Water aversion

[lawson]

This is a long story. I have a 2001 406 HDi90 estate with approx 140k miles. Back in November, in the dark, I drove at speed into about 6" of water. The engine kept going and, although it would not rev above 1500, we drove the 5 miles home. The next morning I dried the air filter thoroughly and, after a bit of coaxing, the engine revved freely. The car ran perfectly for the next few weeks until, on New Year's day I ran into a big puddle - possibly 3-4" deep - and revs dropped right off and would not go above 1500. After about 30 minutes of coaxing it recovered, revved freely and was fine until 14th Feb when, again, I hit a sheet of water flowing across the road, poss 2-3" deep. This time no amount of coaxing would get it to recover and it had to be towed home. It would rev up to about 1500 but it started to make a bit of a clatter so - fearing the worst - I had it recovered to a local garage. The garage has had it turning over and it turned out that the clatter was the crank pulley which needed replacing but now it won't start. To sum up - in between its encounters with water it ran perfectly. When it wouldn't rev it sometimes displayed a 'pollution' fault. It only takes a small amount of water to upset it. I am beginning to think that the water is coincidental and that I actually have a bad electrical connection somewhere which is somehow dislodged by water.

Can anybody help?

[steve_earwig]

Err, hello.

I drove at speed into about 6" of water

That's more than enough to drown one of these.

If the crank pulley lets go it can throw the belt into the timing cover and take out the cam belt, as it was done by a garage I think I'd be checking the cam timing just to be sure. Can this garage do any, you know, actual diagnostics?

[Welly]

My thinking:

If the engine ingested enough water to do mechanical damage it would've been evident straight away. A 'bit' of water might upset other things like the Airflow Meter or maybe the wave of water soaked some electrical connectors under the bonnet? there's a whole bunch of weird connectors under the battery tray etc. it'd be worth unplugging/checking/WD40'ing all the obvious connectors.

Turning the engine over with the glow plugs removed will check if any water is left in the cylinders (glow plugs must be well soaked in WD40 days before though) this would be a good time to do a compression test too.

You'd really need to crank the engine whilst doing a live code read too.

[lawson]

Many thanks for these replies. The car recovered completely from the first two water incidents - it's this last one, which involved the shallowest water, which is causing the problems. After the crank pulley was replaced the car ticked over fine but would not rev and now won't start.

[mjb]

I'm with welly - it does seem to be an electrical issue from the sound of it. First off, if you look underneath, are there any loose bits of plastic which could scoop up water and throw it upwards? That'd be a huge clue as to what's getting a drenching.

If not, there's still the clue that you firstly triggered a limp-home condition (likely something momentarily shorting), which has the capability of causing (providing it's the same thing getting wet each time) complete failure - and there's not too many things which will cause this. Fault reading might tell you what wiring caused the problem, but I've discovered a lot of faults simply disappear (i.e. they're not logged) when they're fixed, in this case by drying out. I'd definitely assume for now the problem's with a connector getting wet, not with a sensor or something itself.

Actually, one of the first things I'd do is check for excessive crud in the ECU box, and signs of corrosion on the connectors in there

[Doggy]

I would check the indicated cranking speed too - needs to be > 60 RPM or it won't trigger the injectors and that you have at least 250 Bar fuel pressure.

While you're at it, check the crankshaft / camshaft synchronisation says it's OK and that the ecu/BSI are matched & unlocked.

[GingerMagic]

There was a thread recently on the coupe club, where a member accidentally poured water over his Map sensor when filling up the washer bottle. It was dried out but never really the same afterwards.
Do you have the plastic wheel arch liners in place, along with the little cover behind the headlight? Maybe water is getting into the engine bay that way...

[lawson]

All running smoothly now. Garage replaced crank position sensor and found a fault with the loom earth. Don't know whether or not this will cure the original aversion to water but - for the moment - the sun is shining. The clutch - which had been feeling scrunchy for a while - failed while the car was at the garage so had that replaced too. Thanks to everybody who proffered advice.

[lawson]

Spoke to soon. Three hundred trouble free miles and then all the lights except the headlights failed. Gathering darkness forced me to pull over and stop. When I first stopped, I thought that turning the ignition off and restarting might clear an electrical fault. The first couple of times that I did this the engine restarted (still no lights) but now the starter cranks but the engine does not fire. The headlights still work but no other lights - no rear lights, no radio, no interior light, no dash display - although weirdly all the dials/gauges are frozen. Even though the battery has been disconnected the needles have not zeroed. No rain or water involved on this occasion.

[lawson]

Continuing saga. The car is now with Peugeot dealer who say that they can diagnose nothing without a new BSI. They are happy to fit a second hand unit if I can find one so I am looking for a complete set of ECU, BSI, key fob and key ring. Do the serial numbers on both the ECU and the BSI have to be identical to the numbers on the existing parts or is it sufficient to match the part number on one or other? Thanks!

[GingerMagic]

Continuing saga. The car is now with Peugeot dealer who say that they can diagnose nothing without a new BSI. They are happy to fit a second hand unit if I can find one so I am looking for a complete set of ECU, BSI, key fob and key ring. Do the serial numbers on both the ECU and the BSI have to be identical to the numbers on the existing parts or is it sufficient to match the part number on one or other? Thanks!

You will need the ECU and the BSI from the same car - ideally the clocks and door locks/keys too to keep everything together. The BSI and ECU need to be 'paired' so they can communicate - I'm not sure a second hand BSI will be the answer.

Have you checked under the carpets on the passenger side for wet connections? Its the failing clocks that are making me think thats the problem...

[lawson]

Thanks for this Gingermagic. The Peugeot dealer insists that they can do nothing without a new BSI. They could sell me a new bsi for £400 odd but it seems cheaper to get a used bsi and ecu and key fob and key barrel all from the same donor. I'm just not sure how closely the serial numbers have to match up to the numbers on the ecu and bsi at presnt in my car to make sure that the 'new' ones will work.