Vaillant TurboMAX 824E problem

hi i have had the Vaillant TurboMAX plus 824E boiler for about 2 and a half years, and it seems to be leaking water from a pump looking feature with a big screw in the middle, which is situated in the right hand side of the boiler. this only leaks when i give the boiler some pressure, which i bring to about 1.5bar. i havent been able to pinpoint where the leak is actually coming from on this pump, but all i know is that the water is leaking from the pump looking thing.
the boiler gives me hot water from the taps, after around 2 minutes of being fired up. and it gives me no central heating. and after a while shows fault; f-28, when there is no pressure(meaning when the gauge is showing 0). and now recently f-29 aswell . as the leaking slows down to a slight drop every 20 seconds, i noticed that the pressure had gone down to zero. i dont know what to do!!!!
i have tried to flush the radiators out and have turned the grey looking handle, which sounded like it had flushed some water out of something. but still the leaking persists. the water being leaked is slightly black in colour, if this means anything!!
please, if anyone has any help they can give me i would be very thankful

Can't picture this pump at the moment but are you certain it is not the auto air vent slowly leaking?

Try investigating with some coloured tissue. This will show up dampness easier than white tissue.

It sounds as you have several faults.

I suggest you call Dave ( above ) to come and fix them for you.

Tony

well from what i can see, i have have found a picture of where i think the leak is coming from if this helps http://www.uk-plumbing.com/vaillant-pump-160949-pi-42027.html
other than that im stuck for ideas but as i say, the fault says f29 or f28 and i can get hot water while i have pressure in my boiler, but no central heating. and the leaks get more like a trickle when the pressure level increases ie at bar 2/3. and when i flush out water from the boiler so there is no pressure the leaks stop.
thanks

Try tightening up the aav valve on the top with you fingers. If the dribble stops then that is where the leak is coming from.

Sounds as though the boiler may need a good service and the min/max burner pressures adjust back to MI's, especially as it appears to only cut out on CH.

Could be when the gas valve modulates down.

if you mean the dust cap looking thing, i tightened it with my fingers and it didnt do anything.
but i have noticed that the leak is kind of seeping out of the split in the pump, you know where the front is kind of attached to the back by four screws, the front being a silver metallic colour and the back being black and plastic feeling. in between these on the under side of it bang in the middle, there is a leak. if this helps
and if the boiler does need a service how much would it cost? and who would i ask to get one done. i dont want to fork out a fortune to fix it i live in yarmouth

Locally, within Yarmouth, a service would be approx £55-£60.

As for the leak on the pump, this would be extra and would depend on what exactly was leaking, or if it needed a new pump.

so someone would come and have a look at the boiler to find a definate answer on what is wrong and how much woulda new pump cost?

If I was local to you a new pump would cost you £206.05 + VAT fitted, plus a service at £55 + VAT.

If a basic service did not cure your problems then extras would be involved.

It would be better (cheaper) for you to get someone in Yarmouth as someone like me would add £40 + VAT for the time/travelling to Yarmouth.

Until the boiler is inspected it is impossible to say what is needed for a full repair.