overthehorizon

Hi all
I'm in the process of recommissioning a "garden find" slate grey 89 C4 coupe.
My current bug bear is the ABS / 4WD ECU (part number 964.618.126.00).
It seems to have significant corrosion issues caused by water ingress.
Has anyone any experience of repairing or recommissioning one?
It looks like a rather expensive part to source - so equally if anyone has a working spare I would be interested in that too.

Here's a pic as found in the garden (in deepest darkest Lancashire)

mark lintott

Actually I have one sitting on my shelf. Thing is it was replaced with a new one (yes, very expensive) by the main dealer here but later experience indicated the part was likely not at fault. I've never checked it or had it tested so I don't know if it's good or bad..... If you're stuck then maybe we could work something out but I'd have to find someone here to verify its good/junk status.

You may find it's simply a problem of corrosion on the connectors and not inside the unit in which case a good clean up might yield results. The plugs and connectors in the frunk seem to be very sensitive to damp in my experience. What symptoms are you experiencing?

Cheers

Mark

LM964

The way the ECU is positioned allows water from the boot lid to collect and pool. Result is the gradual corosion of the pins. Had exactly same issue. I removed the unit, left it in the airing cupboard for the day then gently brushed all the pins and vacuumed out all dust/particles etc. Luckily the pins hadn't corroded enough to break. Cleaned connector female pins, some electrical contact cleaner and now all good. Hope yours only needs the same careful tlc to bring it back to life.

LM964

Post up your 'recommissioning' progress with any pics too.

SyncroGhia

I've done a fair amount of reading up but can't find this so I thought I'd ask.

If the 4WD hydraulic control system fails while driving (say a hose splits and loses all pressure), what happens to the torque split front to rear of the centre differential?

I know that the standard split is 69/31 but is that based on no pressure being used from the hydraulics or based on a certain position of the slave cylinder against the centre differential fork?

Thanks

MG
​​

Goughary

The torque split is mechanical. So if the system is shut down there is virtually zero effect.

You lose your rear differential so there is no "limited slip" across the back. The diffs are open front and rear. But the torque split doesn't change.

r-mm

I've seen electronics dry ice blasted with low pressures. Have personally done miracles putting items in bags of rice (cheap desiccant). But I suspect your problem is damage wrought by old moisture not current moisture. For sure open it and try some home spun repairs.

LM964

Assuming I guess that with no system pressure you wouldn't be able to lock the front/rear diffs either - not that I've ever known anyone who actually has had to use the lock switch!

r-mm

Exactly. All locking f/r and rear l/r is hydraulically activated. Pressure from the bomb is metered by the solenoid and actuated by the slave cylinders.

Goughary

I used the lock switch once. When i first bought the car - i had no garage- it was in a parkinglot and we had a huge snow storm. The plow came and put a big snow bank in front of the car- after a 12 inch snow fall overnight. I had to get to work and i was pissed- so i switch on the pdas and just pushed straight through.

I fixed the damage to the bumper later that year. But wow. The C4 with snow tires on it is an impressive beast in the snow.