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Spongy brakes

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SteveSt View Drop Down
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    Posted: 26 Jun 10 at 21:03
I've had the LT31 2.4 TD Florida about a month now, never been 100% happy with the brakes. Sort of OK - would pass MOT - but not confidence inspiring; pedal seems close to the floor before I feel like I am really going to stop!
Today; took off rear drums - all good there, plenty of meat on shoes, adjusters working OK. cylinders good & looking fairly new, drums have also been recently replaced.
Brake pressure does not improve with hand-brake up.
Same good news with  pads + discs (discs fairly new). Bled system all round - got a bit of air out > got a bit excited Pig> as I thought "that'll be the problem! Went for drive - still spongy. < disappointed  Cry
Got any thoughts/similar experiences anyone - please

LT31 1991 2.4 TD Florida Westphalia • Honda ST1100 • Ford Tourneo Connect
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BigTam Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jun 10 at 09:16
If you dont know when brake fluid was last changed, change it.
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buz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote buz Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jun 10 at 09:43
Did you bleed the load sensing valve on the rear axle. Also a little tip is to give the cylinder/calipers a little knock with a hammer during bleeding to dislodge any air attached to the sides. Do you have access to a power or pressure bleeder ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveSt Quote  Post ReplyReply Direct Link To This Post Posted: 27 Jun 10 at 11:06
Changed the brake fluid as part of the process.
Didn't know about the valve on the sensing unit. Is there a potential 'air trap' in it? Most of the air we expelled came from the rear bleed valves.
Thanks.
LT31 1991 2.4 TD Florida Westphalia • Honda ST1100 • Ford Tourneo Connect
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TwoSheds Quote  Post ReplyReply Direct Link To This Post Posted: 28 Jun 10 at 01:46
Steve St :
 
I have just spent 2 weeks on my LT45 braking system and ended-up replacing everything ( including 2 master cylinders ) and I have been working on cars vans and motorcycles for 45 years. To say that this has been a PIG of a job is an understatement. Twin rears are worse than the singles.
 
The compensator has 2 circuits ( linked only by a pressure interlock and not the same fluid circuit ) Circuit 1 ( which has the bleed nipple on it is a safety override for if the front brake circuit fails and is part of the front brakes ). Circuit 2 is purely rear brakes and bled only via the rear slaves.
 
Best method is use a pressure bleeder - EeziBleed is very good and use at 20lb pressure - PLUS someone pumping the pedal at the same time.
 
Does not matter if you do fronts or rears first but Sequence is :
 
Rears : OS rear slave then NS rear slave.
 
Fronts : Compensator then OS front then NS front.
 
The rear brakes appear to be critical. The VW spec of 1.5mm of drum wear ( 0.75 of wall thickness ) looks to be a problem even with new shoes. Each drum has to be set-up on the auto adjusters repeatedly : Adjust, operate the foot peddle hard to centre the linings, check if there is bite. Repeat until there is bite and back the adjuster off only sufficient to allow the drum to be removed. When both drums have been adjusted then do the handbrake :
 
Handbrake : Lever up by 2 clicks only. Adjust handbrake rod until the OS wheel drags, go and test the NS wheel and keep adjusting until the NS wheel does drag. release the handbrake and check that both wheels move freely. The problem here is that the handbrake cables are very different in length so the NS is lazy compared to the OS. Keep adjusting the handbrake rod, checking between 2Clicks and Off until one of the drums starts to Bite/Drag with the handbrake Off. Back adjuster off a bit at a time until both wheels JUST turn freely in the Off postion. Remember to operate the brake pedal after each adjustment.
 
Brake pedal can still be spongy ( especially late twins ) but a couple of weeks of running / 200 miles then recheck the handbrake adjustment and the pedal should be better plus the brakes should be doing the job!
 
Hope that this helps


Edited by TwoSheds - 19 Aug 10 at 06:45
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SteveSt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveSt Quote  Post ReplyReply Direct Link To This Post Posted: 28 Jun 10 at 12:04
Hi
Thank you.
Have you come across a 'circuit diagram' anywhere? Workshop Manual?
I have tried to find the link to the workshop manual for the LT31. I am sure:-
1/. That I have read somewhere that the brakes (and other bits) are the same twixt Petrol and diesel (mine's a 2.4 TD)
and
2/. That someone has posted this manual on the (a) forum somewhere! But I cannot find it!



LT31 1991 2.4 TD Florida Westphalia • Honda ST1100 • Ford Tourneo Connect
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TwoSheds Quote  Post ReplyReply Direct Link To This Post Posted: 28 Jun 10 at 13:08
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveSt Quote  Post ReplyReply Direct Link To This Post Posted: 28 Jun 10 at 13:26
Hi There
Thankyou
Let's see what that has to say?
Question;is it that there are no paper based manuals around or just that no-one has converted it to a PDF.
Is there a Bentley? (manual)
and
What's the copyright issue for those who take an old VW manaul and put in the 'net as a PDF?

LT31 1991 2.4 TD Florida Westphalia • Honda ST1100 • Ford Tourneo Connect
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TwoSheds Quote  Post ReplyReply Direct Link To This Post Posted: 28 Jun 10 at 14:40

Hi

Haynes did nothing after the 87 Update ( no idea why except that they must have experienced insufficient sales of the 87 book ). The only other WM info is Dealer only and generally only comes to the internet if someone has spent the time scanning ( once obtaining the original ). Generally after 10 years the Mfr's are not interested as they have made their money ( or not ) and are busy enough with current/new product. So; Copyright does not seem to be an issue -----.

Most dealers tend to dispose of their old parts stock at around 10 years as they have not got the room to hold "non-moving" parts.

Parts for pre83 LT's are like Rocking Horse S--t via dealers and post 83 are getting difficult but Germany still tends to pull one out of the hat ( but this can take months and months until a part comes up ).
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TwoSheds Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 10 at 08:30
Thought that I would add some info on the LT brake circuit that may help others.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canada LT28 Quote  Post ReplyReply Direct Link To This Post Posted: 19 Aug 10 at 11:38
Hi there,
I just had a similar, I think, issue with my LT28. After checking out all the other components it turns out that on the vacuum assist on the engine, there are two small check valves and they are a bit weak. It won't allow enough vacuum to get to the booster and it therefore feels like I must stand on the breaks to get it to stop. It still works fine but there is no vacuum assist and I have a much stronger right leg. Damn pain about the left one...gimp.

Mike
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SteveSt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveSt Quote  Post ReplyReply Direct Link To This Post Posted: 20 Aug 10 at 10:11
Update
After much fiddling & faffing bleeding and cursing. Including replacing compensator things were not perfect! So I took both back drums off and found - that one of the automatic adjusters had been fitted the wrong way round. Great improvement!
Steve
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