Club 80-90 Forums

My crankcase breather tower is knackered, the diaphragm has gone so it's blowing all the time.  

I don't really fancy the £70+ price tag of a replacement tower.  Would putting any old crankcase vent valve in the hose to the pancake do the same job?  Lots of PCV valves for various cars available from about £5,  are they all basically the same so it would just be a case of finding one that fits in conveniently?  

Maybe try putting a thread in the wanted section.

Dont see how it work at all to be fair. They vent pressure in the crankcase - hence their location/function.

worth a try I'd say, trying to find one with the same size hose fitting both ends will be the difficult bit, but you may be able to double up with some suitable hose; the universal motorcycle £9 metal one looks a possible it's 1/2" to 3/8" 

I should have searched properly first, itchyfeet has done it and converted the old tower to an oil filler

viewtopic.php?p=8249285#p8249285

I'm wondering if if a hole could be drilled in top of the old tower, the old valve spring removed so the new valve could sit directly on top of the existing tower, with the old vent port blocked up.  The tricky bit would be bonding the two together.  Worth a thought but looks like the inline method would work if not 

In addition to what has already been said, what are the symptoms and indications of a faulty tower and how can it be tested to find out if you do have a faulty one.

TONYT25T25 wrote: ↑01 Dec 2022, 19:22 In addition to what has already been said, what are the symptoms and indications of a faulty tower and how can it be tested to find out if you do have a faulty one.

The valve at the top of the tower is supposed to stay closed at slow rpm and only open when crankcase pressure builds, but according to posts here the diaphragm in most of these valves will have split after 30+ years in hot oily vapours!  I noticed that while I was working with the air box off the top of the carb that quite a lot of condensation was spitting out of the end of the breather hose as the engine was warming up at idle and I could feel air blowing out the hose all the time, that's the most obvious symptom.  I was thinking all that water being pushed into the carb can't be good for a stable idle

In addition I'd got a Gunsons CO analyser hooked up to set the mixture.  With the hose from the tower disconnected CO was  around 1.3-1.5% before I even started (Haynes says 1.5% +/- 0.5% for 1.9DG so I was happy)  Plugging the tower hose back in sent the CO up to over 2.5%; the tester might be getting confused by hydrocarbons here rather than it being a true CO measurement, but still, I'd have thought a working valve should give a result much closer to 1.5% at idle if it was staying closed.  An otherwise good setup is probably still fine for MOT  but I guess having a bad valve in the breather could push some cases over the limits? (unless the hose was disconnected for the test of course  )

aec wrote: ↑01 Dec 2022, 22:40

TONYT25T25 wrote: ↑01 Dec 2022, 19:22 In addition to what has already been said, what are the symptoms and indications of a faulty tower and how can it be tested to find out if you do have a faulty one.

The valve at the top of the tower is supposed to stay closed at slow rpm and only open when crankcase pressure builds, but according to posts here the diaphragm in most of these valves will have split after 30+ years in hot oily vapours!  I noticed that while I was working with the air box off the top of the carb that quite a lot of condensation was spitting out of the end of the breather hose as the engine was warming up at idle and I could feel air blowing out the hose all the time, that's the most obvious symptom.  I was thinking all that water being pushed into the carb can't be good for a stable idle

In addition I'd got a Gunsons CO analyser hooked up to set the mixture.  With the hose from the tower disconnected CO was  around 1.3-1.5% before I even started (Haynes says 1.5% +/- 0.5% for 1.9DG so I was happy)  Plugging the tower hose back in sent the CO up to over 2.5%; the tester might be getting confused by hydrocarbons here rather than it being a true CO measurement, but still, I'd have thought a working valve should give a result much closer to 1.5% at idle if it was staying closed.  An otherwise good setup is probably still fine for MOT  but I guess having a bad valve in the breather could push some cases over the limits? (unless the hose was disconnected for the test of course  )

Thanks, v usefull feedback, another check to do.

Actually, after reading some of a very long thread here:

https://www.thesamba.com/vw/forum/viewt ... p?t=295812

I'm not so sure I really understand this breather stuff at all!

Starting the think now that maybe the valve should be open most of the time and close only if there is high vacuum on the air intake to so that crankcase pressure doesn't drop too far below atmospheric.   Still really confused by what's going on though!

The conception was faulty so the diaphragm doesn't do anything of note to regulate case underpressure. The tower itself is a good thing, column height is essential to oil mist separation, which is always a problem with horizontal engines, but you'll gain nothing by buying a new one. What you have there is working as well as it can even with the diaphragm rotted out.

As to trying off-the shelf PCV's? They are crude little things, yet each one is sized and the spring matched to a particular engine's intake characteristics, so you'd have to get lucky to find just the right one. I've tried a couple, didn't accomplish anything of value.

The late-model restrictor/deicer module they put in the PCV hose does more to regulate than the stupidly-conceived tower diaphragm ever did. Mainly the 5mm orifice will reduce oil consumption via the intake, but the powered deicer can be important in cold wet climates.

If you're obsessed with an oil-free intake tract, the Mann-Hummel oil separators do work fairly well to separate and hold oil and water. But with high maintenance, and few other kinda sketchy aspects that show the products weren't that well-tested, I can't recommend them. If you do go that route, don't get the smallest one, it's filter is almost totally restrictive (one of those sketchy details). The second size up worked OK for me.

Thanks that's reassuring to know.  It wasn't so much oil getting into the air intake I was worried about, it was condensation.  With the breather pipe disconnected from the air intake I noticed how much condensation was spitting out before the engine warmed up.  I figured that this might result in a poor idle during warm up if it ending up in the air intake.  Perhaps an oil separator is the way forward.

A picture is worth a thousand words.



The valve is held down, against spring pressure, by high inlet vacuum (closed or very small throttle opening) this keeps the idle clean on a healthy engine.
At wider throttle openings, vacuum falls and the valve is then open (as shown), enabling the engine to burn off blowby gases and condensate vapours.
The problems occur on engines with worn piston rings that have lost tension, so they blowby more than they should, leading to higher crankcase pressures at all rpm.
In a knackered engine, this could overwhelm the vacuum pressure keeping the valve closed and cause a dirty idle and/or mixture problems.
However, the diaphragm can fail and the valve can still work, provided that it still pulls down onto the seating squarely.

Fitted a catch can to my breather system. I didn't want all that condensation going into my nice clean Weber carb. Bus is my daily driver all year round. Easy install. Block off old breather intake on pancake and vent catch can to atmosphere. Sailed through emissions on last 2 MOT's . I check it every week or so. Usually around a quarter full.


Similar to this kit. Cheap enough

The whole point of a closed loop crankcase breather system is to contain all vapours (cold start condensate, unburned fuel in the oil etc) and to burn this as part of normal running.
The engine was deaigned to work with this system in place. Remove it and the emissions are already compromised.
What do you do with the contents of the catch can?

Contents of the catch can goes to local recycling centre with old engine oil.