redrockets-10

Hi, new to this forum so i'm not sure if i'm doing this right but anyway.

I've got a 1997 S-10 w/4.3L 220,000 miles, with air conditioning. I'm having problems with the engine coming up to proper temperature. It has been like this for a while, however last week it was really cold here in michigan and the temp gague never even came off the 100 degree mark, even after driving for 20 minutes on the expressway (with the heat off). Now i've replaced the thermostat. I put a 195 degree pressure regulating thermostat in it. I've flushed the cooling system, and I placed pieces of cardboard in front of the radiator (in hopes of limiting the airflow cuz i thought maybe the clutch on the fan might be bad). Now that it's warmed up a little bit (it's about 35 degrees) the engine is running at about 130-150, depending on whether or not my heater is on. I'm positive that the temp readout on the gauge is right because i tested through the radiator hose and still maxed out at 143 degrees. I'm just wondering if anyone else has had this problem or if anyone has any ideas on how to fix this. My fuel economy is really hurting.

OverBoardProject

The first thing to check is your coolant, and make sure that you aren't running pretty much straight anti-freeze. I'm told that that would cause the motor to never warm up properly, although I've never tried it. Just about any garage will either test it for you for free, or loan you their tester... or the testers are only around 5 bux

Also how's your rad cap? if you don't have the pressure there the system will also never warm up properly.
remember this if you have an overheating problem during the summer... just loosen off the rad cap, although it's just a tempuary roadside repair.

There is a small chance that the thermostat is faulty.

Mikado14

Just my two cents. Last year, I had the same problem. Put in a thermostat. Did the cardboard thing. Decided to change out the thermostat again. Got a little warmer but not alot. Finally, out of desperation, I bought a brass, higher quality thermostat and the problem went away. Go figure.

The moral of my tale is that bad thermostats do make it off the assembly line. Two in row? Well, the third time was a charm.

redrockets-10

I mixed the antifreeze myself, and I got about as close to a 50/50 mixture as I could eye-ball. So i'm almost positive that the mixture is right. Now i'm a little shakey on the radiator cap because when this was happening last summer i wasn't getting any pressure buildup in any of my hoses, so i replaced the radiator cap and now the pressure is fine, and this still didn't fix the temperature problem. Now while i was trying to find out what was wrong this summer i did replace the thermostat. This is the second thermostat that i put in. I did buy the higher quality, pressure regulated brass thermostat. I think it was made by prestone.

Now if the problem was the thermostat when i took the old one out, it would have been stuck in the open position, right? Or can it randomly stay open at certain times and not others? I'm not entirely certain on how a thermostat can go bad other than getting stuck open or closed.

Thank you guys for the input. I really appreciate it.

vtmecheng

Usualy the thermostat will be open some when you take it out if that is the problem. BTW, does your thermostat have one of those by-pass holes in it. I had one of those and my truck never warmed up, got one without it and no problems. If your thermostat is really working it will let such a small amount of coolent by your engine will over heat. You might want to check the gauge again, your collent temperature will not be as high as your engine block so it isn't always the best indicator. Good luck.

redrockets-10

Do you remember what brand thermostat it was that didn't have the bypass holes? Or where you got it?

Thanks

vtmecheng

You know, I don't remember which brand ended up working. You may just want to try a few different parts stores and she what can be found. Sorry I can't be of more help.

Mikado14

A bind in the shaft of a thermostat is usually what you will see. When you remove it, it will be partially open. However, I have seen thermostats that will not open at the preset temperature. Usually, the open to late (over rated temp) or too early.

If you have a thermometer that will read that high (boiling) you can put the thermostat in a pan of boiling water and see when it opens. If you don't, then put the thermostat in the pan and it will open ( 195 degree) about when you first notice bubbles forming on the bottom of the pan. Not as accurate but it is a good check.

sector95

Just some thoughts here....

Interesting..... usually with the 4.3 and a/c it's usually keeping the eingine cool that's the problem. Since you've replaced the thermostat (195 deg is the stock spec.) and done basic cooling system maintenance, I would begin to look elsewhere. If you haven't already, replace the radiator cap especially if it's the original; see what happens. Are you losing coolant?

If this doesn't fix the situation, I would begin to consider component failure. You might have a bum tempurature sending unit; with over 200K, anything's possible. This would also possibly explain why your fuel mileage is so lousy; the ECM is getting erroneous coolant tempurature info and running on a cold engine or warm-up fuel schedule (rich mixture).....rich mixtures tend also to cause an engine to operate at a lower operating temp and combined with already low outside air temps... you get a double wammy. On some engine/ECM setups, there are seperate tempurature senders for the dash gauge/light and ECM or it may be one component with seperate outputs for the dash gauge and ECM. You'll have to do a little research; run down to your local Chevy dealer's parts dept and ask them. They should have a blow up of the part in question, a picture of where it is on the engine and be able to print you a copy to take home; you can also find out how much it's gonna lighten your wallet.

How did you test the tempurature at the radiator hose?

How cold was it before it warmed(?) to 35 deg?

Just a long shot here..... but have you been using the defroster a lot during your driving? Running the defroster (or any heater mode with a defrost function) will engage the A/C compressor to dehumidify the air to aid in quickly clearing the windshield. The condensor sits before the heater core in the airbox below the dash; incomig air is initially cooled by the condenser then heated by the heater core...... but I think there is an outside tempurature below which the compressor won't kick in.... oh well, just a thought.

Hope some of this helps....

Mike

BlazerLT

All thermostats will heat up to a certain level, open and the temperature will drop to the normal operating range.

If you system is not even climbing up past 210 and then popping open, your thermostat is bad, replace it with a good one, not cheap junk.

Also, replace your rad cap with a good non Acdelco rad cap rated at 15-16psi.

__________________
1995 Factory Blazer Service Manual for sale, PM if interested.

BlazinUP

whats wrong with acdelco caps?
arent they oem........
im using a stant...but still wonder why

BlazerLT

Because they use a fibrous rubber gasket that doesn't seal properly and hardens.

The stant uses a full rubber gasket that seals much better and lasts so much longer.

__________________
1995 Factory Blazer Service Manual for sale, PM if interested.