Brakes - Servo - How much suction - alternatives

Just finished a brake overhaul on a 1984 SWB Series 3 Diesel - one of the few with the early Defender engine and "D" suffix gearbox.

I have replaced all six slave cylinders, most of the brakepipes and all the shoes. All drums are really good and the bleed is fine; done with an professional pressure outfit, which is one of the best tools ebay has provided for me.

I'm very disappointed with the results. No, very, very, disappointed.

The brakes on three other Landrovers I look after, all series 3's but non servo, are better! Another, (1972ish) with a servo and a Transit air-pump fitted has brakes which would put your face through the glass.

So, given that I believe my work to date is good, I am left with doubts about the servo.

I have disconnected the vaccum pipe and I am not impressed by the suction on the end of it. It certainly is not of the "suck a golf ball down a garden hose" proportion, if anyone remembers that film? Good film, don't remember what it was called.

So, after all this drivel, my big question is, does anyone know a quantifiable value by which I can measure the "suck" (room for a bit of smut here?) of the vaccum pipe? I have a vaccum guage.

I have been trying to think of an alternative way of producing a strong vaccum in the pipe whist driving, but, we all remember the trouble Hugh Grant got into?

Digressing a bit, I have just bought a 71 S2A with a Daihatsu lump, which has an alternator fitted with a vaccum pump! (but, no servo)

I took a starter motor to the local magician today and he confirmed that these pumps are quite common on alternators - interesting if one fits straight onto a Landy engine. The Transit conversion seems to be a pain in the arse. Hard to keep both belts tight and no warning if the brake belt goes walkabout.

Using one of these combined units would give warning of belt failure (red light on) which gets my vote.

I'm going to try and find out what fits what, but, anyone already know?

Thanks for reading, if you're still awake, sorry, I do go on a bit.

be sure to check the diaphram in the servo. they split and the fluid passes thro to the other side. if you are loosing fluid, thats where itll be.

why not just get a new servo

I really have a feeling it's not the servo - if it turn out that it is, fine, new one straight away.

Not dropping any fluid (yet) and, as I think I said, brakes are reasonable, but, when you consider that they are larger diameter than the earlier brakes, wider shoes and a servo as well, you would expect a lot more.

I am going to get to the bottom of this and report what I find.

I also use a web site for my other car, a 1954 Riley (could post a pic if you are bored!) and it really ****es me off when people you have never heard of come on, ask questions, get loads of advice and don't come back with an outcome. Guess it's human nature?

I'm really taken by the idea of these alternators with pumps. I guess there must be a weakness in the design for the Transit/Peugeot conversions to have caught on.

Interestingly, if your S3 jammed on full throttle, or an engine failure, you would have no servo assistance to bring it to a halt, with the original system, since the slightest opening of the throttle destroys the vaccum. I don'y think the little reservoir is worth a mention.

Scarey?

Has anyone else messed around with this?

if my accelerator jammed on and i was heading for the rsend of a lorry, i wouldnt be needing any assistance from the servo to stop me. believe me.

Boring fact, but, aeroplanes have throttle springs that jam on full, in the event of a fail - theory being all (airborne) is better than none (nose in the ground). Wouldn't like to put it to the test though.

Hi again Ormus, bow to superior knowledge, but, I didn't think fluid went anywhere near the servo? Air on both sides of the diaphram? I'm a bit confused.

best way to check yer servo is to pump brake pedal about 6 times with engine orf, then with yer foot still pushing hard on pedal start the engine..if yer servo is working yule feel it move down about 1/4 inch.

Yep, this lowering of the pedal happens, but only sometimes; usually when sitting at the lights with hoof on the pedal. Suddenly (sometimes) goes down a bit.

I am going to get right into this in the next few days and will post outcome.

Anyone know how the later (post series) Diesel Landrovers generate their vaccum? I had a look at a Sherpa engined diesel which is here at the moment (respray) it has a pump mounted on the engine block, driven like the injector pump.

there should be a one way valve somewhere between the pump and the servo, check its not full of ****.

Don't think there is a valve, but, will have a look. Weak link here, with Series 3, is that there is no pump! Bastard thing tries to get enough vaccum from the inlet manifold - hopeless.

How does the Disco do it?

well get one and put it in

Best is to source an alternator with a vac pump at the back and connect to the servo. A breaker's yard may be of help. Remove the butterfly and linkages for an unrestricted inlet.

That said, dunno about the cost though.

You need an oil feed for the pump. A tee at the pressure sensor would do for the supply, return will have to be into the sump through a hole punched.

Thank you Sri Lankan, just what I wanted to hear. Oil supply makes sense. Have you any idea what vehicles have these pumping alternators which share the same mountings as S3 diesels? Regards.