I have a Ford focus mk3 and I’ve diagnosed a problem with the vacuum pump. Does anyone know if it’s only got the check valve or is there anything else in the vacuum pump that can leak. It doesn’t hold pressure if I try it from the check valve. I’ve replaced the check valve but still not holding pressure. Is there a diaphragm inside that could have gone or anything?

1. Does the vacuum pump operate the brake servo system ok? If yes, it's unlikely there's a problem with the pump body.

2. The vacuum pump valve (to turbo system) should be checked with engine running using a vacuum gauge. Should a get a fairly steady vacuum reading. If it's not then it's common for that valve to be defective. Usually the orange coloured silicone diaphragm inside is split/torn.

Many people try replacing the the diaphragm with one bought off ebay, usually with success but not always.

Yeah vacuum pump operates brakes. I’ve replaced the diaphragm with no luck. If I put a hand pump vacuum it looses pressure through the valve. So I think it’s a new vacuum pump for me.

Vacuum pumps are quite expensive. If you wanted to check the pump is creating a good vacuum reading, it can be cost-effective to buy a vacuum gauge off ebay.

Note that if using a hand held vacuum pump tool you're pulling air away from the pump. In normal use, the vacuum pump is drawing air in the other direction. 

I connected the gauge using a length of tubing to the vacuum pump valve,  ran the engine and checked it was creating a good vacuum reading.

I've disassembled a vacuum pump and there are very few moving parts inside.  The only realistic place it could lose it's vacuum efficiency is past the driven rotor bearing. That's why I asked if the brake servo is operating ok to rule that out.

Having said all that, I did end up buying a new pump, mainly because of the many turbo related issues I had and was desperate to get it all sorted (fitted new turbo assembly, turbo oil feed filter, vac pump, vac tubing, pressure control valve).

If you do go the new pump route don't forget a new gasket will be required. Good luck. 

 

I bought a vacuum gauge and used it. The needle is jumping around everywhere back and forth. Looks like I’m going to have to get a new vacuum pump. Thanks for your help. 

I had a similar problem. I tried testing the vacuum from the brake servo line on top of the vacuum pump. That showed good constant vacuum, so just changed the little valve on the front with an ebay one, and that solved my problem.

Hi

 

Can I ask please does that valve stop air coming into the pump or going out, I bought a replacement valve and it seems to let air  into the valve and not out is that correct.