16Sammy61

My engine ran hot the other day, decided i'd throw i few simple parts to see what would happen. First i removed the hose to check the thermostat.. There wasnt one at all and someone just used some sealent to close it. So i bought a 180* one and installed it. I started it up topped off the coolant and let all the air get out. Once again, after awhile it got hot. The water pump is working as i can see the fluid flowing through the radiator. The passenger side fan comes on when the engine is running, but it never changes as it gets hotter. It never speeds up or the second one doesnt come on. Theres no radiator or hose leaks, but it continues to run hot. Could it be a bad sensor, or should i suspect a blown gasket/cracked head? It wasn't smoking out the back except when i first started it but then stopped once it warmed a little. Not really sure at this point?

Injuneer

For starters, provide info on your car -year, trans type, engine mods as a minimum. For example, the fan operating strategy varies with year. Describe in numbers what you mean by "ran hot" . Are you basing this on the dash gauge? Are you sure the temp sensor for the gauge is accurate?. Did you install the specific t'stat that the LT1 requires? Have you checked the cap pressure, does it hold 18psi?

16Sammy61

Its a 94 z28 auto. Bone stock except a CAI. After sitting for 5-10 minutes it would rise near to 240-250 and i would cut it. Im not entirely sure the gauge works but as i can feel plenty of heat and the hoses are a lot hotter than usual, i feel it would be. It doesn't completely spike out of control, but just continually rises until its too hot. The thermostat fit perfect and was a 180 temp one and was definetly the correct one, as i know more about older SBC, im new to lt1 and found the correct one for it.

shoebox

How many fan relays does it have? One of your fans does not seem to be working.

16Sammy61

Im pretty sure its 2 in the fuse box under the hood, the only one missing is the one that says "ASR/TCS (Same as ABS relay)" and there isnt even prongs for it to hold one so i assume it is unused

16Sammy61

When i start the engine one fan comes on and stays constant the whole time never changing, nor engaging the second one

Injuneer

Have you scanned it for codes? The fan coming on when the engine starts is often caused by the presence of a trouble code. The PCM turns on the fans to protect the engine.

GM was going to introduce TCS in the 1994 model year, but they never got around to it. And even when it was available starting in 95, it was an option.

The "early" 94 has 2 relays and uses them for Fan 1/Fan 2. "Late" 94 has 3 relays and runs the fans Both low speed/Both high speed.

shoebox

Above from the cooling system info on my website.

You may have a trouble code that is causing the fan(s) to immediately come on, but your primary fan is not working.

16Sammy61

Ive read all about that on your website, i love it and it provides a lot of great info. However, the passenger side fan is the one that is on, and i cant quite tell if the drivers side is due to the angle of the radiator, and i dont currently have a jack to get under it. Ive scanned multiple times, yet recieve no codes when i do. My SES lamp comes on if i get it warmed up and continuously give it high rev's over and over it will flash on, but then back off. As i said before, i dont get any codes back at all

16Sammy61

Also, not sure if this changes anything, but i misread my guide and there are 3 fan relays. Theres coolant fan #1, #2, and #3. Injuneer said the late 94's had these, and mine does. So could it be that they aren't kicking to high speed when needed? Would that cause this to overheat?

Injuneer

If you have 3 relays, BOTH fans should run on low speed, then BOTH on high speed. Only one fan running would appear to indicate the other fan has failed. The PCM sets codes for faulty fan circuits. Could be what's turning the SES light on.

How did you scan it for codes? You can't short the ALDL connector to flash the codes. There are some combo OBD-1/OBD-2 scanners that just won't work. There's a link to free OBD-1 scanning/data logging software download on the "Computer Diagnostics...." forum. It was written specifically for the 94/95 F-Body LT1.

16Sammy61

At first, i scanned through the ALDL with a code reader and didn't get anything back. It said that when it is plugged in it activates the radiator fans(this is how i was sure that they at LEAST worked) and it will put out codes, but never did. Tomorrow im going to get under it and see if both fans operate, if they do then i will be able to tell whether or not they turn on high. I'm pretty sure they don't, i figure i could hear a noticeable change when the fans kick on high, and have yet to see a change.

shoebox

When you short the ALDL (as said, not for retrieving codes) it will make both fans run on high. They will run on low at the low temperature threshold or when the a/c is operated (all this in the information you said you already read on my website).

16Sammy61

Im aware of this, but i'm not sure about the fans on high. They seem to be on low all the time, which could be my overheating reason. Even when i short it, they barely seem to be on.

Injuneer

You've got to get your facts straight... first post you said:

Latest post you said:

Hard to help when the info contradicts itself. HOW MANY FANS ARE WORKING?

BOTH fans should come on low at 226*F, or when the AC is on. BOTH fans should shift to high at 235*F.

It would appear that the "code scanner" was the $30 Actron that simply shorts the pins. IT WILL NOT WORK ON 94 OR NEWER.