Quadcammer

Evening gents. I'm on my way cross country with my new to me 993tt, and since its my first air cooled porsche, I have some questions about whats normal on the gauge readouts and other things.

1. On a cold start, my brake booster pressure light stays on for maybe 20 seconds. Once the car is hot, it turns off immediately. Keep in mind it has been very cold overnight (in the teens). Normal?

2. At a steady state cruise of about 70-75mph, the oil temperature gauge is basically right under the second mark (194 degrees according to p-car). While that seems acceptable, on the first leg of the trip, I felt like the car ran cooler, and I'm not sure why. Car doesn't overheat ever, and it has a manual fan switch. Either way, it seems like thats a bit hotter than normal. Anything to check here?

3. At a hot idle, oil pressure is between 1 and 2 bar, typically closer to 2 bar. At 2600rpm, its basically dead on 4 bear. And at 3k rpm, its almost pegged at 5 bar. This ok?


Knowing how important oil is to these engines, I just want to make sure all is well. The car runs flawlessly, so I'm not too concerned.

Also, one other question:

4. On occasion, at idle, I hear a slight buzzing and feel a slight vibration through the pedals that sounds a bit like a fuel pump or servo. It goes away when you take your foot off the clutch, and it only lasts about 5-8 seconds. Any ideas what this is?

Thanks a lot for your help.

I'll make sure to get pics and more details posted when I get home.

Basal Skull

FWIW

1. normal
2. sounds okay, by manual switch, do you mean someone has a fan override switch put in so you can turn the fan on and it does not come on on it's own? While probably a reasonable thing, have to remember to turn it on when you engine temps get any hotter than the 194 mark. Cruising at those speeds, would have thought the temps may run a little cooler, you can put your hand on the passenger front fender to see it it is getting warm and the thermostat working okay. Usually the temps get up to around 194 or so and then decrease slightly as the termostat opens and temps go down with oil circulating through the oil cooler, should also be able to hear it in the passenger footwell.
3. oil pressure seems okay, good rule of thumb I've heard is 1 bar for each 1000 rpm, figure anything higher is okay. Varies some with weight of oil used
4. don't know.

Enjoy the drive. Going across country in a 911 is a treat you'll remember for the rest of your life. I've gone from one ocean to the other twice.

Quadcammer

Good input, thanks.

The switch is designed so that the fans work normally if its off, and it forces the high speed fan on all the time when its on. I've been running with it off for the most part.

any other input on the other stuff would be great gentlemen.

Cheers,
Oliver

WHB Porsche

1-3 normal. Oil pressure puzzled the hell out of me at first, but it's fine. Brake booster light common on all AWD 993s (C4/C4S/TT) when cold. Oil temp sounds fine.

Not sure about 4.

Texas993

4. May be your clutch accumulator motor running. It provides boost to make your clutch pedal easier to depress.

911/Q45

No clutch accumulator motor. The clutch assist gets it's power from the power steering pump.

Texas993

Shows what I know. I guess it isn't possible to feel the power steering pump that far away. Plus isn't the power steering pump belt driven, thus always running?

ca993twin

There is a brake booster pump that is a bit noisey on 1996 models... fixed on 1997 models. This may be the vibration you are feeling. Normal.

Quadcammer

Interestingly enough, it appears my oil thermostat wasn't opening on the highway. Fender was same temp (read cold) on both sides.

However, I think the reason is that the weather was so cold (no engine tray), that the thermostat never had reason to open.

Thanks for the input guys.

CincyScott

Item 4 could be a throwout bearing? I always attributed a noise when the clutch was depressed that went away when released as that bearing...of course most Porsche things go beyond what I think is normal

Quadcammer

I'm almost 100% sure its not a TOB. sounds more like a pump than anything.

mongrelcat

Get it fully up to temp (as far as it will go while driving, anyway,) and then let it sit for a while. If you let it sit and idle for 8-10-12 minutes the temps will rise to the point where the thermostat should open.

It's been hovering around freezing here and my car's thermostat opens after 15-20 minutes of normal driving (at around 200F.)

Quadcammer

ok, here's an interesting one.

Where the central lock button should be, I simply have a blank switch cover. Any reason this might be the case?

911/Q45

I've got an extra thermostat assembly for cheap if needed.

Felix

It is possible to move the switches around, either intentionally or by accident. From memory there should be 5: hazards, rear wiper, sunroof, central locking, and warning light reset. And then 1 blank. You're saying you have 2 blanks?