canddmf

I've searched the 964 postings for this and can't find it, so am seeking fresh input.

I have a 1989 C4 with around 115K miles on it. Last week I started seeing the interlock and brake warning lights turn on at the same time. At first, I topped off the brake fluid level (which was at the min mark) and that seemed to clear the lights until today.

Today, while driving, the 2 warning lights came on again and stayed on. The brake fluid is around half-way between min and max, so that shouldn't be it.

Any suggestions where to check in the trouble shooting list? Like many 911's, mine's wet underneath and I wouldn't be surprised if some sort of pump were leaking.

The owner's manual doesn't mention how the 2 warning lights might be related, but I thought some of the more technically savy folks here might know.

Thanks and looking forward to your help

canddmf
1989 (1/2) C4

gfunk

I recently purchased an '89 C4 from California and drove it up to Vancouver, BC. Since its been in my garage I have also noticed the PDAS warning light come on at engine startup. If I back out and drive away slowly it seems to stay on, however if I blip the throttle and rev the engine a little I can usually make the warning lights go out. Since I just imported into Canada I am not insured yet so I haven't spent a lot of time on this but I would be interested to hear if others have had a similar experience.

Greg
1989 C4
2000 M5

DaveK

Greg - that's normal from a cold start. The system gradually looses pressure when it's off, and needs to recharge. The lights should go off in 30s or so. If they don't go out for several minutes - and if you do need to rev the engine to make them go out, it's probably some sort of power problem (e.g low battery, low alternator output). I used to have a problem where I needed to rev the engine to make the lights go out - and it was my clock causing it. New clock solved the problem.

canddmf - It could be that the pump is leaking at the pressure switch. It's a fairly common problem - the pump is in the luggage compartment, in front of the battery (under a plastic cover).

Andy Roe

canddmf,

Are you sure that it's brake fluid beneath the pump? It could just be water from a leaky bonnet seal. Either way, get it checked out, as if the pump fails, you'll have no brakes!!

Greg,

On my old C4, I had the Voltage Regulator on the Alternator fail. This caused the same warning lights as you've got, and the buzzer on the first start of the day. Reving the engine stopped this. If you're brake fluid is low, the system will most likely take longer to get up to pressure too.

Andy

gfunk

Dave, Andy:

Thanks for the help!

Greg
89 C4

canddmf

Thanks for the input folks.

New information this morning...Last week (Thursday), I refilled the brake fluid reservoir and today, its at or slightly below min again. Looks like my warning lights are from the low fluid level, after all. I'm going to check out the pump as suggested.

Since I've dumped a pint of Dot-3 in the last week, I'm sure that will be noticable in there.

Sounds like a fun weekend project.

Andy Roe

Sorry to hear of the fluid leaks - just remember that brake fluid will eat away your paint work in now time!!