JimEb

Getting to my wits end with these constant faults. Started last fall when I took my car to an Indy to change out that black plastic coolant pipe.

Since then on 3 different occasions I found two vacuum lines unconnected and the sound symposer COV leaking. Thought I was good after thar last one but a fair amount of miles later it just popped up again.

Car’s a base 991.1. Faults seem to pop up when driving the car in a sporty manner. Warm day, not running the heat. Car was at temp after about 20 miles on a highway, pull onto back roads, engage sport plus and start having fun… few miles later the fault pops up. My first hunch is the transmission cooler COV. Can’t think of any other COV that sport plus would affect.

What baffles me how does the car know a COV is bad? A leaky one would drop the vacuum of the whole system. There must be some sort of vac sensor. Other than that maybe resistance in the COV solenoid coil?

Guess I’m off to buy a bunch of new COV’s, load the parts cannon and hope I can finally put this one to bed.

worf928

There is a MAP sensor on the hardline from the brake booster that provides vacuum measurements to the DME. The DME has an algorithm that predicts what the vacuum should be based upon accessories in use and driving conditions. So, do not assume that you can use black box testing to figure out why the codes are thrown (which I assume are P1432 and P1433) and narrow it down.

If you have a good tester, it will have a COV test which may narrow it down.

You’ll need to bench test each COV and make sure that the switched accessory holds vacuum. And of course make sure that the vacuum source network doesn’t leak.

If you’ve found vacuum lines disconnected (presumably due to previous shoddy work) then I’d also make sure that the vacuum source network and the vacuum release network aren’t cross-connected and that each COV is properly connected to the source, drain, and accessory.

99-911

I'm having similar issue but haven't got it sorted yet. out of the blue & on cold start I got the yellow warning on the MFD "Refill coolant level, observe engine temperature". I went a head & topped the coolant up but strangely I got the red warning "Refill coolant immediately, don't drive on" despite the coolant reservoir indicator (ball) visually being on Max.

I looked it up and so far:
- my PSE is functioning normally so less likely being a disconnected vacuums line.
- there is no coolant leak anywhere.
- the problem still active every time I start the car; I get the yellow warning on start up & in 10 min time I get the red warning.

Appreciate any pointers as to what could be the issue? should I ignore the warning & drive the car at least to a workshop?

JimEb

Are all your warnings about low coolant or is your car actually overheating?

.1 or .2?

99-911

Thank you for taking the time..
It is 991.1

correct, all warning are about low coolant & they happen within 10 min of cold start, while the car is stationary, no fan noise either.
I noticed the MFD red warning is accompanied by "un-natural" (? programmed) rise of the coolant temp analogue gauge to max !!

Jack F

I see a few options. You can take to dealer and tell them to sort it out before giving it back meaning they might keep the car for a few days and drive it a bit and see if the errors pop up after driving or numerous cold starts.

Another is to buy a coolant vacuum kit and hook it up and drain a bit and then slowly refill. These kits are cheap and can be helpful. Best to you!

worf928

This "un-natural" programming of the coolant temperature gauges (analog and MFD) is well-documented. The firmware is programmed to show 194°F (IIRC) from about 185°F to about 205°F if memory serves.

What was the last service prior to you observing this behavior? And how long has it been (in time and miles) since that service.

You likely DO have a problem and should avoid driving it.

99-911

Thank you for taking the time, highly appreciate your input ..

the faults are consistent on every start & I'm afraid to drive the car out of the parking building.

I'm not familiar with coolant vacuum use but is this drain-then-refill procedure meant to "reset" the level sensor?
may be I forgot to mention but the physical ball gauge in the coolant reservoir is at max while the electronic sensor is sending to MFD Low/No coolant signal !!
how can that be explained ?

ADD: I'm thinking I should try replacing the coolant level sensor as 1st step & if that fails then I'll flat-bed it to a dealer.

99-911

Thank you for taking the time, really appreciate your input..

Last oil change was 4 months back, less than 1000 mile ago ..

I already am afraid of driving it just to get out the parking building.

JimEb

If the temp gauge is actually showing overheating then this is more than a faulty coolant level sensor.

Might be coolant isn’t flowing…water pump, thermostat, coolant shutoff stuck closed, etc.

I wouldn’t drive it in this condition. Might be time to flat bed it to a shop.

CSK 911 C4S

Of the 3 that I had go bad on my 991.1 the COV deforms slightly and "puffs up". The sides looks slightly rounded vs square.

JimEb

In those cases the solenoid coils shorted out and got hot. Did that pull a code indicating what COV failed? Because in that failure mode the computer should be able to tell. With a single leaky valve the whole system looses vacuum since they are all connected. It’s like a dead bulb on your Christmas lights killing the whole string. Can’t tell what bulb is the culprit until to check each one.

Reading more about how this system works I think I’ll first check the heater COV. My cars a summer car so I rarely have the heat turned on. Honestly don’t know if it’s working. Whenever the car calls for extra cooling it opens the heater valve….whether or not you got the cabin heater on. That might explain why this fault pops up in sport plus mode when I drive sporty.

I have a manual transmission, the single COV there is used for both heating and cooling the gear oil. Suspect that valve opens up as the car hits temp to put some heat to the cold gear oil. You notice when the transmission is cold because it doesn’t like to shift into first if the car is rolling. Once warmed up it shifts smooth. If that COV was the culprit I’d suspect I’d see the fault pop up when the cars cold in any driving manner and in the time it takes to start shifting smoothly.

99-911

Thank you for taking the time, appreciate your input..

I agree it's risky but my gut feeling is the gauge is programmed to jump at once to max as a safety protocol.
for the time being I'll leave it to be tackled when I have the time to sort it out..

worf928

Your gut is wrong. See my above post. The behavior is well documented if you look for it.

If the gauge shows a temperature out of the deadband (e.g. Max) then the car thinks the coolant temperature is what is displayed.

Yes, the displayed temp might be wrong. But it might also be right.

The good news is that if you drive for an hour or so with the temp display Maxed, and your engine doesn’t seize, then you know for sure that the gauge display is wrong.

JimEb

If you have a scan tool you can monitor live data. View the coolant temp without any of the gauge fudge factor.