VegasJen

[EDIT] Most recent update at post #71.

Hey guys. Need some advice. I noticed a couple weeks ago that in stop and go traffic the temp is getting a lot hotter than I like, running around 225-230 at lights. I don't ever remember this car running that warm before. So today I got into the car to see if I could figure out what was going on. I've confirmed the fan fuses are all good and I swapped out the cooling fan relays as listed in the fuse cover. I also putt 12v directly to each fan to confirm that both fans do, in fact, work. I'm topped off with coolant and have a new T-stat in the car, but even so, I only have the one fan kick on at around 225 (give or take) and kick off at 215. The other fan (bottom, in front of the TCS module) never kicks on. Am I missing something here?

BigGun

You're missing a wiring diagram. Both those fans should be running or off at the same time. The high temp is controlled by the voltage going to the fans. They do not operate independently. There are several relays involved and since you stated both work when 12v are applied I would look at the relays again.

VegasJen

Really? Hmmm. So 225 is when they're supposed to turn on? I don't care for that at all. I know pressurized systems can run hotter than non-pressurized systems, but still I start to get very uncomfortable seeing any temp over 210.

I've swapped out relays several times and it doesn't seem to matter. That fan just does not come on. I thought they were staggered anyway, like one comes on at 215 and the other comes on at 225. Not so?

I hate overheating problems. Just damn!

Smoken1

Factory temp settings are low speed on at 226 degrees and off at 219 degrees. High speed on at 235 degrees and revert to low speed at 226 degrees. Both fans run at low speed and high speed and fans are commanded off by the PCM when the vehicle speed exceeds 35mph.

You can force low speed operation at 185 degrees by turning on the AC. High speed operation with AC on is still 235 degrees.

BigGun

This link has the the wiring diagram and information on how the system works. Scroll down to post #20.
https://www.corvetteforum.com/forums...an-relays.html

VegasJen

They're designed to run this hot? I wonder why I never saw it running this hot before. Very odd. I still don't like it. Can I get a program to turn them on earlier? Like I said, I get nervous at anything over 210*.

knewblewkorvette

Yes, they are designed to run this hot. I don't like my Corvettes running that hot either.
Yes, they can be programed to come on earlier. I have done so in my supercharged 99 as those mods add heat to the engine bay. Now my car stays in the 190-210 range even in the summer heat.
Sac City Corvette makes this. https://www.saccitycorvette.com/COOLITv2.html

ncali

I have the sac city kit as well. it is simple to install, like 5 min and works well

wrmiles

It sounds like you have one fan that sometimes works and sometimes doesn't. I have had several fan motors fail and they were typically intermittent at first.

wydopnthrtl

Potentially the ECT... https://www.ls1.com/forums/f6/list-s...hey-do-159572/

"Engine Coolant Temperature (ECT) sensor

The ECT, like the IAT is a thermistor sensor, so it also changes the resistance based on temperature. The same range of resistance (ohms) is used as in the IAT. The pcm also sends a 5V signal to the sensor and monitors the return voltage. When the engine has not been run for several hours, the scan tool should read the IAT and ECT temperatures close to each other.
The PCM uses the signal for many of the control systems that affect fuel economy, emissions and idle, so any degraded or loss of signal has a great impact on the engine performance.
There are two different ECT sensors. One is a three wire used on very early (1997-98) LS1 engines, where the third wire (usually green) goes directly to the temperature gauge on the instrument panel. The later engines use a two wire sensor and the pcm conditions the signal and a separate signal from the pcm goes to the gauge on the instrument cluster.
The ECT location is in the front of driver's side cylinder head."

grinder11

My 2000 C5 came stock with 212° stamped on the OEM Motorrad thermostat. According to the dash gauge and DIC, once warmed up it was always over 210°. Always. I don't know if the later models had a colder stat, or not. I can only state what mine came with OEM, and what my readouts read. Interestingly, when I took it to the strip often back in '03 and '04, it ran the quickest times and fastest speeds when I made one run after another, after another, without shutting it off. If I did shut it off, for maybe 20-30 minutes, it was always slower! This is the opposite of my own personal experience with cars, and bikes.

helga203

Google how to jump the relay and see if that lowers temp. If doesn't something else is wrong. If it does u can have the fans on and off changed. Jmo

VegasJen

OK, so things have gone from bad to worse.

I have confirmed both fans come on in both low and high speed. I have even pulled the radiator out and made sure there wasn't something blocking the flow. So I thought the only thing else is that maybe the thermostat has gone south on me. I cut out a block off plate and put a 5/8" hole in it and replaced the t-stat with the block off plate. Even with that, the car is overheating. I mean no t-stat and even at idle with both fans running in high, it's getting up to 240.

My next step is pulling the WP. Can't think of anything else it could be. Any ideas?

grinder11

Are you running an underdrive pulley? Are you running ethylene glycol based anti freeze? I once ran Evans coolant (propylene glycol), which doesn't have the same heat dissipating properties as ethylene glycol (less dissipation). Water pumps (almost always) are good until they start leaking. Sadly, if your car is running 240°+ while going 60mph, with a new Stat AND with ethylene glycol as a coolant, you might have a leaky head gasket. But if you're running at 220° while at freeway speeds, it's not a head gasket. I don't think it's the water pump, either. Sounds like you may need to have the radiator flushed, or need a new radiator. One more thing; the A/C condensor, in front of the radiator, may be full of bugs/debris. Try blowing compressed air towards the front of the vehicle. I made up an air nozzle that has a 2 foot long piece of pipe on the air nozzle, with a 90° street elbow on the end. Then I put a cap, with a 3/16 hole drilled thru its center, on the threads of the street elbow.This allows me to blow high pressure compressed air towards the front of the car. If you do this, take care not to damage the fins by clanking against them with your pipe and street elbow. This will work on the radiator, as well. Hope this helps......

VegasJen

Cooling system is stock. Running "Dexcool". I pulled the radiator the other day and flushed it. No blockages. Condensor is clear. Unless someone has something else I haven't thought of, I think WP is the next step.

mmartinez

You state that you flushed it, but what about the fins, are they clear of debris? The C5 sucks air and everything right of the road surface, if it still overheats it could be the water pump.

silver50

I’d maybe have just swapped out the radiator while it was out. I was needing to replace my condenser and saw (Rock Auto) that all the radiators bar the Delco one were circa $100. I need to factor in the same again for UK postage and tax so an aftermarket it was.

My issue (with no front lip fitted) was a bit like you describe. Generally getting too hot but fans working (certainly low speed ok) and cooling things down ok.

I’d already fitted a new Gates water pump and ‘stat. With the addition of a new clean radiator (and new condenser and front air dam back) cooling was massively improved. Nice low circa 190 at speed and so long as generally moving, somewhere south of 220 in the correct range of 200-220. However I notice that in traffic it’ll still heat up and the fans kick in.

My old radiator and condenser were not blocked but nor were they great looking. Bit corroded and some bent fins etc. Perhaps important here, I took care filling and trying to burp the system of air. My 0.5 on this would be to fill very slowly with coolant. If things suddenly seemed worse (re OP saying got worse) it wouldn’t surprise me if after re fitting the radiator you’ve ended up with some air in the system? I found when filling very slowly with a kettle, stopping and starting while pouring a bit at a time, that I could constantly hear air bubbling out when I put my ear to the tank. I’m sure it’s gonna be harder for air to work itself out if you fill a cooling system almost full quickly. I’ve always filled vehicles very slowly.

Being that the cars are getting quite old a cooling system overhaul struck me as a good idea. I’m happy things are ok now. Water pump is easy enough to do.

My AC (so far) hasn’t been operational but I strongly suspect having the AC on (so as fans running) when in city start/stop traffic that this will keep things cool fine. I think the C5 should probably have had a slightly bigger more efficient radiator. I don’t blame people upgrading.

VegasJen

Guys, I'm at my wits end on this problem. STILL overheating within minutes. I mean literally one to two minutes it's running 240+. So here's what I've done so far:

• Pulled radiator and flushed
• Removed T-stat and put in orifice
• Removed water pump, confirmed impeller is in good shape and secure on shaft
• Put new foam tape between AC condenser and radiator, radiator and fans
• Confirmed fans do come on
• Blown out radiator and condenser with compressed air

I just don't know where to go from here. I've done all I know to do. I'm about ready to sell this f*****g thing for scrap!

VegasJen

So here's my next idea. I'm thinking about removing the lower radiator hose entirely. Jam a garden hose into the water pump inlet and let it run like that. See if it over heats with known, constant water flow. Maybe something is going on with the water pump I can't tell just by inspection. I'm seriously out of ideas.

Smoken1

Are you sure you got all of air out of the system after doing all that work?