jackmac Posted September 18, 2017 Share Posted September 18, 2017 Hi all Having a problem with a lack of vacuum assistance on my 300tdi 90 (conversion, running td5 axles with vented front disks for what it's worth) . Having to absolutely stand on the brakes to slow down, it's not great. So far I've replaced the brake servo with a brand new one (not blue box, replaced o ring to master cylinder as well), tested that there is vacuum, tested the one way valve. Nothing has worked! Pumping the pedal until hard when the engine is off, then maintaining pressure as I start the engine and the brake pedal doesn't change at all. When I checked the vacuum I wasn't sure how strong it's meant to be, I found it much more noticeable with the engine a couple of hundred rpm above idle. Incidentally I also noticed when I changed the brake pads a couple of weeks ago that it took a herculean effort to push the pistons back in, which isn't a problem I've had before. The caliper pistons don't look that bad to me either. Not sure if that could be connected? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted September 18, 2017 Share Posted September 18, 2017 Is the vacuum pump working at all? Sounds like it is worn out if it starts working a bit more a few hundred rpm above idle? Quote Link to comment Share on other sites More sharing options...
Ally V8 Posted September 18, 2017 Share Posted September 18, 2017 Does sound like the vac pump has died. In this case a Britpart one may be the best option... Quote Link to comment Share on other sites More sharing options...
jackmac Posted September 18, 2017 Author Share Posted September 18, 2017 It is working, I can feel some vacuum at idle - just it works a lot better above that. I'm not sure how strong it should feel? Using the very non scientific method of sticking my finger over the vacuum pipe Quote Link to comment Share on other sites More sharing options...
western Posted September 18, 2017 Share Posted September 18, 2017 Read you replaced the servo, have you adjusted the servo pushrod ? if not that could give you a long pedal Quote Link to comment Share on other sites More sharing options...
jackmac Posted September 18, 2017 Author Share Posted September 18, 2017 12 minutes ago, western said: Read you replaced the servo, have you adjusted the servo pushrod ? if not that could give you a long pedal The pedal is actually hard quite early, I'm sure it's a vacuum issue because of the lack of change starting the engine having exhausted the vacuum. Not adjusted that though I wasn't aware it was an option, I'll have a look Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted September 18, 2017 Share Posted September 18, 2017 If you exhaust the vacuum, then start the engine and rev it a bit does it change at all then? Quote Link to comment Share on other sites More sharing options...
jackmac Posted September 20, 2017 Author Share Posted September 20, 2017 On 18/09/2017 at 10:09 PM, Retroanaconda said: If you exhaust the vacuum, then start the engine and rev it a bit does it change at all then? Just checked this, no difference. The servo is definitely holding vacuum because I started her up and left running for about 15 seconds, stopped engine and removed the vacuum pipe from the servo. There was a very clear hiss and a pop as I removed the pipe Quote Link to comment Share on other sites More sharing options...
nickwilliams Posted September 21, 2017 Share Posted September 21, 2017 On 18/09/2017 at 6:02 PM, jackmac said: Incidentally I also noticed when I changed the brake pads a couple of weeks ago that it took a herculean effort to push the pistons back in, which isn't a problem I've had before. The caliper pistons don't look that bad to me either. Not sure if that could be connected? I'd focus on this aspect if I were you, and leave worrying about the vaccum pump for the moment. Unless the pistons are rediculously rusty, this can only be the result of some sort of blockage in the system. Quote Link to comment Share on other sites More sharing options...
jackmac Posted September 21, 2017 Author Share Posted September 21, 2017 1 hour ago, nickwilliams said: I'd focus on this aspect if I were you, and leave worrying about the vaccum pump for the moment. Unless the pistons are rediculously rusty, this can only be the result of some sort of blockage in the system. I'm going to drain all the brake fluid and replace the 2 front flexi lines as I've got extended ones waiting to go on, will give it a flush through and make sure it's all clear. Replacing the master cylinder having spoken to a friend who had the same issue, and I've also found an old topic on here with the same symptoms that was apparently fixed by changing the master cylinder. Fingers crossed Quote Link to comment Share on other sites More sharing options...
Landy7 Posted September 22, 2017 Share Posted September 22, 2017 On 18/09/2017 at 8:30 PM, jackmac said: It is working, I can feel some vacuum at idle - just it works a lot better above that. I'm not sure how strong it should feel? Using the very non scientific method of sticking my finger over the vacuum pipe I had a bit the same problem, braking power was very low, took the vacuum pump off and it was missing a gasket.. So I assume it was not 100% vacuum. Put a new gasket in place and fixed. Quote Link to comment Share on other sites More sharing options...
Kaci Posted November 20, 2021 Share Posted November 20, 2021 So we are having masive brake problems so when we are sat with engine off the pedal feels okay then we run the engine on a test drive and the brake pedal on first pump feels good then take your foot of and pump again and nothing we have changed the servo all the cylinders shoes checked the vaccine pump is all good and no splits in pipes I’m now completely lost any help ???? Quote Link to comment Share on other sites More sharing options...
western Posted November 20, 2021 Share Posted November 20, 2021 pinch or blocked hose, duff NRV on the servo Quote Link to comment Share on other sites More sharing options...
chuff Posted November 30, 2021 Share Posted November 30, 2021 On 11/20/2021 at 1:13 PM, Kaci said: So we are having masive brake problems so when we are sat with engine off the pedal feels okay then we run the engine on a test drive and the brake pedal on first pump feels good then take your foot of and pump again and nothing we have changed the servo all the cylinders shoes checked the vaccine pump is all good and no splits in pipes I’m now completely lost any help ???? Have you rebuilt the Master Cylinder and put a seal in the wrong way round? Quote Link to comment Share on other sites More sharing options...
chuff Posted November 30, 2021 Share Posted November 30, 2021 On 9/18/2017 at 6:02 PM, jackmac said: Hi all Having a problem with a lack of vacuum assistance on my 300tdi 90 (conversion, running td5 axles with vented front disks for what it's worth) . Having to absolutely stand on the brakes to slow down, it's not great. So far I've replaced the brake servo with a brand new one (not blue box, replaced o ring to master cylinder as well), tested that there is vacuum, tested the one way valve. Nothing has worked! Pumping the pedal until hard when the engine is off, then maintaining pressure as I start the engine and the brake pedal doesn't change at all. When I checked the vacuum I wasn't sure how strong it's meant to be, I found it much more noticeable with the engine a couple of hundred rpm above idle. Incidentally I also noticed when I changed the brake pads a couple of weeks ago that it took a herculean effort to push the pistons back in, which isn't a problem I've had before. The caliper pistons don't look that bad to me either. Not sure if that could be connected? The vacuum pump At idle should make a red swollen ring on the pad of your thumb and hurt enough that you remove said thumb. The brake pedal should sink on start-up as vacuum servo assistance is delivered. Exercise the front pads with a pry bar and someone pressing Hard on the peddle, they could be jammed and you only have rear brakes. Quote Link to comment Share on other sites More sharing options...
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