Souster Posted November 26, 2015 Author Share Posted November 26, 2015 You must have disturbed whatever it was that was not right. Whtever you took off, I'd look at it all very carefully in a good light, with a loup or magnifying glass if need be - you don't want a sudden reversion to how it was All i did was pull the vacuum pipe off the servo, nothing more. All i can think of is possibly caused seals or pistons ( I have no idea) to seal better in the vacuum pump, and its providing more vacuum/suction. I couldnt have disturbed anything else. Is there a gauge of some sort i can test the vacuum pressure? Quote Link to comment Share on other sites More sharing options...
western Posted November 26, 2015 Share Posted November 26, 2015 All i did was pull the vacuum pipe off the servo, nothing more. All i can think of is possibly caused seals or pistons ( I have no idea) to seal better in the vacuum pump, and its providing more vacuum/suction. I couldnt have disturbed anything else. Is there a gauge of some sort i can test the vacuum pressure? lots if you google vacuum testing gauge ------------- https://www.google.co.uk/webhp?sourceid=chrome-instant&rlz=1C1ASUC_enGB582GB582&ion=1&espv=2&ie=UTF-8#q=vacuum+testing+gauge&tbm=shop Quote Link to comment Share on other sites More sharing options...
Souster Posted November 26, 2015 Author Share Posted November 26, 2015 lots if you google vacuum testing gauge ------------- https://www.google.co.uk/webhp?sourceid=chrome-instant&rlz=1C1ASUC_enGB582GB582&ion=1&espv=2&ie=UTF-8#q=vacuum+testing+gauge&tbm=shop Cheers Ralph. I'll look into that. If the good brakes aren't sustained. I will invest in one of those and find out if the vacuum pump in intermittent. Despite being new! It was only a "briturk" branded bearmach pump Quote Link to comment Share on other sites More sharing options...
pete3000 Posted November 27, 2015 Share Posted November 27, 2015 have you changed the vac pump at any point? they do pack in as the diaphram can wear/split. it is cam/plunger driven from the engine Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted November 27, 2015 Share Posted November 27, 2015 Yep, first post, was new bearmach part. Quote Link to comment Share on other sites More sharing options...
Souster Posted November 27, 2015 Author Share Posted November 27, 2015 have you changed the vac pump at any point? they do pack in as the diaphram can wear/split. it is cam/plunger driven from the engine I changed it about 3/4 months for a bearmach part, it did have a sticker on it called briturk though. Which didn't give me much confidence. Cheers Pete Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted November 27, 2015 Share Posted November 27, 2015 Even a genuine part can be faulty.... Does seem like you are narrowing it down though Got anyone with a second hand one (even your own old one?) to swap in and test? Could even go electric.... Boydie has done this very successfully. Quote Link to comment Share on other sites More sharing options...
Souster Posted November 27, 2015 Author Share Posted November 27, 2015 Even a genuine part can be faulty.... Does seem like you are narrowing it down though Got anyone with a second hand one (even your own old one?) to swap in and test? Could even go electric.... Boydie has done this very successfully. Cheers Bowie. My dad has virtually the same vehicle as me,so I was thinking of getting a vacuum gauge and comparing the readings to mine. A friend has a 200tdi and td5 defender too,so I can get some figures of what it should be. I know for certain that the one I removed wasn't providing as much vacuum as this one. But that pump I removed was also inconsistent, sometimes brakes very just about ok, sometimes it felt like new servo assistance at all. Henc e me replacing it Quote Link to comment Share on other sites More sharing options...
western Posted November 27, 2015 Share Posted November 27, 2015 Nick [borrow] your Dad's vacuum pump on to your 90 or test yours on his & see if the fault transfers with the suspect vacuum pump. Quote Link to comment Share on other sites More sharing options...
Souster Posted December 11, 2015 Author Share Posted December 11, 2015 Hi All. Sorry to bring this one back up, but ive been doing some testing, and getting closer to the one problem, or maybe both.Firstly, i purchased a vacuum gauge and tested the vacuum the pump produced at tickover (apologies if this isnt the correct teminology to follow):-my 300tdi: 24 inches mercury with a warm engine, 23 with a cold engine (seems odd that this differs between days? Beleive it could be temperature though?)-A friends 200tdi: 24 inches mercury with a cold engine -A 2002 td5 defender: 25 inches mercury cold engine -My dads 300tdi: Very low reading of about 18 inches mercury One thing i did notice, was the 200tdi and td5 engine held the vacuum on the gauge as soon as the engine was switched off and remained at that pressure for a while, where as my 300tdi loses the vacuum. Im yet to try my dads as i forgot, but his pump is seeming worn compared to my new one.Next test i did was on my servo with a mityvac which produces a vacuum, using the connection into the servo acting like a vacuum pump. I tried producing a vacuum on my servo, and had absolutly no luck at all, couldnt get the mityvac to budge off zero. I then tried my friends 200tdi and td5 defender, and managed to get almost maximum vacuum reading on the gauge despite it being hard. I removed my vacuum pipe from pump to servo and pressure tested it, no leaks or issues at all. So its clear i have a servo leak so that will be replaced (hopefully under warranty). My question i have is, should my vacuum pump hold pressure as soon as the engine is switched off? like the 200tdi and td5... or doesnt it matter when the one way valve is working correctly in the servo?Thankyou all and sorry its been long winded. Quote Link to comment Share on other sites More sharing options...
western Posted December 11, 2015 Share Posted December 11, 2015 Yes the servo should hold vacuum after engine is switched off, mine does for a decent amount of time. as yours doesn't hold hardly any vacuum, then it must have an internal leak or the body joint is not correctly sealed. Quote Link to comment Share on other sites More sharing options...
Souster Posted December 11, 2015 Author Share Posted December 11, 2015 Yes the servo should hold vacuum after engine is switched off, mine does for a decent amount of time. as yours doesn't hold hardly any vacuum, then it must have an internal leak or the body joint is not correctly sealed. Cheers for that Ralph. Should the vacuum pump hold vacuum though? Like my mates td5 and 200tdi does. My vacuum pump just drops off when the vehicle is turned off, the other engines don't. Quote Link to comment Share on other sites More sharing options...
western Posted December 11, 2015 Share Posted December 11, 2015 don't know what mine does, but would believe it would be the same as the 2 vehicles you've tested with the gauge. Quote Link to comment Share on other sites More sharing options...
pat_pending Posted December 12, 2015 Share Posted December 12, 2015 Providing you have a one way valve either at the pump or the servo, or both, the vacuum pump itself doesn't need to hold vacuum. I "think" a 200tdi has a one way valve built in to the top of the pump, in which case if you put a vac' gauge on the servo end of the pipe you will see it hold, that would be just vacuum in the pipe though. I'm not sure about the td5 or 300 pumps. If you can't get the servo to hold a vacuum, then you have a fault there. Change that before you go any further. Keep in mind that any loss of servo assistance will manifest itself as a hard pedal/less travel. Quote Link to comment Share on other sites More sharing options...
Souster Posted December 13, 2015 Author Share Posted December 13, 2015 Thank you both. Managed to test my dad's vacuum pump this evening, his also drops the vacuum when turned off, so it seems exactly what you said pat_pending. I've finally proved the servo is faulty, again my apologies for it being a long winded one. It just not expected with new parts from good manufacturers, but maybe that's the world we live in now. As for the brake pedal travel increasing when turning, I'm fantasising the new servo may also cure that. But I highly doubt it, every suggestion has now been tried. Thank you all who posted Quote Link to comment Share on other sites More sharing options...
deep Posted December 13, 2015 Share Posted December 13, 2015 If a new servo is faulty and you kept the receipt, you should be able to get an exchange or refund, surely? Quote Link to comment Share on other sites More sharing options...
western Posted December 13, 2015 Share Posted December 13, 2015 new parts normally have a minimum 12 month garuntee anyway. Quote Link to comment Share on other sites More sharing options...
Pawl12 Posted December 13, 2015 Share Posted December 13, 2015 This might sound like a daft suggestion - but have you tried removing the brake fluid reservoir cap & checking if you have the problem still ? I've just read most of this thread (I used to work in brake systems for a long time - so was interested) & agree with the thoughts that you have 2 problems : 1 relatively quick vacuum loss - which doesn't seem to be causing you any real braking issue as the vacuum is "topped up" by the vac pump & 2 something is causing the caliper pistons to retract more than they should - creating significant pedal travel increase to push them back to the disc. If your reservoir cap is sealed - eg via damage, dirt or bad manufacture - the brake system is sealed & as the brake pads wear, a vacuum can be created in the system which will try to pull the caliper pistons inwards. If the caliper seal friction is low, the pistons can move quite easily & may only need a small bit of extra force from the wheel & brake disc moving with the wheel bearings as you turn. I've actually seen vehicles where the brake pedal had to be pushed right to the floor more than once before there was braking due to this. Releasing the cap removed the problem until the vacuum was re-created due to a lot more pad wear & increasing vacuum. Where are you based ? Quote Link to comment Share on other sites More sharing options...
Souster Posted December 13, 2015 Author Share Posted December 13, 2015 This might sound like a daft suggestion - but have you tried removing the brake fluid reservoir cap & checking if you have the problem still ? I've just read most of this thread (I used to work in brake systems for a long time - so was interested) & agree with the thoughts that you have 2 problems : 1 relatively quick vacuum loss - which doesn't seem to be causing you any real braking issue as the vacuum is "topped up" by the vac pump & 2 something is causing the caliper pistons to retract more than they should - creating significant pedal travel increase to push them back to the disc. If your reservoir cap is sealed - eg via damage, dirt or bad manufacture - the brake system is sealed & as the brake pads wear, a vacuum can be created in the system which will try to pull the caliper pistons inwards. If the caliper seal friction is low, the pistons can move quite easily & may only need a small bit of extra force from the wheel & brake disc moving with the wheel bearings as you turn. I've actually seen vehicles where the brake pedal had to be pushed right to the floor more than once before there was braking due to this. Releasing the cap removed the problem until the vacuum was re-created due to a lot more pad wear & increasing vacuum. Where are you based ? I'm processing a warranty claim on the servo, I've just had to buy a new one to be refunded the faulty one. And thanks Pawl12. I'll certainly give it ago removing the reservoir cap,I have nothing to lose. Although I still can't get my head round why that would only work when the steering is turned? Quote Link to comment Share on other sites More sharing options...
western Posted December 13, 2015 Share Posted December 13, 2015 where did you get the new brake flexy hoses from ? as IIRC one of our fellow members had some that had a solid liner inside instead of a tube. so no fluid could get to caliper Quote Link to comment Share on other sites More sharing options...
Pawl12 Posted December 13, 2015 Share Posted December 13, 2015 The theory is that the vacuum in the system may not be enough to pull the pistons in on its own. But the flex in the wheel brgs as you turn to full lock may be enough to push the discs against the pistons, aiding the vacuum to move them inwards. Without the vacuum in the system the caliper piston seal friction is designed to be enough to resist "knock-back" - as long as the wheel bearing play is not excessive. Quote Link to comment Share on other sites More sharing options...
Souster Posted December 13, 2015 Author Share Posted December 13, 2015 where did you get the new brake flexy hoses from ? as IIRC one of our fellow members had some that had a solid liner inside instead of a tube. so no fluid could get to caliper They were terrafirma Ralph. I regret changing to braided flexis really, as with the rubber ones it'd easier to diagnose problems. Quote Link to comment Share on other sites More sharing options...
Souster Posted December 13, 2015 Author Share Posted December 13, 2015 The theory is that the vacuum in the system may not be enough to pull the pistons in on its own. But the flex in the wheel brgs as you turn to full lock may be enough to push the discs against the pistons, aiding the vacuum to move them inwards. Without the vacuum in the system the caliper piston seal friction is designed to be enough to resist "knock-back" - as long as the wheel bearing play is not excessive. Now that's very interesting. I will try that tomorrow evening as it sounds quite promising. Do you recommend removing the reservoir cap fully? Or slacken it and leave it on a couple of threads? It did always make me wonder if it would have happened with old calipers and rusty pistons, so your logic sounds promising. Thanks a lot Quote Link to comment Share on other sites More sharing options...
Pawl12 Posted December 13, 2015 Share Posted December 13, 2015 Remove the cap briefly & re-fit - you can then guarantee any vacuum is "lost" (if present). If the problem disappears, replace the cap with a good one ! To generate a large enough vacuum to pull pistons in (more than 0.3 bar), the brake pads need to wear a fair bit - I'd guess more than 50%. So if the pads haven't worn anywhere near that since the brake reservoir cap was last removed, a blocked cap is unlikely as a cause. If it wasn't for the work you've already done on wheel bearings, I'd have been certain 1 or more having excess clearance would have been the cause ! Quote Link to comment Share on other sites More sharing options...
western Posted December 13, 2015 Share Posted December 13, 2015 They were terrafirma Ralph. I regret changing to braided flexis really, as with the rubber ones it'd easier to diagnose problems. IIRC mine are goodridge braided hoses, Dave of Llama4x4 can sort you a decent set, if you decide to replace the hoses. Quote Link to comment Share on other sites More sharing options...
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