1993 Z28 M6

My cooling system has given me problems since I bought the car 5 years ago. I live in AZ which bears part of the responsibility. Most of my problems have revolved around overheating and a sensitive low coolant sensor. I've had issues with faulty thermostats, sensors, antifreeze/water ratios, and fans dying/blowing fuses. All work up until now have been performed by certified mechanics.

More recently, the low coolant sensor has been acting up more than usual. For the first time, it was coming on reliably after 20 minutes or so of driving in 90+ degree weather. When it's colder out, the light doesn't seem to come on so easily or reliably. Regarding heat, while in heavy traffic for 15 minutes or so creeping from light to light, the car would heat up to just above the 3/4 mark and the fan would kick in. Sitting, I'd say it took about 2 minutes between when the fan goes off and when it comes back on. When it's going through this cycle, it seems as though the engine runs rough and doesn't smoothly go from a stop to rolling without some shaking. I used to think this was some sort of a clutch issue, but I just don't know. Cruising at 50+, it seemed to like resting just above the 1/4 mark.

After a successful oil change, working on my girlfriend's car, and doing a lot of research online, I decided to tackle this problem myself over the weekend. The fact that I've discovered several mistakes made by certified mechanics that charge quite a hefty fee also contributed to the decision to do it myself. Note that since I started this process, it's been very cloudy with thunderstorms, so the outside temperature has only been around 50 degrees.

I ordered a Hypertech 160 degree thermostat and a bottle of water wetter. Drained my radiator, opened the bleed screws, removed the reservoir, drained the drivers side of the block. I then ran into a problem. I had to give up on the passenger side of the block due to lack of hand room and a rounding nut/knock sensor. That side wouldn't be drained. I then opened up the thermostat housing and trashed the old 180 degree thermostat. Flushed water through the housing to flush the block as best as I could. I then put the housing back together with the 160 degree thermostat and put the block plug back in place. I flushed water through the radiator until it came out pretty clear. Pulled the plug from the block to drain it again, put the plug back in the engine block and closed the radiator drain. Install the reservoir. I took a gallon of prestone antifreeze and mixed it with the bottle of water wetter and three gallons of distilled water. Filled the radiator until it came out the bleeder screws (I had a towel under them to save the Optispark), closed the bleeder screws and the radiator cap, and filled the reservoir to the full cold mark. Ran the engine, opening the bleeder screws from time to time to get out any extra air.

The first time running on idle, it seemed to take a long time (Maybe 25 minutes) to get up to the 3/4 mark where the fan kicked in and lowered the temperature. It then took about 4 or 5 minutes for it to heat back up to where the fans kicked in again. I let it cycle through this stage about 6 or 7 times and felt satisfied when I saw that the low coolant light wasn't coming on. When I killed the ignition, I was even more satisfied to not hear any boiling noises from the radiator and see that the coolant resevoir level was at a healthy full hot mark.

After driving it around yesterday afternoon and this morning, I've noticed two things. At 50+, it now likes to sit just above the 1/8 mark. Sitting at a few lights without enough speed to blow air and cool it down, it got up to the 1/4 mark. I can't wait to get in heavy traffic and hot weather and see the results!

I do have some questions though. Right now it's fairly close to our winter temperatures, so this is a good test for the low end of the local climate. What temperature is the 1/8 mark? I've read that the gauge isn't incremental, but I can't find any diagrams to go by. Is this too low? If so, what should I bump it up to? After all my research, I'm under the impression that changing to a 160 degree thermostat alone isn't a problem and may help keep the engine running cooler. I've read some posts that say the fan timing should be changed to match, but in reality, how much of an issue is this? I'd rather just get the hypertech chip if the fan really needs to be adjusted. Also, I'm a little pissed that I couldn't get that damned knock sensor removed. I sqeezed the sides to remove the connector, then used a 7/8" socket deep enough to make it to the base. I had to come from the bottom in front of the driveshaft. Any suggestions? Any idea how much coolant remained with just the drivers side plug removed?

Thanks in advance for any thoughts and/or suggestions!

-Lucas

 

I managed to answer my own question about running the 160 degree thermostat without a fan switch/reprogramming. Basically, the thermostat will help and not hurt anything. The thermostat keeps the engine running cooler when the car's moving along with air blowing by. When sitting in traffic, a reprogrammed fan will kick in at a lower temperature, keeping the engine from getting into the higher temperature readings. The only trick here is that in order to lower the fan settings, it's best to also toss in a 160 degree thermostat. Otherwise, the fan will cool it down to the point where the thermostat closes (With a 180). This means that I'll get lower temperatures while moving, but no benefit when sitting in traffic. I'll see how the 25/75 antifreeze/water mixture with Water Wetter helps once I'm stuck in traffic in our desert heat.

-Lucas

 

I recommend the Jet fan switch. You can get it from Summit for about $45. Not expensive and works very well. Along with a 160 degree thermostat it will keep your engine nice and cool.

 

It says that it's for third gen. It should be fine in fourth as well?

 

Apparently Summit doesn't list it anymore. I bought mine from them a couple of years ago. I did find it at Jeg's website, though.
p/n 561-60602, 1993-95 Camaro/Firebird LT1, $49.99