JC3D

I am finally installing my third radiator and was wondering how much adding vents to the top of the bumper would help to get airflow through like on the gt3 bumpers. I have seen other 996's at the track and not sure how great the advantage in cooling is. I have been plaqued with cooling problems since I've owned this car, and Streets of Willow next month is the worst since I can't get enough airflow to cool the car off.

The other question, so I don't have a big gaping hole in my bumper, Can you buy the vent piece separately and what is the price/part number?

1999Porsche911

I would think if you are serious about tracking your car, the last thing you would want to do is add weight? You don't need a third radiator. Do my fan mod and you'll be fine. (Search) Additionally, the flow in the 99's is much too restricted and removing the thermostat will greatly increase flow and reduce both coolant and oil temps even further.

JC3D

I would have to disagree with you. Tracking them in southern california needs the radiator. I am living proof. I don't want this to turn into another thread suggesting what cooling issues might be because the last thing we need is another one of those. Fan mod might help me sitting in traffic, but that's not where my issue is.

1999Porsche911

You are wrong. The suggestions I made will keep your engine cooler than putting in a third radiator alone in any kind of heat. Coolant flow is your problem if you cannot maintain proper temps at speed. I would also suspect worn impeller in the pump.

Increasing the surface area of the radiators will do little to cool the engine when coolant flow is the problem. Personally, if I tracked my car alot, I would not be running a thermostat in the 99. As a matter of fact, I don't run a thermostat most of the time in my 99.


There are many many 99's tracking in hot weather with no heat problems.

How hot is your coolant getting, anyway?

Loren

I have a 3rd radiator - put it on 2001. The additional weigh is minimal. My ontrack temps are averaging 10-20 degrees F lower than before the 3rd radiator. I would call my current track temps "acceptable".
I don't know how much more you get with a vented bumper - but that is easy enough to add later.

Paul 996

1999Porsche,

Are their any negatives to running without a thermostat? Also, how easy/hard is it to swap on the 996?

Thanks!

Eharrison

The Mojave desert, Rosamond is a different breed of weather. I suspect when I dive into the tracking bug at Willow Springs the third radiator would be the first track mod.

As to the comment on increased flow, I would say that you would need more surface area of cooling because with the lack of moisture in the air the cooling capability is not there, speeding up the flow would only reduce the time through the radiator.

I hope someone can give you the answer regarding the vent.

1999Porsche911

The only downside is that it takes more time for the engine to reach normal operating temperature. I have extensively tested the 3.4 engine with and without the thermostat and the engine maintains a more consistant, lower temperature in all conditions without the thermostat. The tests also included using various size washers in place of the thermostat to test the optimum restriction needed for best flow. Cooling was best with no washer.

Removing the thermostat involves draining the 2 gallons of coolant sitting in the block which is accomplished by removing a small plug on the back of the engine. You then have to remove ends of 2 small water house connected to the pump. 4- 10 mm bolts are removed from the thermostat housing which then pops off.

Running around without a thermostat is not necessary for the average 996 owner to maintain acceptable engines temps. However, for extreme driving conditions and tracking, doing so can be a great benefit by maintaining lower coolant and oil temperatures which will provide better protection and better performance.

Someone mentioned that increasing the flow of the coolant will reduce the ability of the system to cool. IF the cooling system was providing optimum flow to begin with, this would be true. However, flow on the 3.4 engine is too little to begin with. You can easily test the flow of the cooling system by letting the engine idle while monitoring the coolant temperature. Let the temperature climb and then raise the idle speed to at least 1500 rpm. If the temperature starts dropping, it is evidence that flow is your problem.

The third radiator also lowers temps but not to the entent that increasing the flow does. For many, a third radiator is all they need or the raditiator fan mod. However, IMO, for the serious tracker who is looking for a car with less weight and lower engine temps, adding componants to acheive cooler temps is the wrong approach.

But, serious trackers would have already removed all the "bling" componants on their cars such as A/C and condensers which by itself would increase air flow for cooling.

There are many ways to keep the engine cooler. This is just one of them.

roberga

John: BBI Autosports Huntington Beach can help. Both guys are from ALMS and Rolex. Lancaster in August is pretty warm 100+ air temp.

jmla

The RS/Cup vents are more for front end stability than for cooling. With the standard 3rd radiator (Tiptronic, X51, GT3) the airflow is directed under the car, with the top vented bumper the air exits up and over the car creating downforce instead of lift. Contact Chads996 (on this board), I believe that he recently installed a third radiator.

Chads996

Agree 100%. As Loren said (with his actual temp statistics), these are worth doing in warm climates. I will be doing the same modification for my car this summer. As for the vents, I have been advised to do it for additional cooling and radiator ventilation. If you add the ducting, there is a slight gain in frontal down force. But...it is nominal. my .02

1999 - If you are correct, why does Porsche add the 3rd radiator to all MY's of the GT3 (MkI & MkII) as well as the GT3RS, GT2, and Turbo? It is well documented that the 3rd radiator works VERY well for reducing temps. The weight gain is nominal and the flow characteristics result in a slight gain in performance (when applied properly). Note that where you live, there is significant difference in temps during the summer months. Not to mention, ambient temps on the track are much, much higher. For most who track their cars, this is a must. Especially in warm to hot climates.

C.

1999Porsche911

I am not suggesting that there is not a benefit to adding a third radiator to control cooling. What I am stating, for those who want to lower coolant and oil temperatures even more and not have to add weight tot the car, there is an alternative. Whether you have a third radiator or not, running the 996, including the 04 GT3 without the restriction of the thermostat, will substantially keep your engine cooler and improve performance. Doesn't matter whether you are running in 70F or 130F track temps. Even more beneficial if you run a TIP.

bella1

I agree with you the third radiator is the way to go. I replaced my 3.4L engine at 57K miles and did the third radiator at the same time. According to my indy guy, the flow works without that top vent since this was not around when the original 996 GT3 was made. Also, wrt cooling problems, check to see if you have any oil in the coolant. That was my problem and it got really bad toward the end. Of course, the oil reduces the flow of coolant and that could be an issue for you.

Also, you just cut out the middle bumper area at the back of the bumper. The third radiator has a rubber like peice around it just like the side radiators.

Galun

I have the third radiator. I don't think you need the "vent" on top. The third radiator kit comes with "air scoops" that direct air from the center opening of the bumper toward the radiator. I imagine air flow will not be a problem.

LVDell

The vents on top of the bumper are for downforce and for it to work properly you need to cant the rad at the proper angle. There is a kit IIRC you can buy to do this.