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rogerowen

Brake Servo advice please

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47 minutes ago, Bfg said:

 

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A brake servo maintains the vacuum until the brakes are released (.. note the characteristic hiss of articulated lorries when they stop),  but 99% of the time its valves are closed,  ie. whenever the brakes are in use or not in use - it's only the very short time-span of brake release where the vacuum is lost, and that soon recovers even though the engine is just ticking over.   So what I'm saying is that Y or T connector from the inlet manifold connector will all but maintain the partial vacuum of the original closed crankcase breather system.    That was only on vacuum over fluid operated brakes that went out in the early eighties most now have proper air type bakes which are a completely different system and run on air pressure not engine vacuum.

However if you Y piece connect to an open vented system (either just a drop pipe or via a catch tank) then the vacuum in the brake servo is compromised, and a one way valve in line (see Stuart's photo) to the breather is necessary to prevent air coming back in through that pipe. 

Thats not a one way valve its a flame trap.

Should the one-way valve, or the Y connector pipe to it, fail - then you loose your brake servo.  So as Malbaby suggests  "a dedicated single vacuum source for the booster to operate efficiently"  and is the safer option.


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You should always rub a servo off a dedicated drilling in the inlet manifold and there should be a one way valve in the line or in the servo itself.

Stuart.

Edited by stuart

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11 minutes ago, stuart said:

That was only on vacuum over fluid operated brakes that went out in the early eighties

Sorry I'm just an old fart trying to be helpful, and I'm not familiar with later systems but is that not what we are considering here  and the brake servo booster illustrated in the original post.?

 

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1 hour ago, Bfg said:

 

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Roger, I'm glad you're managing to get you head around crankcase breathers.  Your previous post imply concern about moisture inside the crankcases, to which I simply ask - how does that moisture get in there ?   And that would be through a non-regulated (by one-way valve) crankcase breather system allowing atmospheric humidity to be freely drawn back into the crankcase.  The early TR's with an open vented breather system were like this, and so your experience was to see a lot of creamy coloured condensation goo dripping out of the end of the breather pipe, and so quite understandably are now keen to extract it.   But pressure regulated (one-way valve) and closed breather systems are quite effective in preventing that humidity from getting inside in the first place  (the inside of your oil filler cap for example should be clear of any such creamy coloured residue).  Aside from that, the everyday practical advantage of a closed breather system is to provide negative crankcase pressure which helps avoid crankcase oil being pushed out of the engine seals. 

A brake servo maintains the vacuum until the brakes are released (.. note the characteristic hiss of articulated lorries when they stop),  but 99% of the time its valves are closed,  ie. whenever the brakes are in use or not in use - it's only the very short time-span of brake release where the vacuum is lost, and that soon recovers even though the engine is just ticking over.   So what I'm saying is that Y or T connector from the inlet manifold connector will all but maintain the partial vacuum of the original closed crankcase breather system.     

However if you Y piece connect to an open vented system (either just a drop pipe or via a catch tank) then the vacuum in the brake servo is compromised, and a one way valve in line (see Stuart's photo) to the breather is necessary to prevent air coming back in through that pipe.  Should the one-way valve, or the Y connector pipe to it, fail - then you loose your brake servo.  So as Malbaby suggests  "a dedicated single vacuum source for the booster to operate efficiently"  and is the safer option.

Regarding the twin cylinder engines. The 2cv has a boxer engine where the crankshaft is a 180 degrees - so the pistons go the opposite direction at the same time (ie. both simultaneously going away from the crankshaft, or both coming towards it).  And yes these masses tend to balance each other out.  However their firing is one side and then the other so they still rock.  Four and six cylinders are naturally very much smoother.  

Parallel twin motorcycle engines were at one time commonplace. Most had a 360 degree crankshaft  (both pistons go up and down together) - primarily because a top-hat shaped crankshaft is easier (and therefore cheaper) to make, and it's stiffer (for the same weight) than an S-shaped 180 degree crankshaft.  Drillings to feed oil to the big ends is also much easier, and less oil pressure was needed.  And then, although the reciprocating mass of the pistons and con-rods needed counter balancing with bob-weights on the crankshaft,  the engine's secondary balance (felt as sideways rocking on a motorcycle) was much better.   
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Thanks, again this is helping me get an understanding. I'm not worried about water moisture (no usual evidence), it's more the soggy black and carbonated junk that I found in the rocker cover. I haven't ventured into the sump as yet - it's going to very very nasty I'm sure - previous ownership neglect no doubt. Having cleaned out the very clogged PCV - I just thought a catch tank would be more successful at keeping the internals a bit cleaner.

Cheers,

Roger

IMG_2146.JPG

Edited by rogerowen
More to add.

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Roger, I'd agree - that looks to me as if the car's previous owners have operated on a zero budget for yonks and engine oil changes have been neglected.  I'm sure the residue in the sump will be positively horrid.  Personally speaking I'd clean that out,  consider upgrading to an easier-to-change oil filter,  wipe off the crud around the rockers ..followed by a series of frequent oil changes ..and I'd expect to see that much improve without disturbing anything but the sump and rocker cover.  Mind you,  I'd suspect finding a similar neglected situation with the cooling system.   

A catch tank will make absolutely no difference to the state of the engine oil or the crud it deposits inside the engine cases.  A catch tank will however help keep your induction tracts and combustion chambers clearer of oil mist deposits.  Although the photo implies your valve stems haven't been replaced on this engine for half a century ..so whatever mist you might have from the breather will be next to nothing compared with oil seeping passed those.  What are your plugs like and do you have oil dripping from joints in the exhaust system.?  If wet then I'd personally first suspect the valve guides.   

A finger in place of the rocker cover breather pipe will give you an indication of how much pressure is in the crankcases. If you just feel the pulsations but not a lot of pressure then your bores and piston rings are in decent condition,  but if there's a build up of pressure then piston rings are due for replacement.  NB. Compression tests won't tell you this because those figures are also a factor of how well the valves are seating. 

P.

 

Edited by Bfg

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6 hours ago, Lebro said:

1960's to 1970's Triumph twins (motorbikes) had both pistons traveling up & down together, one on its compression stroke, the other on it exhaust / inlet stroke. difficult to balance which is why they always vibrated rather a lot.

Bob.

Also all BMW Boxers do that,

with a spring loaded (no return) valve on top they blow out when both pistons are "down",

from there on there is low pressure in the crankcase, good to loose less oil through gaps, until they are both "down" again.

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Let the PCV valve where it is, it is a vacuum reduction valve, oil separator and flame trap.

It guides the separated oil back to the engine if it is installed correctly, and always keeps a low vacuum on the engine to get a "positiv (active) crankcase ventilation".

I'm convinced about its sence and benefits for the engine - guess I'm the only one.

Edited by Z320

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49 minutes ago, Z320 said:

Let the PCV valve where it is, it is a vacuum reduction valve, oil separator and flame trap.

It guides the separated oil back to the engine if it is installed correctly, and always keeps a low vacuum on the engine to get a "positiv (active) crankcase ventilation".

I'm convinced about its sence and benefits for the engine - guess I'm the only one.

Maybe you are, but to understand how the PCV evolved you need to understand why it was designed in the first place. The TR4 would not meet the new US emission regulations so for the TR4A Triumph designed the PCV so the TR4A engine would  digest its own pollution.     The downside of this was that the engine was fed with all the corrosive gunge which the PCV separated out to the detriment of polluting the Engine instead of the Atmosphere and not helping the control of the fuel/air mixture.   Interestingly for all competition applications the first thing to be removed from the engine was the PCV valve which was replaced with the snorkel tube from the TR4,block fitted to the TR4A block next to the fuel pump where the original hole is sealed by an easily removable core plug. When regulations were changed the snorkel and the rocker cover outlet were routed to catch tanks. The PCV valve contributes nothing to the performance or lifespan of the engine and is just another item which can fail (split diaphragm) and leave you stranded with maybe a clutch flooded in engine oil which will need replacing.

Chris

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All modern cars have a PCV, seems to be not so bad...

And with a look in the inlet manifold it looks not dirty or oily.

Edited by Z320

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5 hours ago, Bfg said:

Roger, I'd agree - that looks to me as if the car's previous owners have operated on a zero budget for yonks and engine oil changes have been neglected.  I'm sure the residue in the sump will be positively horrid.  Personally speaking I'd clean that out,  consider upgrading to an easier-to-change oil filter,  wipe off the crud around the rockers ..followed by a series of frequent oil changes ..and I'd expect to see that much improve without disturbing anything but the sump and rocker cover.  Mind you,  I'd suspect finding a similar neglected situation with the cooling system.   

A catch tank will make absolutely no difference to the state of the engine oil or the crud it deposits inside the engine cases.  A catch tank will however help keep your induction tracts and combustion chambers clearer of oil mist deposits.  Although the photo implies your valve stems haven't been replaced on this engine for half a century ..so whatever mist you might have from the breather will be next to nothing compared with oil seeping passed those.  What are your plugs like and do you have oil dripping from joints in the exhaust system.?  If wet then I'd personally first suspect the valve guides.   

A finger in place of the rocker cover breather pipe will give you an indication of how much pressure is in the crankcases. If you just feel the pulsations but not a lot of pressure then your bores and piston rings are in decent condition,  but if there's a build up of pressure then piston rings are due for replacement.  NB. Compression tests won't tell you this because those figures are also a factor of how well the valves are seating. 

P.

 

Brilliant, yes agreed - the oil I drained out was as black as, and the oil filter was the worse I've ever seen! Compression test was pretty good apart from cylinder 2 which was down a bit. When started there was a right old clatter and I was worried about a collet coming off a sticking valve and dropping a valve down the pot. But, after a while - all settled down.

In the long distant past I was a keen user of flushing oil, but stopped using that as it creates more problems - especially with crankshaft seals,

My winter project list includes head rebuild - new valve guides, valves, springs etc. Sump drop and clean, as well as toothbrush cleaning of the crankcase interior - upside down on axle stands - YUM!

Many thanks for the tips.

Cheers,

Roger

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Ref Z320 post (quote omitted)

Agreed, but all modern engines use fuel injection, either direct or indirect and more often than not utilise turbocharging  all of which combined with ECUs allows them to run with hitherto unheard of fuel to air ratios and higher combustion temperatures. These features render them far more capable of digesting the much smaller amounts of contaminants that they produce mainly due to modern synthetic oils with additives and finer engine build tolerances.

Chris

Edited by ChrisR-4A
Quote omitted

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Roger, back to your original post, 

One of the mail reasons for build up of contaminants in the rocker cover and that creamy yellow sludge, is an engine running at too low an operating temperature as when used on frequent short journeys. The TR with the original crank mounted fan  was under cooled when driven hard or in high ambient temperatures and over cooled on short trips and in winter. 
That’s why the TR will benefit from removal of the existing fan and the fitting of a thermostatically controlled electric fan.

Chris

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.

3 hours ago, ChrisR-4A said:

Maybe you are, but to understand how the PCV evolved you need to understand why it was designed in the first place. The TR4 would not meet the new US emission regulations so for the TR4A Triumph designed the PCV so the TR4A engine would  digest its own pollution.     The downside of this was that the engine was fed with all the corrosive gunge which the PCV separated out to the detriment of polluting the Engine instead of the Atmosphere and not helping the control of the fuel/air mixture.   Interestingly for all competition applications the first thing to be removed from the engine was the PCV valve which was replaced with the snorkel tube from the TR4,block fitted to the TR4A block next to the fuel pump where the original hole is sealed by an easily removable core plug. When regulations were changed the snorkel and the rocker cover outlet were routed to catch tanks. The PCV valve contributes nothing to the performance or lifespan of the engine and is just another item which can fail (split diaphragm) and leave you stranded with maybe a clutch flooded in engine oil which will need replacing.  Chris

I apologise if I'm misreading or misunderstanding your summary,  but to my mind emissions "pollution" come from the combustion of carbon fuels,  and is not a factor of crankcase oil mist pulsating back n' forth at piston velocities within too tight a space.  So unless the piston rings are shot or the bore is terrible condition, either resulting in massive piston blow by - next to nothing of the breather fumes are "corrosive gunge"  and similarly next to nothing is (re)digested by the engine.

And surely, if the majority of the breather's oil mist is separated from its air,  courtesy of the PCV valve which drains oil back into the crankcase, then very  little oil mist is carried into the combustion chamber to be incinerated.  If this were otherwise, then it would be clearly evident in the colour of the exhaust "smoke".  Certainly in my (albeit limited) experience - most of the oil in a combustion chamber comes via the lubrication of the valve guides (particularly so if they worn, inaccurately machined, or damaged) ..and from the necessary oil lubrication of the pistons in their bores. 

Regarding control of the fuel/air mixture..  Well, the low pressure manifold take-off facilitates a lower than atmospheric pressure within the crankcase.  For that to happen  - air  IN  to the crankcase has to be limited (because if there were free flow of air in - then it would be impossible to lower its pressure), therefore the amount of air drawn through the breather into the manifold is equally limited and reasonably steady.  So with an engine, in pretty well any running condition, the ratio of fuel to air can be adjusted.  The fact that some of the air is drawn in after the carburettor is incidental. It is still a measured amount.  I do however accept that it may not be measured accurately enough to knock one-hundredth-of-a-second off a racer's lap time,  but for normal road use I don't see it as a problem.  

To be perfectly honest, I really cannot speak of racing practices  ..perhaps Mickey might drop in to advise us on this.   But just guessing like - I suspect a large part of the reason they do not use a PCV valve is more a matter of inlet manifold design.  Looking at  Stuart's photo of a twin Weber setup - just where exactly would you take 'just one'  manifold low pressure take-off from ?  Indeed I cannot determine if the front and rear cylinder manifolds even have a balance pipe between them. 

And with regard to leaving you stranded should a PCV diaphragm fail. Not so..  just disconnect it. Vent the breather to the atmosphere,  bung the hole in the manifold (to prevent excess air being drawn in) and drive on.   Sorry I don't understand  "maybe a clutch flooded in engine oil".       

 

6 hours ago, Z320 said:

Let the PCV valve where it is, it is a vacuum reduction valve, oil separator and flame trap.

It guides the separated oil back to the engine if it is installed correctly, and always keeps a low vacuum on the engine to get a "positiv (active) crankcase ventilation".

I'm convinced about its sense and benefits for the engine - guess I'm the only one.

I'm with you B)

 

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12 hours ago, ChrisR-4A said:

Roger, back to your original post, 

One of the mail reasons for build up of contaminants in the rocker cover and that creamy yellow sludge, is an engine running at too low an operating temperature as when used on frequent short journeys. The TR with the original crank mounted fan  was under cooled when driven hard or in high ambient temperatures and over cooled on short trips and in winter. 
That’s why the TR will benefit from removal of the existing fan and the fitting of a thermostatically controlled electric fan.

Chris

Thanks  Chris, luckily I'm not experiencing creamy sludge - just a mix of gunky oil and carbon. All due to poor maintenance from previous owners. Now pretty much cleaned out - the engine runs much better, but I'm not too keen on the idea of oil mist being re-ingested by the engine..... and so i'm looking at installing a catch tank of some description (The highly recommended  Racetorations one is beyond my meager finances, and probably overspecified for my intended poodling down country lanes). 

But mainly I do want to free up the inlet manifold intake so I can fit and connect a remote brake servo.

Cheers,

Roger

Edited by rogerowen
Spellig!

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Roger, the catch tank in not really relevant. All it does is stop any oil that comes from a crankcase breather from dripping onto the road. Try a length of hose from the rocker cover into a milk carton or similar. I just have a hose hanging down and pointing towards the chassis, and I haven't noticed any more oil on that part of the chassis than on any other part.

Pete

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20 minutes ago, stillp said:

Roger, the catch tank in not really relevant. All it does is stop any oil that comes from a crankcase breather from dripping onto the road. Try a length of hose from the rocker cover into a milk carton or similar. I just have a hose hanging down and pointing towards the chassis, and I haven't noticed any more oil on that part of the chassis than on any other part.

Pete

Thanks Pete, sounds like a good idea.

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17 hours ago, Malbaby said:

Have you considered fitting the TR6 booster M/C combination.

Good suggestion. No, didn't think of this, have already fitted a new TR4A Master Cylinder and have bought an after market remote servo. But that's a good tip for others.

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The necessity for a catch tank is more about track use.

If an engine blows and pressurises the crankcase you don't want to belch a pint or two of oil onto the track.

For road use the catch tank is less important.

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18 hours ago, Malbaby said:

Have you considered fitting the TR6 booster M/C combination.

Isn’t it a dual braking system on the TR6 with a different pedal arrangement, so not as easy as fitting a remote aftermarket servo?

Chris

Edited by ChrisR-4A

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4 hours ago, Andy Moltu said:

The necessity for a catch tank is more about track use.

If an engine blows and pressurises the crankcase you don't want to belch a pint or two of oil onto the track.

For road use the catch tank is less important.

If course I realise that a catch tank is mandatory for track racing, but as I am considering losing the standard PCV arrangement in preference of a brake servo take off, I thought it might be worth fitting a catch tank to my road car rather than just a pipe dropping down onto the road. Also - it would be helpful to know what's actually coming out of the engine as a kind of diagnostic tool?  I've found suitable catch tanks between £30 - £60, some even have a gauge to advise when full.

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6 minutes ago, rogerowen said:

If course I realise that a catch tank is mandatory for track racing, but as I am considering losing the standard PCV arrangement in preference of a brake servo take off, I thought it might be worth fitting a catch tank to my road car rather than just a pipe dropping down onto the road. Also - it would be helpful to know what's actually coming out of the engine as a kind of diagnostic tool?  I've found suitable catch tanks between £30 - £60, some even have a gauge to advise when full.

I return to my age old suggestion of a plastic milk bottle.. Comes with 1ltr milk that you can drink, is see through so you can check oil level, and the cost is under a pound.

Peter W

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Although not quite as cheap as a plastic milk bottle, a plastic cycling drink bottle works very well and its wire carrier makes mounting it a simple task.Just make sure that it can breath and is mounted as high as possible in the engine bay otherwise it will tend to fill up.

Edited by TR4TUNE

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I'm getting the notion that the 'vacuum / pulling' effect of the connection of the standard TR4A breathing system to the  the inlet manifold is of no value whatsoever?

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2 hours ago, rogerowen said:

I'm getting the notion that the 'vacuum / pulling' effect of the connection of the standard TR4A breathing system to the  the inlet manifold is of no value whatsoever?

On the contrary for drawing emulsified air out of the engine then it works well, the downside is it then dumps it into the intake of the engine

Stuart.

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