Another vacuum pump issue

[SilverSnailTDi]

That'll teach me for not checking what I pasted onto the page before clicking post


So
2.0 wet belt Transit
Belt has been done. When being undertaken it was pretty clear it had been done very recently to me getting given the van. The van had done around 150 miles between my customer collecting it from auction and me getting passed it to do some bits to.

So, belts changed along with some MOT prep work. MOT completed and passed on to the driver. Driver completes 80-120 miles and the vacuum to the servo drops out.
Brand new genuine VP fitted, no broken cog/gear to the old pump. Oil without any debris flows from the holes when the pump is turned by hand.
Still no change.

Vacuum measured from the new pump is giving me around 0.6 bar. Which is the same as Autel is telling me the sensor is reading. My reading was taken directly from the pump itself rather than at the end of any pipework.

I guess my main reason/question for this post is:
What should the vacuum pump be creating in terms of bar/psi?

I'm heading back to the van later tomorrow afternoon with the hope I can find a reason for the lack of vacuum without me needing to pull the sump off and searching from every angle. I will check the cam side of the pump key to make sure it's being spun from that side too of course.

Any other pointers would be greatly appreciated of course

[SilverSnailTDi]

Post edited to actually read what was meant to have been posted

[MinorMatt]

Well 1 bar would be a total vacuum - and I wouldn't expect a vac pump to deliver that.

Based on engineering judgement only (I've never measured vacuum from a pump) I would think 0.6Bar (8.7 PSI) is probably not far off the mark? It would certainly be giving a reasonable amount of pedal assistance. On an 6" servo that would be

My vac pump checks have always consisted of pulling the pipe from the servo - a qualitive assessment of "if I cover the end of the pipe does it make vacuum".

This is all earlier stuff though

[SilverSnailTDi]

Well 1 bar would be a total vacuum - and I wouldn't expect a vac pump to deliver that.

Based on engineering judgement only (I've never measured vacuum from a pump) I would think 0.6Bar (8.7 PSI) is probably not far off the mark? It would certainly be giving a reasonable amount of pedal assistance. On an 6" servo that would be

My vac pump checks have always consisted of pulling the pipe from the servo - a qualitive assessment of "if I cover the end of the pipe does it make vacuum".

This is all earlier stuff though

Yep, this makes sense to me too. The connection to the servo on these is fairly sizable due to the one way value, so it may be a case of having to man up a bit and double checking the continued vacuum through the pipe by hand/mouth and see what the outcome is there before delving too far.

As for the desired vacuum pressure, I can't find anything anywhere to say what I should be getting, I've spoken to a few ford guys who say it should be much closer to the 1bar mark, but I'm not sure if they're just guessing too or what

[MinorMatt]

1 bar is an absolute vacuum. Its certainly possible to get it - but it would collapse the plastic pipes between the pump and servo.

I don't know how big the servo unit is on the van - but if it were an 8" servo - (i.e. a diameter of 8" of surface area) a quick calc says that would be nearly of 198kg of additional effort that the vacuum/servo can provide.

[SilverSnailTDi]

1 bar is an absolute vacuum. Its certainly possible to get it - but it would collapse the plastic pipes between the pump and servo.

I don't know how big the servo unit is on the van - but if it were an 8" servo - (i.e. a diameter of 8" of surface area) a quick calc says that would be nearly of 198kg of additional effort that the vacuum/servo can provide.

Love how when you know and understand then it is just a quick math... And for the rest of us simpletons it's enough to boggle the mind

[MinorMatt]

8.7 Lbs/square inch x surface area of an 8 inch circle / 2.2 lbs per kg

[knobby1]

Love how when you know and understand then it is just a quick math... And for the rest of us simpletons it's enough to boggle the mind

What our MinorMatt says is correct...or very close to it, the area of the servo diaphragm is Pi x the radius squared...so 3.142 x 4^ which equals approx 50.272" of total area...we also need to factor in the variable atmospheric pressure on the ambient side of the diaphragm in the servo which is assisting the vacuum on the opposite side....I love numbers, they never lie.

A little useless information for you, I'm full of it

It's very difficult to get an "absolute vacuum" or zero psia, even out in the far reaches of space, for a "perfect vacuum" to exist, all matter must be removed. I use an absolute (PSIA) vacuum pump at my work for simulating altitude and the best we see is about 0.5psia or -14.2psig which is well above 60,000ft altitude, (1.61psia is 50,000ft), the forces on the chamber are enormous, the larger the chamber, the more force is exerted and is a square of the surface area increase. Altitudes above ~ 62miles or ~100km (approx 328,000ft) is considered leaving the atmosphere and entering space as we know it, also known as the "Von Karman Line".

Sorry...can't help myself.

A little light reading:
https://www.sciencefocus.com/space/is-s ... ect-vacuum

Lord Knobrot

[metalworker0]

That's it now knobby ..you're really John Cadogan

all the best.mark

[SilverSnailTDi]

Love how when you know and understand then it is just a quick math... And for the rest of us simpletons it's enough to boggle the mind

What our MinorMatt says is correct...or very close to it, the area of the servo diaphragm is Pi x the radius squared...so 3.142 x 4^ which equals approx 50.272" of total area...we also need to factor in the variable atmospheric pressure on the ambient side of the diaphragm in the servo which is assisting the vacuum on the opposite side....I love numbers, they never lie.

A little useless information for you, I'm full of it

It's very difficult to get an "absolute vacuum" or zero psia, even out in the far reaches of space, for a "perfect vacuum" to exist, all matter must be removed. I use an absolute (PSIA) vacuum pump at my work for simulating altitude and the best we see is about 0.5psia or -14.2psig which is well above 60,000ft altitude, (1.61psia is 50,000ft), the forces on the chamber are enormous, the larger the chamber, the more force is exerted and is a square of the surface area increase. Altitudes above ~ 62miles or ~100km (approx 328,000ft) is considered leaving the atmosphere and entering space as we know it, also known as the "Von Karman Line".

Sorry...can't help myself.

A little light reading:
https://www.sciencefocus.com/space/is-s ... ect-vacuum

Lord Knobrot

See, I can follow the first part of that, and the remainder of it you put into terms I can also follow. Still far beyond my side of things, but makes good sense...

I followed the post above also, once it was explained and my memory shot back to math lessons and physics... Apparently some of the private school education went in for the couple of years I was subjected to it, who would have thought


So back on to the topic.

Tested vacuum in the servo this evening with my little hand held pump, created .6 bar (and w*nkers cramp) pressed the brake pedal and there was movement like I'd expect from a working system. So this means the servo is working and holding vacuum.
Tested the pipework from pump to servo. No leaks and holding a vacuum. One way valve working as it should do too
Removed the pump. Again, no swarf from a belt, plenty of oil in the pump housing that spews out when the pump is turned by hand.

PXL_20241210_185805898.MP.jpg

This, however, is the state of the key on pump.
This looks to me like it is not sitting into the cam and spinning and wearing down.
I know that every time I have fitted it I have lined up the key to the cam and had it sitting snug before putting any bolts in. But also now, if I make sure that the cam and pump are at 90⁰ angles to eachother, the pump still fits snuggly against the block to be secured in place.

Now I'm at a bit of a loss!! How on earth can this be possible?
If somehow I have secured the pump to the block with the alignment way out, surely the small 8mm headed bolts would snap or take out the thread on at least one of the holes.
And if not, surely there's not enough force in those three little bolts to push the cam over so much that the pump now won't sit in the holes...?

Anyone seen or heard of this previously?

[metalworker0]

i don't see damage in the picture

i thought the whole drive was designed like an "oldham coupling"

a coupling designed to take up out of wack alignment

https://www.youtube.com/shorts/oBqERJjrMBI


all the best.mark

[Airthies]

Looks like either the drive coupling has moved back or cam moved forward. To give those marks on the drive

Is there any way to check cam end float?
Something you can grip or a thread up the end of the cam to let you move it with a bolt up it's end.

[SilverSnailTDi]

i don't see damage in the picture

i thought the whole drive was designed like an "oldham coupling"

a coupling designed to take up out of wack alignment

https://www.youtube.com/shorts/oBqERJjrMBI


all the best.mark

So there's a plastic bit that sits between the two? Or the VP key moves?

[SilverSnailTDi]

Looks like either the drive coupling has moved back or cam moved forward. To give those marks on the drive

Is there any way to check cam end float?
Something you can grip or a thread up the end of the cam to let you move it with a bolt up it's end.

Good shout, I'll check this out later this week. It feels pretty snuggly in place, but I'll check when I get the chance if there's any movement in there

PXL_20241210_185913742.jpg

This was the cam side of the junction. Unfortunately I've not been able to find any pictures taken from this angle to check against so far

[Airthies]

I remember previously I think it was a mini or maestro thing(many haircuts ago) that they had two different pumps one long drive one short, other than that exactly the same
That if you fitted the wrong one you'd be cranking it forever trying to get oil pressure