3rd Radiator for Street Use?

[BruceP]

My '00 C2 (manual) runs hot in slow city traffic. All components of the cooling system are functioning as designed, but it's not hard to get the coolant temps well above 105C in town in the summer. As soon as air is moving through the rads again, it cools right back down. So, my question:

Given that the cooling problem is in low speed/no speed conditions, would adding the 3rd center rad be of any value, or is it really only useful as a track mod?

(I am aware of the fan mod, BTW, but I don't think it's a real answer. When the car is hot, the fans are running on high speed anyway).

TIA as always,

Bruce.

[White987S]

Don't forget that more than 50% of the engine cooling comes from the 9 quarts of synthetic oil in there.

[Brad Roberts]

We install them in ALL conversion cars and ALL BoxsterSpec cars :) Easy peasy.. figure $550 or so for every nut/bolt/screw/radiator/brackets/clips/rubber bellows :)

B

[Brad Roberts]

Anyone know for a fact that the 997X51 oil cooler will fit under his intake plenum? I know it is nearly double the size of the 3.4 stock cooler :)

B

[BruceP]

So, Brad, should I take that as a yes? The 3rd radiator is useful for cooling in my situation?

[Loren]

So, Brad, should I take that as a yes? The 3rd radiator is useful for cooling in my situation?

The 3rd radiator won't do much in stopped traffic - since it has no fan. In that case all you get is a little added capacity.

But once you start moving it should cool a little more quickly - you can see my results in the 3rd Radiator DIY here.

[Foster]

Have you cleaned the radiators?

I'm thinking of doing that before it starts getting hot this summer.

Of course 'hot' is relative. Canada hot and Florida hot are slightly different. :D

[Brad Roberts]

So, Brad, should I take that as a yes?

Sorry Bruce :) Yes. Run it.

We remove our fans from the 996+986 race cars when we add the 3rd radiator (and no factory race car came with fans)

I have tested an idling car on an 85degree day with 3rd installed and NO fans. The car could sit for upwards of 25minutes before it started past the 210 mark. The minute I drove it away (no fans) it dropped below the 180 mark in less than 300 feet at 30mph.

Not only is it a capacity increase as Loren mentioned, it also radiates (it is a radiator after all) a LOT of heat :)

Lorens writeup is EXCELLENT!!

I can do them at the track in about 20min total before I start putting coolant in :)

B

[KevinMac]

LN Engineering is now offering a 160 thermo and housing as opposed to the stock 180. This might help! It fits the M96 and M97! Cost $171.95

http://www.lnengineering.com/lowtemperaturethermostat.html

[pjalexandre]

I think that is a great idea and one we needed for some time. The stock thermo doesn't even start flowing until well past 180 in reality. But isn't the Porsche tax on a low temp thermostat kinda high?

LN Engineering is now offering a 160 thermo and housing as opposed to the stock 180. This might help! It fits the M96 and M97! Cost $171.95

http://www.lnengineering.com/lowtemperaturethermostat.html

[KevinMac]

I think that is a great idea and one we needed for some time. The stock thermo doesn't even start flowing until well past 180 in reality. But isn't the Porsche tax on a low temp thermostat kinda high?

LN Engineering is now offering a 160 thermo and housing as opposed to the stock 180. This might help! It fits the M96 and M97! Cost $171.95

http://www.lnengineering.com/lowtemperaturethermostat.html

L&N assured me there are no issues using this thermo setup! I also raised the concern!

[perryinva]

+100 on radiator cleaning. If you've never had the bumper cover off and cleaned out the radiators, including between the radiators and condensers, then you are probably running hot all the time. My car, with only 37k miles on, was fully 1/3 or more blocked with leaves, trash, sand, etc. and it took me a good 2 hrs to vacuum, flush and blow out everything. Of course, now it can be done in less than 30 mins, as I stay on top of it. My temps dropped significantly. Also make sure both of your radiator fans are running, one of my load resisters had burned up, so only one fan was working. Be VERY careful following the front bumper removal guide, as one thing it does not mention, is you really have to free up (not remove) the inner forward front fender liners (2 screws, 3 plastic expansion fasteners per side), in order to get that one friggin, screw up near the side markers, or you risk breaking the plastic mounting part that holds the side marker. Ask me how I know. Turning the wheels to far L&R help also.

[flyingpenguin]

Bruce,

I live in Houston, TX so I have seen temps upto 112 C (on my 2000 996 C2, I can get the coolant temp on my AC display).

I track the car quite a bit and installed the 3rd radiator. In stop and go traffic over 70 degrees F ambient, coolant temps creep over 100 C, even with the 3rd radiator, so I decided to do the radiator mod. Still waiting on the relay for the toggle switch, but with that I guess the temps should stay in the safer sub 100C range.

Let's see if the next step needed is the LN thermostat.

Joost

[BruceP]

Bruce,

I live in Houston, TX so I have seen temps upto 112 C (on my 2000 996 C2, I can get the coolant temp on my AC display).

I track the car quite a bit and installed the 3rd radiator. In stop and go traffic over 70 degrees F ambient, coolant temps creep over 100 C, even with the 3rd radiator, so I decided to do the radiator mod. Still waiting on the relay for the toggle switch, but with that I guess the temps should stay in the safer sub 100C range.

Let's see if the next step needed is the LN thermostat.

Joost

Yes, I get my coolant temps the same way. This is where I got my observation about the importance of airflow, because as you already know, the OBD readout is really accurate and instantaneous.

To the other posters, thank you. Some replies: Yes, the rads have been cleaned out. Toronto hot is hotter than you might think, just not for as many months! Appreciate the comments about track performance, but as I mentioned originally, the car cools just fine when it's in motion. The issue is exclusively when it's idling in traffic. I totally believe the car could run without fans... I'd be a happy guy if I could commute to work at 200kph!

It sounds like this might be a good mod, just not a transformational one.

Thanks, guys.

[jyoteen]

You know, I know it's a popular mod and a lot of folks have had overheating issues (maybe '00 specific), specially on the track, but I've NEVER had overheating issues, let alone high temps in my car with the standard 2 radiators, even on the track during the middle of the summer at places like Buttonwillow and Thunderhill, which get 100 degree temps in the summer ambient.

I will say though, every time I wash the car, I spray high pressure water at the radiators to keep them clean.

Oh, and it's a C4s.

[1999Porsche911]

Or you can keep your coolant temperature below 200F at all times by doing my simple fan mod. Cost is virtually nothing.

[BruceP]

Or you can keep your coolant temperature below 200F at all times by doing my simple fan mod. Cost is virtually nothing.

I am familiar with the mod. As mentioned earlier, I don't believe it's an answer for me. When the car is hot and stationary, the fans are already running anyway. When the car is moving, it cools down quickly and doesn't run as hot. Thus, being able to manually activate the fans is not helpful.

[BruceP]

You know, I know it's a popular mod and a lot of folks have had overheating issues (maybe '00 specific), specially on the track, but I've NEVER had overheating issues, let alone high temps in my car with the standard 2 radiators, even on the track during the middle of the summer at places like Buttonwillow and Thunderhill, which get 100 degree temps in the summer ambient.

I will say though, every time I wash the car, I spray high pressure water at the radiators to keep them clean.

Oh, and it's a C4s.

I agree that the cooling system works brilliantly when there is airflow through the rads, as would be the case on a track. The problem is sitting in traffic. Indeed, it might only be a problem in my head; the car is working as designed. I just don't think the car was designed with the stresses of urban commuting strictly in mind.

Regarding the model year, I think that I've read that the early 996s had only one temperature sensor, located at the engine. The later ones had a second sensor at the rads, and the OBD read out the average of the two readings, thus making the later cars appear to run cooler than the earlier ones did. C

[1999Porsche911]

You know, I know it's a popular mod and a lot of folks have had overheating issues (maybe '00 specific), specially on the track, but I've NEVER had overheating issues, let alone high temps in my car with the standard 2 radiators, even on the track during the middle of the summer at places like Buttonwillow and Thunderhill, which get 100 degree temps in the summer ambient.

I will say though, every time I wash the car, I spray high pressure water at the radiators to keep them clean.

Oh, and it's a C4s.

I agree that the cooling system works brilliantly when there is airflow through the rads, as would be the case on a track. The problem is sitting in traffic. Indeed, it might only be a problem in my head; the car is working as designed. I just don't think the car was designed with the stresses of urban commuting strictly in mind.

Regarding the model year, I think that I've read that the early 996s had only one temperature sensor, located at the engine. The later ones had a second sensor at the rads, and the OBD read out the average of the two readings, thus making the later cars appear to run cooler than the earlier ones did. C

The target coolant temperature is 90C - 95C. You cannot run at that low of a temperature if moving in slow traffic without getting more air past the radiators.

[tholyoak]

As I'm sure you are aware what the arrow points to is not the oil cooler. The M97 motor has a more elaborate AOS system containing three separate chambers. One on each cylinder bank and another central one. The larger oil cooler on the M97 motor is not specific to the X51 it is also on the base 3.8.

-Todd

Anyone know for a fact that the 997X51 oil cooler will fit under his intake plenum? I know it is nearly double the size of the 3.4 stock cooler :)

B

Edited March 1, 2009 by tholyoak

[Brad Roberts]

I just grabbed one of my stash of pictures shot from documenting everything I have done.. that particular picture just so happens to have had an arrow already on it. I use them to point out *things*.. I **assumed** that everyone would know I was not point to the oil cooler :)

B

[BruceP]

You know, I know it's a popular mod and a lot of folks have had overheating issues (maybe '00 specific), specially on the track, but I've NEVER had overheating issues, let alone high temps in my car with the standard 2 radiators, even on the track during the middle of the summer at places like Buttonwillow and Thunderhill, which get 100 degree temps in the summer ambient.

I will say though, every time I wash the car, I spray high pressure water at the radiators to keep them clean.

Oh, and it's a C4s.

I agree that the cooling system works brilliantly when there is airflow through the rads, as would be the case on a track. The problem is sitting in traffic. Indeed, it might only be a problem in my head; the car is working as designed. I just don't think the car was designed with the stresses of urban commuting strictly in mind.

Regarding the model year, I think that I've read that the early 996s had only one temperature sensor, located at the engine. The later ones had a second sensor at the rads, and the OBD read out the average of the two readings, thus making the later cars appear to run cooler than the earlier ones did. C

The target coolant temperature is 90C - 95C. You cannot run at that low of a temperature if moving in slow traffic without getting more air past the radiators.

I'm sure you're right. The only really correct, effective fix would be fans that moved more air.

[1999Porsche911]

You know, I know it's a popular mod and a lot of folks have had overheating issues (maybe '00 specific), specially on the track, but I've NEVER had overheating issues, let alone high temps in my car with the standard 2 radiators, even on the track during the middle of the summer at places like Buttonwillow and Thunderhill, which get 100 degree temps in the summer ambient.

I will say though, every time I wash the car, I spray high pressure water at the radiators to keep them clean.

Oh, and it's a C4s.

I agree that the cooling system works brilliantly when there is airflow through the rads, as would be the case on a track. The problem is sitting in traffic. Indeed, it might only be a problem in my head; the car is working as designed. I just don't think the car was designed with the stresses of urban commuting strictly in mind.

Regarding the model year, I think that I've read that the early 996s had only one temperature sensor, located at the engine. The later ones had a second sensor at the rads, and the OBD read out the average of the two readings, thus making the later cars appear to run cooler than the earlier ones did. C

The target coolant temperature is 90C - 95C. You cannot run at that low of a temperature if moving in slow traffic without getting more air past the radiators.

I'm sure you're right. The only really correct, effective fix would be fans that moved more air.

The method for correcting your problem is to have the existing fans come on sooner in the temperature range. This will provide you a consistantly cooler engine in all conditions. There are many ways to acheive this, including my fan mod as is outlined on this site, changing the inline sensor for the fans, intercepting signal to DME, etc.

[perryinva]

Have you checked both radiator fans to feel if they are moving about the same amount of air? Easy to tell if you stick you hands right in front of the front tires. (Turn on the AC or you'll have to wait until summer..) Could you have a weak motor, or part of the resistor is bad on one, and that it simply is not moving enough air? The fan runs at two speeds, but is dependent onte resistor to do that. You may only have one speed.

Perhaps you have a defective T-stat that's not opening all the way? I've never understood going with lower temp t-stat, as the stock one should be full open at well below 95C. Full open is full open. AFAIK, a lower temp T-stat does not open more than the stock one. Same thing if fans are already running. Running them sooner does not keep the top temp cooler. If fans are running, then the system will reach the same equilibrium temp, regardless of when they turn on. What you may gain, is less of an excursion before they reach equalibrium. This doesn't sound like Bruces problem. I assume you've done a coolant change, and the system was properly bled. You might try Water Wetter, or as Brad inferred, a larger or additional oil cooler. though the 3rd radiator might be less expensive than the oil cooler. It's certainly cooler looking.

[1999Porsche911]

Have you checked both radiator fans to feel if they are moving about the same amount of air? Easy to tell if you stick you hands right in front of the front tires. (Turn on the AC or you'll have to wait until summer..) Could you have a weak motor, or part of the resistor is bad on one, and that it simply is not moving enough air? The fan runs at two speeds, but is dependent onte resistor to do that. You may only have one speed.

Perhaps you have a defective T-stat that's not opening all the way? I've never understood going with lower temp t-stat, as the stock one should be full open at well below 95C. Full open is full open. AFAIK, a lower temp T-stat does not open more than the stock one. Same thing if fans are already running. Running them sooner does not keep the top temp cooler. If fans are running, then the system will reach the same equilibrium temp, regardless of when they turn on. What you may gain, is less of an excursion before they reach equalibrium. This doesn't sound like Bruces problem. I assume you've done a coolant change, and the system was properly bled. You might try Water Wetter, or as Brad inferred, a larger or additional oil cooler. though the 3rd radiator might be less expensive than the oil cooler. It's certainly cooler looking.

Running the fans on high, sooner, does in fact keep the engine cooler in all conditions. Themostat is not the problem, airflow is. You can remove the thermostat and you'll have the same problem.