ZX TD Air filter - damp and wet ???

sooty · Post by **sooty** » 11 Jan 2007, 20:28

I took out my air filter as a routine check for leaves etc. and found the filter to be quite wet.

I have not gone through any floods or roadside pools as I travel 99.5% of the time on Motorways. So I assume it must be the constant deluge of rain and spray I've travelled through the last few weeks. I noticed too that the performance has dropped off, maybe due to this where the filter is sodden and not free flowing as it should.

Anyone else had this problem or know a cure, as the intake is behind the headlamp and alongside the rad, I think.

James.UK · Post by **James.UK** » 12 Jan 2007, 17:04

Hiya Sooty..

I can't think of a cure as the spray on motorways can be very bad these days. It may be possible to re route the pipe so it is up higher and catches less spray but I'm not sure.. I guess the only solution is to change your filter more often, maybe you could dry the old one out and swop them over when they get wet.. ?

jeremy · Post by **jeremy** » 12 Jan 2007, 17:50

What we don't know if its wet through inhaling rain or spray drops or simply damp air. I'd have thought that damp air could cause a problem - as after all a TD inhales loads of it.

If its droplets I suppose a trap could be made. I think the theory is that the air stream should hit a baffle at right angles - so the droplets collect on the plate and the air bypasses it. The drops then run down the plate and into a sump from which they are disposed of. This is basically the old oil bath type of air filter in its layout and function.

I think your loss of performance is actually due to air saturated wuith water vapour - which if my physics is correct means that there is less density of oxygen due to the water vapour basically taking up some room. Charge density is vital for diesels - which is why your car has an intercooler (it gets less dense as it expands - so the intercooler reduces the problem) Atmospheric pressure is generally less in rain too.

sooty · Post by **sooty** » 12 Jan 2007, 19:59

Thanks both,

But I think my drop is due to restriction of flow through the element. I am going to look at fitting a deflector of some sort in front of the intake instead of facing the elements with a wide open mouth.

As you say about a catcher for the droplets, this would be differcult where the air enters the side of the filter chamber at the base, straight into the side of the filter element.

I shall replace the fliter and keep the old as a spare as its not too old and see what effect it has.

citroenbx · Post by **citroenbx** » 12 Jan 2007, 21:18

Hi all..........Well i think your all correct and there are contributing factors but the ZX does suffer from a bad sealing/rusting air box.

Start your car up and put your hand underneath the airbox and feel for suction if you can get a little helper they can also just rev the engine slightly and you can listen to air being pulled into the box.

It only takes a few years on the road for the air box to start corrosion due to damp air being pulled from the radiator intake this dampness sits in the bottom of the box and starts the rust.

i'm sure a lot of paper filters get very wet because the box is so close to the road and with the airbox leaking, water splashed up is pulled straight into the element and wetting through.

When Citroen designed the Air intake you will note they introduced a flexible tube half way down its length.Like a tumble dryer this is the bit that traps the moisture and keeps the filter dry.....But if water is being draw in from Underneath the car this is being bypassed.

The best way to solve the problem is to reseal the airbox...Take off the base plate and wire wool it smooth again removing any rust then repaint it,grease it up and re fit it,that should be all.
Good Luck

jeremy · Post by **jeremy** » 12 Jan 2007, 21:38

CitroenBX - do Turbo-diesel BX airboxes suffer from the same problem? I ask as all of the air inlet system of my BX is plastic - as is the sytem of my ZX 1.9D.

AndersDK · Post by **AndersDK** » 12 Jan 2007, 22:36

The last couple of months have been endless rain & high winds here, with lots of water & mist on the roads. My BX TD has not in any way degraded in performance.
But then again the BX TD air intake is located high on top of the radiator in the cars LHS - like the petrol (monopoint) 16/19TRI's have.

Only thing is this week it has started to stall when idling cold. Guess I have either a cabling or cold idle timing solonoid problem.

BonceChops · Post by **BonceChops** » 13 Jan 2007, 06:39

jeremy wrote:I'd have thought that damp air could cause a problem - as after all a TD inhales loads of it.

Damp air is supposed to have the opposite effect. As the fuel ignites the water is turned to steam which expands in volume many more times than in its water state. This is supposed to increase power. Water injection has been played with for years as a method of increasing power and economy.

citroenbx · Post by **citroenbx** » 13 Jan 2007, 12:21

Yes the ZX-TD has a metal airbox running close the road surface...The 1.9d use's plastic and is located higher up the engine bay this doesn't suffer the same problem.

Hope this helps........

Stewart(oily) · Post by **Stewart(oily)** » 13 Jan 2007, 12:39

I had a similar problem with a motorcycle a number of years ago, after riding in freezing fog the bike just would not start, inspection of the air filter revealed the element to be coated with ice and not passing any air, half an hour in front of the fire dried it and the engine started, the ZX TD filter canister is in rather a vulnerable place and is quite prone to rusting and sucking water in, as previously suggested,cleaning of the filter body and ensuring a good seal should prevent more getting in.
Stewart

sooty · Post by **sooty** » 13 Jan 2007, 20:47

Good point about the base of the Air filter as it has a drain hole aswell as the possiblity of a poor fit of the spring clip fitted base/cap.

I think I'll sneak the element into the oven while she's out shopping on Sunday to dry it out and try sealing the base/cap.

Village · Post by **Village** » 16 Jan 2007, 20:29

would it be worth considering truncating the tubing and adding a K&N type cone filter further up the engine bay? I have a nice big hole where the ABS pump isn't...

Stewart(oily) · Post by **Stewart(oily)** » 16 Jan 2007, 20:41

Cone type filters sound rotten on diesels, just tidy up the original, theres little room for anything else under the hood.
Stewart

sooty · Post by **sooty** » 19 Jan 2007, 21:16

Up-date.

Since my last post, I dried out the element and greased the edging of the Filter housing cap to seal any gaps as suggested. But not the little drain hole incase any water does get in via the intake.

By doing this (drying the element), the performance has returned. Its too early yet to say whether the sealing job of the bottom cap has made any difference to the problem of the element getting wet.

If a cone type filter was fitted elswhere in the engine bay other than near the existing intake point for cold air, you would draw warm air which on these cars is the worst thing you could as they already struggle keeping a cool head.

If the results are no better over a period of wet weather driving, I'll post it.