Hey all,

I've been having some problems with heat, and I'm really at a loss here. I have a Procharged car with a custom FMIC setup that restricts flow the the radiator a fair amount. I have made the following changes to the car to alleviate heat problems:

1) I have a gigantic Ron Davis radiator with two 12" Spahl fans. I'm not sure what the CFM on them is, but they move a lot of air. The radiator is a beast... 2-3 times as thick as the stocker with much larger tanks.
2) I have a brand new LS3 water pump (which included a new 180* T-stat).
3) The top radiator support was cut so that the radiator could be stood up.
4) I run straight distilled water (no antifreeze) and Red Line's Water Wetter.
5) Low fan speed starts at 198* and turns off at 190*. High fan speed starts at 212* and turns off at 207*.

Despite these changes, the car will still run what I believe is too hot. For example, it's 75*F outside today, and I drove to work with the car bouncing between 200 and 210 degrees while going 70MPH cruising in 6th gear at about 1900RPM. When it's over 100*F outside, this is going to be much, much worse... especially with the AC on.

The other day it was about 80*F outside, and I was going about 20MPH in stop-and-go traffic with the AC on, and the temp started rising very quickly. I turned the AC off at about 225*F, and it very slowly started to come down into the 200-210 range. I feel quite sure she would have eventually overheated (240+) had I not turned off the AC.


I'm not sure what else to do here, guys. I'm not getting a bigger radiator in there, or bigger fans, or another water pump. I'm wondering if I should just take the T-stat out entirely?

I'm also wondering if perhaps I don't have a good bleed on the cooling system. I did what GM's shop manual says and loosened the bolts for the "bleeder pipe" going between the two heads to let the air out. Water came out immediatley when I loosened the bolts. I let it flow for about 20 seconds on each side and tightented them back down.

I just feel like something must be amiss here, but I don't know what to look for... ideas?

 

bump?

 

Do u have a fan shroud and a front air dam? Just placing the fans on the radiator will not cause a vacume on the entre cooling surface. Also try having the low fans kicking on at 160 and high coming on at 190.

 

I do not have a shroud anymore. The intercooler sits right where the shroud used to be. Now, all air is drawn through the front bumper. I know this isn't ideal, but this wouldn't explain why the car runs so hot while sitting still.

 

A 50/50 mix of distilled water and Zerex G05 antifreeze would be your ideal mix. I would add a waterwetter, only thing I've found to date that actually works is Redlines waterwetter, available at most AutoZones, (8-10 oz,) with the 50/50 mix your good to about 250 degrees before boil. With a 70 percent concentration of G-05 (70/30, MAXIMUM recommended) your good to about 280 Degrees before boil. Not that you want to see these kinda temps, these are the boil ratings for antifreeze/ H2O mixes, straight water is a NO-NO, as is straight Antifreeze! You will see no benefits running either one straight, cooling or otherwise! I’m not a big fan of Dex-cool crap, Zerex G-05 is very performance proven, and alot more friendlier to your cooling system, to date nothings better than Zerex G-05, 50/50 mix, with Redline waterwetter, do run a thermostat, fan shroud, etc, optimize your system.

 

A shroud around the electric fans will make a massive difference in cooling.

 

@bigboykilroy: It was my understanding that straight water cooled better than a mix of water and antifreeze.

@46Coupe: I have a shroud around the fans. The shroud that is gone is the one in front of the radiator going from the bottom bumper support to the under side of the top radiator support. That area is now filled with an intercooler


I'm particularly concerned that perhaps there's still air in the block. How often do you guys find that you have to "bleed" the cooling system, and what method do you use? When following the GM service manual, I got no air the first time... just water.

 

Gauge,

You really have me puzzled.
I suppose bleeding the system as you suggest. I know that the heater box in F bodies can be a problematic thing to bleed because of their placement. Get the nose as high as you can and hope to get more air out?

I guess it IS possible that your brand new thermostat is malfunctioning. Might be something to check. I would certainly try to avoid running without a thermostat entirely.

Off the wall question, but you don't have some kind of shut-off valve in your heater line do you? If it is still stock, then I suppose the question is no. But if it is something you have messed with, some people have reported strange heating issues like this when using a heater valve for aftermarket A/C systems like Vintage Air, Hotrod Air, etc.

Here's a thread where a guy described how he bleeds the system:
https://ls1tech.com/forums/pontiac-f...ng-system.html

 

I still stand by my mixture recomendation as a whole solution, but to answer your question directly Pure water carries and transfers heat energy better than a 50/50 mix. But the mix has a higher boiling point under pressure, and a lower freezing point.

 

I did some research and troubleshooting today. I started by following the steps in the thread 46Coupe linked to bleed the system, and it made no difference... almost no air came out before I got water. So, I started checking things.

First thing I noticed was that while my radiator was full, my overflow was dry. Strange that the GM service manual never mentions the overflow in the steps to refilling the cooling system. This could have caused the cooling system to suck in air at some point.

The next thing I noticed is that if I squeeze a radiator hose while the cap is on, I can hear air/water moving in and out of the overflow. I don't know if this is because of a faulty cap or not, so I bought another one... same behavior.

Finally, I started the car and just held on to the radiator hose until I could feel it warming up. When it did, I got in the car and checked the Autometer gauge... 195*F. That's not good. I don't know if this is normal for an LS3 (since it's an LS3 pump and t-stat), but I need a 180* t-stat. After letting it sit for a while with the AC on full blast and the hood closed, the gauge got up to 200*F, and HPTuners showed 196*F consistently for 5+ minutes. This is in 55*F temperatures.


In conclusion:

1) I don't think my t-stat is opening when it should.
2) I'm curious if my radiator cap is holding pressure like it should.
3) I needed to add water to the overflow.
4) My bleed on the block seems good.