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A hissing noise...


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So recently my 1987 90 has developed a hissing noise. Its coming from between the brake servo and the master cylidner. I have noticed that braking can be a little spongy at times as well. It doesnt do to well when I have alot of weight in the car either.

I had been planning on upgrading the brakes for a while but it was a job for when I can afford it. However the new noise has pushed it to the top of the pile. (Oh its a 1987 90 CSW with a 300tdi).

My plan is to fit vented discs and change the callipers as requried. Does anyone have a part number for the bigger callipers? I think they are from 110's if I'm correct? And am I right in thinking they are a direct relacement? Or will I need to change other parts to make them fit? (Also guessing this will change the pad size as well?)

Also I had read about upgrading the servo to a newer one? Does anyone have the part number for that? Also is there any upgrade I can do to the master cylidner?

And just to check I cant do much with the back brakes (Drums) without changing the axle?

Also any other tips? I had heard about using higher spec brake fluid?

Thanks

Stephen

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Look around the face of the servo 'can' where the m/cyl bolts to it. The metal on some servo cans is thin and cracks (because it's subject to quite a bit of stress) then allowing the vacuum to escape.

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Okay :) so new servo it is! Is there an upgraded one to use? Or just the standard? It's a 1986 defender. I was sure I had seen somewhere that I could use a 300tdi one but I could be wrong!!

Cheers

Stephen

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  • 3 weeks later...

Just wondering if anyone can help me find the right servo? Im guessing the direct replacement is STC2878 but I'm not sure. I had also read that I can use a more recent servo from a newer defender to improve braking. What part number would this be?

Just wanting to check, I recently was approaching a green light that I was hoping to make, however I didn't. So I hit the brakes. I couldn't push the pedal any harder without using another foot and I couldn't get it to lock up. Ended up across the line. I would have only been going 30mph as well with no heavy loads or anything. Usually it would have locked up and skidded to a stop but not this time.

Is this todo with the servo or is there more going wrong that I haven't noticed yet?

S

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replace with the same type you already have, this one --- http://www.paddockspares.com/stc2878-brake-servo-non-abs-90-to-ha701009-110-130-to-ha901219-1-2-port-or-type-50-227mm-non-return-valve-aperture-at-btm-right.html

the 300tdi servo is a bigger diameter & thinner front to back, the master cylinder studs are offset, so you would have to change that as well & then the pipe end fittings are different too, so they would need changing, to much hassle for no gain/improvement, plus 300tdi servo's crack around the MC studs/central hole.

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One last thing to check. Am I right to say that the bleed nipples on the callipers are 11mm? I'm guessing I will have to bread the brakes after and wanted to have a flare nut wrench.

Stephen

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So I tried to change the part but failed :(. The replacement is smaller than the original, the connection for the vacuume hose is also in the wrong place. (New is top right, old is top left, as you look it the front of it). It also didn't seem to want to sit flush, seemed like something was pushing from the bottom as the bottom was sticking out.

When I had the old unit I had a look for holes/cracks but couldn't see anything. I can feel the suction on my finger between the servo and master cylinder. On the underside. Is this a seal between the servo and master cylinder?

Thanks

Stephen

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post a photo of your old & new servo, because going by the year it should have the smaller diameter/thicker servo, maybe a previous owner has changed it for a non LR servo, as I said earlier a 300tdi bigger servo/master cylinder is different

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This one here also looks the same as mine.

If I put my finger under the master cylinder I can feel the suction from a gap between the servo and the master cylinder. Im guessing its maybe a seal or something? Im tempted to fill it with some kind of sealent (I know its not a long term fix though and would rather just sort it properly)

Cheers

Stephen

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So an update, thought I'd try some instant gasket, between the servo and master cylinder. It helped but there is still a hissing. Which makes me think a seal needs changing?

Stephen

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Okay so a new servo it is. I just need to work out which kind is mine. I found this website http://www.expeditionlandrover.info/dual_brake_conv.htm

It looks to me that I have a type 80 servo. Found in 1980 110's. Part number NRC4772. I'm making this assumption based on the photos and the position of the vaccume hose on the servo.

Would that possibly be right?

Stephen

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If the type 50 was smaller than the one you had, then a type 80 would be the next guess, so nrc4772 is a good shout. You can never be sure what is factory fitted or not, depending on what other owners have done in the past. You can only try and replace what is there if it was working for you.

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So the part arrived and is fitted. And it fits!! However the break pedal now feels really soft. It still breaks and stops but only with the peddle pushed down. I'm still struggling to get it to lock up. Not obviously what you want but at least then I know the breaks are giving everything.

I didn't disconnect any break pipes while changing the servo. Managed to move the master cylinder with everything still attached. So I shouldn't need to bleed the breaks? Or do I?

Stephen

Some extra info, with the car switched off the pedal goes solid. Start the car and the pedal sinks quite a bit. With the car running, pumping the pedal does nothing. The pedal doesn't go hard. Is this maybe just me experiencing "proper" defender brakes?

Stephen

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Sounds like your vaccuum is working then, good news. you probably do need to do a mini bleed, if you filled your master cylinder open both ports slightly and push slowly to dribble any air that has risen to unions and push fresh fluid in. then with pedal still down use an assistant to tighten the two unions up and let the reservoir fill the master cylinder up.

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probably need to adjust the new servo's pushrod,

I had a simialr problem after converting my rear brakes from drum to disc, had to adjust the pushrod to get some clearance between the rod ball end & brake master cylinder piston face, opposite to what you have.

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