Temp and Oil Pressure

Lately I have noticed a strong correlation between oil pressure and coolant (oil temp). I know these are directly correlated, and was curious if other people are seeing the same pressure changes; didnt think it would be as strong as it is, and yes I am running 0w40 (I know Jims feelings on 15w50). This is on a 74K 01 3.4l Engine. Temp ------------------ Oil pressure @ ~4k RPM cold -------------------4.25 needle on 8 ----------4.1 (Normal opp temp, ambient <75F) Needle end of 0-------3.6 (Slow traffic) Needle right of 0 -----3.3 (Excessive heat, traffic, ambient > 85F) Are people seeing similair. Car rides great regardless of temperature, just wanted to get a better feeling for the correlation. Thanks, Ross

That's about the same as my '99

The small size radiators and front bumper design on the 996 (especially 3.4 engine) encourages the engine to run extremely hot when it is not moving fatser than 60 mph as is indictaed with your 225F+ coolant temperatures. These high temperatures, which are almost 20% higher than the engine is designed to run at, will cause your oil pressure to be low, especially at idle (dangerous) and particularly low using the Mobil Water. There are 2 solutions to your probem. First, as you referenced above, stop using the 0W40 and properly protect your engine. Second, do my fan mod and you will be able to keep your engine temperature below 200F regardless of the type if driving you do and what the ambient temperature is. At 3,000+ rpm, oil pressure should ALWAYS be higher than 4 bar. Idle pressure should NEVER be below 1.5 bar. There is also a direct coorelation between oil level and pressure. Cooling System Mod The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance. The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan. Radiator Fans Connect a wire to the ground of the 2 high speed fan relays located on the relay carrier located in the driver�s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point. With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. Engine Compartment Fan Connect a wire to the ground of the relay located in the relay carrier behind the passenger seat, driver�s side. Relay #8. . Feed this wire to where your switch will be located. I simply fed the wire along the driver�s side of the car and under the door sill. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and connect the other end of this wire to a chassis ground point. With key on, this switch will now immediately turn on the fan drawing air into the engine compartment. When you turn the key off, the fan will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. This mod helps keep the engine compartment much cooler when driving around town and is particularly beneficial to any engine that draws its intake air from inside the engine compartment, such as the EVO SC. If you are adventurous, you can automate the operation of these switches so they will switch off at a specific speed, or operate when vacuum is present only, etc. You can choose any style switch you want and even use Porsche switches. I simply used 2 toggle switches that I installed in the batwing, Jim

Jim, what I don't understand is why the fans don't just stay on when the car is hot? Why would we need to install the modification? Are the fans inoperative at slow speeds for some reason? I remember reading up on this some time ago but can't remember.

The fans do not come on full speed unless the A/C is on or the coolant temperature reaches ?? degrees. The ?? temperature is too high a setting to properly maintain normal coolant temperatures.

The option I use is to put the A/C on when it gets real hot outside!!

Turning the AC on does NOT turn the fans on full speed and therefore the coolant temp will still rise higher than normal. Full speed fan speed is sensor dependent. Manually turning on the fans full speed with AC will keep the temps down.

What does that mean? If I'm travelling slower, the fans should spin faster, right? I mean, what's the point of even having a fan when I'm moving 60 mph?

Why would the fans spin faster when you go slow? The cooling system, without the fans, is inadequate to maintain coolant temps below 200F in warmer climates when moving at speed less than 60 mph. Once above that speed, there is enough air moving over the radiators to maintain proper temperatures. So, if you want to keep the engine temperature below 200F when driving below 60 pmh, you have to have the fans on full speed whether the AC is on or off.

I see the perfect excuse for always driving 60mph plus. Now I can explain to the officer that I am merely attempting to keep my precious cool due to the manufacturer's oversight. LOL

What would you say the odds are you could throw in some pics to help with this write up? Thanks for the info though. Very helpful. Lower temps = more horsepower too.

I have no pictures of the relays, just where I mounted the switches. The relays are quite simple as each contact is clearly numbered. Just pull the relay, stick a wire in the slot for #85, reinstall relay, and ground the wire through a swtich. You simply want to ground #85 to start fan. If I have time, I may take some pics later today.

Here you go: This is the relay panel on the left side of the footwell on driver's side. 1 wire for each high speed relay (#85) goes to ground via a 1 switch installed on batwing of center console.

Nice. Thanks Jim.