2 very weird problems, any ideas? (996 C4)- resolved!

[FLGirl]

Well, I've had my wonderful 996 for a month now, and I love it more each day.

But she has just developed a very weird problem, made odder by the fact that she just spent 5 days at Paragon Porsche having a whole heap of work done.

I picked her up from Paragon from Tues just gone. I drove the 45 mins home (lovely twisty roads) & she felt absolutely amazing, like a different car, completely planted, focused & direct.

The car then sat unused until Saturday, when I went for an hour's drive. I came up to a tight lefthand bend, and was doing about 60mph through the bend (car could have easily coped at 90mph through said bend, so wasn't hammering it). Almost exactly as I hit the apex, I think I heard a noise & the car swerved quite suddenly. It felt similar to losing traction through the rear, except it wasn't loss of traction. After this it suddenly feels like there is loads of play in the steering, and over 80mph the steering goes really 'light', to the point where changing lanes causes the car to wobble.

I thought it was just me, but this morning drove the car to Goodwood (about an hour) & it was very noticeable. Then the second strange thing happened. Wide country road, approach roundabout at approx 50mph, brake (hard, but not excessively so) & there was a horrid grinding sound, it felt like the brake just locked & all the dash lights flashed up. The car did slow, thank god, and as I gingerly drove on I tested the brakes again & they were fine. No more problems at all on the drive home with the brakes either.

Below I have listed the work Paragon did, which is why what has happened baffles me, & I was hoping someone here may be able to throw a few ideas around before I call them tomorrow please.

- Replace engine poly belt
- Replace front & rear brake discs & pads
- Replace engine coolant blanking plate gasket, bleed & refill system
- Replace rear anti roll bar bushes
- Replace both OS droplinks
-Replace front & rear metal brake pipes from flexis to calipers
- Replace all coil packs
- Check 4 wheel alignment (rear TCA bolts seized) adjust front steering geometry
- Full MOT (passed obviously)

They did note that the rear track arms were seized, as above, & the MOT had an advisory about some play in a pin or bush in the front suspension which they talked to me about & we agreed it would be fine until I bring her back for a service in Sept.

Paragon did a great job, & the car felt absolutely fantastic when I collected her from them on Tues, hence I am so baffled about what could be the issue now (suspension related, given the advisories??)

Help please!

 

[Wattie]

I'm not at all sure, but that front bush sounds as though it may be the issue here... It sounds like one of the front wheels is waggling about in a way that it shouldn't do! That would explain both the cornering and high speed problems, and possibly the brake noise if the disc is moving inside the calipers?

I presume you have checked silly things like tyre pressures?

I would get it checked ASAP: If you have anything loose at the front end it will only get worse the more you drive it and could cause consequential damage (or even an accident).

Another possibility is front differential failure?

 

[NXI20]

First problem sounds like a loose or broken droplink, probably the front one given the symptoms. Easy to check visually if you don't mind crawling under the car.

Don't have a clue on the brake problem :dont know:

 

[Stuart]

My advice us take it back to paragon and get them to resolve it, could be a abs fault with all the lights flashing?

 

[FLGirl]

Thanks for the quick replies

I jacked the car up earlier & couldn't see anything amiss at all. Gut feeling is it something at the front & suspension/droplink/bush related in some way, & there is something 'loose' going on. Tyre pressures checked yesterday before I took her out properly.

I'll be giving Paragon a call in the morning & taking her straight back in, but just wanted to see if anyone had pointers so I could run through it with them.

 

[oze172]

+1 for definitely taking it back. Could be a number of things working loose or not properly seated. Hopefully nothing expensive. BTW, make sure all the wheel nuts are still present and torqued to 130Nm.

Good luck and let us know what it is when you get to the bottom of it

 

[Wattie]

BTW, make sure all the wheel nuts are still present and torqued to 130Nm.

Good point, well made...

I had a quattro coupe once that developed similar symptoms soon after I took delivery and the wheels had just been refurbished.

Couldn't see anything wrong, but it got worse and worse and eventually I decided to drive it to the nearest Audi dealer - front wheel fell off as I drove onto their forecourt!

 

[FLGirl]

Just back from Paragon. They could find absolutely nothing amiss. Head tech guy (Mick) took it for a spin & says it fees better than many 996s with much lower mileage.

He did point out that as discussed, the front track control arms do need doing & this will affect the handling at higher speeds, as I'm experiencing. This is due to be done in Sept when she is also due her next service.

But on the drive home 'it' happened again, twice, & now I have a clearer idea, so another question.....

Same scenario, entering a tight-ish bend at around 60mph. Again, a bend I thought the car could easily manage at a much higher speed. Right on the apex it felt like the car suddenly slowed & a dash light flashed on. It felt much like a jab on the brakes would. It happened again at the next corner, exactly the same speeds & sudden slowing plus warning light.

Could this be the PSM kicking in? If so I am surprised as I feel I am nowhere near the limit of grip of the car. The brakes are new all round, the rear tyres are new, so why would it do this? I am no rally driver, but I am certain the car should easily have handled a corner like that in excess of 90mph without breaking traction.

I figured maybe it was worth switching the PSM off & testing the car's cornering, but am a teeny bit wary of pushing hard & ending up in a hedge! Any willing volunteers in Sussex want to come for a spin & help me assess what is happening?

Or any other ideas? I can only guess PSM, but it seems odd that it is quite so cautious, or feels quite so abrupt as it did (which actually caused a loss of stability right on the apex, rather than helping me stay the line!)

Any further ideas would be greatly appreciated...

 

[wizard993]

You need to leave the car with the garage until this issue is resolved. You don't want to hurt yourself if something lets go going around a bend.

Even an advisory on a 911 should(IMO) not be ignored.

 

[Stuart]

My guess is you are experiencing PSM. Had this on my C4 once or twice, never on a sweeping bend though. Maybe it's sensing a tyre about to break traction and kicking in. Just out of curiosity what pressures are you running, maybe too high in this weather?
You sound like you know what you're doing, try a few progressively quicker runs with the PSM off. Check that pressure first though... :thumb:

Edit to add, be safe though...

 

[GD]

What light is flashing on, did you manage to see it? Was it red or orange/yellow? Did it go off again?

It might be a faulty ABS sensor on the wheels. If the light is going on and then off again, that usually indicates a loss of grip and the PSM or ABS coming on.

If you have PSM, does it happen with it turned off? Was there any error codes in the system?

 

[FLGirl]

It is definitely a yellow light, on the left hand side of the panel, but it flashed too quickly for me to see what the symbol was! It came on each time the car 'stopped'.

I have a friend over on Weds(excellent driver & used to performance cars) & we are going to take the car out & test it out with & without PSM in an empty car park. I'm also meeting a few of the Porsche guys from PH this coming Sun, so will get one of them to test the car as well, and take it from there if it persists. Meanwhile, I shall stick to pottering & not provoke the car!

Thanks for the input, I will report back

ETA: What tyre pressures would you recommend, car is on 18" alloys? Currently they are stock pressure as per manual, perhaps letting them down a little will help?

 

[Stuart]

ETA: What tyre pressures would you recommend, car is on 18" alloys? Currently they are stock pressure as per manual, perhaps letting them down a little will help?

Did you measure the cold pressure? The days have been pretty hot recently and a spirited drive would def increase temp and pressures. I run:
cold 34 front 40 rear
hot 34 front 38 rear
But these are just what I've found to work best with the MPS2 tyres.

IIRC the PSM light is an amber ! in a triangle... :dont know:

For a 997 though...

 

[dzung]

I don't think it is the PSM that is the primary problem. I have PSM and it acts very subtley. PSM works when more than 7 degrees of angle slip detected to brake individual wheels and reduce power. Should not be on/off as you describe. The fact that it happens at the apex of the corner when you are applying power makes me think it could be something to do with a problem maybe with the front diff not transfering power to the front properly. Is there any front diff whine ? Normally only 5% of power to the front but when diff detects front and rear wheels spinning differently applies more power to the front up to 40%. The fact that you have some lock on tends to exascerbate any underlying problems with the diff and the PSM light then goes on as a secondary sign that the car is confused. I had the PSM light going on randomnly when I had the geo redone but they didn't redo the slip angle sensors on the steering. Either way get Parragon to sort it out as definitely shouldn't do that. Your Porsche should be inspiring confidence not playing up at the apex of corners. Porsche's due to their rear weight bias have amazing traction out of corners and you should not have the PSM going off. I previously had M3 and Subaru WRX and traction really high in my Carrera 4 in comparison with abilities of car far higher than my limits. Good luck finding a solution. Get plenty of people to try it out and you will get plenty of good ideas on this forum

 

[FLGirl]

:thumb: Thanks everyone for all your input. I will redo the tyre pressures tomorrow when I go out again, then test the car with PSM on & off.

dzung - what you have said sounds very close to what I am feeling, especially that the PSM should not kick in carrying only 60mph round a sweeping bend. It only happens on right handed bends as well (??) The car jerks, & the yellow light comes on very briefly, then it rights itself, but for the very small moment the car feels like it is applying just one (maybe 2) brakes very suddenly & quickly right on the apex. You're right, before it started doing this I had every confidence in its ability to corner at speed, now even at lowish speeds there is an issue.

Paragon did do a geo alignment, & the car has only done this since coming back from the garage. I owned & drove it every day for the 3 weeks since I bought it & leading up to the time I took it in. The bend I took at the weekend where this first happened is a very familiar piece of road which I drove frequently in that time, & this never happened before at the speeds mentioned, in fact, I kept pushing the car as I grew more familiar with it.

I'll give Paragon another call tomorrow.