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Having rebuilt my 1989 CSW it is now time to get an MOT

It is now a solid 200tdi with disc brakes all round.

I have rebuilt the brake system with a disc braked rear axle, rebuilt callipers all round, new pipes and flexi hoses.

The pedal box, servo and master cylinder are form a 300tdi vehicle, and were bought as a complete second hand unit from a breakers.

 

Upon test driving the vehicle I was shocked at how poorly the brakes performed, and after some reading on here I found the usual crack in the front of the servo.

I fitted a new TRW servo for a 300tdi defender (LR013488) this looks identical to the old one, however when fitted it simply would not cause the brake pedal to sink under pressure when the engine was started.

I spent several hours messing around with this, it did seem to hold a vacuum, but I just could not get the pedal to sink when the engine was started.

 

I eventually removed the new servo and refitted my old cracked unit with some tape over the crack to seal it up, when tested this seemed to work as it should, the pedal sank when the engine was started, and upon test driving the vehicle the brakes felt fine.  (The rest of the system remained unchanged during this test, I simply swapped the new servo for my old unit)

I concluded that the new servo must be faulty, and the vendor although shocked that someone had a bad TRW unit agreed to accept it back for a refund.

 

I purchased another replacement TRW unit  but upon fitting it behaves the same as the one I returned.

It holds a vacuum fine.

When driven, the brakes are excellent, probably the best Land Rover brakes I have ever had, the servo clearly works.

HOWEVER  if you hold the Brake pedal down and start the engine the pedal does not drop.  (I am pressing the pedal a few time prior to starting empty the vacuum)

I believe this to be an MOT failure?

 

I am at my wits end with this the brakes are excellent now, I simply can not get the pedal to sink when it is held down while the engine is started.

I have tried a second vacuum pump.and also a second new non return valve, purely out of desperation.

I have tested the vacuum from the pump by putting my thumb over the end of the pipe, and it seems to suck very well.

With the old (bodged with tape) servo re-fitted every thing works as expected.

 

Is this an MOT failure?

Does any one have any ideas as to what the problem could be?

 

My set up looks the same as the one pictured here

Is it possible that I have purchased and fitted the wrong servo?  I only have the breakers word that my pedal box / master cylinder was from a 300TDI.  The new servo looks to be the same size and shape as the one I removed.

 

I am at my wits end with this now and any input would be greatly appreciated.

Many thanks, Hippo

 

 

 

 

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1989 servo is quite thick front to back & smaller diameter & a diferent master cylinder/fluid tank. 

 

 

the later 300tdi on servo is thinner front to back & bigger diameter, master cylinder is different, fluid tank is straight sided, & the maste cylinder studs are diagonally offset, whereas the earlier studs are horizontally opposite each other.

 

300tdi servo & MC.

post-3901-1213697813_thumb.jpg

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Upon re reading, I could have explained that better, and with less typos.

Alas the edit button has gone.

 

In short.

With the new servo fitted, and excellent brakes:

If you start the engine with your foot on the brake pedal, the pedal does not sink.

 

Will this be a problem for the MOT?

Also what could be causing this?

Everything I have read uses the above test as a way of testing if a brake servo is working.

 

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Those servos in good condition will hold a vacuum for hours after engine is turned off so pedal will not necessarily sink when engine is started. To test whether pedal sinks, you neeed to expel the vacuum first - pull the vacuum hose off the servo and then replace it again. Then start the engine and pedal should sink after a second or two.

 

BTW the later servo and master cylinder with diagonal MC mountings is always referred to as 300tdi onwards servo but they were fitted to 200tdi with rear drums from 1992 onwards.

Edited by oneandtwo

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Thank you for the replies.

 

I have tried pushing the pedal a few times prior to starting to deplete the vacuum.

I have also tried starting the engine after prising the non return valve out. (and pushing it back in)

The pedal simply will not sink.

It is certainly easier to press the pedal with the engine running than it is without, and the brakes feel fine when driven.

Edited by MR-HIPPO

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Hi. Any chance the new servo's are for ABS models? Just a thought mind you as you seen to get everything working as it should with the old servo.

The pedal should go down with the engine running but when I say down it is only slightly, like a softer pedal.

Just spotted rust on my own servo and my small screw driver went straight through. (You are not alone)

Let us know if you get it sorted.

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The two new TRW servos are non ABS (LR013018)

 

As for the original cracked unit:

The complete pedal box assembly came from an online breaker, so I am uncertain of the original vehicle that the servo was from .

 

Is it possible that my cracked unit (pictured above) is not LR013018?

So far I have been unable to find a different servo that looks like my cracked one.

Edited by MR-HIPPO

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Your original from the pics is a 300tdi type identical to my 300tdi diagonal studs for m/cyl I've just taken off. Did the two new servo's look like the old?

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Yes both the new servos look the same as the old cracked unit.

newservo1.jpgnewservo2.jpgnewservo3.jpg

 

The part number of the replacement servos is LR013488

Edited by MR-HIPPO

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Update:

I have just fitted a new master cylinder and the problem is still haunting me.

 

Rebuilt brake callipers all round.

New solid brake lines.

New brake flexi hoses.

New servo LR013488  (TRW)

New master cylinder LR013018  (TRW)

New non return valve. STC493

The vacuum pump is not new but seems to work ok, I have also used a known good replacement vacuum pump.

 

The pedal refuses to sink when it is held down (after depleting the vacuum) and the engine is started.

This is driving me nuts.

 

 

 

 

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Why are you so obsessed about getting a sinking pedal? Ask your MOT tester what he thinks.

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I phoned my MOT station.

The tester I spoke with explained that holding the pedal while the engine is started is the test they would use to determine if the servo is good.

Defective servo = major fail.

Inoperative servo = Dangerous Fail.

 

However when test driven the brakes feel pretty decent.

Edited by MR-HIPPO

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that's not much help, if the brakes work well & stops the vehicle quickly, & a new servo which holds vacuum  for a long time surely shouldn't fail a MOT test.

ask him to drive the vehicle & give you a better response.

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I know, I think this is one of those catch 22 situations.

 

This is at the end of a fairly major over haul, during which the MOT expired, and the vehicle was SORNed.

I think I am therefore unable to drive it, other than to an MOT.

Also if I understand the new MOT rules correctly, should the MOT result in a Dangerous Fail, then I would not be able to drive the vehicle home.

i do not remember MOT time being awkward in the past.

 

Thanks for the replies, your input is appreciated.

 

Edited by MR-HIPPO

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How do your brakes feel with the vacuum hose disconnected? I.e are they noticeably worse when driving?

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I was going to reply and say they are different, but I thought I would take the time to actually try this in the vehicle on the move.

 

With out the vacuum hose connected, (so no servo in the system at all) the brakes are scarily bad, worse than they were with the fractured servo.

Reminded me of an old  Commer caravanette that I briefly owned back in the 80's

 

With the servo plugged back in, the difference is very apparent, chalk & cheese.

The brakes feel excellent, certainly the best brakes I have ever had on a Defender.

 

The engine had not been run for at least an hour and a half prior to disconnecting the hose from the servo, but there was  still a good vacuum present.

Everything clearly works, yet the servo fails the classic servo test. Very strange.

 

Disclaimer: Do not try disconnecting you vacuum hose from your servo while driving 😉

Thanks again, Hippo.

Edited by MR-HIPPO

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Old thread revival , but was this ever resolved as i have the opposite issue , Mine does go down and i wish it didn't  

  • Haha 1

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4 hours ago, bongo321 said:

Old thread revival , but was this ever resolved as i have the opposite issue , Mine does go down and i wish it didn't  

Have you looked at the master cylinder yet? Internal leakage (seals bypassing) will cause premature/ unwanted pedal drop.

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