Water from the exhaust on cold days…what’s that all about?
 

Hi all,
My wife’s 740 (B200E) tends to have a bit of a splattery discharge of water from the exhaust from time to time. Usually when it’s cold, but occasionally when it’s been running in the drive warming up and is up to temp.

It doesn’t loose coolant, runs very well and, whilst a bit crotchety with regard to cold starting (always fires up but is a bit lumpy/flat for the first ten seconds or so) is always reliable. No clouds of steam, bubbles in the header tank or mayonnaise in the rocker cover to indicate HG issues, and the water from the exhaust isn’t coolant (yes, I tasted some on my finger to check…don’t judge me! :confused_smile:)

What could this be? Just condensation? The exhaust is past it and the back box has some minor perforation, to be replaced soon when we can afford it.

It’s a pre-Cat car. I’m not worried, just curious. Any ideas?

Perfectly normal, just condensation

All perfectly normal for a K-Jet Phil. Remember they were designed to run on 4-star and not unleaded which has a naturally higher water content. Also if you're running it on that E10 muck, that attracts water so is likely to produce a bit of condensation, the E5 (super unleaded) isn't as bad but still produces more condensation than the original 4-star leaded fuel.

I agree with the other posters, 'AHKV', it is almost certainly condensation. If, as you say, the exhaust system is past it, and if the car is a 'keeper', it may pay you to consider fitting a stainless replacement. Acidic condensation can be responsible for the premature demise of most mild steel systems.

Regards, John.

Don’t forget basic chemistry you are burning a hydro carbon with oxygen.

The carbon burns to produce carbon monoxide CO an carbon dioxide CO2 and the hydrogen produces water H2O. All of this comes out the exhaust pipe the water as steam and is much more visible on cold mornings.

My 940 LPT does the same thing.

A few days ago I replaced the rear backbox(£34) as rusted through/ advisory on MOT. Fitted new BM box and fired up to cure exhaust paste and water was dripping out of join until hot enough to set. Then spitting out of tailpipe! Always done it when weather cold and no coolant loss.

The new Klarius tailpipe is so badly bent/ formed I didn't fit it as so restrictive. Re-fitted old one. Will be going back to ECP.

The exhaust is Euroflow and lasted 5 years. The over axle pipe will need doing next, about a year but midbox to cat still looks OK. Downpipe and BM cat good. May try a Volvo system next time, although didn't last 3-4 years on my 240. Parked on grass and not used much. At least should be bent/formed well.

James.:thumbs_up:

Thanks all! I’m glad it’s nowt to worry about. I did suspect that all was fine as the car runs like a peach (and is surprisingly good on fuel too, the least thirsty redblock car we’ve had by some margin) but good to know for sure.

A stainless system isn’t a bad idea at all. I have one on my diesel 940 which was fitted for the previous owner eight years or so ago and is still in excellent order, so I’d definitely consider one for the 740. I was tempted to go stainless when I fitted a new cat-back system on my petrol 940, but I got such a blinder of a deal from my local main dealer that I ended up fitting a genuine system. Next time!

"May try a Volvo system next time, although didn't last 3-4 years on my 240 because it was parked on grass and not used much."

Added a little to your words to give the most likely reason your genuine 240 exhaust failed. For some reason parking cars on grass causes them to rot quite badly underneath.

The genuine exhaust I put on my 940 is beautifully made-once I’d got the old one off (took about five mins as it was rotten as a pear!) it took me a total of 15mins to fit the Volvo system. It fitted together like butter, no issues whatsoever and the hoop clamps are superb quality. I’d definitely go OEM again, so much easier than the cheapie ECP stuff and seems to have lasted well, it’s been on the car for a couple of years now with no significant deterioration at all.

Not being used much will also be a major factor as the condensation will just sit and rot exhaust from the inside