Air Filter 740
 

Hello

Just out of interest, wondering how the air filter housing works, 740 B230E K- Jet.
It has a metal pipe to the exhaust manifold, and a larger pipe to the front of the car. The metal pipe has broke in half. I presume its to allow the engine to warm up quicker using the heat from the exhaust, just not sure if this one works, I put some heat down the exhaust air inlet, and the flap remained closed. Thought might get a few more horses if it works correctly.

Thanks

Andrew

The idea is the thermostatic flap valve in the part that combines the cold air intake and the heated air intake from the exhaust manifold heatshield allows for a faster warm up and prevents manifold icing in winter while mantaining an average temperature in the summer.

In practive they very often fail and will only admit hot air.

You will get the most power using cold air only as cold air is more dense than hot air, however you will notice hesitancy and flat spots in the winter witha lack-lustre performance.

If you renew the corrugated aluminium hose before winter and only connect it to the thermostatic flap valve when the weather gets colder and you start experiencing hesitancy/flat spots and disconnect again come spring next year, you'll emulate (for the most part) what the thermosttic flap valve is meant to do.

If you have a couple of pics that would help ...... but as you suspect the metal pipe off the exhaust manifold is there for exactly the reason you suspect.

I would also suggest that there is a diverter flap (between the hot air intake and that from the grille) in the intake attached to the filter housing which is operated by an air thermostat. Unless the piston of the thermostat is sprayed with a lubricant (WD 40 or the like) it seizes with intake crud.

You can dismantle the lot and, with difficulty these days buy a new air thermostat. The originals were made by a German firm Wahler (spelling?).

I can put some pics up later of the details when on my PC where they are stored if you want, but I think I put up a thread here a few years ago.

Bob :)

Here's a few pics assuming this is what you have got .... Bob :)

These were common on 140 and 240 too , they mixed cool and warm air with the thermostat to give an intake air temperature of 35 C The 340 had the system too on the 1700 cc engine . It makes driving away from cold a lot smoother even on fuel injection engines and reduces emissions . I remember the silver tube was very expensive 40 years ago , I see halfords sell something similar now , you may need a couple of pieces joined with a tube .

740 Air Filter
 

Many Thanks for all the replies, the pics are very helpful plus the advice. Will also see if I can get some new aluminium pipe, will try Halfords.

That be the kiddy Bob! Wahler Waxstat seems to ring a bell, some also had vacuum overrides so when you opened the taps, it would divert to cold air only for improved performance. Vauxhall also did this on some models and if memory serves, the vacuum pod pulled the Waxstat to bias it towards the warm air, when the vacuum went (for example when you bury the loud pedal) it relaxed a diaphragm allowing colder air to come in.

The vacuum assisted ones didn't seem to seize up for some reason, i'd forgotten about lubing the piston in it to get it working again, might have to give that a try, thanks! :thumbs_up:

One of the only people that do the air thermostats in Europe is Skandix.de at Euro 9.50 from whom I got a couple but, you do have to take account of their excessive delivery costs on top.

If you do want to separate the diverter from the air filter box you will need to take the box out of the car as drifting out the diverter assembly from the box is a bit of a buggxr.

You have to tap two plastic holding lugs in (they may well snap off) and, then with the whole assembly mounted at a suitable angle in a vice, or the like, with a decent heavy hammer and, a wooden drift , gently thwack parts of the diverter near the joint to separate the two parts. Once it starts to move it's a doddle.

If the plastic holding lugs have snapped off you will have to drill a couple of holes near the joint to insert a couple of self-tapping screws to hold the diverter in place and, wrap a length of duck tape over the holes at the original securing lugs.

It's not too difficult really.

Bob :)

Yes, mine is on a B200F (LH 2.4). Cheers, Bob :)

... and guess what Skandix also 'do' the flexible tube between the exhaust manifold and the air diverter intake for my motor for Euro 7.90 (Volvo Pt no 9438274) .... so, if you buy a couple of air thermos + the tube you might well find the shipping is reasonable. Buy now be4 Brexit!!

http://www.skandix.de/en/spare-parts...00-mm/1019018/

Haven't checked a Main Dealer price but, that might be a worthwhile exercise.

Bob :)