Hello. My first post. To explain, I recently purchased a 1994 25th anniversary Trans Am. It has 70K on the clock. It has some problems and I'm trying to work them out. Mechanically, I'm fairly adept since I've restored some 2nd generation Trans Ams and have owned a few Fieros in my day. I'm in uncharted waters with this LT1 however and I need your help please.

The problem is that the car runs very well as long as your cruising. But if you're at stop light for very long the temperature shoots up quickly.

What I've done so far:
I brought the car up to temp and opened both bleeder screws and verified a steady stream of coolant from both. Verified coolant levels in the radiator and in the overflow tank.
Removed the air intake box and verified that the coolant temperature sensor is installed in the water pump.
Verified that the temperature sensor for the gauge is plugged into the passenger head (and must be working since the gauge works).

What I've been told and know as fact:
I was told by the previous owner that they had recently replaced the water pump and the opti.
I know as a fact that the fans are all running as soon as you fire it up.

Today I data logged it using the Scan94/95 software with my ALDL cable. Here's where it gets weird. The real time display showed the coolant temperature at roughly 75 degrees, comparable to the outside air temp. I let it run for a minute or so while I checked for codes, electrical faults. I saved the data log. I shut it all down before it even came up to operating temp since I was mostly looking for codes even though there was no CEL. I did notice while it was running that both fan relays showed to be active and I could hear the fans running.

Then I came inside and played the data log back. When I did, from cold start, it showed the coolant temperature at 169 F. and went up from there. So I guess that explains why the fans are on.

So what the heck is going on here? Has someone screwed with the program to keep the fans on always? And why? To disguise or delay the overheating? And since the fans are running all the time this has nothing to do with the root problem of overheating, does it?

Thanks in advance for all responses. Much appreciated.

 

I have my fans wired to run all the time.

 

How hot does it ultimately get? That 169 degree temperature is not bad and the LS in my El Camino and Camaro lurk around 210-220 with no harm done. My fans come on separately - pass side first at around 195 and drivers side at around 205. Pass side comes on immediately if the AC is on. I would think yours should also not run all the time.

Can you see or otherwise detect coolant flow in the radiator?

Does the engine smell or feel hot? Do you have access to an infrared temperature gun?

As the temperature increases, do the fans continue to run?

Rick

 

I honestly don't know how hot it really gets. This happened while my wife was waiting on me to get the dog in the house (garage is his dog house) but when she pulled it in and said it was pegging the gauge I had her shut it down. I could hear gurgling in the cooling system when I popped the hood. I ran it up to temperature again the other night while cracking open the bleeder screws and getting that stream from both but shut it down quickly after it started shooting up. I don't need a warped head. LOL.

I hope to get it into my steep driveway this weekend and go through the burping steps. I will say the heater did blow hot when I was doing that second session to get it hot.

I do have a gun and intend to use it. Probably try the radiator hoses and passenger head when I do the burping thing this weekend. Does that sound logical?

From what I can tell the fans never shut down. I'm wondering if the previous owner has screwed with the ECM in order to mask the problem?

 

So called new water pumps and thermostats have failed quickly and hopefully this will be an easy and inexpensive repair for you.

Rick

 

I've also wondered if the splines on the shaft that goes into the water pump are worn off. I guess testing that can be verified when I try to burp it. No flow, we have a pump problem. I think I'll pull out the thermostat before I do it. I want to test in using the old pot of boiling water thing.

 

Okk ,, silly suggestion but it only takes a second. Check the rotation direction of the fans, I've seen where someone working on the system reversed the wires and they ran backwards, Fine at speed but at lower speeds you overheat.. I've also seethe wrong fan motor installed and it was reverse rotation for a different application..

 

There are no silly suggestions. Working on mechanical stuff means you investigate every option until you fix it. Anyone know what the proper rotation is?

 

Depends on the fan blades, I just put a piece of paper in front of the radiator and make sure its sucking it into the engine compartment not pushing it out the front.

 

To kill 2 birds with 1 stone on the rotation and if the pumps working, while it’s running stick your hand down between the fan and motor (watch your fingers) and feel if it’s blowing hot air at you. My EWP died and that’s how I quickly figured it out, my gauge was at 200 but I put my hand behind the fans and it was blowing ambient air, so no water moving.

 

It's raining today and I want to get the car out on my steep driveway before doing the cooling system purge work so it may be tomorrow before I report back with anything.

I do believe my fans are working. I can hear them and did stick my hand down there and felt air moving. Also the data log shows the relays kicking in and out. I watched it with an eye toward more of the relays kicking in and out. It spiked up to about 230, both fans kicked in and it dropped to 198. It stayed there. Then it went to 215 with the fans only running intermittently. This is at idle in my garage. This sounds fairly normal.

So until I can get it out and let it really run a while and double check it with the infrared gun I'm not 100% convinced it's really getting hot.

I'm still not sure why Scan9495 is showing the cold car with a temperature of 169 degrees however. That's frying my noodle. Anyone else use this application?

This may turn out to be the sending unit in the head. More to follow.

 

How do you remove the plastic cover in front of the AC condenser? I want to wash it out.

 

Honestly, I want a ever convinced that it was getting hot to begin with, especially from some of your posts. What you've got going on in your last post sounds reasonable. I personally like my car to run a little cooler but with your thermostat not being a 160 and the fact that the car is sitting still sounds about par.

 

Today’s adventure:


Backed the car out into the driveway. I have a steep driveway so that got the nose pointing up.


I had pulled some of the plastic out of the way to expose the AC condenser and the radiator last night. When I did I found what looked like corn leaves stuck in there. Not enough to cause overheating but it made me think it wouldn’t hurt to take a water hose and wash out the fins on both so I did. I did manage to wash some crap out of there.


With the radiator cap off I let it idle to come up to temp. The gauge in the car was showing 210 before the thermostat ever opened. My computer showed 180. FYI, the fans come on almost immediately when you start the car. This leads me to believe someone has messed with the programing or wired them direct. I suspect programming since I could see in yesterday’s data log where they kicked in and out a few times. But I digress.


With the cap off it pulsed up and down a couple of time and some air came out before it dropped down and settled. I topped off the radiator with fresh 50/50 mix and put the cap back on. Both bleed screws gave me a steady stream. A few minutes later Tammy (my able assistant and wife) was reporting it was going into the red on the gauges. My infrared gun wasn’t showing anything alarming under the hood and it didn’t really seem to be hot. I checked the computer and it was showing 215. I had her shut it down but due to a malfunction behind the keyboard (me) I didn’t get that data log saved.



I let it cool back down below 180, fired it back up and in short order it was climbing into the red again and giving the “check gauges” warning. I did save this data log and it never got over 211 degrees at idle.


I think I’ll replace that sensor that feeds that gauge as a first step.

 

Just to confirm, the AC Delco part number I'm looking for is 213-77, correct?

 

That’s right according to Shbox

 

Much appreciated.

 

Some times you have to back up and call yourself a dumbass.


Remember how I kept talking about the data logging software showing the starting temp at 169 and the fans being on all the time? Well this IT guy missed a bitch screen on the installation of the software that said if you didn’t extract all these files the program would behave badly. I found that when I decided to reinstall it today.



So tonight I hooked it back up. No fans until I manually told them to come on. Temperature of the coolant was about the same as ambient. Everything looks normal.


Hey, what does an AIR pump do?

 

Glad it worked out!

 

We're not fixed yet, but this all points to a bad gauge sensor. I'll replace it tomorrow night and see what I get.