Mom drives a 1997 Saturn SL1.
Last winter it had great heat. Once Warned up, temp guage was solid at 1/2.
Over the summer, the radiator died. Replaced with brand new. I also replaced the thermostat with a standard replacement.
Now, the temp guage only barely gets to 3/8, and it isn't hot enough to make good heat here in MN.

Help Please?

Could be that either the replacement t-stat is bad, or is the wrong temperature range for the car (ie - not the 'correct' replacement). Does it not heat up much, no matter how long you have been driving? Have you tried blocking off the radiator to see if that makes a difference?

Check the coolant level. Coolant could be low and not able to circulate through the heater core. Also I think if the T stat fails it fails in the open position. This would prevent the engine from warming properly.

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Could be that either the replacement t-stat is bad, or is the wrong temperature range for the car (ie - not the 'correct' replacement). Does it not heat up much, no matter how long you have been driving? Have you tried blocking off the radiator to see if that makes a difference?
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The max the temp gets to is 3/8, no matter how long it is driven. I have not tried blocking off the radiator.

After putting in the new radiator, and it only got to 3/8, I assumed that the thermostat was stuck open. So I replaced the thermostat. It made no difference. So, if the thermostat is bad, the old one and the new one were both bad.

Could the new radiator be that much more efficient?
Is it possigle that there is an air bubble in the system?
Could the wrong mixture of antifreeze and water cause this?

Thanks

FWIW...I used to work in a rad shop, where I learned that 3 in 10 thermoststs are not accurate (defective) from the manufacturer....

Again, I would reccomend you look at the temperature range of the replacement thermostst....it's easy to get the wrong one.

A 1997 saturn is 10+ years old....have you ever flushed the cooling system? much of that crap could be blocking your heater core....it's also possible th heater core is plugged (just as your old radiator probably was)

The wrong antifreeze/water ratio will NOT cause a lack of heat....if the mixture is too weak (or old) the coolant freezes and your block/head/head gasket cracks. Well, maybe if you left the car for a week in sub zero temperatures and everything froze solid (not likely) you could have frozen the system....if you did, it will start leaking as soon as the car engine warms up. FWIW the coolant also boils at a higher temperature than pure water in the summer...both get screwed up with the wrong ratio.

Air could be trapped in the system especially if the thermostat is defective. Upon installation the vehicle must be run until the t-stat opens and the system "burps". if this was not allowed to happen and the cap was just put on when the system was filled you could be in trouble.

When the car is cold take off the rad cap...check the level. it will be low as the coolant has not expanded. start the car...wait for the car to warm up. The coolant should be HOT...steaming hot. Fill the system to "full level" and wait to see if the system "burps". If you are satisfied the t-stat is open (and working) close the cap and look for temperature anomolies at lines, and valves.

The new (stock replacement) radiator is not more effective...it just restores the system to factory levels.

I am not familiar with Saturns, but see if you can get access to the heater hose supply and return lines...feel them to see if they are both hot/warm ....if one side cool....you probably have a blocked heater core...if both cool ...a defective t-stat or bypass valve (if so equipped).

Personally, I'd put it outside and warm it up with a match and a small pile of paper/dirty rags underneath the car....and let insurance do the rest. (just kidding!!! don't actually do that)

Good luck

I just helped a friend do a coolant system flush and t-stat replacement on his wife's mid-90s saturn 4dr (don't know model number). If your coolant system is the same, the coolant tank is the 'highest' point in the system, so any bubbles would naturally circulate out (we didn't have to bleed his system, and with the cold weather here she reports everything warms up fine on her short commute). The t-stat was a beeotch to remove and replace...

Did you refill the coolant system with the GM specified fluid? That _might_ make a difference, but it still seems like you are dealing with a bad/wrong t-stat. Try blocking off the radiator with something to see if that makes any difference before you spend any more $$ on parts.

The mixture could cause that much of a difference becasue it's not that much of a difference.

Isn't the temp guage reading the block temp?

If your heat inside the car is not blowing enough hot to keep the inside of the car toasty then I'd assume:
You are not getting coolant in the block and head to flow through the heater core.
and
You are probably OK in the winter becasue it's cold enough to keep your car from overheating.
and
If not fixed you will probably have issues in the summer.
and
IM experience if you have air in your cooling system your car get's hotter but that was on a car with the temp sending unit in the head.

Check the coolant level when the car is cold. If there's not enough fluid in there it will be obvious.

Remember coolant keeps the fluid in your system from freezing when the car is not being used in the winter. It's the water that actually cools the engine down. So a previous mixture that had too much coolant in it could have made the temperature guage register 1/8 higher. This might happen when you have a bad radiator and you keep adding coolant becasue it's leaking out.

Although it's unlikely you have a bad t-stat, if none of the other easy remedies check out, it might be the case. Also to throw something else into the mix, the climate control switch may not be redirecting air to flow through the heater core any more. Check that out. It's easier than a t-stat.

If you bought it from a FLAPS, it was probably made in an Ornamental Country and their QC sucks to put it mildly.