We've been seeing 100+ regularly here in CenTex and my 99 vert has been running hot - especially in traffic with AC on.

I cleaned the condenser and radiator with brushes and water hose - not much came out and no change in heating issue. I checked fan ops and they seem fine - on-off at close to factory spec temps.

While following recent threads on other guys heating problem, someone suggested increasing water percentage and lowering antifreeze percentage to improve cooling.

So, thinks I, since my 99 was delivered in Chicago and lived in Detroit for a while, it probably has at least 50-50 anti freeze/water and maybe more AF than that.

I ordered a hydrometer from Amazon for $10 that was reviewed positively and tried it out on the mix in the surge tank.

Result? freeze protection to -50F! Since I've never seen temps below +10F in Centex (and that was only for a few hours), I'm thinking -50 is a bit much. And the extra, unnecessary antifreeze is hampering cooling.

So, now I'm using the hydrometer and working my way down to freeze protection to 0F by suctioning out the existing mix and replacing it with distilled water. I remove a pint or so, drive for a couple of days and test again. Repeat as necessary to achieve desired freeze protection level..

Currently I'm at freeze protection of -20 and I've seen a noticeable difference in engine temps. And when driving conditions (i.e., city traffic) push the temp up, it now comes back down much more quickly.

Another problem solved with help from CF......

 

Thats an interesting project. I could benefit from that here in San Diego county as well. The most ive done is put Royal Purple's "Purple Ice" in. Good stuff, but I bet using the hydrometer and distilled water is way more effective.

 

Antifreeze also RAISES the boiling point of the coolant, I think your going to shoot yourself in the foot here.

 

Interesting point. What is your recommendation as the best water-antifreeze mix for cooling in a climate that rarely sees 20F?

 

I notice from an on line search that Dex-Cool at 40% protects to - 12 degrees F. That provides some leeway for unanticipated cold snaps and should provide corrosion protection also.

Whether the coolant is providing corrosion protection can be determined by using a test strip, one supplier being www.acustrip.com

Once coolant becomes acidic, it can eat headgaskets and other important parts.

 

What the factory puts in, 50/50. These cars have been tested in subzero and Desert conditions. Why dispute decades of tried and true??

 

It will not Give you a boiling point issue. The system is pressurized to control that by your radiator cap. I run distilled water and water wetter in my race bikes that operate at 10000 rpm without problems. We have to remove the coolant so we don't spill it on the track.

 

In terms of the coolant's ability to carry heat, water with one of the numerous water wetters available is much more able to carry heat than a blend of antifreeze and water, or a blend of water, antifreeze and water wetter. As the percentage of antifreeze is reduced, the ability of the blend to carry heat is increased. For that reason, a cooling system which is compromised in some way might be able to operate within normal temperature limits if the percentage of antifeeeze in the coolant blend is reduced.

As noted, some tracks will not allow antifreeze in on-track cooling systems.

Another issue is that, as the percentage of antifreeze in coolant is reduced, the boiling point of the coolant is also reduced, which could result in boiling and coolant loss even though the coolant is operated within otherwise normal temperature and pressure limits.

 

IMHO if you are overheating and you have the correct coolant in the car then something else is off.

 

BTW how old is the coolant? if it's over 5 years old it's time to change it out.

 

Bingo. My vote is the OP didn't do a good enough job cleaning out the radiator/AC. I first used pressurized air and I got a ton of dirt out (100k mi), then a garden hose and got a ton more out, then I said fvck it and busted out the pressure washer. Need to be careful here, if you don't hit it straight on it'll bend fins. The radiator came out almost like new (because I removed it) but the AC is still pretty dirt. That said the car ran 194-196 on the street and 230ish on track. Next up I thinned down the existing coolant without a hydrometer, just drained the radiator and refilled with water and a bottle of Redline water wetter, and coolant temps on track stayed just below 230 and temps on the street are 192-194 on a 90 degree day with the AC cranked. Can't wait to see what they do when I put a new GM AC condenser in and a single Spal fan to increase airflow across the radiator at speed.

Yes, thinning the mixture does help with cooling, but you really shouldn't be running hot in the first place. Now if the OP is talking about putting around town in humid, 100+ degree TX weather with a stock tune, the car could be easily hitting 220-230, but on the highway with all systems good it should run 195 almost no matter what the conditions.

 

I'm surprised nobody has asked what temps he's seeing. These cars run hot normally. 235° in stop and go traffic or at idle isn't unusual. If the temp drops back down in normal driving there is nothing wrong with the cooling system.

But if you're like me and hate to see the temp run over 200° then I'd switch to a lower temp thermostat and reprogram the fans. In 95° temps in stop and go traffic I'm not going over 190°. Cruising speed temp is below 180. I'm not going to argue why I chose to run my car cooler, and it hasn't died because of it.

 

Don't know - I've owned the car for 18 months.
flushing and replacing the coolant is prob a good idea.

 

BUT, you should NEVER run this combo all the time, Antifreeze has rust inhibitors and lubricants for the water pump (at least the better ones do).

 

Before I started the dilution process, I saw 255 in traffic ( 105 outside) a couple of times and the AC shut down on high temp.
Now, after washing the radiator and condenser with a garden hose and diluting to freeze protection of about -20 (from -50), I'm seeing 225-230 in traffic in 100+ outside temps. At speed, temps are in the 200-205 range.
As far as I know, my tstat is a 190.

 

And then you add water wetter to the thin mixture to get those corrosion inhibitors and lubricants back. . .

 

Why don't antifreeze sellers like Prestone or /dexcool add surfactants to their mix if it improves cooling as advertised?

 

Your at speed temperatures sound perfectly normal to me.

In my case, I installed a Sac City Cool It so that I could call up high right fan at will. I did not like seeing the temperature cycle up to 230 (AC off) when driving slowly at 90+ air temperatures. I am not sure if the high right fan is called to the on condition when the AC is engaged. Someone else might be able to clarify.

If the high right fan is not called on when AC is engaged, then a Sac City Cool It would help reduce the temperature spike that occurs while awaiting that fan to be called at 228 degrees.

As an aside, I like my Cool It-

 

Because a correctly functioning cooling system doesn't NEED IT. I'm also "guessing" there are downsides to surfactants over time.

 

Hot Rod Magazine ran an article this month where a water wetter was tested, got solid improvement, 10 degrees drop as I recall, and while the system was marginal during long term idle, temperature kept climbing before adding the wetter, it refused to overheat afterward.