I've got a 1994 Camaro Z-28. I'll try to go through everything as best as I can remember. (I'm going to apologize now, but this is a long story.)

In late 2009, my waterpump seal started leaking. Unfortunately, by the time I noticed the leak, the Optispark was already damaged. So, I went ahead and put on a new Optispark, new water pump, new spark plugs, oil and filter change, obviously changed coolant, new thermostat, etc. I also purchased a Delteq system used off eBay and put that on. After putting everything back together in late 2009 or early 2010, I ran it and it seemed to be running fine. Shut off the engine and look under the car and find a puddle of oil. So I take everything back apart... I found the oil leak at the timing cover seal for the water pump. At that point I remembered the water pump being exceptionally hard to get on. I know I had the splines matched up on the water pump driveshaft, but I still had to muscle on the waterpump (had to use a crowbar to push one side of the pump out to get it over the lineup pegs). Because the water pump shaft wasn't lined up properly, the timing cover seal was ruined. So, I figured defective cast on the pump housing. At that point I was so irritated, I left it sit. For a long time.

Early this year, I decided that I needed to get this thing going again. I got the water pump exchanged for a new one. I replaced the timing cover seals. The new pump went on smoothly, as it should. No crow bar needed. Got everything going, got it inspected and it passed (after replacing the brake master cylinder). On the way home from the inspection, it starts hesitating. I figured it was bad fuel. Drained the fuel tank as best as I could with a siphon pump. Went and got new fuel. Same problem. The car runs fine until it warms up. Then once it warms up (5-10 minutes), it runs like crap. Like one of the coils is dying. So, I decided to convert back to the old optispark system, to eliminate the Delteq completely from the equation. Ran new spark plug wires, installed old coil. Started it up, and it ran fine. No more stumbling, no more hesitation after it warms up.

Now to my current problem. I noticed that the coolant system was VERY dirty. So, I drained all the coolant. Put in water, ran the car for 10 minutes, bled the system. Then I drained the system. I then put in two containers of radiator system flush (Prestone Super Radiator Cleaner) and filled the rest with water. The bottle says to run it for 3-6 hours (not continuously, but total over however many trips). I ran the car, bled the system. Decided to install a new radiator cap (Stant), as I still have the original cap on the car. I bled the system and ran the car today. The coolant temp level seemed fine this morning on the drive to work (15 minutes). After work I went to an appointment (15 minutes away, but some highway driving). I noticed when I got to my appointment that my coolant temperature was very high, almost to the red. I shut it off and figured I would bleed the system again after my appointment. I came out, started the car, bled the system. There was a little air in it yet. So I figured that was the problem. On the way home, I was driving and the temperature would go up and down, up and down. I didn't really correlate the rising temperature to any specific driving condition. When I got home, I did some research. I saw that a lot of people were having a problem with their radiator cap causing high coolant temperature. I still had my old cap, so I put that on and went for a drive. The drive was around town for the first 5 minutes, then I was on the highway for about 20 minutes. The temperature was within normal range. Once I got off the highway and sat at the stop light, my coolant temperature skyrocketed. It went almost all the way up the red. It doesn't ever seem to go up high enough to trigger the check gauges light. Once I started moving again, the temperature went back down, not quite to normal level but close (a little above mid range on the gauge). I noticed this whenever I would go slow or come to a stop. It would only take literally 15 seconds to go from mid range on the gauge to almost red. When I stop the car, I can hear the coolant boiling in the engine (most notably on the driver's side of the engine, towards the front).

So... I'm at somewhat of a loss here. I haven't scanned codes yet, but I will probably do that next to see if there is anything there. Is it possibly because the system is mostly water (and whatever is in that cleaner) that is causing this? I know that the ethylene glycol helps increase the boiling point of the water/fluid in the cooling system. I suppose the next step would be to remove all the water/cleaner and try putting the 50/50 mix in and see what that does...

I've also noticed that my A/C no longer works. The compressor doesn't cycle on. I'm guessing that is another, unrelated issue.

Any other ideas?

Thanks in advance!

 

When at idle and the temps get high, do the fans turn on? Also, does the coolant (water) reach the boiling point? It should just past the gauge's mid way point with 100 percent water if the gauge reading is accurate.

Are you able to read the coolant temps at the PCM using a scanner or data logger? You need to determine if it's really getting that hot, or ther gauge is lying.

 

Sorry, in my verbose reply I forgot to mention that at least one of the fans is coming on properly. I can hear it running. I haven't visually been able to make sure that both fans are on, but at least one is on.

Yes, the water is boiling. I can hear it when I turn the car off. When I turn the car off, the temperature gauge is almost to the yellow/red.

I haven't been able to put a scanner on it yet. I do have an ALDL serial cable that I can hook up (which hopefully still works, I haven't used it in years). Are there any free or cheap OBDI data loggers? I see that RT Tuner and DataMaster are both $100+... I suppose I can pick up an evaluation copy of DataMaster just to get my by this time.

Thanks!

 

Have the fans turn on/off tempertures been changed in the PCM tune? If not, the stock Fan 1 turn on temp is 108C (226F), Fan 2 is 113C (285F). And high enough that the 100% water may already be at the boiling point with the standard 18lb cap. So it sounds like the temp gauge is giving accuarte results.

I suggest you drain the water and refill with 50/50 coolant. Since your cooling system is pretty clean, if repairs are need after the 50/50 refill, you can recover and reuse it.

 

Depends whether his 94 is an "early" model year producton or "late" model year. Early has a 2 relay system thar operates as Fan 1 / Fan 2. Late has a 3 relay system that operates as Both low speed / Both high speed. Initial operation is at 226*F as noted above, secondary action at 235*F.

 

Free scan software:

FreeScan

TTS Power Systems

 

Oops - sorry for the typeo on my last post for Fan 2. 113C is 235F as Fred noted.

 

Could the WP DS have gotten damaged when you had to pry the old one off with a pry bar? Mine got damaged when I took it off or put it on and I was having similar issues with my Z. Turned out the WP DS had actually snapped right off and the WP wasn't circulating coolant