Alex Barnes

I posted this on a Facebook group yesterday but I need to get some more suggestions as to what may be wrong. Here is the original post:

Ok, after replacing the 6000 mile old water pump in my 96 LT1 Camaro with a new one, I'm still faced with the ever-present overheating problem that occurs after about 20 mins of driving. What happens is that when the car gets to the 20(ish) minute mark, the [aftermarket] gauge hits 210, and continues until I rev up the engine, at which point the temp begins to rapidly drop to about 190. When I let off the gas, the temp begins to rise again.

I thought this was the result of a bad water pump, but apparently not. I have also flushed the cooling system and added new coolant, going through the proper procedure of venting out the excess air from the system.

Today, after installing the new pump, the car did this again. I took it home and loosened the vent screw on the heater hose, and let out a LOT of hot air from the system. What on earth could cause this? I don't have oil in my water or vice-versa. The only two things I could think of this that one of the heads has a crack in it or a bad gasket that's letting exhaust gases through or that one of my hoses has a very small leak that's letting air in but not water.

As of yesterday I've replaced the radiator cap and gotten ALL of the air out of the system. I test drove it after I put the new cap on and completely burped the system at 180 degrees and it still did this. I have also taken a video of the problem, which is currently uploading to Youtube. There is no smoke coming from the exhaust. I also believe the water is flowing well as the radiator and hoses are correctly hot and pressurized. My airdam is intact and both fans are wired to come on at full blast on ignition.

I have a feeling it's my heads but I'd hate to throw any more parts at it. Any help is appreciated.

Update: Here's the Youtube video

Injuneer

If you feel exhaust gasses are getting into the coolant, check using a hydrocarbon test kit for the coolant.

The engine is designed to operate at 210*F, which is the midpoint of the gauge. It's not clear what you mean when you say "gauge hits 210, and continues".... do you mean the temp continues to climb? If so, how high? The fans don't come on at low speed until 226*F, and do not increase to high speed until 235*F. How does the reading of the aftermarket gauge compare to the stock gauge?

Are you using the stock t'stat (180*F) with stock PCM programming for fan on/off temps? Are you saying it takes 20 minutes before the coolant even reaches 210*F?

Is this the coolant bleed procedure you are using?

4th Gen LT1 F-body Tech Articles

Alex Barnes

Sorry about the clarity. The needle will continue to go up to 280. When this started, the stock gauge behaved the same way, so I installed the aftermarket gauge. If I leave the car at idle when it begins to act like this, it will peg the gauge (I've only done it once)

I'm using a stock 180 thermostat that's LT1 specific. The PO wired the fans to the ECM power feed so they're always running at full blast (my next item to fix on the list).

Something I should've mentioned in the first post is that I can idle the car for hours and it'll never go above 180 but about 5 mins after I begin driving it is when it will begin to overheat.

And yes, I used Shoebox's guide for bleeding the lines.

Injuneer

Is the plastic air dam still in place under the front bumper?

Alex Barnes

It is. It has some scrapes on the bottom but it's in pretty decent shape.

John95z28

This looks like typical thermostat sticking. I realize you may not want to think this, but I had the same exact problem. I was sure that the thermostat was new, but I ended up being wrong, for some reason the new one got hot once before bleeding and damaged the diaphragm. Exact symptoms you have. I had to drive it in a lower gear to keep the RMP up, just to get it home. Quick check will verify this. Otherwise it will get hot and leak fluid out around the overflow bottle, causing recurring air bubbles as you have. You need to bleed again and again... Otherwise a leak is causing the bubbles(air pockets)

PS, Don't be shy to jack up the passenger front side of the vehicle while bleeding. Works quicker as I found out afterwards.

GaryDoug

Because you mentioned the PO's fan modification, I suggest you check for proper airflow direction (front to rear). Reversed wiring could cause them to run reversed. Another long shot...

Alex Barnes

I'll definitely be trying a new thermostat after reading your post. I've had to do the exact same thing to keep the car from really overheating (to the point where I'd need new heads).

The fans blow in the correct direction, they just have stupid wiring lol

Alex Barnes

Well, it was the thermostat. What's weird is that I tested the old one and it seemed to work...

By the way, are you guys able to idle with the AC on in the summer without cooling issues? I can pull it off until the temps get to 105ish and then I have to be moving to get enough air to go over the rad. Either way, it sucks living in the desert.

Injuneer

Do you still have the botched fan wiring in place?

Have you verified that "they're always running at full blast " means they are both running at high speed, and not at low speed?

And I know you responded to Gary that the fans were turning in the correct direction, so hopefully you are positive this is the case.

Have you checked the front of the radiator for debris?

Alex Barnes

The current wiring job is still in place. I'm going to figure out how to get the fans hooked back into the proper place tomorrow morning.

It seems like they would be running at high speed but after looking in a few different threads it seems that it's common for people's cars to be cooled down by running the AC and the fans running full blast. Is there any way to tell how much voltage they're getting while running? I know there's a 6v and a 12v setting (or at least I think lol) but I'm not sure how to monitor their power feed.

The polarity is the one thing I'm certain of though, as it pulls air in from the front and sends it toward the back.

I cleaned the radiator well when I did the water pump so I'm certain it's dissipating heat well.

Injuneer

Follow Shoebox's fan wiring diagram (Late Production). Your 96 should be the same as the 95 diagram:

http://shbox.com/1/1995_pcm6.jpg

Alex Barnes

Ugh. I have no idea what's going on with this wiring. The wires to the PCM are intact. They aren't severed down the line. They connect to the fans. What has me stumped is that in the series wires running between the two fans, there is a dark blue wire that ran into the PCM's fuse (this is where the fans got power). Where is it supposed to be hooked up to?

On a similar note, I ask this: Why do people have to screw with perfectly good setups?

Injuneer

Shoebox also has a diagram for adding a manual switch in parallel with the stock PCM wiring. Perhaps this is what someone did????

http://shbox.com/1/fan_sw_diagram2.jpg

Often, when people can't solve a problem the right way, they ghetto-rig something as a band-aid to minimize the problem. I'll never understand how anyone could use that approach on a vehicle they have any pride in.

Alex Barnes

I seemed to have further opened Pandora's Box. I don't know how I didn't notice it but, only the passenger side fan works...

I have a feeling that I should open a new thread in a more appropriate section. My initial question was answered.