Relegate

Yo Rennlisters! I have a 99 996 with 100k on the clock. When I am on the track I am seeing temps in the 245 range, and only if I run the heat full blast do they come back to the 230, maybe a little lower. On hot days I was dangerously close to the red. I have an OBD2 bluetooth Kiwi3 so I am getting the temps directly from the ECU (and overlaid onto my track vids through Harry's LapTimer).

Here are my mods for cooling/preservation:

FVD Baffled oil pan (+.6L of oil capacity)
Motul 8100 or Joe Gibbs 5w40 oil
Distilled Water + Water Wetter
CSF Center Radiator
Stock side radiators
LN Spin on filter adaptor (with Mag)
NGK spark plugs
93 Octane
Fabspeed Tune
Brand New MAF
O2 sensors (Bank 1) are within normal voltage range. Bank 2 are spaced because I have no cats.
Catless X pipe and full exhaust

I track the car with 93, and I push it hard, but even shifting at 6800rpm (my PCA instructor's recommend threshhold for longevity) we still had to run heater full on in 70-76 temps last weekend in 20 or 30 min sessions.

Shop who did radiator install also made holes in under tray to let heat to escape from center radiator, and I have GT2 front bumper with the upper vent (but not the baffle behind the radiator for those familiar with the GT2 setup).

Previous owner did a 160 thermostat I'm told.

Compression is great, cylinders look great, everything is great overall.

Now, my instructor runs the same radiator setup in his 996 Spec race car (also a 99). He does not have AC Condensers, and has a standard pulley (I have an under drive), but said at our engine speed the water pump is going to be spinning enough regardless of pulley. He was running the same day an his temps were a good 20-30 degrees lower. His car is 110lbs lighter.

From my motorcycle days, we would start with one temp range colder plugs if we saw high temps and most of the time that worked. I might try that, but I am assuming the tune could be lean?

I don't know that my shop cleaned my side radiators but assume they did since they had everything apart for the install of the CSF center radiator. I am considering doing the CSF side radiators as well.

Car also has a custom installed motorsport AOS and all of what I mentioned was done by me in the last 10 months.

Anyone have experience with this?

5CHN3LL

Wow, no, that's really not right. For comparison, I have run my '99 C4, also with a center radiator, earlier this summer I ran from sea level up to nearly 9,000 feet in nearly 100-degree ambient temps and I have never seen temps anywhere near what you're seeing; that's about 40 minutes running uphill between 5K and redline.

I'm guessing your water pump is shot, you have some other issue preventing coolant from circulating properly, or maybe there is air in the system from the shop's install of the center radiator.

RngTrtl

any chance that your radiator fans are not working correctly? check to make sure that both the low speed and the high speeds are working.

Relegate

Low speed definitely works and deck lid fan does as well. High speed not sure... Can I test those with the Durametric software?

The water pump def looks "original". I am very certain it was run with the pressure release on to bleed it, they know I like my track days.

I appreciate the fast feedback! Doesn't seem right to me either!

5CHN3LL

Yes, there are fan activations for both speeds in Durametric.

If your water pump is original, I suspect:
* If you look at the shaft, you'll see some crystallized coolant and/or you will be able to wiggle the water pump pulley
* If you remove it, you'll find that the impeller vanes are chipped up, probably significantly

If you find missing impeller vane bits, you need to try to flush them out before another track day. Those suckers have a reputation for causing hotspots and subsequent cracks.

RngTrtl

do some searching on here for the on/off temps of the fans speeds, i cannot recall off hand what they are. your tempos are def way too high. Ive ran the hell out of my n/a and turbo 996s in 100+ dallas heat and never got over 220.

Macster

I'd add the T-stat has to be suspect, that it is not opening fully.

Let me 2nd the radiator fans suggestion.

I've had two cases, make that 3 cases, where a radiator fan wasn't working right. A fan motor shaft snapped. A ballast resister failed. And in the last case while the fan motor was running the air being moved through the radiator was clearly much less than the other side. No fan stage errors but the tech found the fan motor drawing way more current than the other one and I had him replace the fan motor.

But in all of the above cases even in 90F+ heat and running the A/C there was no sign of overheating.

I have to also question the GT2 front bumper setup. While this works quite well on the GT2 I'm not so sure how well it works, and with some pieces missing, on the 996.

Any chance the radiator plumbing got mixed up with the install of the 3rd radiator? Perhaps a radiator got bypassed?

5CHN3LL

> Any chance the radiator plumbing got mixed up with the install of the 3rd radiator? Perhaps a radiator got bypassed?

I was wondering the same thing, but was reluctant to suggest that OP's shop screwed the pooch.

Sneaky Pete

I'll only add the Joe Gibbs 5W40 (DT40) is not meant for the track. If you want to use a Driven race oil go with either XP5 / 6 or 9.

ZuffenZeus

I assume when you say "baffle", you mean the Porsche GT2 center air duct, right? If you don't have one installed, this may be part of the problem. You need the air duct (item#13) part#99657532530 as shown in the image. From what I read about the GT2 aero bumper (with center radiator vent), it's vital to pipe air up and through the vent. If you don't have the proper air duct installed, hot air will get trapped and actually cause the radiator to be inefficient.

5CHN3LL

^That's true, but OP also indicates that the installer vented the tray area under the nose (which bothers me for an entirely different reason - venting air through the belly dicks up airflow; based on OP's description, OP now has a ram air intake that will be pushing the nose UP the faster he drives)...

OP, you also listed a Fabspeed tune; I would advise against cooler plugs or anything else that can affect A/F unless you're certain that your tune will not react negatively...

ZuffenZeus

^I'd cap them and install the proper center duct to funnel air upwards the way the bumper was designed. I can't see how just venting is going to promote proper air flow. I'm sure it will help it breath, but IMHO, the hot air will be trapped... and maybe cause resistance since the air is not properly vacated?

mattie_k

Venting and airflow aside, if it were my car I would be inclined to change water pump and TStat out as a starting point as well as inspect the coolant lines. As mentioned above the duct for the 3rd rad should be there to maximize efficiency, otherwise that 3rd rad isn't doing much.

DBJoe996

I agree...something is not right. Start by replacing water pump and get a new low temp thermostat. Do not use an underdrive pulley on the water pump. If it is strictly a track car (or not a DD), ditch the AC condensers in front of the radiators.

Sneaky Pete

It could be the venting......on my 997 I added the center rad myself. The instructions said to cut 4 vent holes on the bottom of the bumper cover. In my case the baffle that came with the kit directed the airflow down. I think in the OP's case his rad vents upward. You need that baffle because it directs the hot air upward though the "smile" duct on the top side of the bumper cover.