Xantia 'buzz' through brake issue...

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jonathan_dyane
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Xantia 'buzz' through brake issue...

Post by jonathan_dyane »

Interesting one this, on the Xant in my sig, which does not have ABS.

This weekend I did a few jobs on the old girl, which with regards to the hydraulics consisted of replacing the flat accumulator sphere, changing the LHM and removing the idiot spring from beneath the brake pedal, and replacing it with a solid piece of tubing in order to give me proper brakes as M. Mages intended. Since doing this work however, I have realised that as I caress the pedal, I feel a high frequency buzz through the sole of my foot, which occurs regardless of whether the car is mobile or stopped. I don't know whether it always did this and the spring camouflaged it, or whether this is a new development, but it is a rather unpleasant sensation. I do not think it is air, as there is non of the delay which air would cause. Is this perhaps a sign that the doseur valve is rather worn? This said, I never noticed this occurring in my BX, which given the speed at which it sinks clearly has a doseur which is past it's best.

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DickieG
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Post by DickieG »

I've had this when there has been air in the brake lines, invariably when air is in the rear brake lines the rear of the car lifts under braking (it should dip slightly to provide anti-dive), obviously bleeding is the answer.

citronut
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Post by citronut »

i agree with Richard
air in the system, you might also find there is no brakes at the first presure on the pedel (normal braking) before locking up, or did you have this before the work as to what prompted you to remove the spring in the pedel

regards malcolm

jonathan_dyane
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Post by jonathan_dyane »

I noted today that the tail of the car does lift slightly on braking, so I guess air must be the cause of the excitement; I shall look forward to dealing with the (almost inevitably siezed solid) brake nipples at a later stage. There is no noticeable 'brake delay' so I guess it must be trapped in the rear, possibly due to previous sphere replacement.

Why did I remove the spring?
Having driven many miles in GS and CX I am used to their excellent braking response, and the sensitive brake pedal. Citroen chose to dull and camouflage this in the Xantia (undoubtedly to make the car drive more 'normally') by the aberration of fitting a spring 'twixt brake pedal and doseur valve. This corruption, aside from ruining the splendid brake response also serves to make braking often a somewhat clumsy experience in the Xantia, the engineering nonsense of having movement in both the doseur and the spring making progressive braking often difficult. I do concede that it did a good job of hiding the 'buzzzz' however :-)

Toby_HDi
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Post by Toby_HDi »

I need to try this spring mod, what kind of tubing do you use to replace the spring?

jonathan_dyane
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Post by jonathan_dyane »

Toby_HDi wrote:I need to try this spring mod, what kind of tubing do you use to replace the spring?
It's easy, and transforms the car. I used a piece of tube that was originally part of a dyane hood, but anything the same diameter and length of the spring will do; I suspect domestic copper piping may work. Simply lift the brake pedal and withdraw and manipulate out the plastic housing attached to it's underside (no tools or dismantling necessary) then you will find the plastic housing has a collar which is slid down, then two segments will remove permitting the housing to be seperated and the spring removed. It is harder and more time consuming to describe that it is to do!

Pleiades
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Post by Pleiades »

You say that one of the jobs was to replace the LHM.

What brand did you use?

When running a car using hydraflush, you sometimes can experience this brake pedal buzz, I put it down to the fact that you can feel the brake valve working, this buzz is normally damped out when the LHM in in the system.

Why?? Because the Hydraflush is thinner than LHM.

Some of the cheaper brands of LHM on the market are thin, like the Hydraflush, I rekon that using the cheaper brands can give you the brake valve buzz.

I would only use LHM from a Castrol or a Total bottle as this seems to be the only quality stuff.

Regards
Martin.

jonathan_dyane
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Post by jonathan_dyane »

Pleiades wrote:You say that one of the jobs was to replace the LHM.

What brand did you use?

When running a car using hydraflush, you sometimes can experience this brake pedal buzz, I put it down to the fact that you can feel the brake valve working, this buzz is normally damped out when the LHM in in the system.

Why?? Because the Hydraflush is thinner than LHM.

Some of the cheaper brands of LHM on the market are thin, like the Hydraflush, I rekon that using the cheaper brands can give you the brake valve buzz.

I would only use LHM from a Castrol or a Total bottle as this seems to be the only quality stuff.

Regards
Martin.
Thanks Malcolm, that was very useful, particularly as I have now realised that the buzz only appears when the car is thorughly hot, when of course the LHM is at it's thinnest...

I used what GSF had on their shelf, which was 2 bottles of Total and 2 of the 'cheap brand', however I still have a 1/2 bottle of the Total stuff left over, so most of the LHM is indeed the cheap crap...

Given that the problem does not occur when the car is cold, I guess this rules out air?

Cheers,

citronut
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Post by citronut »

jonathan i think you ment to thank Martin not me, and i agree with martin on this, also not that i will use it but i think GSF's cheaper citro blood is morris oil's brand which i dont think is as bad as other non genuine LHM

regards malcolm

jonathan_dyane
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Post by jonathan_dyane »

I did mean Martin :oops: Dyslexia bites...

jonathan_dyane
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Post by jonathan_dyane »

superloopy1 wrote:Not wishing to hijack this thread but has anyone any experience of 'other' LHM makes ie Unipart or Comma?

Both are certified to Citroen/BS standard (that's what it says on the bottle).

Is it a bit like oil changes ... change it often and you'll not experience any problems?

If so then could the cheaper makes work out more cost effective ??
If you read above, you will find that Martin (who has more experience of Citroen hydraulics than most) doesn't seem to rate the cheaper varieties...

Pleiades
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Post by Pleiades »

The thing is that if you take a sample of hydraflush and let it drip through a small hole (I use an empty syringe) and see how many seconds it takes to drain say 20cc of fluid, then do the same with decent (Castrol of Total) LHM, you will find that the LHM takes a bit longer to drain than the hydrafush, this is really a simple viscosity test.

Now take some cheapy LHM and do the test and you will find that it flows more on the same rate as the hydraflush.

I allways rekon that you get the brake pedal buzz because the lower viscosity does not damp out the actions.

Now I am not saying that cheaper fluids are not up to the specs on the can, because they are still fit for purpose, just not as good as the quality.

The old saying about engine oil was, "The cheapest oil that you can get will turn out to be the most expensive"

As for changing the LHM.

You cannot realy work a hydraulic system to a mileage, so the best test is the jam jar test...

Get 2 x clean jam jars and a newspaper, put about 3 inches of clean new LHM into one of the jars and place it on the newspaper, look down through the top of the jar and you will be able to read the print through the fluid.

Now get the second jar and put the same amount of LHM from your cars reservoir in the jar, stand it on the newspaper and see if you can still read the print.

If the LHM is just a bit off colour but basicly clean, change it, if it's filthy, flush it.

By the way, the problem will not be down to air. Air in the brakes on a Citroen ALLWAYS shows up as a slight delay from pedal to calipers and whilst the delay is only for a split second, it will scare the s*@t out of you.

Regards
Martin.

jonathan_dyane
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Joined: 10 May 2004, 23:32

Post by jonathan_dyane »

Thank you for your very informative reply; I for one shall be buying only Total LHM from this day forth :-)