v8250

v8250

Well-Known Member
Upgraded front disc brakes from 90 to 110 [new calipers. discs] + new brake servo and master cylinder.

Q? do the servo and MC need to be 110 items? [I read that std 90 units work correctly]

I ask as am getting bugger all braking. This morning have checked the following:

1. locked up rear drums on cams - no effect :. by passed potential rear of system fault = check
2. getting full vacuum at servo NRV output = check
3. NRV working - blow through uni-direction = check
4. servo test at start up and switch off - no servo felt = fail

All advice greatly received as about to rush out and buy 110 servo and MC

Thank you
v8250

ps - there is zero air in system
 
As far as I remember the 90 had a small valve system of sorts built into the brake lines near the front of the vehicle, something to do with accounting for the short distance between the servo/MC and the rear brakes. I don't know if the 110 kit would affect this or not
 
Think it’s to do with fluid movement.unsure what the difference is between the 2MC are.
The 110 callipers need more fluid to engage them

clamp the rear flexi & O/S flexi so all the fluid only goes to 1 brake to see if they work.
Then release rear & check again.
 
Thanks Phil, have looked into this more, it's that the 110 calipers need greater hydraulic movement :. pressure than the early 90 MC. The 110 MC's [post '91] are much smaller than the 87-91 90's. Have just picked up a 110 servo and TRW MC from AllMakes who are, luckily, just up the road in Abingdon, now to strip down and rebuild.

Can't clamp flexible's as have braided hoses :rolleyes:

I will report back on this once done as this issue resolve may help others...

eta: if this fixes the problem, yes I've been an arse :oops:
 
I did this mod to my 1990 ninety some years ago. Just fitted one ten callipers and pads and everything worked and still does.
Not much help for you but when the tdi's came out 90's and 110's had the same size callipers fitted. Recon servos are the same as well.
 
tottot said:
I did this mod to my 1990 ninety some years ago. Just fitted one ten callipers and pads and everything worked and still does.
Not much help for you but when the tdi's came out 90's and 110's had the same size callipers fitted. Recon servos are the same as well.
Click to expand...

Thanks @tottot , I have something niggling in my mind with this and had read many times that there was no need to change servo and MC...and the pressure's on as booked to drive chugga-boom to the Alpes on Thursday o_O

Have just come in for a cup of tea before breaking down the servo. From earlier, nothing's changed except I've measured if there's any permissible adjustment to extend the servo rod into the MC. The rod can be extended ~5mm before becoming too wobbly [even with the lock nut] but the distance between the MC piston face to servo rod is too tight to extent as this would put constant pressure on the MC. For ref' the MC neck that slots into the servo is 15mm, same as the MC inner to piston.

So the Q? is, apart from it being a Land Rover, where's my bloody problem? :(
 
tottot said:
Not much help for you but when the tdi's came out 90's and 110's had the same size callipers fitted. Recon servos are the same as well.
Click to expand...

Yes, but the later servo and MC's are quite different to pre-91 models. I'm going to de-install and strip the MC just in case one of the seals has reversed/is letting by...even though this is a brand new TRW unit
 
Did you have brakes before :)

Then youll have brakes after......

The 90 servo/master cylinder will work the 110 calipiers no bother....the pedel travels a few mm more but youd expect that as it needs to shift more fluid.

The servo should make no difference to distance of brake travel. The master cylinder would if its a different diameter.

Some mathimatical inclinded person with nothing better to do could easilly work out how much further the mastercylinder would move and the extra distance the brake pedal would travel....its simple maths......who is going to pick up the challenge....just need a couple of dia measurments and a bit of pi
 
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Thanks @EeEk , now sat at kitchen table with old Girling MC and TRW MC.

I'm glad to hear from you and @tottot that the original Ninety servo and MC work with 110 brakes and calipers :. the fault lies within the existing system. As background, as part of full mechanical refurb' the braking system is all new, and did work correctly with old components.

Let me strip new MC and take some measurements...this is 'LIVE' LZ diagnosis...
 
I haven’t read the whole thread but did you measure and set the length on the new master cylinder actuating rod?
 
flat said:
I haven’t read the whole thread but did you measure and set the length on the new master cylinder actuating rod?
Click to expand...

no, understood it comes pre-set. thanks @flat , any idea what this is meant to be?

??are you saying servo rod adjustment or internal MC spring resistance @2-3Nm ??
 
okay, 'LIVE' diagnosis continues, all is well with the new TRW MC, but I have noticed something...the reservoir to MC seals supplied by TRW do not look the same as the original top hat type and looking at their fitment look as though they block the reservoir [!!] Luckily have a spare set, back in a little while...

Ignore last not, have re-inspected TRW MC, it has a different port profile to the Girling unit
 
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okay, I think the problem lies with the MC to servo seal/not seating properly :. leaking vacuum, though there's no hissing. But, it's the seal with the lug that sits in the MC body notch and I cannot find a part number for this...does anyone know where these can be bought?
 
If you have no vacuum you should have a rock solid high up btake pedal .....but you will not stop unless you have both feet pressing it :)
 
v8250 said:
no, understood it comes pre-set. thanks @flat , any idea what this is meant to be?

??are you saying servo rod adjustment or internal MC spring resistance @2-3Nm ??
Click to expand...

the rod that pokes out the servo before you bolt the master cylinder on, that can be adjusted - to far ‘in’ to the servo and the pedal has loads of travel and doesn’t really actuate the brakes. To far ‘put’ of the servo and it can hold the MC open (thereby holding the brakes on). There is a clearance measurement it has to be set to - I can’t remember it- but it’s mentioned in the maintenance manuals.
I’m wouldn’t trust that it’s ‘preset’.

I measure the clearance on mine by sticking blue tack on the end of the rod then activating the brakes and seeing what ‘thickness’ of blue tack wasn’t squashed.
If that makes sense….
 
Guys, an update here...it was the new TRW/Delphi master cylinder + distance between servo rod & MC + air in system. Combined they had me chasing tail for quite some time. For others who experience long pedal travel after new brake components, this should be the fault finding process...

  1. prove servo/vacuum side of system is working - if yes, the long pedal issue is mechanical
  2. measure servo actuating rod end distance to MC head up - the magical figure is 15mm recess with rod end crown near flush with servo face [this for up to 1991 model years]
  3. if still long/to floor pedal travel....bleed, bleed, bleed & bleed...and then bleed some more - at this stage you should have either tiptop hard mechanical pedal feel [engine off] or some firm pedal feel towards lower end.
  4. if brakes still not stopping test the MC by removing both front and rear primary brake pipes [cap off with dust caps] and fit bleed nipples in the MC - this gives a guaranteed go/no-go test function on the MC
  5. if still no hard pedal/long play, re-instates primary piston brake line [rear cct] and test - if still poor brake feel it's the secondary piston [front brake cct] that's faulty
:. either rebuild or replace with good quality MC

I chose to buy new and will send faulty unit back - I chose this route as the secondary piston would only release so far out of the MC and then stick firm.

+++ I spoke with Keith Gott Garage on Saturday morning, they were very helpful. During fault discussion they mentioned issue with new calipers [from multiple manufacturers...] where the calipers do not sit 'true' on caliper mounting. This forced the cylinders to be held back by at angle brake pads. They overcome this by taking the vehicle out for an Italian brake service, often driving with brakes part on until...ping! they settle into place.

Now, I'm not totally convinced with this as all calipers, and therefore brake pads, are in line with the brake disc with fixed caliper. But, if it works for Keith Gott Garage it should work for others too.
 
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