Engine Won't Heat Properly

SkyWalker209 · April 16, 2010

I have '94 Full-size Chevy Truck with a 4.3 liter. It doesn't seem to be heating up all the way. About 155 degrees is all it will heat up to. I changed the thermostat and replaced it with a 192 degree stat, thinking it was stuck open. Well that didn't work. I also noticed that the coolant reservoir is basically holding a half gallon of rusty water. It's not the Dex-Cool orange either, looks like rust big time. Should I flush the system or is that not a good thing to do at this point? Or, what should I do to get it running at the proper temperature? Also, I'm in California, it only gets about 30 degrees on the coldest nights and not any higher than 70 during the day.

jblakeney · April 16, 2010

I have '94 Full-size Chevy Truck with a 4.3 liter. It doesn't seem to be heating up all the way. About 155 degrees is all it will heat up to. I changed the thermostat and replaced it with a 192 degree stat, thinking it was stuck open. Well that didn't work. I also noticed that the coolant reservoir is basically holding a half gallon of rusty water. It's not the Dex-Cool orange either, looks like rust big time. Should I flush the system or is that not a good thing to do at this point? Or, what should I do to get it running at the proper temperature? Also, I'm in California, it only gets about 30 degrees on the coldest nights and not any higher than 70 during the day.

Interesting....... Do you have any antifreeze in the system?

If you see rust a flush is in order. Remove thermostat and flush without the thermostat. Re-install and fill system with 50/50 mix of antifreeze and distilled water... Also, test with a scan tool to rule out the gauge (which can be off at times gauge or temp sensor).

Jbo

az'03Silverado · April 16, 2010

+1 on the coolant temp sensor and the flush.

nickvrebel · April 16, 2010

you either have a bad temp sensor / gauge or got a defective thermostat.

Irv · April 16, 2010

Definitely time for a complete flush and also make sure your thermostat is a GM one and not some piece of aftermarket crap!

My bud use to work in a rad shop and they would not warranty any rad/heatercore work unless you were running a OEM thermostat.

KMGZ400 · April 16, 2010

I have '94 Full-size Chevy Truck with a 4.3 liter. It doesn't seem to be heating up all the way. About 155 degrees is all it will heat up to. I changed the thermostat and replaced it with a 192 degree stat, thinking it was stuck open. Well that didn't work. I also noticed that the coolant reservoir is basically holding a half gallon of rusty water. It's not the Dex-Cool orange either, looks like rust big time. Should I flush the system or is that not a good thing to do at this point? Or, what should I do to get it running at the proper temperature? Also, I'm in California, it only gets about 30 degrees on the coldest nights and not any higher than 70 during the day.

Interesting....... Do you have any antifreeze in the system?

If you see rust a flush is in order. Remove thermostat and flush without the thermostat. Re-install and fill system with 50/50 mix of antifreeze and distilled water... Also, test with a scan tool to rule out the gauge (which can be off at times gauge or temp sensor).

Jbo

do you have to use distilled water? i have had to add coolant a few times to my silverado and i didnt use distilled water and i only guessed the 50/50 mixture

Irv · April 16, 2010

do you have to use distilled water? i have had to add coolant a few times to my silverado and i didnt use distilled water and i only guessed the 50/50 mixture

Distilled water is the only way to go unless your in an absolute pickle and need water bad.

Non distilled contains minerals and can block small passages etc over time, some is worse than others depending on where your getting your water from?

I use water out of a dehumidifier but I also know you can buy distilled at grocery stores etc.

It is also very important to make sure you have the proper mixture!!

I run a 60/40 mix of prestone/water but depending on your climate, you may want to change the ratio.

Read the instructions on the bottle and do it correctly, it is much easier, cheaper than replacing a cracked or plugged block.

C. Charles Hahn · April 16, 2010

I just use the Prestone pre-mixed stuff.... works fine.

SkyWalker209 · April 17, 2010

Just flushed the whole thing and filled 50/50. Now it runs colder than it did before. Guess it must be the sensor, which I have no idea where it is. Does anybody know? Remember, it's a 4.3. Might be different than the V8 models, not sure though. Also, the radiator cap looks dirtier than $#!T. If this thing malfunctioned, would it make me run cooler than normal?

az'03Silverado · April 18, 2010

The coolant temp sensor should be up by the thermostat housing on the intake plenum somewhere. I have a book for the 4.3 at home. When I'm off work I'll look it up.

jblakeney · April 19, 2010

I have '94 Full-size Chevy Truck with a 4.3 liter. It doesn't seem to be heating up all the way. About 155 degrees is all it will heat up to. I changed the thermostat and replaced it with a 192 degree stat, thinking it was stuck open. Well that didn't work. I also noticed that the coolant reservoir is basically holding a half gallon of rusty water. It's not the Dex-Cool orange either, looks like rust big time. Should I flush the system or is that not a good thing to do at this point? Or, what should I do to get it running at the proper temperature? Also, I'm in California, it only gets about 30 degrees on the coldest nights and not any higher than 70 during the day.

Interesting....... Do you have any antifreeze in the system?

If you see rust a flush is in order. Remove thermostat and flush without the thermostat. Re-install and fill system with 50/50 mix of antifreeze and distilled water... Also, test with a scan tool to rule out the gauge (which can be off at times gauge or temp sensor).

Jbo

do you have to use distilled water? i have had to add coolant a few times to my silverado and i didnt use distilled water and i only guessed the 50/50 mixture

Water that contains extra minerals will affect the cooling system... Weather it is erosion, corrosion, electrolysis (yes, yes, electrolysis, if it is floating iron and certain other particles it can cause this problem), etc, etc, etc.

Tap water will run warmer than distilled also............. But has an adverse problem in the extreme cold....... Tap water will freeze first.

If you have a problem with the Tap vs distilled water just keep doing it the way you like.... I grin when I sell parts......

Jbo

SCHSIERRA · April 19, 2010

I believe the 4.3 has two sensors. One on or around the thermostat housing that the ECM uses and one on the right side of the block between two spark plugs. The one on the right side of the block is the one that goes to the gauge.

This info is from a 91 4.3 TBI so it may have changed in 94.

SkyWalker209 · April 19, 2010

Just realized something odd. The sensor that is described above, on my truck, only has one wire going to it. It looks like there is supposed to be two. Could this be why I'm getting a false reading? Or is it supposed to have only one wire? Also, when I flushed it, obviously I removed the radiator cap. This thing was filthy and covered in red "gunk." I cleaned it off as best as I could. Does this need to be replaced, could it be a reason I'm getting a false reading?

SCHSIERRA · April 20, 2010

Just realized something odd. The sensor that is described above, on my truck, only has one wire going to it. It looks like there is supposed to be two. Could this be why I'm getting a false reading? Or is it supposed to have only one wire? Also, when I flushed it, obviously I removed the radiator cap. This thing was filthy and covered in red "gunk." I cleaned it off as best as I could. Does this need to be replaced, could it be a reason I'm getting a false reading?

It should only have one wire (Green wire?). The connector looks like it should have two wires but there should only be one.

Crazy Canuck · April 20, 2010

Just realized something odd. The sensor that is described above, on my truck, only has one wire going to it. It looks like there is supposed to be two. Could this be why I'm getting a false reading? Or is it supposed to have only one wire? Also, when I flushed it, obviously I removed the radiator cap. This thing was filthy and covered in red "gunk." I cleaned it off as best as I could. Does this need to be replaced, could it be a reason I'm getting a false reading?

I doubt the cap would cause it to read lower. The caps are designed to pressurize the system to 15 psi (I beleive) for more optimal cooling. If I were you, I would replace it anyway if it is all gummed up as they are pretty cheap.