Not sure about the different part numbers but I do know there were several different casting numbers over the years.

 

Coolant pushing into overflow. ... cheap thing to try first is rad cap.... not an lt1 but i had this happen to me

 

Brand new rad cap.. its a head gasket .. the harder i drive it the more water it pushes out.. I want to buy higher flow heads and a mild cam for it.. Suggestions??

 

Lloyd Elliot port works has head & cam packages designed to work together

 

I'm experiencing kind of the same situation. I fixed my SES light by changing out the MAP sensor, this stopped the fans from coming on (they do that when there are active codes). I actually don't recall seeing the temp gauge get above middle mark the few times I've driven it in the last few years. Anyway, I'm test driving and the temp gauge goes high (above middle) after the MAP replacement, and I smell some coolant. I get it home, open the hood and see the rad cap is hissing. The next day, I swapped out the rad cap, went to check the coolant reservoir and it was way full - overfull. Like coolant went into the overflow and didn't get sucked back in when it cooled down. I guess it wouldn't if there was a suction leak from like a bad rad cap. I started it up, added some coolant to the radiator, capped it with a new radiator cap and burped it at the bleeder till steady stream was flowing. Plugged in my scanner and waited for the coolant temp it to get to 226, bingo, the first fan came on. That's good news. I also noticed that the new radiator cap was NOT hissing and spitting, but after I shut it down I noticed some coolant on the ground in front of the passenger side tire, and the cover above that spot under the car was full with a couple of cups worth of coolant. So what happened: 1) the coolant I added on day 2 maybe overflowed from the radiator. I added it cold engine off or 2) maybe most of that coolant was from the previous day test drive when the thermostat opened and it overflowed and didn't return when it cooled because of the old rad cap leak or maybe 3) the hose to the overflow has a small leak and loses suction and can't suck it back up as it cools. Action plan: Remove the battery and reservoir - inspect the reservoir for any leaks/cracks etc and clean it up or replace it if needed. Inspect the feed line to the res for any cracks or leaks or lose clamps etc. Try to clean up any coolant down by the passenger wheel coolant catcher if I can get to it. I might have to jack the car up to take that apart and clean that out. Reattach all that if it looks good and refill to cold fill line. Take her for a test drive and see if it overflows again. The only place I saw any coolant where it should not be was on the ground under the overflow reservoir. The thermostat is opening. The cap is not spitting, and the line is bled. I even ran the def/heater on day 2 to get flow in the heater core. If its a head gasket it may be the end of its long career. I will post updates. Well, at least the MAP is fixed and the codes resolved. I think my coolant res cap is no longer functioning, now that I think about it. It doesn't really close tight, like a stripped screw that wont go in all the way.

 

A leak in the pipe under the battery is a common issue. Also, the remote reservoir is not a sealed unit or under pressure, so tightness of the cap is not an issue.

 

Thanks Rob. I'm gonna check that part of the system before I swap out the t-stat. Maybe it was just the old rad cap. My hoses are correct and not swapped. Now that the fans don't come on when I start the car, because I resolved the codes, I'm seeing fallout perhaps from some design issues, based on stuff I've read, and experienced in real-life. I don't want the MAP codes to return, but if it makes the car run cooler, then maybe I do. Most seem to think 226 is too hot for the fans to start, and I kind of agree. I'm wondering if I could jumper the fan relays with a paperclip so that they come on when I start the car, or do I need a command from the PCM for those to start? Fans start when I jump A&B at the DLC on mine, but I've only done that with KOEO guessing I don't want to start the engine with those jumped. I see a plug and play fan control mod for about $65 for manual turn on of the fans. Any thoughts on those?

Thanks for you input and expertise.

Dylan

 

Fan reprogramming is what I consider the best way to control temps. A 160° thermostat would also help, just on its own.

 

I got the reserve tank out of there, it and the coolant are really pretty clean. Hose looks original and I did not detect any leaks or clogs in it with a water rinse and a lung blow. Gonna change it anyway now that its out. There was no clamp on it at the radiator, I'm gonna clamp it on the new one. Do they make a 160 long therm (not sbc) for the LT1? Recommendation on how or who can tune the PCM to 160 for the fans are appreciated. I get jittery thinking about DIY on the PCM module. Custom shop? Your thoughts.

ps found the alt temp t-stat so that's a for certain. Blew air through the hose/pipe under water and got bubbles at the bend. Could be an issue on reclaim. lol

 

Decided to go with the Fan Control Module F Body 1993-2002 from Caspers Electronics. Plug and play without shipping off a 30 year old PCM in the mail or trying to find someone with the old equipment for the reprogram. I know I could cut / splice wires for less, but 85% chance I'd mess it up. I know myself well enough to know me. Thanks!