good deal. When you pulled the old one out did you notice if it was backwards or not.

Yeah I did, it was never backwards.

[81coupe]

Yeah I did, it was never backwards.

Good Deal then.

[81coupe]

Yeah I did, it was never backwards.

Good Deal then.

[greenphantom85]

I had a buddy with same problem that was a huge car guy. Just put thermostat in backwards 3 times. Not saying that's the problem but have seen it happen.


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[erratic50]

From experience - EFI cars get terrible gas mileage with anything colder than a 195 degree thermostat and send you to tuning jail if you go hotter.

My experience while running 14 degrees of base advance and premium fuel looked like this:
160 = 16 mpg highway, 10 city
180 = 17 mpg highway, 12 city
195 = 22-23 mpg, 18 city

All with 235/60/R15's so my speedometer read low slightly. The car had 2.73:1 rear gears, 3.35:1 low and 0.68:1 OD T5 gear set. City mileage was achieved with never more than 2500 RPM and 1/3 throttle off the line in low. I'd run 2nd up to speed then get to 4th for 35+ or 5th at 45+. Hitting green lights was a key part of why the strategy worked. I would often shut it off at the light if I was on a hill that permitted roll starling it. I'd use 2nd gear for that.

It was more powerful with the 160 but it was fat all the time. Hopelessly even. Doesn't take long for a 195 to pay for other speed parts.

I went to a 3 row radiator and up to a one off 210 that NAPA could special order at one time. Was fine even in Texas and Oklahoma and southern Kansas summer with the AC blasting but it didn't really yield any MPG improvements and the car pinged at times so I switched back to a 195. That's all I will run now.

Ive also had problems with fail-safe thermostats but I have also had one fail safe when a fan clutch failed - it may have very well saved the engine.

Backwards install is a common problem but air pockets are a lot more common. You can't be afraid to rev it up with the clutch in while going around a few corners after it's been tore apart. Overflow tank is absolutely critical too.

my dad would loosen the temp sending unit in the manifold and have someone squeeze the bottom hose to help let air escape. It's one of the highest points in the system so it works a treat. It sucks coolant in to replace the air then.

The other thing is adding a back flush fitting on the heater core lines. Then you can open the top one just slightly and bleed the air off.

I run mine hard enough that I blow heater cores about every 4-5 years. I bought a flow restrictor from LMR and I run underdrive pulleys now but it was too late for my last core so it's bypassed now. If I blow another one I swear I'm going to the nearest truck stop and buying the biggest 12 volt direct to battery cab heater they have and eliminating the heater core.