Vacuum Pipes

[Guest neil_wiles]

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[seatkid]

Has anyone any experience of the symptom of reduced power due to vacuum leaks from the plastic pipes from the pump to the brake servo on a 1.9 TDi 1999 Gal ?

 

I am having a stuttering in terms of power and it appears to be related to the pipes as they are beginning to crack and leak. If not then this could be another MAF issue (oooh too expensive)

Can't see that brake vacuum pipes having any bearing on engine power problem, athough this is a serious safety issue and you should change them if they are damaged or leak.

 

Has fuel filter been changed recently? Check all other pipes to inlet, turbo etc etc. Maybe try disconnecting battery (- terminal) for a minute and reconnecting to reset the ecu (You will need to reset the radio code) - otherwise looking like a MAF.. :rolleyes:

[seatkid]

:unsure: Ok I'll give it a try tomorrow.

But whats the connection? Is the vacuum pump used for anything else? I would have thought for safety reasons, the brake vacuum circuit was exclusive.

 

Braking gently as you describe would cause very little rise in brake servo vacuum pressure, isn't this more likely to be an ECU response to seeing the brake applied (from brake switch).

 

BTW my brake servo "loses" its vacuum when parked up in about 2-3 hours (pedal goes hard) - Seat dealer told me this was normal :rolleyes: All other cars I know still have vacuum even left overnight!

[Dave-G]

Fredt; :unsure: I cant explain HOW it does it, but the application of brakes "resets" the throttle to (idle probably?) as a safety factor, much in the same way as it would cancel cruise control :rolleyes:

[william]

On my Auto the throttle is electronic and therefore fairly easy to "reset".

 

- I also think that your not expected to press both the accelerator pedal and the brake pedal at the same time - so safety is the only reason.

[seatkid]

Fredt, you're right and you're wrong! :rolleyes:

Tried your suggestion - yes the power drops, but this is due to the ECU cutting power as others suggest. Most likely triggered from brake switch(es) and throttle input. Some safety issue must be the reason, most likely if the throttle input develops a fault leading to a stuck part or full setting, it may also be because of some issue with ABS operation.

 

Strange they don't do it with handbrake..

 

On a similar tack, my 96 TDi, when accelerating hard through the gears,

used to hold the revs for a second when you dipped the clutch, which led to clean (and stress free) changes. :lol: Doesn't happen with my 98 Tdi though. ;)

 

Which leads me to repeat - I don't think brake vacuum pipes would affect engine performance or running. B)

[seatkid]

Well blow me down! I stand corrected :rolleyes:

 

You learn something new every day.....

 

:lol:..Glasshopper... ;) ...you have much to learn..B)

 

Of course....(sound of penny dropping).....silly me...

 

Turbo wastegate (or vvt - 110 bhp) is operated by vacuum (via a solenoid). Hence no vacuum (or serious leak) = no turbo blow! BTW the turbo sensor measures boost pressure and is not in vacuum circuit.

 

Anyway when vacuum system is working correctly, operating the brakes wont affect turbo..

[ridway]

As an aside to this thread and those who may be interested.

The strange and seemingly unrelated symptoms of engine power and brake vacuum made me think of a strange occurence I had with a Ford Orion diesel some years ago.

I used this orion for several years commuting and did many cheap reliable miles. I was particularly alarmed one day while approaching a roudabout on the A1 to see the oil warning light illuminate. Using the brake to slow for the coming junction, I found the brakes to be non exsistant, there was nothing, or very little. Fortunatley, heart in mouth, I negociated the roundabout and pulled in the first layby some 100 yards hence, slowing using the handbrake (sorry Ivor). Rolling to a stand still I could hear the knock of the bigends protesting at the lack of oil.

I switched off and began my investigation into why I had had two major failures at the same time.

I could find nothing, Oil level, brake fluid level integrity of all pipes. Everything was spot on. I tentatively started the car and immediatley the oil light extinguished and the engine sounded normal, bigend knock gone. Totally puzzled, but slightly happier my thoughts turned to the brakes. Rolling backwards in the layby I found that the footbrake was perfect. Slighty happier again but even more puzzled, I needed to get off the A1 on to a side road and try and get my head around this.

Getting onto a quiet country lane I tried everything possible to make either or one of these problems re-occur. I even drained a cup full of oil into my thermos flask cup to see if it was some sort of oil level indication problem. Nothing. I was totally lost for an answer.

Using the back roads I rightly or wrongly carried on at a much reduced speed, trying the brakes every second as you can imagine. Faultless, got me home, not a hiccup. Explained to the local garage what had happened. I got the the impression they did'nt beleive me - I was begining to disbeleive myself. They found nothing and could not give an explaination.

The commuting continued for several months uneventfully, even had a new clutch.

Then one cold morning just pulling onto the carpark at work the same thing happened again. I was pleased in a way especially this time because the bigends still knocked when I stopped the engine and restarted it and the brakes still did not work right.

Luckily we had a vehicle work bay at work and a helpful manager who was as intrigued as his mechanics to see the problem when I explained.

They and I persued the mystery for most of the morning and eventually found the problem. It was the servo vacuum pump.

 

On the 1.6 diesel unit the pump was driven off the cam shaft. It had its own eccentric lobe on the cam to drive a push rod through the cylinder head to an external vac pump. The push rod returned under coil spring pressure to follow the cam lobe. Although the pump itself was never stripped down it was obvious that my problem was caused by it sticking mid travel. The push rod shaft passed through the head and was lubricated by an oil feed from a main oil gallery. The push rod had a cut out to allow oil to briefly flow into the shaft guide. It was unfortunate that the sticking pump was stopping the shaft in a position that allowed the full pressure of the oil feed system to be dumped straight back to the sump via the cut out.

 

So the brakes, or lack of and the loss of oil pressure were both caused by a strange set of circumstance.

 

The Orion has almost, long gone, especially the 1.6 diesel model. I dont know whether a recall for this problem was ever issued by Ford. I suppose it could be a serious problem but I never heard or read about any other incidents.

 

So the moral of the story is always expect the unusual, however vague and unrelated.

Thanks for reading, perseverance preserved my sanity in this case.

 

Rich

[Ivor_E_Tower]

Very interesting.

Did you know that the MOT test of a handbrake is to make sure you can use it to stop the vehicle, and NOT a test to see if it will hold the vehicle when parked?

[seatkid]

;) ;) :huh: ..wot r u trying to say Ivor.. ;) ;) ;)

[seatkid]

I decided to check mine as it has a slow leak (2hrs) on brake servo, plus the engine has always been a bit asthmatic.

 

There is a right angle plastic piece on top of the vacuum pump before going into plastic pipe (see pic below) - is this the non-return valve? Anyway this bit is a loose fit on the pump in that I can easily move it (finger pressure) left/right and it wobbles. Should it screw on or is it a push fit? (I have been unable to remove the plastic vaccum pipe for fear of breaking this plastic bit.)

[Guest DBAG]

Hi, I had the same power-loss problem when i drove the car, at about 80 kmh the power would cut out, almost as if the turbo just wasn't there. Took it to the shop to get some idea of what was going on. Luckily, the turbo was fine, but an animal had chewed on one of the pressure hoses on the turbo. No more juice. 60 Euros and a new hose later we were back on the road... It happened again, but this time on the air-intake regulater, one of the wires, an easier fix. Both problems had the same problem, no power.

 

Just gotta keep these animals from biting my hose.... :angry:

 

Adam