LS-coupe cooling saga continues :(

[DC COBRA]

Is the heater hooked up in this car? If so when she starts running warm, turn the heater on full blast, if the temperature goes down the slightest, than you don't have enough radiator or the radiator effiency is poor. If it a new radiator, I have had poor effiency radiators new out of the box only to replace them with another. I use this test alot to solve some heating problems with customers cars.

DON

[71chevellejohn]

As for the AC system, it's not a matter of it loading the engine as much as it is a matter of air temps across the cores.
Just like above, If your AC condenser sees 100*F and discharges 130*F air back toward your radiator... then your radiator is seeing 130*F air instead of the 100*F you're measuring as ambient. In turn your engine cooling capability is cut by that same 30*F (same as a 130*F day w/o AC running). Jacket water cooling is pretty linear and straighforward; a degree here equals a degree there.

If you are running ok w/o the AC operating but then overheating when the AC is on then the answer is your radiator itself. It's a borderline choice that is overloaded when there is an air temp preheat introduced.

Since the problem seems to center around the use of the AC system, could there be a problem with the charge(over or undercharged) that would be causing the excessive heat? Could there be a problem with the sizing of the AC condenser or some blockage in that system?

Dville, Does the A/C system seem to be working correctly?


I'm far from an expert regarding A/C systems, so I'm just looking for some type of cause/effect.

[Txstang1]

ya, paul and i toyed with this idea, @ idle i am seeing about 25-30 degree's of advance (which is about what the large cam ls motors like), cruising off throttle i am seeing about 25 degress and on throttle about 40 degrees.

Well shit. Last time I had an issue like this that I couldnt trace down, it ended up being a blown head gasket. water out the exhaust. Im interested to see what it ends up being.

[dville_gt]

First off I dont know dick about ls motors, but I have heard that if you have too little timing in it, that could also cause it to run hotter.

ya, paul and i toyed with this idea, @ idle i am seeing about 25-30 degree's of advance (which is about what the large cam ls motors like), cruising off throttle i am seeing about 25 degress and on throttle about 40 degrees.

[Txstang1]

First off I dont know dick about ls motors, but I have heard that if you have too little timing in it, that could also cause it to run hotter.

[dville_gt]

The radiator core itself could be ok though which moves you to an airflow or water flow problem. Are you using a mustang AC core? How does that compare to the LS1 AC core? Especially the fin density (fins per inch)... Too much static restrition in the AC core will kill the airflow across the radiator and work the shit out of your fan motor.



I'm looking around here for a portable thermocouple reader we could use (laptop based logger is a bit cumbersome). I would be curious to log a couple temps just sitting in the driveway.
1. Ambient
2. Jacket water
3. Air going into the AC core
4. AC core discharge / Radiator supply air (AC off then AC on)
I lost my anemometer so we couldn't measure airflow through each core.



There have to be a bunch of other people out there who have done LSx swaps... is there a parts list from someone else's build posted earlier in this thread? Have you narrowed down what you have done differently from people who have managed to get it working?

1: 100*
2: 205*
3: via i/r thermometer pointed at condenser a/c off 115-120*, a/c on 140*
4: hard to get a consistant reading with an i/r thermometer, looked like 150* and 160* or so w/ac on but this is just a reading of the core..

system was showing about 40psi on the low side (system might be a tad undercharged)

[2165 Turbo Rail]

he is using the same water pump, thermostat, radiator that I am... diff is my condensor is an aftermarket AC system BUT.. I have more BS infront of my radiator then he does (I have a large intercooler, ac condinsor, and large oil cooler.)
even when I have the AC blowing in the GTO sitting in traffic it still has temps that are fine

[Strychnine]

hard to believe it is a borderline choice, it is a massive unit, the thing is 3in thick and it has 2 x 1" cores. compare that to the factory ls1 radiator which only has 1 x .75" core. i have trouble believing (not doubting what you are saying, but i have trouble with) the concept that the only solution here is to put a bigger radiator on it, i literally can not fit anything larger. oem's don't have to resort to a gigantic radiator to keep cars cool, seems strange that i have to.

The radiator core itself could be ok though which moves you to an airflow or water flow problem. Are you using a mustang AC core? How does that compare to the LS1 AC core? Especially the fin density (fins per inch)... Too much static restrition in the AC core will kill the airflow across the radiator and work the shit out of your fan motor.



I'm looking around here for a portable thermocouple reader we could use (laptop based logger is a bit cumbersome). I would be curious to log a couple temps just sitting in the driveway.
1. Ambient
2. Jacket water
3. Air going into the AC core
4. AC core discharge / Radiator supply air (AC off then AC on)
I lost my anemometer so we couldn't measure airflow through each core.



There have to be a bunch of other people out there who have done LSx swaps... is there a parts list from someone else's build posted earlier in this thread? Have you narrowed down what you have done differently from people who have managed to get it working?

[dville_gt]

If you are running ok w/o the AC operating but then overheating when the AC is on then the answer is your radiator itself. It's a borderline choice that is overloaded when there is an air temp preheat introduced.

hard to believe it is a borderline choice, it is a massive unit, the thing is 3in thick and it has 2 x 1" cores. compare that to the factory ls1 radiator which only has 1 x .75" core. i have trouble believing (not doubting what you are saying, but i have trouble with) the concept that the only solution here is to put a bigger radiator on it, i literally can not fit anything larger. oem's don't have to resort to a gigantic radiator to keep cars cool, seems strange that i have to.

[Strychnine]

Well, maybe I spoke too soon. Just cruised it and it is still running pretty warm. About 225 in the city, 230 on the highway. Didn't stay on the highway too long, but it was staying fairly steady at 230 and it's only 103* right now, I imagine at 110* it'd have a real problem.

Kind of lost now. Replaced radiator with huge radiator, replaced fans with high powered fans, replaced waterpump, block tested, vacuum filled, air dam installed, shrouding built, tune is spot on a/f wise, and still it runs this hot.

I hate to even ask this, but could this be an issue with the compressor? It definitely loads the engine pretty good, could it be introducing such a load that the engine simply can't keep the temp down?

For example, pulled into my garage @ 228 degrees a/c on, turned a/c off and within 5 minutes the temp was at 198* degrees. I know a motor is going to run hotter with a/c on, but 30* at idle seems a bit excessive.

For what it's worth, one degree of ambient temp is worth one degree of engine temp (water side). Air sides (turbo / charge air cooler) is a bit different, but if you are running 230*F water temp on a 103*F day, with other factors the same you will run 237*F on a 110*F day.


As for the AC system, it's not a matter of it loading the engine as much as it is a matter of air temps across the cores.
Just like above, If your AC condenser sees 100*F and discharges 130*F air back toward your radiator... then your radiator is seeing 130*F air instead of the 100*F you're measuring as ambient. In turn your engine cooling capability is cut by that same 30*F (same as a 130*F day w/o AC running). Jacket water cooling is pretty linear and straighforward; a degree here equals a degree there.

If you are running ok w/o the AC operating but then overheating when the AC is on then the answer is your radiator itself. It's a borderline choice that is overloaded when there is an air temp preheat introduced.

... remember?

Haven't had a project in a while Being an adult is getting in the way.

[dville_gt]

Well, maybe I spoke too soon. Just cruised it and it is still running pretty warm. About 225 in the city, 230 on the highway. Didn't stay on the highway too long, but it was staying fairly steady at 230 and it's only 103* right now, I imagine at 110* it'd have a real problem.

Kind of lost now. Replaced radiator with huge radiator, replaced fans with high powered fans, replaced waterpump, block tested, vacuum filled, air dam installed, shrouding built, tune is spot on a/f wise, and still it runs this hot.

I hate to even ask this, but could this be an issue with the compressor? It definitely loads the engine pretty good, could it be introducing such a load that the engine simply can't keep the temp down?

For example, pulled into my garage @ 228 degrees a/c on, turned a/c off and within 5 minutes the temp was at 198* degrees. I know a motor is going to run hotter with a/c on, but 30* at idle seems a bit excessive.

[46Tbird]

Backwards.

The T-stats job is to prevent overcooling and allow the engine to maintain a safe minimum operating temp (reducing wear, emissions, etc).

I don't disagree, but that's only in the event that the cooling system is efficient enough to keep an engine from being able to reach its operating temp.

That's not the case here, or for most hot rods using V8s and early Mustang radiators... remember?

[Strychnine]

I haven't read the whole thread yet, but assuming some mechanical parts are ok (correct cap, no blown gaskets, etc)



1. radiator is sized too small - physically doesnt have enough surface area to reject heat

2. lack of airflow - debris in the fins, flattened fins, fan too small, core to restrictive, frontal obstruction, recirculation of heated air

3. lack of coolant flow - undersized water pump, slipping pump drive, blocked coolant passages, air in system



Pick one and start checking them off.

[Strychnine]

Don't put a 160 thermostat in it. If it can't maintain 200, how would it maintain 160?

The purpose of a thermostat is to allow coolant to stay in the radiator long enough to be cooled off well below the operating temp of the engine

Backwards.

The T-stats job is to prevent overcooling and allow the engine to maintain a safe minimum operating temp (reducing wear, emissions, etc).

A partially open or modulating t-stat might cause coolant to take longer to travel through a radiator but that's not it's designed intent. By design you want to get to operating temp ASAP and then be able to reject heat to atmosphere at the worst case condition (full open t-stat)... anything in between is really inconsequential.

When we do full load cooling tests we will block open the t-stat (to prevent modulation and get steady data). If cooling capability were dependant on the t-stat causing the coolant to spend more time in the radiator we would have a completely different test procedure.



But you're right about 160 vs 200 in this case... either way the t-stat is wide open in his engine and it's not rejecting enough heat. Changing to a 160 is as good as throwing away money.

[dville_gt]

Don't put a 160 thermostat in it. If it can't maintain 200, how would it maintain 160?

The purpose of a thermostat is to allow coolant to stay in the radiator long enough to be cooled off well below the operating temp of the engine. So when it opens, the coolant reduces the temperature of the engine. Pretty basic, but if the stat opens back up before the radiator sufficiently cools the coolant, the engine temp will steadily rise with the thermostat standing wide open and ineffective.

Cars that are already overheating due to ineffective cooling do not magically start running cooler with a lower temp thermostat lol. If anything, put a HIGHER stat in it to increase the amount of time the coolant stays in the radiator. I only use 195 stats myself, the car runs better, gets better mileage, and keeps a rock steady temp.

This is what I have thought from the beginning, a low temp thermostat would compound the problem.

The only logic I could see behind the low temp is either

a: a 187* thermo begins to open at 187 and is not fully open until 10-15* over that, so you are not getting "full flow" until 200-205* vs 175*

or b: the higher coolant temps cause a snowball effect whereas the heat from the engine/coolant running warmer acts as heating element to only compound the problem by heat soaking everything. thus running a cooler thermostat keeps everything cooler, including the air around the engine/radiator that is used to cool everything.

i am not saying i agree with either of these two hypothesis, but i have gotten advised by more then one person to run a lower temp thermostat and i have to believe there is at least some explanation to why. i will probably keep the factory 187 for now, it seems like a good compromise between too cool and too warm.

i would be interested to see how it acts with a 160 and a 200 just for shits and giggles though.