New water pump: worse fuel consumption

[BMWDriver]

I've noticed my fuel consumption has gone up about 12% since my water pump busted and got replaced. Was not done by my usual mechanic unfortunately, not even a bimmer specialist. The thermostat has also been replaced within the operation. From 8.4L/100km on the highway I now show 9.4L/100km on the OBC. Naturally, my driving habits are quite the same as before on the highway (±105 km/h).

But, the car runs nicely, the temp is right on, and performance is no change (a slouch at low revs: M50 pre-Vanos)

I have not made calculations yet (will need to fill up soon), and my fuel guauge is playing tricks on me again : showing empty when half full. Also, the fuel consumption needle seems to wobble a bit even on a level road. I'm beggining to suspect the cluster might need new capacitors again.

Strangely though, I keep one of the two consumption numbers without a reset, and that one seems to show a pretty consistent number.

Was anything overlooked I wonder? Does engine management need anything done after such a change?

[Ken35i]

Maybe the mechanic took it for a thrash...
Or he idled the engine for a while to make sure everything was working properly.

[tim eh?]

mine varies between 8 and 9.5 depending on all kinds of things - you probably took it out on a windy day or something. that was i while ago you changed that pump tho no? bad gas maybe? maybe your plugs are getting old?

i have the same fuel guage problem - i'm convinced it's not the capacitors, i actually had my local tv repairman check them for me - i think it's either the wiring somewhere or the guage itself as my obc reading is fine and my reserve light came on the one time i let it get that low (before replacing the fuel tank).

btw i never said but that tip you gave me about resetting avg speed to get mph works like a charm - common sense but it takes brains to think of it - thanks, sure beats multiplying by 1.6 on the fly.

[Rus]

The best way to estimate fuel consumption rate is using your odometer and the amount of fuel used. The OBC is rather inaccurate, at least in my car.

[BMWDriver]

Could be any number of things I suppose. I'll probably let it fly for now.

Thanks for the compliment Tim !

[BMWDriver]

Update: looked at the intake from MAF to engine to notice some cracking on the big hose, below where two other tubes hook in. One of those two hoses could use replacing. Somebody got lazy and used duct tape... as if that was any help.

I unplugged Mr. Big Tube a bit to look at it, rehooked it up. Now on the highway I did 8.8L/100km, which is more like it. I'm on the right track.

An air leak around there can affect fuel consumption, have I found out as I researched here on the posts.

[tim eh?]

...I unplugged Mr. Big Tube a bit to look at it...

nice- i like your style, brother. :D