timnuttuk
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| posted on 2/9/05 at 12:45 PM |
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Brake problem
Hi,
I'm new to the list, but an old timer on the Tiger forum. They couldn't help (it's a smaller forum so I thought I'd come here
 . I promise to stay...
Sierra brakes all round, drums at the rear. New m/c, and everything is working fine, except:
When driving and as the engine gets hot the brakes slowly come on - only a little, but enough to make them hot, and my MPG to go down, etc. If I stop
and leave the whole car to cool down then brakes come off. I'm currently having to stop every 10 mins to let the pressure out of the front
calipers by undoing the bleed screw and letting a little fluid out - not good  .
I've checked that the push rod is going in far enough and that it is going in straight and not catching the plunger.
Anyone had this problem or offer any advise...
Thanks!
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David Jenkins
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| posted on 2/9/05 at 12:48 PM |
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Is the push-rod coming OUT far enough? In other words, is it fully retracted, preferably with a tiny bit of free play?
Most master cylinders (mine, certainly) have a system for returning unwanted fluid back up to the reservoir when the piston is in the off position -
maybe yours is blocked, or the piston's not coming right back?
Good luck,
David
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Hellfire
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| posted on 2/9/05 at 12:50 PM |
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Front and rear? Sounds like the fluid is expanding...
Are the pads/shoes new? If so, are the calipers new/recon?
You've probably heard all this before but we need to know what we have to start with... 
HTH
Oh - welcome to the LB community! You'de better stay now!!!
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timnuttuk
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| posted on 2/9/05 at 12:53 PM |
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>>Front and rear?
Yes, discs are roasting, and drums are v hot too - burnt my finger ;(
>>Are the pads/shoes new? If so, are the calipers new/recon
Pads are new (done a 100miles now). Shoes/drums are old from a crashed Tiger
I'll wind back the push rod a bit, but isn't there a danger that the plunger will come back too far and let air in? Heard this from
someone else..maybe wrong
Thanks for the responses so far - promise to stay!
[Edited on 2/9/05 by timnuttuk]
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NS Dev
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| posted on 2/9/05 at 12:54 PM |
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Do you have the sierra servo as well?
If so, more than likely the non-return valve is leaking and allowing engine vacuum to pull the brakes on slightly.
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timnuttuk
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| posted on 2/9/05 at 12:56 PM |
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No servo! pedal straight to the m/c via a push rod.
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NS Dev
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| posted on 2/9/05 at 01:02 PM |
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it won't let air in, the circlip stops the piston retracting too far and popping out, don't worry about that!
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mookaloid
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| posted on 2/9/05 at 01:05 PM |
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quote:
I'll wind back the push rod a bit, but isn't there a danger that the plunger will come back too far and let air in? Heard this from
someone else..maybe wrong
Yep wrong!there should be a little bit of play at the end of the plunger the piston cannot come out as there should be a circlip holding it in - if
the piston can come out then you have a problem!
Cheers
Mark
Doh should type quicker
[Edited on 2/9/05 by mookaloid]
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timnuttuk
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| posted on 2/9/05 at 01:18 PM |
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Thanks guys! I'll wind it back and leave a little play and let you know how I get one!
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Hellfire
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| posted on 2/9/05 at 01:26 PM |
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Is your brake line route or M/C high up in the engine bay? Or nearby a heat source?
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DarrenW
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| posted on 2/9/05 at 01:33 PM |
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If its Pinto engined i would guess the exhaust might be close by. I was going to fabricate a single downpipe exhaust system for mine using the std
Sierra manifold but would have needed to incorporate some daft bends in it within the engine bay to keep it away from the MC. I had to fit rather nice
4 branch instead. I would guess if the exhaust is close this could expand the fluid a touch.
I had a similar problem with a Mk1 Golf that i did a full disc conversion on a while back. I basically had the brakes set up a bit tightly such that
they got hot due to binding which caused them to bind more. IIRC this was mainly due to handbrake adjustment. Having the mC pushbar a bit tight would
also do this i would guess.
Did the brakes work OK for a preiod of time or have they always done this? First step in root cause analysis is to determine what has changed then
explore possible other root causes. The final fix may not be something that is immediately obvious until you have done the brainstorm bit (ie what we
are doing now).
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timnuttuk
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| posted on 2/9/05 at 01:35 PM |
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>>Is your brake line route or M/C high up in the engine bay? Or nearby a heat source?
Yes I stupidly followed the Tiger manual, and it runs along the chassis member over the exhaust. I have wrapped it (and the exhaust headers) in
exhaust wrap.
Are you thinking of the fluid expanding? This was my initial thought, but surely it should just just expand back into the m/c reservoir...
Moving the brake line will be a major job
>>Did the brakes work OK for a preiod of time or have they always done this?
Always like this. First time I drove it for more than 2 mins was to my MOT and then last month to the SVA.
Thanks.
[Edited on 2/9/05 by timnuttuk]
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NS Dev
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| posted on 2/9/05 at 02:07 PM |
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quote:
Originally posted by timnuttuk
>>
Are you thinking of the fluid expanding? This was my initial thought, but surely it should just just expand back into the m/c reservoir...
[Edited on 2/9/05 by timnuttuk]
should do as long as the pushrod is going slack, if not then it might be keeping the ports in the cylinder covered and not allowing this to happen.
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DarrenW
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| posted on 2/9/05 at 02:15 PM |
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Ok, if it was me id do the following first;
step 1 - check the pushrod on MC (ill be checking mine tonight now as well so thanks for the heads up).
Step 2 - check handbrake adjustment at lever and shoes.
Step 3 - check all of the calipers and shoes etc have good free float in them and that when brakes are applied and released they all move back
correctly to allow wheel free movement.
Are you absolutely 100% sure you have correct pads / shoes fitted. i had terrible trouble sourcing front pads. All of the reference books qouted one
type but in reality my donor had different type installed. i dont know why but can only assume the donor was on a cross over year.
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britishtrident
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| posted on 2/9/05 at 03:02 PM |
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This is definitely a push rod clearance problem
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locogeoff
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| posted on 2/9/05 at 04:11 PM |
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I had a similar experience with a land rover that I'd rebuilt the master cyclinder on, it was as others have suggested the pushrod clearance
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timnuttuk
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| posted on 3/9/05 at 06:13 PM |
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Well, I wound out the end stop on the brake pedal to allow the m/c piston to return fully, and add a little play between the push rod and m/c.
It seems to have worked, although I didn't get a chance to get the engine up to full temperature. However, now the pedal is much squasher that
previously - I guess there is still air in the system. Hitting the brakes hard still managed to lock up the fronts so I'm not too worried, but
I'd prefer it hard ....(ok no jokes!)
Thanks
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JoelP
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| posted on 3/9/05 at 06:26 PM |
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air in the system would also expand more than brake fluid as it gets hot, this might've made it worse before.
Eazibleed is a great way to bleed your brakes alone.
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timnuttuk
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| posted on 3/9/05 at 06:55 PM |
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True!
I have an Eazibleed which is great for.... well bleeding Sadly I mounted my brake compsenstor upside down so air can get trapped in there - I had to
turn it around to 'encourage' the air to escape - Hey ho!
Thanks for all your help guys!
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