Hello all,
Whilst doing a 300 mile round trip over the weekend I noticed that my ZX was a bit lacking in power and also that the brakes didn't seem as effective. I immediately suspected the vacuum pump. Lo and behold, with the bonnet up, I can see that the ACAV diaphragms hardly move at all when the throttle is opened. Before, like other members have noted on this forum, they always opened (or closed, whatever it is) almost as soon as the revs pick up. They almost seem to move slightly, so I'm assuming that they are being signalled to move, but can't because of insufficient vacuum. The fact that the brakes didn't feel as good as normal would also point to this, but I might be jumping to conclusions.
Has anyone got any useful advice on the best approach to finding the source of the problem? I haven't got a vacuum gauge to hand, so can't tell if the vacuum pump is sucking properly. It sucks the skin on the end of my finger quite hard though. Some of the pipework goes off forward under the throttle assy and is impossible to get at. I can hear a hissing noise, but can't tell where it is coming from.
Any ideas would be most appreciated !
Thanks in advance.
ZX 2.0 16v Vacuum Problem?
Moderator: RichardW
furyspyder
you could make a simple vacuum gauge out of a u-tube made of clear pvc tubing filled with water and food colouring. I don't know to what level the vacuum should be but the very worst it can be is 10 metres of water (32 feet) which is absolute zero. I suspect it will be lower than this so you won't need a 10m high u-tube!.
The hissing noise would seem to be the root of the problem. Sounds like a leak in servo, vacuum pump or the vacuum piping somewhere.
To locate the source of the noise make yourself a one-eared stethoscope using a piece of - yes you've guessed it - clear pvc tubing. Stick one end in your ear and roam around the engine bay with the other. The end of the tube makes the sound directional and will be loudest when pointing at the source of the noise.
best of luck
noz
you could make a simple vacuum gauge out of a u-tube made of clear pvc tubing filled with water and food colouring. I don't know to what level the vacuum should be but the very worst it can be is 10 metres of water (32 feet) which is absolute zero. I suspect it will be lower than this so you won't need a 10m high u-tube!.
The hissing noise would seem to be the root of the problem. Sounds like a leak in servo, vacuum pump or the vacuum piping somewhere.
To locate the source of the noise make yourself a one-eared stethoscope using a piece of - yes you've guessed it - clear pvc tubing. Stick one end in your ear and roam around the engine bay with the other. The end of the tube makes the sound directional and will be loudest when pointing at the source of the noise.
best of luck
noz
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Thanks noz, but as it happens I have an update as I have been doing a bit of investigating.
I did actually have an old vacuum gauge lying around (cheap gunsons 'lo-gauge' thing) with which I checked the output of the vacuum pump - haynes says 19inHg minimum, gauge says 28inHg, so no problems there. Incedentally, with the gauge connected straight to the pump, the hissing noise was still present underneath the right hand side of the engine so I guess that was a red herring.
Then I put the gauge onto the output of the little solenoid valve which I presumed supplies the vacuum to the diaphragms at the right time, and lo and behold the gauge flicked over at the same revs as the diapgragms used to move, so this was working okay.
I then blew down the pipe which I had removed from the solenoid valve and found that there was a leak and a hissing noise coming from the LH diaphragm. I took the pipe off this, blocked it, blew again and this time there was no leak and I couldn't blow anything through it.
Therefore, I am assuming that my diaphragm is knackered and I need a new one. Does anyone know the best source for obtaining one? I will have a look at GSF but I doubt something like this will be stocked by anyone other than the citroen dealers.
I guess that this was also causing the lack of power in the brakes, as whenever the solenoid opens the line to the two diaphragms, there is basically a leak in the whole vacuum system. Is it safe to drive like this or should I try to replace it immediately?
The unit itself seems to be sealed anyway, with "no user serviceable parts inside" !!
Any ideas?
I did actually have an old vacuum gauge lying around (cheap gunsons 'lo-gauge' thing) with which I checked the output of the vacuum pump - haynes says 19inHg minimum, gauge says 28inHg, so no problems there. Incedentally, with the gauge connected straight to the pump, the hissing noise was still present underneath the right hand side of the engine so I guess that was a red herring.
Then I put the gauge onto the output of the little solenoid valve which I presumed supplies the vacuum to the diaphragms at the right time, and lo and behold the gauge flicked over at the same revs as the diapgragms used to move, so this was working okay.
I then blew down the pipe which I had removed from the solenoid valve and found that there was a leak and a hissing noise coming from the LH diaphragm. I took the pipe off this, blocked it, blew again and this time there was no leak and I couldn't blow anything through it.
Therefore, I am assuming that my diaphragm is knackered and I need a new one. Does anyone know the best source for obtaining one? I will have a look at GSF but I doubt something like this will be stocked by anyone other than the citroen dealers.
I guess that this was also causing the lack of power in the brakes, as whenever the solenoid opens the line to the two diaphragms, there is basically a leak in the whole vacuum system. Is it safe to drive like this or should I try to replace it immediately?
The unit itself seems to be sealed anyway, with "no user serviceable parts inside" !!
Any ideas?
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- Posts: 23
- Joined: 24 Jun 2003, 06:00
- Location:
- My Cars:
I'll have 'em!![:D] Both of mine have broke and I'm gonna need spares to experiment on fixing them. I haven't got £60 lying around...
oh, but I have got a head gasket to change.
Bloody British Weather!!![:(!][V]
I'll sort out an address and some postal money with you.. Drop me a line at gjb41@hotmail.com
oh, but I have got a head gasket to change.
Bloody British Weather!!![:(!][V]
I'll sort out an address and some postal money with you.. Drop me a line at gjb41@hotmail.com