TD4 Brake servo problem - no vacuum assistance

Hi, I hope someone help me with a problem I've been trying to fix for months now.

The brake vacuum assistance is no longer working as it should. When driving along you can press the brake pedal and the car slows down OK, if you release and re-apply the brakes the pedal is rock hard and nothing happens !!

I've done plenty of research as this seems to be a common problem caused by chaffed pipes that run to the EGR solenoid and the turbo.

I did find a chaffed hose from the main servo pipe to the EGR, I replaced this but it made no difference.

I bought a good 2nd hand servo from ebay and fitted it, again , it made no difference.

I've tested the servo pipe one way valve by blowing through it as suggested in the Haynes manual, this works ok.

I've replaced the sealing grommet in the servo, made no difference.

I've tested the Vacuum Pump with a vacuum gauge, it showed 700 millibars at idle and full revs - I'm not sure if this is within spec, i found a page on the Pierburg website - http://www.ms-motor-service.cn/ximages/pg_si_0066_en_web.pdf

Can anyone help me? I think the next stage is taking it to a garage (god knows how much that will cost) otherwise I'm tempted to set it on fire...

It's a 51 plate TD4 Freelander with 82k on the clock.

Many Thanks

Scott.

check the small pipes thoroughly it will be a leak on one of them put you finger over the end of each pipe is the vacume pump located on the side of the engin ok

Yes, the vacuum pump is seated against the engine ok from what I can see.

As far as I know, it's the original factory item, I haven't removed it from the engine block.

To check if the problem is one of the 2 small hoses coming off the main pipe, I put tape over the T'pieces. That way ALL the Vacuum effort would be running to the servo. This made no difference, so I'm thinking its the servo.. I'm just very worried about buying a brand new servo for over a hundred quid to find it wasn't the cause...

It's really frustrating to not be able to find the cause of the problem because I know I can easily fix it...

It's very hard to spot a Vacuum leak !! It would be easier it was an oil or water leak !!

Should have read your post properly before I posted my reply. Have a look in the Haynes manual for the correct vacuum figures.

I think you need to get hold of a handheld vaccuum pump & test each section individually to see which section is leaking. Don't know if you can rent them from somewhere but a place like Machinemart might sell them

teddywood1 said:

check the small pipes thoroughly it will be a leak on one of them put you finger over the end of each pipe is the vacume pump located on the side of the engin ok

Click to expand...

There are 2 pipes located right under the EGR valve. Due to heat one could have easily split or dislodge without being noticed, since they are well hidden.

nickcc said:

Should have read your post properly before I posted my reply. Have a look in the Haynes manual for the correct vacuum figures.

Click to expand...

Ok I'll have another look later but I can't remember seeing the figures in the Haynes manual..

scottnb said:

Ok I'll have another look later but I can't remember seeing the figures in the Haynes manual..

Click to expand...

Just done a search and the minimum vacuum figure I can find is 16 to 17 inch. There is a very good Lexus check list that explains the workings and set up of a brake servo, just do a google search and you should find it without any problem (I just put in "minimum vacuum for power brakes" ). Hope this helps.